X " iNIS-mf —11396 >̂v

S.A. INSTITUTE OF PHYSICS

S.A. INSTITUUT VIR FiSIKA

32nd Annual

Conference

32ste Jaarlikse

Konferensie

Durban

1987

UNIVERSITY of NATAL

DURBAN

Pittwir«rilzburg

SOUTH AFRICAN INSTITUTE OF PHYSICSSUID-AFRIKAANSE INSTITUUT VIR FISIKA

32ndAnnual Conference

22ndAnnual Theoretical

Seminar

5th Winter School

32steJaarlikse Konferensie

22steJaarlikse Teoretiese

Seminaar

5de Winterskool

DURBAN13-17.7.1987

Physics DepartmentsUniversity of Natal

Organisation - Reelings

Durban & Pletermaritzburg

Flslks DepartementeUnlversiteft Natal

ATC combjnaa M-tach South Africaninnovation with tba bast that over-seas technology can offar. This haslad ATC to bacoma tha only manu-facturar of optical fibre in SouthAfrica.

1. A chemical deposition process,producing optical fibre preforms.

2. Preform inspection.3. The drop at the start of optical fibre

drawing.

;abling the fibre . . .ATC opanad South Africa's firstoptical cabling plant in 1882 andproducas a wida range of cabfassuch as:Underground and aerial, metallicand non-metallic.Stogie- or multi-fibre.Single-mode or multi-mode.Composite fibre and copper cables.Armoured or unarmoured.

1

1. Stranding the fibre.2. Buffering the fibre.3. Quality control of optical fibre.

nd putting the fibre to work . . .Th# crGasUvo drtvai BOO bow Jooov>*lion that lad ATC to bring opticalflbra to South Africa is now beingapplied to optical flbra systemappacattena.Our range of products and servicesinclude:a Computor links and LAN'S.e VMeo Inks for CCTV.a 2and*megabit PCM Hne

a Unks for process control andpfotaction.

a Connectors, taHa, fly-leads and

e InataWatlon. and maintenance.

1. Bbn» optics connectors an) tails.I kwMng ton optics.& Fix* optic termin»t*quiptJmt.

Contents InhoudWelcome from the Principal and Vice-Chancellor 7

Boodskap van die President van die SAIF 9

Keynote Speaker: Dr H.B. Dyer 11

Genooide Sprekers 15

General Information 23

Algemene Inligting 25

Student Sessions 29

Vergaderings 33

Winter School Programme and Abstracts 37

Konferensieprogram 45

Abstracts of Papers 67

Acknowledgements Dankbetuigings

The Organizing Committee would like to thank the many advertisers, exhibitors and sponsors whose financialsupport has made a vital contribution to the success of this Conference. In addition to firms appearing in thisProgramme, a particular word of thanks goes to Shell SA (Pty) Ltd for providing the attractive Conference bagsand to the Coca-Cola Bottling Co. for a donation.

Ondersteun asseblief ons adverteerders. uitstallers en borge — sonder hul guile ondersteuning sou dit onmoontlikgewees het om die Konferensie in sy huidige vorm te reel.

We acknowledge with gratitude the unstinting assistance given by various service bodies within the Universityof Natal in the preparation of this Conference, in particular Multicopy Centre (Durban).

This page sponsored by the De Beers Diamond Research Laboratory

3

Any chief executive of a large company will understandthe enormous complexity of co-ordinating 60 000employees and an annual turnover of nearly R5 000million. In addition, Escom is over 60 years old and is thesole supplier of 94 percent of South Africa's electricity.It's a situation that could invite complacency andbureaucracy.

Aware cf these problems, Escom's management haslaunched the most dramatic restructuring programmeever undertaken by a major South African company.It involves the optimum use OT human energy bycreating an atmosphere of enthusiasm, commitmentand dedication amongst employees at all levels.By encouraging employees to voice their ideas of howimprovements can be made within their own depart-ments, combined with wide-spread initiatives by manage-ment, dynamic solutions are being generated on cost-saving, better service to customers and generalefficiency.

From this programme, it is expected that millions of Randcan be saved each year, which will be translated intolower tariff increases. Already, electricity from Escom isamong the cheapest in the world - despite the difficultiesexperienced in generating and distributing electricitythroughout a country as vast as South Africa.

But we're not using the rest of the world as a criterion.Our concern is the role we have to play in the economicadvancement of South Africa. We are intimately involvedin the well-being of the public, of industry and agricul-ture, and in preserving our natural resources and theenvironment. This means that our efficiency affects notonly our credibility with customers and investors, but alsothe future of our country and its people.

And that is why human energy- from management,and throughout the entire organisation - has become asimportant to us as the energy we sell.

All our energy for you.

ORE" PHILLIPS BUNION WJNllb I BLAK! T9003

IT PAYS T O IIAV1- A POLICYFHAr MANAGES I JIT'S DI-MANDS,

ASVVI-ITyYSVOUDOllie demands of modem life can be

challenging: the expectations to do well inone's career, to be a caring father, a lovinghusband, and a good provider may pull indifferent directions.

Your experience enables you to cope. Yourlife insurance should be flexible enough toback you all the way.

That's where the real value of life insurancethrough Old Mutual's FlexiProgram lies.

From your first premium you'll beproviding your family with a financialsafeguard and a growth asset that builds asubstantial capital base.

If you're 32 now, and put away say R100per month, in twenty years you could beworth Rl 14 000* and, after thirty years,almost half a million - tax free!

That store of wealth created byFlexiProgram is accessible later on loo - forchildren's education, or for setting yourself upin business, for example.

And if you are disabled, FlexiProgram paysout a lump sum to use in providing a regularincome.

Feature for feature, rand for rand, OldMutual's FlexiProgram offers outstandingvalue for money. No wonder it's SouthAfrica's first choice for life insurance.

Especially among those who manage life toget the most out of it.This projected value is not guaranteed and is based on aFledProgram Endowment with Disability Benefits. Full

details will be provided with eachindividual quotation.

MUTUALMAKING THE MOST OF LIFE

VerweBkoming Welcome

On behalf of the University of Natal. I should like toextend a warm welcome to all delegates attending the32nd Annual Conference of the South African Instituteof Physics, and to participants in the associated 22ndTheoretical Seminar and 5th Winter School. We trustthat this Indaba of physicists from within the Republicand from overseas will prove most fruitful.

From the programme it is clear that the papers presentedat the Conference will cover a broad spectrum of disci-plines within the field of Physics and include much re-search at the very frontiers of mankind's understandingof the fundamentals of Nature. On the other hand, suchareas as the teaching of Physics and industrial appli-cations have not been neglected. The discussion of theChernobyl disaster and its aftermath will. I am sure, be ofinterest to a wide audience of South Africans concernedwith the impact of nuclear technology on the environ-ment.

Dit is verblydend om te sien dat die Instituut vir Fisikabesondere aandag aan die volgende geelag van natuur-wetensteplikes skenk. Ek verwys natuurlik na die Win-terskool oor Aspekte van die Moderne Optika. wat opHonneursstudente gemik is. en die verskeie Studente-sessies. Dit is 'n prysenswaardige manier om die jongergeslag na die Konferensie te lok. Buitendien sal dit bydraom die kennis van fisici van alle ouderdomsgroepe in diehuidige era van toenemende spesialisering te verbreed.

Dit is nou twaalf jaar sedert die Universitiet van Natallaas as gasheer van u Konferensie opgetree het. en onsis bly dat u besluit het om weer Durban te besoek. Onsvertrou dat u verrigtinge vrugbaar sal wees en dat u almalu verblyf in die Tuinprovinsie sal geniet.

Hartlik welkom!

P. de V. BooysenPrincipal and Vice-ChancellorUniversity of Natal

This page'sponsored by the De Beers Diamond Research Laboratory

7

The National Accelerator Centre

It's reallysmashing!

Yes, we're smashing protons into things . . .. . . at 170 000 kilometres per second!

Fast enough to go around the earth in j of a second.Or to reach the moon in l\ seconds.

Our new separated-sector cyclotron has delivered its first beams of protons with anenergy of 200 MeV for the first nuclear physics experiments.

We also use this cyclotron to produce carrier-free radioisotopes for medical and in-dustrial use.

And 66 Mev proton beams are being used to produce neutrons for radiotherapy with oneof the largest isocentric neutron therapy units in the world, now being commissioned.

We also operate:

• a 6 MV Van de Graaff accelerator at Faure• a 16 MeV deuteron cyclotron in Pretoria, and• an 8 Mev injector cyclotron at Faure.

Soon we'll start installing a second injector cyclotron, this time with the most modernexternal ion-sources for heavy ions and polarized ions.

And we're now busily assembling a very large magnetic spectrometer for nuclearphysics.

Prospective users in the physical or biophysical fields are invi:ed to registerthemselves as such, and to submit research proposals during January

or July each year, for evaluation and allocation of beam time.

Information regarding facilities, procedures and employment opportunitiesmay be obtained from

The Chief DirectorNational Accelerator CentrePO Box 72 FAURE 7131 Tel.: (024) 4-3820

CSIFW

Message from the President of the SAIPBoodskap van die President van die SAIF

Someone once said: "Nobody has ever had a brilliantidea in a dress-suit". The annual conference of the SouthAfrican Institute of Physics is the opportunity providedby its Council for physicists to get together, take offtheir jackets and roll up their sleeves tc do some hardthinking. We all do this at our home institutions butbecause we are few in number and spread out geograph-ically, cur contact with colleagues is limited, apart fromthis annual event at which more than fifty percent of ourcommunity get together. It affords us the opportunityto work together, not only with those of us that shareour own field of specialization, but also with others indifferent fields. That is the environment in which newideas are generated. A great social responsibility restson us as physicists to generate new ideas. Doing moreof the same thing does not contribute much to the de-velopment of our people: it is new ideas that create newopportunities and new jobs. Often such new ideas havehad their beginnings at the SAIP conference.

Die reelingskomitee sien elke jaar die konferensie as 'nuitdaging om beter te organiseer. beter sprekers te nooien 'n beter en meer omvattende program daar te stel.Elke jaar wen hulle deur in hul doelwit te slaag. Dieenigste verloorders is die mense wat nie die konferen-sie bywoon nie. Vanjaar is die mense wat die uitdag-ing aanvaar het ons kollegas by Universiteit van Na-tal — beide te Durban en Pietermaritzburg. Aan hullewat al die werk gedoen het byvoorbaat my en die Raadse hartlike dank en goeie wen&e vir 'n baie suksesvollebyeenkoms. Dankie ook aan al die ander persone enorganisasies wat bydraes lewer deur advertensies. uit-stallings of borgskappe. Die konferensie sou onmoont-lik kon pl&asvind sonder die geriewe wat die Universiteitvan Natal aan ons beskikbaar stel. Ons het al vanievoredaarvan gebruik gemaak en ons weet hoe goed hulle aanons beantwoord. Ons hartlike dank daarvoor.

Dr G. HeymannPresident, SAIF

This page sponsored by the De Beers Diamond Research Laboratory

9

SIEMENS

An idea becomes a realityEMS 601-OC the office communication PABX

At Siemens we like to think of the EMS-601 with it's officecommunication package more as a computer than a straightdigital voice switch - that's because a customer can have allhis data equipment such as mainframes, terminals and printerscommunicate with each other over this existing telephonenetwork, while still providing all the features of voice switching.Today most organisations realize how critical it is to manageinformation efficiently - after all information is a key resource.So the choices you make today for voice, text, data and imagecommunication will determine to a large extent your futuresuccess.A future orientated customised project demands total masteryof the technology both in the private and public sectors.Siemens has this global experience and a universal technicalknow-how in telecommunications. Nowhere is this commitmentto digitise the analogue telephone network more far-sighted

than with ISDN (Integrated Services Digital Network). A globallyuniform digital network for voice, text, data and image.The process of integration will continue well into the nextmillenium, but the foundations of this communication networkof the future - digital switching systems - are already a reality.

SiemensWhere the future happens first.

1200

Opening Address OpeningsredeDRHB DYER

Henry Brooke Dyer was born Ut Durban in 1927. Afterobtaining an MSc in Physics at the University of Na-tal, he proceeded to Cambridge University where he wasawarded his PhD in 1951.

The same year. Dr Dyer joined the staff of the De BeersDiamond Research Laboratory and, after three years sec-ondment at Reading University studying irradiation dam-age in diamond, was recalled to join the team of sci-entists who successfully succeeded in synthesising dia-mond in 1959.

In 1962 Dr Dyer became Director of Research at theDiamond Research Laboratory and was appointed Tech-nical and Research Director of De Beers four years later.He was Managing Director of the Ultra High PressureUnit diamond synthesis plant at Springs from 1968 untilhis appointment as Managing Director of the De BeersIndustrial Diamond Division in 1971.

Dr Dyer became Manager of the Anglo American Cor-poration in 1967. a Director of De Beers ConsolidatedMines in 1975. and a Director of the Diamond TradingCompany in 1981.

In addition to the above. Dr Dyer is on the Boards ofnumerous other companies throughout the world.

In 1982 Dr Dyer was awarded the degree Doctor of Sci-ence Honoris Causa by the University of the Witwaters-rand.

Dr Dyer is married to Joan Gwendoline and has a son anda daughter. He is a keen sportsman and. being too oldfor rugby, enjoys waterskiing. squash, deep sea fishingand various other sporting activities.

Tuesday 14 July Dinsdag 14 Julie

•CEIIINOSSSTTUV'tRobert Hooke. 1676

Robert Hooke stated in 1576 that solid bodies perform in a predictable way when acted upon by external forces.So it is with human institutions; the body of physics in South Africa is increasingly likely to be subjected topowerful forces for change. The nature of these forces and the way physicists react to them will determine theshape of physical science in this country for many decades to come.

t Hooke's anagram of his law: "UT TENSIO SIC VIS".

iThis page sponsored by the De Beers Diamond Research Laboratory

11

So comeon in totheNBS

HUNT LASCARtStBWA 8705023

The Fabric of SocietyClay. The stuff of life first mentioned in

Genesis. And recognised since then as the idealmaterial to help shelter the family of man.

Yet mankind's inventiveness hasdiscovered uses for clay other than makingbrick. The sculpting and moulding of clay intoimmaculate ceramics is an example of theversatility of this raw material.

Thus Corobrik strives alongside society toenhance the quality of life in our country.More than producing a variety of quality facebricks which beautify our towns and cities. Alsosupporting a wide spectrum of cultural andartistic endeavours.

So extending our rich heritage for thebenefit of generations to come. And helpingtoday to keep the fabric of society intact.

COROBRIK

SUMOUND VOUHSELF WimlHE STUENCTH OF COKOIHK

Vw*mCTD 240680

PHYSICALMETALLURGY

ATMINTEK

The Physical Metallurgy Division of Mintek carries out R&D work on

• selected alloys, so that the use of locally produced metals can bepromoted;

• the wear and corrosion of the materials used in the mining andmetallurgical industries, since the replacement of these materials coststhe industry several hundred million rands annually.

There are openings in this Division for graduates and technicians witha background in physics, chemistry, and materials science, and inmetallurgical, chemical, and mechanical engineering. Bursaries are alsoawarded for university and technikon sludy.

If you want to know more about the work, write to the Director, PhysicalMetallurgy Division, Mintek, Private Bag X3015, RANDBURG 2125.

YESTERDAY FICTION TODAY FACT

_ Satellite images ol the courts j expected

as warm sea currents

Qlbng o> ancient ~natera thai sheds • q*> or the history c' the w f 1 \ :

patterns

Measurements wlfi an accwacy o' \

Clean ai' and clear 'am •• •"• "•- •-

Manipulation and Tieasu^.,,^,, u- ,u» .* -u. *y. . - . ^»^. >., „

Electric currents show the hidden st't/cL'e o' t*e W ' / ^ s :rJSl and cont\

Fifty years ago many of these examples wv^rp sr iprt f» f.(.tion

Physics above a]1 s the disc p 'np th,it p r j v r fps . i t s w v s t ) th

TODAY FICTION TOMORROW FACT1 b u t <i f e w p x , ) r " ° p i t »

NATIONAL PHYSICAL RESEARCH LABORATORYEnqu.nps The Cn ef Dir*>. for. NPRL CS'H P O B J I V)'> Pr.-l . '

invited Speakers Genocide Sprekers

DR J B CLARK

James Brian Clark, who is now Group Executive of the Research, Developmentand Implementation Group of the CSIR. started his career at the National PhysicalResearch Laboratory of the CSIR in 1965 and at the same time commenced hisundergraduate studies at the University of Pretoria, obtaining a DSc in Physics in1973 for research on phase studies at high pressures and temperatures. Dr Clarkhas received several awards. He has worked in Germany and the USA.

Brian Clark has travelled extensively representing the CSIR in an official capacityoverseas. He is the author/co-author of 85 publications for scientific journals and 2book chapters, was co-editor of a book entitled " Speciality Steel it Hard Metals'and is co-inventor of four patents. He also serves on a number of advisory boards.His current responsibilities include corporate management for eleven institutes in-corporated into the Research. Development and Implementation (RDI) group of therevised CSIR structure. The major function of this group is to service the research,development and implementation demands from a diverse range of identified prioritymarket areas.

TRENDS IN SOLID STATE PHYSICS

The presentation will review highlights from the past and identify current trends in the field of Solid State Physics,internationally and nationally. The major current demands and unanswered questions in the field of Solid State Physicswill also be highlighted.

PROFESSOR C GOODMAN

Charles Goodman is an eminent nuclear physicist from the Physics Department.Indiana University, USA. who has a long fist of publications in the following anas:nuclear structure, nuclear reactions, neutron time-of-dight spectroscopy. nuclear in-strumentation, and computer-driven data acquisition systems. His PhD is from the'University of Rochester (1955). He has worked at the Oak Ridge National Labora-tories, and has held visiting posts at the Weitzmann Institute and the University ofColorado. Professor Goodman is a fellow of the American Institute of Physics, andin 1983 received the Bonner prize in Nuclear Physics from the A.P.S. for his work inthe study of(p.n) reactions. Professor Goodman is married and has two children.

PROBING THE NUCLEUS WITH NUCLEON CHARGE EXCHANGE REACTIONS

Quantitative relationships for transition rates have been established between the weak interaction nuclear probe, betadecay and the strong interaction nuclear probe, nucleon charge exchange. These relationships are used to study the roleof the intrinsic properties of nucleons. i.e.. spin and isospin. in the structure of nuclei. These relationships are also usedin the measurement of certain characteristics of the nucleon-nucleus force. Some of the findings remain as unsolvedpuzzles. The possible relevance of these discoveries to underlying nucleon structure, perhaps quarks, will be discussed.

This page sponsored by Addison-Wesley Publishing Group

IE

II PNI Scientific C&NBERR&

Canberra.The world's leading range

of NIMS and multi channel analyzers.From South Africa's leading supplier.

PNI Scientific

SERIES 35 PLUS. MULTICHANNEL ANALYZER

Introducing the analyzer for today, theoptions for tomorrow.

The Series 35 PLUS is the finest MCA we've ever built.The basic high performance qualities you have come toexpect - precision, versatility and reliability - havenever been more evident in an "off-the-shelf' product.

Features:• Stand-alone data manipulation and analysis or

fully automated control and analysis via a PC• Multiple input capability• Battery-backed data and parameter storage• Peak Search and automatic analytical

sequences

CANBERRA, NIMS RANGE

• Amplifiers and Preamplifiers• Single Channel Analysers• Timing• Linear Electronics• Ratemeters• Digital NIM• Power/Bias supplies• Calibration and Test

Plus the widest range of detectors tomeet ALL requirements.

For further information, please contactMike Andrews or Dieter Geppert at PNI Scientific, Johannesburg (Oil) 786-3647

CANBERRA

PNI ScientificA division ot Protea Technology Ltd.

PROFESSOR R H LEMMER

Richard Lmmer obtained his undergraduate degrees at the University of the OrangeFree State and his PhD in Physics from Florida State University in I960. Afterspending the period 1960-68 on the Physics Faculty of the Massachusetts Instituteof Technology, he returned to South Africa as Professor of Theoretical Physics atUNISA. He is now a Professor in the Physics Department at the University of theWitwatersrand. His current research interests lie in many-body nuclear and quarkphysics. In 1986 he was awarded the De Beers Gold Medal of the South AfricanInstitute of Physics.

THE STRUCTURE OF MATTER AT HIGH ENERGIES

An overview of our current understanding of aspects of the structure of matter at high energies is presented togetherwith the various theoretical models that appear to be successful for describing this structure.

DR G NICOLSON

After receiving the degree BSc(Eng) (Witwatersrand). George Nicolson joined theNational Institute for Telecommunication Research in 1960. After a year at theNASA Minitrack Satellite Tracking station, he transferred to the new NASA DeepSpace Station at Hartebeesthoek. with a brief to develop a local research programmein radio astronomy using the facilities there. This work led to an MSc(Eng) andhe was subsequently appointed as a full time astronomer in 1965. During theperiod 1970 — 1974 he collaborated in the first southern hemisphere experimentsbetween Australia and South Africa using the new technique of very-long-baselineinterferometry (VLBI) and used the results to study the nuclear regions of quasars.He was awarded a PhD in 1975 by the University of the Witwatersrand.

When NASA closed the Deep Space Station in 1975, George Nicolson was appointedHead of the newly-formed Hartebeesthoek Radio Astronomy Observatory and led thedevelopment of the 26m antenna and associated equipment into a national facility,which is accessible to South African astronomers and which regi'lariy cooperatesin global VLBI networks spread over five continents. His research interests areconcerned with radio emissions from X-ray binaries, quasars and active galaxies andthe application of VLBI in astronomy and geophysics.

RECENT ADVANCES IN THE TECHNIQUES OF VERY LONG BASELINE INTERFEROMETRY AND ITSAPPLICATIONS IN ASTRONOMY AND GEOPHYSICS

The technique of VLBI utilises global networks of radio telescopes to map nuclei of quasars with an angular resolutionof 0.001 arc seconds. By then using quasars as a precise reference frame, the baselines connecting the telescopes can bedetermined with accuracies of 2 to 5 cm. VLBI thus finds applications in both astronomy and geophysics, and has ledto discovery of "superiuminai motions" in quasars on the one hand, and to the direct measurement of current motionsof tectonic plates on the other. This paper reviews the basic techniques of VLBI and then discusses the implications ofrecent work on theories of the central energy source in quasars and active galaxies. The results of recent geodetic andgeodynamic studies and their impact on the measurement of tectonic motions, variations in the rotation of the earth,and the measurement of polar motion are also discussed.

This page sponsored by Addison-Wesley Publishing Group

17

Challenging and rewarding career opportunities await

PHYSICISTSRadiationPhysics

studies oo the enaracteriratlon of radiationsources, radiation fields and radiationeffects as determined by the source

properties, interaction of the radiation withmaterials and geometric conditions.

Application to scientific, technologicaland economic uses of radiation m

various disciplines.

who wish to apply their knowledge ofphysics and are interested in the

dynamic and advanced research, designand technological development at the

11 Atomic Energy corporation of SA LtdkU I, in one of the following fields:

HealthPhysics

Monitoring of man and environment, doseassessment, radiation protection, evaluation

and control, radiation safety,and aerosol physics.

SafetySafety evaluation, guidance and supervision.

safety control measures, hazards analysis.emergency planning and preparedness

PlasmaPiiysics

Trie achievement of controHeotnermonudear fusion is the ultimate goal ofresearch on hot piasmss. At PeilndaDa workcentres around Tokotoshe. a tokama* with

interesting features A muKKlisciplinaryteam aims to understand and comrot plasma

disruptions in an effort to con tributeto international knowledge, A variety

of sophisticated and challengingdiagnostic techniques are being

used.

Solid-statePhysics

use of neutron and ion-beam prones tostudy the sow state. Neutron diffranion

studies of magnetic prose transitions.Associated x-ray, ultrasonic and resistivity

measurements Cryogenic studies.Small-angle neutron scattering

analysis of materials,lon-oeam probe analyses of surfaces

NuclearTechnology

Development and application of radiationand radioisotope technology In mining.

industry and agriculture, study ana controlof Industrial processes through nuclear

methodology. Development of analyticalnuclear techniques. Doing of

supportive research.

NuclearPhysics

Research into Nuclear and Atomic Physicsusing neutron and accelerated km Beams.

study of reaction mechanisms.spectroscopy, charge exchange, electron

emission... Application of nucleartechniques for material analysis.Development of computer data

accumulation and analysissystems.

ReactorPhysics

Research and develop cafcmationaltechniques Cased on sound physical

principles for modelling the behaviour ofnuclear reactors under a variety of

operating conditions.

ATOMICENERGYCORPORATION

Physicsof MaterialsA study of the physical and chemical

properties and behaviour of alloys, ceramicsand other materials with special referenceto their application and utilization m the

nigh-radiation environment of menuclear-energy industry.

use is made of sophisticated instrumentsand tecrmioues such as electron microscopy

Auger and photo-eiectron spectroscopv.x-ray and neutron diffraction.

optical metaNograpnv. fractograpnyand many more

PO BOX 4587 PRETORIA OOC1

OR E NIELSEN

Erilng Nielsen Is » Danish citizen working In West Germany. Born in Copenhagen in1940. he obtained an MSe In electro-physics engineering at the Technical Universityof Denmark. The year 1969-1970 was spent north of the Arctic Circle when hewas employed as a scientific observer at the Air Force Cambridge Research Lab-oratory Geopole Station at Thule. Gnentind. This was followed by several yearsat the Band Research foundation of the Franklin Institute, at that time locatedin Philadelphia. This culminated in a PhD in Space Physics in 1974. Since thenhe has Lien employed as a physicist at the Max-Planck-lnstitut fur Aeronomie atLindau-Han, near Gottingen in West Germany.

He has been Principal Investigator of the narrow beam riometer project since 197Sand Principal Investigator of the STARE/SABRE* project since 1979. Theseprojects have been highly successful in elucidating the highly dynamic behaviourof the aurora/ionosphere. Dr Nielsen is married with four children.

* Scandinavian Twin Auroral Radar Experiment/Sweden and Britain Radar Experi-ment.

CURRENTS AND ELECTRIC FIELDS IN THE EARTHS MAGNETOSPHERE AND IONOSPHERE

The concept of magnetospheric convection is introduced and the overall time-independent (or average) pattern of plasmaflow and electric field in the Earth's magnetosphere. and the associated flow and field in the ionosphere is outlined.Dynamic time-independent processes are then considered. It is outlined how ground-based experimental techniquesoffer possibilities to make contributions to the observation of ionospheric and magnetospheric processes.

DR D VAN AS

Dannie van As studied at the Universities of Stellenbosch and Pennsylvania (USA)and has been with the Atomic Energy Board for 22 years. He is closely involved inthe environmental impact of the nuclear industry, which was also the subject of hisPhD study at SteHenbosch. From 1977 to 1979 he was with the international AtomicEnergy Agency in Vienna, where he was responsible for coordinating internationalresearch and findings on questions of radioactive waste disposal for the purpose ofestablishing international guidelines on safety standards and practices.

Dr van As is now manager of the Department of Isotopes and Radiation of the AtomicEnergy Corporation of South Africa Ltd (formeriy the Atomic Energy Board). Hisresponsibilities cover the promotion of the use of radioisotopes as welt as protec-tion against radiation, which includes the protection of workers, the public and theenvironment.

CHERNOBYL—A CRISIS IN THE NUCLEAR INDUSTRY

The nuclear accident at Chernobyl in the USSR is a "worst case" in terms of of the risks of nuclear energy. The accidenttook place during an elementary test carried out on a turbogenerator, and resulted in a third of the core being destroyed,releasing the total gaseous inventory of the reactor and 10% of the other radionuclides. This relates to the concept ofa maximum credible accident as understood by the nuclear industry.

The presence of radioactive contamination was detected over thousands of kilometres. In close proximity to the reactorthe effects were catastrophic. Further away, it varied in severity from evacuation sf the population to a ban on foodstuffs,and on a global basis intense human concern and anxiety.

Now one year later, after an exhaustive study by different international bodies, the sequence of events that resulted inthe accident has been established, the causes of the mishap have been determined, and the health effects have beenquantified. Valuable lessons have been learned which would hopefully prevent such a catastrophe from ever happeningagain.

This page sponsored by Addison- Wesley Publishing Group

19

Heout-ihfawhe

TteStmknf Bank of SoulhMtoUiriM(F!«giMrMI Bank) R^No«2n»73«r06

PNI Electronics

PNI Electronics brings you the widest spectrum oftest and measurement equipment from the world's

leading manufacturers.

See our show ofKeithley, Fluke, and Tektronix equipment

PNI ElectronicsA division of Protea Technology Ltd

P.O. Box 39127, Bramlcy 2018, Tel: Johannesburg (Oil) 786-3647;Cape Town (021) 591-5121; Durban (031) 23-4368.

20

ISM

South Africa'sleading computer company

12-BIT 16 CHANNEL HIGH SPEEDANALOGUE-DIGITAL

• Typically 35^S conversion time• Lotus 1-2-3 compatible file mode• From 1 sample per hour to 30KHz• 16 channel multiplexer• Sample & hold reduces error• Complete with sampling software• PC-28 high speed software available• Bipolar & monopolar operation• Software or onboard timer• Successive approximation converter• With programming information

12-BIT 16 CHANNEL HIGH SPEEDANALOGUE-DIGITAL & DIGITAL-ANALOGUf

16 channel 12-bit A/D converterTwo 12-bit & two 8-bit D/A converters3 x 8-bit programmable I/O portsLotus 1-2-3 compatible file modeA/D conversion time typically 35^SD/A conversion time < 1MSPC-28 high speed software availableA/D samples: 1 per hour to 30KHz16 channel A/D multiplexerI/O ports TTL/CMOS compatibleWith programming information

for IBM PC-XT/AT

eagle electric co (pty) ltd9(021)24-4071 tmlotmx 550063 td«c 520713 cap* town 8000

The EdwardsFTP range ofturbomolecularpumpsNin* mcdels - pumping speeds from80 to 90001s"' with many flange optionsUnique and efficient Made structureglvts high pumping speed with highcompression ratios for light gas«sHigh precision bearings wKh provenoil lubrication system for reliableoperationPumps available with FomblinlubricationLow vibration and noise levelsSolid state or rotary converter driveunitsPumps have thermal overload asstandard

For further informationPlease Contact

Protea Laboratory Services(031)473747

OurSpeciality?Special gases are not just a sideline for Air Products, they are our speciality. For years wehave maintained high standards of gas purity, mixing accuracy and quality control. We'rededicated and are expanding our facilities to meet your every requirement. But for all ourtechnical achievements we still operate like a grand hotel of Europe and take pride in ourold-fashioned service and reliability.Whether you are in a laboratory, research, or a demanding manufacturing environment,Air Product's speciality is special gas. ^ ~^^^

AIRPRODUCTSMr Products South Africa (Pty) Ltd (Reg No. 89/03571/07}

Call Wessels Els of Special Products Department for technical advice or the Air Products branch nearest you (011) 763-5290

General InformationConference VMHMApart from the Opening Ceremony and Reception, all conference proceedings take place in theScience Lecture Theatre Complex.

i DeskThe Reception Desk is situated in the foyer of the Complex. It will be staffed daily from 07h45 to17h00.

Name Tag*Delegates wear WHITE name tags;The Organizing Committee RED name tags;Assistants, e.g. projectionists, wear BLUE name tags.

SlidesRoom 251 is available for checking slides and for speakers to load cassettes at least 10 minutesbefore their session starts. Materials for producing overhead transparencies may also be loanedthere.

ExhibitionThe exhibition of scientific equipment is located in a second floor laboratory in the DesmondClarence Buildina. The following firms are exhibiting: Computer Wholesalers, Hewlett PackardS.A., Labotec Natai, Logan's University Bookshop, Philquip Scientific, PNI Electronics, WiliistonBin.

Science LibraryThis is located on the fourth floor of the Desmond Clarence Building.

AnnouncementsImportant announcements and messages will be displayed on notice boards. Essential changes inthe programme must be directed to the Organizing Committee and the Chairman of the sessionmust be consulted.

Telephone NumbersConference Reception Desk (031) 816-3179Conference Organizers (031) 816-2775/6Mabel Palmer - Women (031) 81 -1297/8Mabel Palmer - Men (031) 81 -3118; 81 -4116Ansell May (031) 81 -5802/7

BankFirst National, Nedbank and Standard Bank have agencies located in the Shepstone Building.

Travel AgencyBraby-Ross Travel will be manning a desk in the foyer at certain times.

PostLetters for posting may be handed in at the Reception Desk. A mobile post office is available out-side Howard College daily (08h30 to 09h30).

Lunch and BeveragesThose delegates not staying in University Residences will be served lunch in Charles Smith DiningHall on production of a lunch ticket. These may be purchased at the Reception Desk before 10h00.Meals are available in the Students' Union.Tea and coffee will be served in the foyer area of the Science Lecture Theatre Complex during themorning and afternoon breaks.

University ClubDelegates may become temporary members of the University Club at a fee of R3. The Club has abar and offers lunches as well as snacks in the evening.

TransportThere is a regular municipal bus service (Numbers 70 to 73) from the Campus (bus stop outsideAdministration Building) into the City (Pine Street Terminal B5, near the Post Office).DepartCity : 08h45;10h25;11h30;12h45;13h10;13h50;15h05;15h35;16h20.Depart Campus : 07h55; 08h30; 09h10; 10h15; 11h15; 12h30; 13h25; 14h10; 15h30

This page sponsored by Industrial Development Corporation of South Africa

23

I analysed mypresent costs andfound I couldnow affordICP!

ARL's new 3410 ICP spectrometerbrings ICP within your reach

Now every laboratory involved in solutions elementalanalysis can afford to employ the fast, sensitive ICPtechnique. The new affordable ARL 3410 ICP withMinitorch™ and IBM-PC-XT makes it all possible,and offer these advantages over other systems:

• lower instrument cost, with ARL's Minitorch™;

• lower operating costs - lower power usage,lower argon flow give savings of up to 40%over conventional instruments;

• easier to operate - ARL's ICP software is spe-cially written for the powerful IBM-PC-XT.

The ARL 3410 offers the high performance and flex-ibility of ICP in the most cost-effective package.

Can you afford to be without it?

ARLABS (PTY) LTD.Mars StreetP.O. Box 557, RhodesfieldKEMPTON PARK 1620Tel. (011) 394 14 10

ARL Headquarters:ARL Applied Research Laboratories SAEn VallaireCH-1024 ECUBLENS / Switzerland

Am.•IIIHHMIH

APPLIED RESEARCH LABORATORIES

Algemene InligtingKonfw«n*l«tokMiAfgesien van die Openingsptegtigheid en Onthaal vind alle konferensieverrigtinge in die Lesing-saalkompteks van die Fakulteit Natuurwetenskappe plaas.

Ontvangstilt«!Oie Ontvangstafe! is in die portaal van die Kompleks. Dit sal daagliks vanaf 07h45 tot 17hOC oopwees.

NaametikotteAfgevaardigdes dra WIT naametikette.Lede van die Reëlingskomitee drs ROOI naametikette.Assistente, bv. projektor-assistente, dra BLOU naametikette.

SkyfiesKamer 251 is beskikbaar waar skyfies getoets kan word en waar sprekers hulle kasseïie kan laai.Dit moet minstens 10 minute voor die aanvang van die betrokke sessie gespied. Materiaal vir diemaak van transparante kan hier geleen word.

UitstallingDie uitstalling van wetenskaplike apparate vind plaas in 'n laboratorium op die tweede vloer van dieDesmond Clarence-Gebou. Die volgende firmas stal uit: Computer Wholesalers, Hewlett PackardS.A., Labotec Natal, Logan's University Bookshop, Philquip Scientific, PNI Electronics, WillistonElin.

Natuurwetenskapllke BiMioteekDie biblioteek is op die vierde verdieping van die Desmond Clarence-Gebou gelee.

KennisgewingsBelangrike aankondigings en boodskappe sal op kennisgewingsborde aangedui word. DieReëlingskomitee moet in kennis gestel word van enige noodsaaklike wysigings aan die program,en die Voorsitter van die betrokke sessie moet geraadpleeg word.

TelefoonnommersOntvangstafel (031 ) 816-3179Reëlingskomitee (031 ) 816-2775/6Mabel Palmer - Dames (031 ) 81 -1297/8Mabel Palmer - Mans (031 ) 81 -3118; 81 -4116Ansel! May (031 ) 81 -5802/7

BankEerste Nasionale Bank, Nedbank en Standardbank het agentskappe in die Shepstone Gebou.

ReisagentskapBraby-Ross is gedurende sekere tye in die portaal op diens.

PosAs u briewe wil pos, kan u huile by die Ontvangstafel inlewer. 'n Mobiele poskantoor is daaglikstussen 08h30 en 09h30 voor die Howard Coilege-Gebou gestasioneer.

Middagete, Tee en KoffieKongresgangers wat nie in die Universiteitskoshuis gehuisves is nie, word in die Charles SmithEetsaal met middagete bedien. Kaartjies vir middagetes moet vooruit by die ontvangstafel gekoopword voor 10h00. Maaltye kan ook in die Studente Sentrum genuttig word.Tee en koffie sal gedurende die oggend- en middagpouses in die portaal van die Lesingsaalkom-pleks bedien word.

UniversiteitsklubKongresgangers kan tydelik by die Universiteitsklub aansluit teen 'n fooi van R3. Die Klub het 'nkroeg en bedien middagetes, sowel as snoeperye in die aartd.

VervoerDaar is 'n gereelde munisipale busdiens (Nommers 70 tot 73) vanaf die Kampus (bushalte buite dieAdministrasiegebou) na die binnestad (Pinestraat Terminus B5, naby die Hoofposkantoor).Vertrek vanaf Stad : 08h45; 10h25; 11h30; 12h45:13h10:13h50:15hO5; 15h35; 16h20.Vertrek vanaf Kampus : 07h55; 08h30; 09h10:10h15:11h15:12h30; I3h25; 14h10; i5h30

Geborg deur die Nywerheid-Ontwikkelingskorporaste van Suid-Afrilu

25

CEGELEC

FOR THE BEST OF FRENCH ELECTRICAL ENGINEERINGIN SOUTH AFRICA

Health Physics Systems.

High Security Access and Movement Control Systemswith particular reference to Nuclear Installations.

Software Packages for Control of Accumulative RadiaticDosages and Radiation Level Calculation.

High Speed Data Sampling Systems.

Purpose Designed Electrical Power Panels andControl Systems.

On-line Chemical Sampling and Analysis Systems.

DESIGN, MANUFACTURE, SUPPLY, INSTALLATIONAND COMMISSIONING

An Affiliate of CGEE-ALSTHOM

CEGELEC (Pty) Ltd11 Gross StreetTunney Industrial TownshipP.O. Box 8023ELANDSFONTEIN1406Tel. (011) 974-5201Telex 4-28822

We work fast, cleanly — and under pressure. But we neverrush anything. Quiet operation and precision are ourstrengths. We can generate a vacuum of from 1,000 to10-'° mbar with a stable and always reproducible ultimatepressure. Water vapour and aggressive substances — wewithstand them without difficulty. In every situation ourcirculating-oil system seals, lubricates, cools. And of coursewe are also expandable — to meet the many varied re-quirements of industry and research. If you want to learnmore about us, our names are RUVAC, TURBOVAC andTRIVAC.

E.V.J. Krisch Engineering Co. (PTY) CTD. P.O. Box 50206, Randburg 2125, 287 Samantha Street,Stydom Park Ext. 18, Randburg 2194Tel.: 793-8831/2/3/4/5

IS THIS YOU?MEET JACKWhen Jack joined the National Institute forMaterials Research in 1985 we asked himto make semiconductor epitaxial layersequal in quality to those made at the bestlabs overseas. He said he needed onemillion rand and a small team of people.

The OMVPE reactor designed andconstructed at the NIMR forms the basis ofthe South African drive in Solid StateMicrowave technology and OpticalCommunications.

We got Jack his million rand and a team ofcapable people. He started building hisOrganometallic Vapour Phase reactor in1985. He grew his first layer in August 1986and by March 1987 he couid grow materialto match the best in the world. He nowgrows GaAs layers in which electronsmove 60 times faster than in Si and to apurity of a couple of parts per billion. If youare, like Jack, the kind of person who canhandle a challenge . . .

CSIR

THEN CONTACT US! or phone Harry Booyens 869211 x 362Stewart Hart 869211 x 27£

or Neville Comins 869211 x 28£

Student Sessions StudentesessiesThese reviews are aimed at students and non-specialistsHierdie oorslgte is gemik op studente en nie-spesialiste

Ptasma Physics C1 PlasmafisikaWednesday 09h00-09h30S1 Woensdag

Professor RJ. Barrett (UND)PLASMA WAVES IN LABORATORY AND SPACE

Solar-Terrestrial Physics E1 Son-aardfisikaWednesday 09h30-10h00 S1 Woensdag

Professor J.A. Gledhill (RU)SOLAR-TERRESTRIAL PHYSICS: THE IONOSPHERE

AND THE MIDDLE ATMOSPHERE

Astrophysics and Astronomy F1 AstrofisikaenSterrekundeWednesday 10h00-l0h30 S1 Woensdag

Dr. M.W. Feast (SAAO)SUPERNOVAE

Solid State Physics AS VastetoestandfisikaWednesday 12hOO-12h30 S9 Woensdag

Dr. H. Booyens (NIMR)SOLID STATE PHYSICS AND MICROELECTRONICS

Optics and Spectroscopy D7 Optika en SpektroskopieThursday 09h00-09h30 S2 Donderdag

Dr. D.J. Brink (NPRL)NON-LINEAR OPTICS: SOME PRINCIPLES AND APPLICATIONS

Nuclear and Particle Physics B15 Kern- en DeeltjiefisikaThursday 11h0O-11h3OS4 Donderdag

Professor J.P.F. Sellschop (WITS)SOME CURRENT CHALLENGES IN NUCLEAR PHYSICS

AND ITS FIELDS OF APPLICATION

Physics Education G3 ' Fisika OpleidingThursday 12h00-12h30 S1 Oonderdag

Dr. G.E. Oberem (RU)WILL COMPUTERS REPLACE PHYSICS PROFESSORS?

Applied and Industrial Physics H29 Toegepaste- en NywerheidsfisikaFriday 09h00-09h30 S6 Vrydag

Dr. G. Gafner ( Intergold)SOME RESULTS OF INTERGOLD'S RESEARCH PROGRAMME

Theoretical Seminar 126 Teoretiese SeminaarFriday 11h0O12h00S5 vrydag

Professor R. VlolUar (UCT)ON THE CREATION OF MATTER IN THE UNIVERSE

This page sponsored by Logan's University Bookshop

29

Redstone

COMPUTERS AND PERIPHERALS

AN ABSOLUTE BARGAINFROM

REDSTONE COMPUTERSS.A. c.c.

NEW RELEASE:

Enhanced model onlyJust arrived from factory at prices too good to advertise

Fully IBM compatible

FEATURES:

2 Panasonic drives, 640k Turbo, Hercules or Colour Cards. Printer Portand Cable. 'RT' keyboard. Amber Monitor. 1 year Warranty.

With unsurpassed service and client support from 6 top people.Our prices are among the best, because we are the best!

CAN 200 CLIENTS LAST MONTH BE WRONG?

Call at Powell & Associates. The BEST Agents.100 Clarence Road. Morningside, Durban.

Phone (031) 3031687

PROFESSIONAL FINANCINGFROM

NEDFIN BANK

Nedfin has a financing formula that is futuristic and innovative that offers a wide spec-trum of financial services to corporations, businesses, professional practices, govern-ment institutions and private individuals alike.

We believe in creative financing with the concept of leasing and instalment sale asour tools.

For all financial needs phone Nedfin Bank (031) 304-7311

IMPROVED MASS FIDW SYSTEMSACCURACY. CONVENENT CLEANING Of SENSOR TUBES

ATTITUDE MSENSmVITY • NO OVER OR UNDERSHOOTNO DRIFT . NO SNTERED ELEMENTS

Series AF2600 Systems for State of theArt Metering and Controlling or Gases.

Applications in semiconductor manufacturing,process controls and laboratory applications.Transducers are interchangeable with other majorbrands. Transducers are attitude insensitive andunaffected by inlet pressure changes and vibration.

To eliminate clogging, sensor tubes are straight withlarge inside diameters and access ports for cleaning.Response time is 1 second or better with virtually noovershoot or undershoot. Accuracy is ± 1 % of fullscale. Flow ranges from 0-10 ml/min to 0-100 l/min.

ANAVACPica Centra, Cotawold Road, Florida Hllia

Box 5283, Wertevreden Park -171B South AfricaTel.: (011) 674-1190/1 Talax: 4-24980

The Chamber of Minesof South Africa

RESEARCH ORGANIZATIONFunctionally, the Chamber's research organization is split into a number oflaboratories and branches which cover the multi-disciplinary fields of research.

The Coal Mining Laboratory conducts research into mining, strata control andenvironmental problems in coal mines. Coal mining methods and equipment areadapted to suit the particular geological, economic and labour conditions found inSouth Africa.

The Engineering Services Branch essentially performs a support role to otheractivities by providing a service which covers design, manufacture, inspection repairand assistance in conducting experiments.

The Engineering Systems Laboratory provides specialist R & D in the fields ofmechanical, hydraulic, electrical and electronic engineering. Much of (he effort of thebranch is related to leading slope mechanization.

The Environmental Engineering Laboratory devises methods for reducing heat flowinto mines and develops improved methods of dust suppression, pollutant control,refrigeration and ventilation.

The Gold Exploitation Laboratory is involved in developing methods for predictinggold distribution and improving gold valuation. Techniques which enable a lowergrade ore to be mined are also being examined, as are methods of backfilling toimprove stoping conditions and gold extraction.

The Human Resources Laboratory is engaged in manpower planning for the goldmining industry, improving the work performance of miners and assessing theirattitudes and behaviour for the maintenance of peace, harmony and the quality of life.

The Industrial Hygiene Laboratory is concerned with air pollution and itsmeasurement, control and effects on the worker. Detailed research into work stress isconducted and much effort is given to the improvement of acclimatization procedures.Research and services are provided to outside organizations on a contractual basis.

The Mining Branch is responsible for conducting trials and financial evaluations ofnew mining methods and associated equipment. The human engineering aspects ofmechanical mining are also investigated.

The Rock Mechanics Laboratory is engaged in designing mine layouts, developingnew rock support systems and research aimed at improving the understanding of rockbehaviour in deep level mines.

The Stoping Technology Laboratory develops improved method* and machinery forgold mines. Mechanized systems for use both with and without explosives are beingdeveloped.

OpportunitiesThe South African mining industry is working at the forefront of mining technology,whose traditional methods and equipment are not always practical or efficient.Currently, the deepest mines are at some 3.8 km below ground level and this createssubstantial additional problems in terms of working conditions. The Chambertherefore offers opportunities to a wide range of graduates to become involved in avariety of problems and projects.

Long-term career prospects are excellent, as are the opportunities to undertake workleading to higher degrees.

Salaries and other conditions of employment are highly attractive.

Application forms can be obtained from: The PersonnelManager, Chamber of Mines Research Organization,P.O. Box 91230. Auckland Park 2006. CA/I

Meetings VergaderingsMONDAY 13 JULY:1 (a) SCOPS WORKSHOP ON MAGNETIC STORMS, 14h00- 17hOO, S4.

DINSDAG14 JULIE:1 (b) SCOPS WORKSHOP ON MAGNETIC STORMS, 09h00 - 13h00, S4.2. F1SIKAWOORDELYSKOMITEE, 15h15, Kamer 253.3. RESEARCH PROGRAMME IN HIGH-TEMPERATURE SUPERCONDUCTORS, 14h30 Romatex Room4. SSPMS EXECUTIVE MEETING, 16h00, Room 052.

WEDNESDAY 15 JULY:5. REDAKSIONELE ADVIESKOMITEE MESON, 08h00 - 09h00, Kamer 253.6. PHYSICS - THEOLOGY GROUP: "Present Physics-Theology concerns", 13hOO, Principal's Dining Room,

Students' Union.7. SAIF RAADSVERGADERING (saam met Voorsitters van Spesiialisgroepe), 13h00, Universiteitsklub.8. SOUTH AFRICAN JOURNAL OF PHYSICS EDITORIAL BOARD, 17h00, Room 253.9. FISIKAHANDBOEKVERGADERING,17h15, Kamer 052.

DONDERDAG16 JULIE:10. SAIF RAADSVERGADERING, 13hO0, Universiteitsklub (Barend's).11. PHYSICS - THEOLOGY GROUP: "The Anthropic Cosmologioal Principle", 13h00, Principal's Dining Room,

Students' Union.12. SAIF ALGEMENE JAARVERGADERSNG, 15h30, S8.

FRIDAY 17 JULY:13. PHYSICS - THEOLOGY GROUP: "Ethical Issues - Faith, Science and the Future)113h00, Principal's Dining

Room, Students' Union.14. HOOFDE/VOORSITTERS VAN FISIKA DEPARTEMENTE, 13h00 - 13h50, Universiteitsklub.

Voortsetting: 15h15 - 16h30, Kamer 253.

15. SCOPS MEETING ON POLICY AND OBJECTIVES, 15h15 - 18hOO, Romatex Room.Continuation: SATURDAY 18 JULY, 08h3O- 18h00.

InstitutionalMembers of the SAIPInstitutional Members of the SAIP are a group of com-mercial and scientific organisations who believe it isvaluable to them and to South Africa to maintain avigorous growth in the physical sciences. By their par-ticipation and membership dues they give significantsupport to the South African Institute of Physics in thepursuit of its objectives - the advancement of the prac-tice, and the diffusion of knowledge, of the science ofphysics and its applications for the benefit of the com-munity. The SAIP is grateful for their assistance.

Institusioneie ledevan die SAIFInstitusioneie lede van die SAIF vorm 'n groep vankommersiele en wetenskaplike organisasies wat gtodat dit vir hulle en vir Suid-Afrika waardevol is om 'nkragtige groei in die fisiese wetenskappe te handhaaf.Deur hul deelname en lidmaatskapgelde word beteke-nisvolle steun aan die SAIF verleen in sy strewe na diebevordering van die beoefening van fisika en sy toe-passings en die verspreiding van kennis daarvoor totvoordeel van die gemeenskap. Vir hul ondersteuning isdie SAIF dankbaar.

Boart Research CentreDe Beers Industrial Diamond DivisionEloptro Plant of Kentron (Pty) Ltd.National Institute for Materials ResearchNational Physics Research LaboratoryNational Accelerator CentreRustenburg Platinum Mines Ltd.SMM Instruments (Pty) Ltd.Thorn EMI Technology SA (Pty) Ltd.

This page sponsored by the Allied Building Society — Durban Branch

33

PSITEC CPTYJ LTD

THE COrtPUTER GRAPHICS HARDWARE SPECIALISTS

Since ue began our operationsin 1983, the name Psitec hasevolved into a namesynonymous with plotter anddigitiser specialization andexpertise..

The range of graphics productshas increased to covervirtually any application.Couple this with a superbafter sales service, technicaladvice and guidance, plus theassurance of a quality productrange and you have an obviouschoice For all your plotterand digitizer requirements.

Our devices will interface tomost graphics softwarepackages such as Autocad,PCad, Harvard, Chartmaster,Orawbase, Caddie, Allycad,Procad, etc., plus directconnection to IBfi mainframeenvironments such as SASBraDh.

Just some of our product range

IDLINE AO PLOTTERSnulti-pen and single penoptions - fully adjustable

ZETA AO, Al & A3High throughput devices

SP600 & SP700A3/A4 plotters for businessgraphics or engineers

SP1OOOAl adjustable for architectsand CAD/CAH

GTCDA complete range of digitizingtablets from A4-A0

2ETAUUEA device which creates slidesfrom your PC or mainframegraphics drawings.

Contact us now for furtherinformation on these and otherexciting graphics products.

PSITEC CPTY) LTDP 0 BOX 333RANOBURG2125TEL.: C011) 787-0343

~"3!»-«#.

At tiistm merely looked

"Wip^|ffi:;;6iiiSSfliaii

Winter School S8 WinterskoolASPECTS OF MODERN OPTICS

ASPEKTE VAN DIE MODERNE OPTIKA

Monday08h45 Dr. G. Heymann (CSIR)

OPENING

Maandag08h45

09h00 Dr.GRitter(NPRL)PHOTONICS - HIGH TECHNOLOGY OF THE 21ST CENTURY

09h00

10h30 Dr. H.M. von Bergmann (NPRL)HIGH-AVERAGE-POWER EXCIMER LASERS

10h30

11h30 Dr. E. Ronander (AEC)HIGH-RESOLUTION LASER SPECTROSCOPY

11h30

14h00 Dr. P.F. Cunningham (UND)LASERS IN INERTIAL CONFINEMENT FUSION RESEARCH

14h00

15h30 Mr. C.J. van der Hoeven (NPRL)SOME ASPECTS OF MODERN HOLOGRAPHY

15h30

Tuesday08h30 Professor R.E. Raab (UNP)

THE INTERACTION OF RADIATION WSTH MATTER

Dinsdag08h30

09h30 Dr. H.S.T. Driver (UCT) 09h30COHERENT ANTI-STOKES RAMAN SPECTROSCOPY OF GASES

11h00 Dr. C Graham (UNP)POLARIZATION THEORY

11h00

12h00 Professor E. van Rooyen (UP)OPTIESE SEINPROSESSERING

12h00

14h00 Mr. R.N. Phillips (Aberdare)OPTICAL FIBRE COMMUNICATION SYSTEMS IN SOUTH AFRICA TODAY

14h00

15h00 Dr.G.Ritter(NPRL)CLOSING

This page sponsored by Hulett Aluminium Limited

37

15h00

WINTER SCHOOL WINTERSKOOL

W1 WOTONICS - HIGH TECHNOLOGY OPTHE 21ST CENTURY

a Ritter, NPRL, CSIR

The Held of Optic* hat frown and matuttd to such anextent duting the pjtft 2$ • 26 y t a n sine* the advent ofthe iMtr, chat it necessitated the creation of a mm t«rm-inology in order to properly dMciibt the diran* and trow-ing activitiat in t!» field. Just M tbt tt im •Electronics*was invented for describing tha host of dosaly relatedtechnologies based on the control of electrons, so the tetn.•Photonics' has bean coined to daacriba tho technologiesof generating light and hamtssing it in a vast number ofdiffetant applications. A discussion of racant highlightsin modern optics provides tha background against whichthe state of photonics in the RSA will be seviewed.

W2 HICH-AVEMCE-POWBH. EXCIMER LASERS

H.M. von Btrgaaoa, NEM./CSU

During the last few years exciaer lasars have beendeveloped into reliable powerful laser systeas thatare eoaDereially available and have found a largenuaber of applications in ell areas of science, tech-nology and aedicinc.

Ihe lecture will esplain the physics of Che exciaerlaser, it will discus* and suaaarixe present day ex-ciaer laser technology and give an overview of theaost iaportant applications in aatarial processing,photocheaistry and nedicina.

W3 HIGH-RESOLUTION LASER SPECTROSCOPY

E. Ronander, AEC

The laser as a source of coherent optical radiation hasmade it possible to investigate nonlinear interaction of op-tical radiation with atoms and molecules. Its availabilityhas given rise to new research fields, such as nonlinearoptics, laser spectroscopy, laser photochemistry, that lieat the boundary between quantum electronics and physicaloptics, optical spectroscopy and photochemistry, respectively.The use of coherent optical radiation in each of these fieldshas led to the discovery of qualitatively new effects andpossibilities; in particular, some rather subtle effects ofinteraction between highly monochromatic light and atomsand molecules, in optical spectroscopy, have formed thebases for certain methods of so-called nonlinear, laserDoppler-fret spectroscopy. These methods' have made itpossible to increase resolution of spectroscopic studies frombetween 10 and 10 limited by Doppler linear broadeningup to about 10*! Various applications of laser and diode-lasers for the study of high-resolution features which havecontributed significantly to a better knowledge of atomsand molecules will be discussed.

W4 LASERS IN INSRTIAL CONFINEMENT

FUSION RESEARCH

P.F. Cunningham, U.Natal, Durban

Fusion may be expected if D-T fuel is simultaneously com-pressed and heated tc many times solid density and fceVtemperature* respectively. Spherical implosions caused bytaut-driven ablation may produce the necessary parameterThe pertinent processes of absorption, scattering and gen-erated usabilities will be reviewed. The use of secondarylasers for probing and diagnosing these and other plasmasdirectly and indirectly will be discussed. Up-to-datetrends in the field will be reported.

W5 SOME ASPECTS Of MODERN HOLOGRAPHY

C.J. van der Hoeven, NPRL , CSIR

The general principles and some applications of modemholography will be discussed.

W6 THE INTERACTION OP RADIATION WITHMATTER

R.B. Raab, U.Natal, Pietermaritxburg

Optical effect* result from the interaction of an electro-magnetic wave witb matter. Theoretically this is convenientlydescribed by the energy of interaction of the electric andmagnetic field* and field gradients of the wave with theelectric «nd magnetic multipot* moments induced in matterby the radiation. A semi-classical Hamiltonian (i.e. fieldsnot quantized) of this interaction is presented, and aparticular choice of gauge is shown to describe the multi-pole interaction in a natural way. This Hamiltonian isused to obtain quantum-mechanical expressions of molecularproperties responsible for certain optical effects.

W7 COHERENT ANTI-STOKES RAMANSPECTROSCOPY OF GASES

H.S.T. Driver, UCT

In the non-linear optical process of coherent anti-StokesRaman scattering (CARS), a pump beam at frequency^is mixed in a medium with a Stokes beam at frequency «*(w, < «,) to produce a new coherent beam at the anti-Stokes frequency wa • 2M t - « , . Maxwell's equationswill be used to derive the amplitude of the anti-Stokeswave in terms of the third order susceptibility {"ofthe medium and the amplitudes of the two incident waves.The relation of if to the molecular properties of themedium will be discussed. With this theoretical background,the practical implementation of CARS can be delineated.After a d ;ription of the CARS facility a: present in useat UCT, tne diagnostic capabilities of the system wtil besurveyed.

This page sponsored by Hulett Aluminium Limited

39

Optieaf

ciirimunication systems'SAs leading industrial Optical Fibre Cable and systems suppliercan offer you:

• Metal-free cords and cable for duct, cable tray and aerialapplications.

© Armoured cable for direct burial and harsh environments.» Composite cable lor high-voltage applications.• Full range of industry standard connectors.•-Computer links for IBM 3274, RS232C, LAN etc• Data iinks for TTL, 4-20mA, 0-10VDC etc• Video links for CCTV, PAL/NTSC, RGB.• Installation equipment: fusion splicers, repair kits, and tools.• Test equipment: OTDR, power meters, light sources.• Installation, commissioning and repair serviceu.

Contact us for a fully engineered solutionto all your communication problems.

At the forefrontof today'stechnologyMain Road • Eastieigh • EdenvaleTel: (011) 609-4020 • Telex: 4-29517

BERDARROUP

There are smarterways to spend moneythan on leaks.

If you deal with high-vacuum pro-cesses, you know that a leak canbe a nightmare. Leaks always costmoney, be it in terms of ruined pro-duction batches, process crashes,substrate replacement costs orjust plain system downtime.

Now, there's a sensible way tocurb the risk of a costly leak: theBalzers HLT100 helium leak tes-ter. It gives you real, no-nonsensequality control. It eliminates thenuisance and expense of liquidnitrogen. It is remarkably easy tooperate. And it is a precise anddependable system for repairs ormaintenance, too.

•alitra L imit*FL-9496Balzare

Ubotac(Pty)Ud.Baiz^ra DivisionPrincipalityof Liechtenstein 516 Richard Road

Tel (075(44111Telei8B9 78BbvallTelefax 10751 44413

Industrie North43161 Induiln. 2042Tel 16731 4140Tele»4S9117

W8 POLARIZATION THEORY

C Grahamt U. Natal, Pietetmaritrbutg

afferent models of polarised light are reviewed and syn-thesized to reveal a rationale behind the Poincare sphere atthe Mueller calculus. The usefulness of the Poincare spheras a mental aid in simple polarization problems at the optiiworkbench is demonstrated; and areas of application of thMueller calculus are discussed. The Junes calculus isbriefly introduced and the Jones and Mueller calculi arecompared and contrasted.

W9 OPTIESE SEINPROSESSERING

E,vtn Rooyen, U. Pretoria

Die gebruik van 'n akoesto-optiese Bragg-sel, as inset(component, vir 'n optiese prosesseerder bied die moontlik -heidom byvoorbeeld die spektrale aard van RF seine praktuintyds te kan bepaal. Die aanwending van optiese operatoinl Fourier-cransforme, konvolusie en korrelasie bied diegeleentheid vir vele ander toepassings soos optiese teiken-herkenning, rekenkundige berekenings en nog veel meet.Alhoewel die tegniek van optiese prosesseerers en die AO-interaksie reeds lank bekend is, het dit in die afgelopepaar jaar moontlik geword om met nuwe AO materiale enkoherente ligbronne die nuwe generasie toerusting te ont-

werpen realistter.

In die lesing sal die fisiese eienskappe van die komponentewat vir die opbou van die stelsel vereis word beskryf enontleed word. Die teorie van die AO interaksie, optieseargitekture en holografiese filters wat vir die stelselsgebruik word sal toegelig en behandel word.

Optika is 'n analoogtegnologie en vir die verkryging vangroter noukeurigheid kan die aanwending daarvan uitgebreiword sodat dit moontlik is om syferverwerkings te Joea.Daar sal aangctoon word hoe optiese prosesseerders gebruikkan word om sistoliese berekenings deur te voer vir dieoplossing van onder andere linere stelsels.

W10 OPTICAL FIBRE COMMUNICATION SYSTEMSIN SOUTH AFRICA TODAY

R.N. Phillips, Aberdare Group

Optical fibre provides an alternative digital communicationmedium to digital microwave and coaxial cable systemboth for long distance broad band systems as well asintra-office local area networks. This paper will discussthe relatively new technology of optical fibre communica-tions, its advantages over conventional systems, the basicsof system design, and will describe the systems currentlybeing installed in South Africa and internationally.

41

Were you wondering if TrustBank had afinancial package to suit you?

What precisely is a TrustBankfinancial package? Hie answer is,whatever you want it to be.

Because it can be as extensive asembracing all your finance-relatedmatters.

Or it can merely cover your day-to-day banking needs (with exceptionalbenefits, such as cheques guaranteed upto R200).

There is a veritable menu ofservices available to you. From a starter,the cheque account, to specialities suchas investment advice, estate planning,tax advice, and any form of finance.

Each package is as different as the

person for whom it's tailored.There is only one common

denominator - every package comeswith an expert TrustBank adviserattached.

And he is not just a voice on thephone. He is ever willing to visit youwhere and when it suits you.

For the personal touch.

EPICON 87CONFERENCE ON EPITAXYKRUGER GAME RESERVE

18-20 November 1987

The intention of the conference isto bring together scientists and en-gineers in the general field of epi-taxy. This includes theory, growth,characterization and device designand fabrication associated with epi-taxial structures.

For further information contact:

The Secretary - EPICON 87c/o EM UnitUniversity of the NorthPrivate Bag XI106, SOVENGA0727 South Africa

Tel: 01522-4310 X 2804 or 2264; Telex: 3 22798 SA

42

Social Programme Sosiale Program

Monday 13 July 16h45 Foyer

Dinsdag 14 Julie 19h00 Elizabeth Sneddon-Teater

Wednesday 15 July 17h30 Foyer19h30 for 20H00 Elangeni Hotel

Donderdag 16 Julie 18h00 Durbanse Stadsaal

Winter School Reception

Openingsrede en Onthaal

SherryConference Banquet

Skemeronthaal

Sharp has a range of pocketcomputer* to suit anyengineering, scientific orbusiness application. Sharpprovides computing speedand power In an economical

pocket sized design. Theseportable powerhouses offerBASIC language capability,combined with typewriterkeyboard layout, andmemory back-up.

Quick Answers forStudents on the Go

Faster Computing Speed in a Pocket-Size Package

eooDaaiiiBODDCifiaefiftdfifififilffflfiBf

WORLD NUMBER ONE IN CALCULATORS AND POCKET COMPUTERS

HITECH LASERSSouth Africa's leading laser specialistsOur highly qualified and internationally trained team hasin-depth knowledge and experience in lasers andrelated optics.

We supply equipment ancjl professional, advice in alllaser-related fields such a£ the industrial, scientific andmedical. •*& .

Argon/Krypton Ion LasersCarbon Dioxide LasersCopper/GowJ Vapour LasersDye Lasers•Excimer Lasers

HE-NE LasersND-YAG LasersAll Laser AccessoriesUV. Visible and IR Optics

HITECH ^LASERS (Pty) LtdRepresentatives of world leaders in lasers and optics.

\•3o

or

r1

LARGE LECTURE THEATRES(PLENARY SESSIONS)

LIFTS

4TII FLOORPHYSICS DEPT.OFFICE

4TH FLOOR "' 'SCIENCE 1.1HKAKY

PHYSICSENTRANCE(LIFTS)

GROUNDPHYSICS WORKSHOP

SECOND FLOOREQUIPMENT EXHIBITION

SMALL LECTURE THEATHE(PARALLEL SESSIONS

CONFERENCE ENTRANCE

WEDNESDAY 15 JULY MORNING

- 9HS0 REGISTRATION Foyer

S7SOLID STATE PHYSICS 1Chairman: Dr S Bart

9hOO - $hlS AI

THE STABILITY OF CERTAININSTRUMENTS WHICH AREESSENTIAL IN THE FUNCTIONINGOF AN OHVPE REACTOR

0 J Lombard (MMR)

Ai9hlS - 9h30

THE DESIGN OF AN OVERALLSAFETY SYSTEM FOR THE SAFEOPERATION OF AN OMVPEREACTOR

A P Vya, A P 3&tha,

J C Q Fletaher (SIM)

9h30 - 9h4S AS

A SIMPLE FAT-FET GROWNBY OMVPE

Jaak C Q Fletoher (NZMIt)

9h4S - WhOO

THE GROWTH OF AlGaAs BYMOVPE

D Faubenheimev, A W R Leitohand -I S Vemaak 'UPE)

A?

lOhOC - 2OhlS A9

THE GROWTH OF AlCaAs-GaAsQUANTUM WELL LAYERS BY MOVPE

A U R Leitah and J S Vevnaak(UPE)

lOhlS - lOhlO All

EFFECT OF ANNEALING ON THE1 . 4 9 eV BAND IN SEMI-INSULATING LEC G«A9

H I Ehlers, J S Ver-mak andA V R Leitah (UPE)

S9SOLID STATE PHYSICS Z

Chairman: Dr T E Derry

ShOO - ShlS A2

USING ACRT FOR THE GROWTHOF CdHjTt

J R S Roodt, M A fkzrais andB J duller (SINR)

ShlS - 9hZ0 Ai

CORRELATION BETWEEN CARRIERCONCENTRATION IN HgCdT. ANDCHLORINE DENSITY AS DETER-MINED BT SINS AND FAB

B J Strydan, M A Haraie,DEC Rogers and J B Basaon(SIHR)

9hlO - AS

HALL EFFECT ONTe GROWN

ANOMALOUSa-TYPE g a QBY THE SOL&3 STRECRTSTALLIZATION TECHNIQUE

J B Baeaon and B. Booyene

AS9h4S - lOhOO

SURFACE LASERS ON F« FORMEDDURING PLASMA NITRIDINGSTUDIED BY XPS AND EELS

I le R Strydom IHIMP.)

lOhOO - lOhlS A10

THE ROLE OF AN INTERFACIALLAYER OF Ni IN AuGc OHMICCONTACTS TO G*Aj

A P Botha (nntl), E Rellingand R 0 Copperthwaite

lOhlS - 10M0 Alt

METALLURGICAL AND ELECTRI-CAL INVESTIGATIONS OF Au-CeBASED OHMIC CONTACTS TOn-TYPE GaAs

W 0 Barnard (SIHR),J 3 Malherbe and A J Uillia

S4

H'^LEAR AND PARTICLE PHYSICS

Chaiman: Dr U R Holttrray

9h00 - 9hlS Bl

STATUS VAN DIE NASIONALEVER5NELLERSENTRUM, FAURE

D Rtitmann en A H Botha (SVS)

9hlS - 3h30 BS

OPWEKKING VAN REUSE HULTI-POOL RESONANSIES

V J SatuM (US), D J Suanepoel,W da X Loubaer, J A Standeren J V Koen

9hS0 - 9h4S S3

INTRODUCTION TO THE KNOCKOUTAND CONTINUUM DECAY STUDIESWITH THE NAC SEPARATEDSECTOR CYCLOTRON

A A Cowley (SAC)

9htS - lOhOO Bt12C(p,2p) " B AT 66 M.V:EXPERIMENTAL METHOD AND DATAANALYSIS

J J Laurie, A .', Coaley,D U Uhittal, J Hlahtr (SAC)

lOhOO - lOhlS BS

MODEL CALCULATIONS FOR THEl 2 C ( p , 2 p ) REACTION AT 66 HtV

D M Uhittal, A A Cowley,J J Laurie and J Pitcher

SI

PLASMA/ SOLAR-TEHRESTRIhU'•oTROPHYSICSChairman: Dr I H A OUdhill

9h00 - 9HS0 a

STUDENT SESSION"PLTiSHA PHYSICS'

PLASMA HAVES IN LABORATORYAND SPACEP J Barrett (USD)

9h30 - lOhOO El

STUDENT SESSION"PHYSICS

SOLAR-TERRESTRIAL PHYSICS:THE IONOSPHERE AND THEMIDDLE ATMOSPHERE

J A Gledhill (RU)

f/

lOhOO - lOhZO Fl

STUDENT SESSIONASTROPHYSICS AND ASTRONOMY

SUFERtnVAE

M W Feast (SAAO)

COINCIDENCE STUDY OFCONTINUUM DECAY INDUCED BYPROTONS OF 200 HeV ON 1 2 C

J Pilaher, A A Cowley,J J Laurie, D.H. 'Jhittal and 'SJIHIU (SAC) d

10h30 - lOhSO (Ct/vWfWlT- W'

UhOO - IZhOQS8

3 E J 7 / ™ r T E A ' ?oy,r

OR 0 VAN AS

Chairman: Or D Reitmam

WOENSDAG 15 JULIE OGGEND

7*1« - «MO REGISTRAS IE Portaal

S2

OPTICS AHO SPECTROSCOPVChairman; Dr D J Brink

9hOO ' 3MS Dl

SISTEMATIESE HEIGINGS IN DIELBEFTYE VAN VUKXE IN DIEKOOLSTOF EK STIKSTOF ISOELEK-TKIESE SEKWENSIES

f J Coetzer (US), FJ Mo3t*rten F van dar Weatkuisen

S6APPLIED AND INDUSTRIAL PHYSICS

Chairman; Dr A S H d» Jttu»

3hÛO - 9hlS B:

BEVOLKIKGSBLOOTSTZLLING AANRADON: BRONNE EN METINGS

g Strydom an A B LmscfmerlAEki

THEORETICAL SEMINAR S 5Chaînon: Dr F J Kok

3H30 - »hOO I.FORMELE UIÎDRUKXINCS V « DTOESTATOVEKÏLYXINCS VANCASSEJ J Binning (AEK)

9M0 - QhSO I-

STUDIES VAN DIE EMC-EFFEK

S C Haraiê en C A Engel-breaht tué)

9hl5 - 9h30 D2

LEEFTïD-ANALISE VAN DIE3J, ' B ' ENERGIEVLAKKE IN 0 I I IT C Kotzê tStralingsbaheerl,F J Zoatzer an P van darUeathuïzen

9hlS - 9h30 BS

CHARACTERISATION OF THE NACNEUTRON THERAPT BEAM

g T ù Jonas (SAC), M Tudalevand V L J Bandrikae

9hîO - 10h30

SPECIALIST GROUP MEETINGOPTICS AND SPECTROSCOPY

*******SPESIALISGROEPVERGAOERING

OPTIKA EN SPEKTROSKOPIE

9h30 - 9h*S Bî

STRALINGSTRANSPORTBEREKENINGSVIR DIE ONTWERP VAN 'N GANMArBESTRALIHGSFASILITEIT

G P da Baar »n D E SartoriIMKi

9hîO - 9h4S

ELECTRGKAGNETIC NEUTRONSTRUCTURE FUNCTION

Kouiohi Sakano (UCT)

3h4S - lOhÛO m

A ONE-DIMENSIONAL LIGHTWATER REACTOR SHIELDINGBENCBURIC STUDT

D S Sartari, S Tavio,O P de Baar (AEC) and C DeLuca

9h4S - lOhOO II

EMC EFFECT AT SHALL X REGIC

Kauiahi Sakano (VCT)

10M0 - lOhlS «S

DIE OPTDŒRDfG VAN 'N TEL-GEOMETRIE BY 'N INDIREKTESTRALINGSMETING VANAF 'NGAMCABRON

J B Venter (AEK)

lOhOO - lOhlS

PECULIARITIES ASSOCIATEDWITH THE WIGNER ROTATION

C 3 van Wyk (UOFS!

lOhlS - 20h30

THE SHALL ANGLE NEUTRONSCATTERING FACILITY ATPELINDABA

36

C B Pranklyn (AEC)

lOhlS - 10h30 IISYMŒTRY VECTOR FIELDS ANDSIMILARITY SOLUTIONS OF ANON-LINEAR FIELD EQUATIONDESCRIBING THE RELAXATION 1A MAXWELL DISTRIBUTION

g SuUr and W-R Steeb (SAU,

10H30 - ÎOhîO T E E Portaal

CHERNOBYL - A CRISIS IN THE NUCLEAR INDUSTRY

49

WEDNESDAY 15 JULY HORNING

12H00 - 12hlO

M S9

STUDENT SESSION : SOLID STATE PHYSICSChairman; Or £ Albert*

SOLO) STATE PHYSICS AND MICROELECTRONICS

S Booyn* IHIHR)

AS

S7

SOLID STATE PHYSICS 1

Chairman: Dr S Luyckx

12hlO - 12MS A13

HALL MEASUREMENTS ON UNDOPEDOMVPE-GROWN GaAs

R Thavaf INIMRl

S9SOLID STATE PHYSICS 2

Chairman: Prof S Kritzingtr

WHO - 12htS AH

THE GROWTH OF PURIFIEDPOLYOtYSTALLINE SILICON INGRAPHITE CRUCIBLES

MEL** (UXT), A M Letaoalo,J a Janteky and S Bart

NUCLEARs soPARTJCLEPHYilChairman! f'DrC B Frmklyn

12H0O - IZhlS 87

(p.Y) izACTioNS AT nrroi-HEDIAR ENEKGIES AND GIANTDIFOU EXCITATIONS

David A$ohnm (VCT)

BS12H1S - 12h3O

TESTS OF NEUTROH DETECTORSFOR NEUTRON TIME-OF-FLIGHTSPECTRCHETER FOR ( p , n )STUDIES AT NAC CYCLOTRON

David Atahnm (UCT)

12h20 - 12h4S B9

'BE • l l C ELASTIC SCATTBRIKGREACTION

E Sidtrae-Baddad, Bit Ftariakand J P F Stlltehop (WITS)

SI

12HO0 - IShOO

SPECIALIST GROUP MEETING

SOLAR-TERRESTRIAL PHYSICS

**»•*••

SPESIALISGROEPVERGADERING

SON-AARDHSIKA

12h.4S -13h00 A1S

SKUIFSLYTASIE EIENSKAPPE VANVERSTUIWINGSIOONPLATEERDEPLATINUM LAGIES

0 •/ de Wez en A Wella (NIMH)

12MS - IZhOO A1S

DETERMINATION OF IMPURITYCONCENTRATIONS IN POLY-CRYSTALLINE SILICON BY MASSSPECTROMETRY

D E Rogers (RIMR), U E Letand J A A EngeIbraoht

IZhOO - 13hS0 L U N C H Charles Smith Dining Sail

SO

W0ENSDA6 IS JULIE OGGEND

S2 S3 S6 S5

IShOO - IShOO IZhOO - IZhOO 12h00 - IShOO IShOO - 13hO0

SPECIALIST GROUP MEETING SPECIALIST GROUP MEETING SPECIALIST GROUP MEETING SPECIALIST GROUP NEETIflPLASMA PHYSICS ASTROPHYSICS AND ASTRONOMY APPLIED AND INDUSTRIAL PHYSICS THEORETICAL PHYSICS

******* ******* ******* *******SPESIALISGROEPVERGADERING SPCSIALISGROEPVERGAOERING SPESIALISGROEPVERGADERING SPESIALISGROEPVERGADERII

PLASMAFISIKA ASTROFISIKA EN ASTRONOMIC TOEGEPASTE EN NYWERHEIDSFISiKA TEORETIESE F I S I M

IShOO - 13hS0 M I D D A G E T E Charles 9nith Seteaal

SI

HMO •

li. 00 -

WEDNESDAY

lihOO

S8

IShZO

15 JULY

/i! f PROFESSOR CHARLES D GOODMAN

1 VooTjitttn Proftnor D AioHnm

' T E A

AFTERNOON

S7VASTET0ESTWDF1SIKA 1

Voortitter: Df A 0 Every

ishio - ish4S A:?

ELECTRICAL ASSESSMENT OF SiNLAYERS ON G*As

c B Mils imm)

S9VA5TET0ESTANDF1S1KA 2

Voorritter: Prof E Friedland

IShSO - ISMS

THE THERMAL CONDUCHVITIESOF SOLD) PRESSJJRF-TRANSHIT-TING AND GAS&T MATERIALSAS A FUNCTION OF PRESSUREAND;

Qumoa and 1 Sigalae (NIMH)

IShiS - IShOO A19 7Sh4S - lehOO A20

THE PASSIVATION OF (HgCd)TeSURFACES

C J Botha, M A Marais andR ,' Mullet-

ELASTIC CONSTANTS OF ONEGLASS AND ONE GLASS CERAMIC

5 Graoatt, I Sigalas andP R Clayton (NIMBI

IShCO - 17hO0

S8 SPECIALIST GROUP MEETINGSOLID STATE PHYSICS

SPESIALISGROEPVERGADERINGVASTETQESTANDFISIKA

S4

KERH- EN DEELTJIEFISIM

Voortitttv: I ftp D V Mingay j

\Q0 Si IIShZO - t$hO BIO

lShOO - IShlS Bll

ON THE PHENOMENOLOGY OFDECONFINEMENT AND CHIRALSYMMETRY RESTORATION

J CUymane (UCT), K Ridlieh,S SatM *n E Suhcmen

IShlS - lBhZO B12

EMPIRICAL EFFECTIVE INTER-ACTIONS FOR SHELL-MODELCALCULATIONS AROUND MASS 40

B J' CoU (Wits) and W.I.Gadinabokao

IShSO - 1SH4S BIS

DINAMIESE SIMMETRIE - fa NUWEGESIGSPUNT VAN DIE SRILMODELI . AGTERGROND EN STRUTTOUR

8 B (layer (US)

16h4B - 17hO0 B14

DINAMIESE SIMKETRIE - fa NUWEGESIGSPUNT VAN DIE SKILMODELI I . TOEPASSINGS EN RESULTATE

SISOfl-AARUWSIKA

7oortxtUr; Or P R Sutoliff*

IShiO - IShlS El

AURORACEBEURTEHIS VAN27 JUNIZ 1982

P S Stoker and A 0 Cottttr

1SH4S - lBhOO E3

DATAVERUERKINGSMETODES VIRKLEIN ABSORPSIES INRIOMETERDATA MET NIE-NORMAAL-VERDEELDE STEDRIHGS

D g Serfontvin en P B Stoker1W)

16H00 - IShlS E4

ELECTRON PRECIPITATIONEFFECTS IN THE DAYTIMEE-REGION IN THE SOUTHATLANTIC ANOMALY

R Saggard and J A Glcdhill

lBhlS - lShiO BS

AN EVALUATION OF COM-PUTERIZED METHODS FORHF MUF PREDICTION

S Lambert (Him)

lShSO - 16h4S E6

OBSERVATIONS OF GRAVITYHAVES AT DURBAN

H D Barker (USD)

1SH4S - l?hO0 E7

INCLUSION OF A WAVY NEUTRALSHEET IN A TWO-DIMENSIONALDRIFT MODEL

R A Burger, H S PotgieterandBHoraal (PU)

•.•"rOO

IThlO

19hS0

- 2?h3J

- IBhOO

for ZOhCO

n POSTER SESSION : ALL GROUPS

S H E R R Y

CONFERENCE 8ANQUET

EXCEPT SOLID STATE (Pl-PW i/ppar Foyer

Poy&r

'Great tlanga' Elangeni Hotel

52

W0ENSDA6 IS JULIE MIDDAS

PROBING THE NUCLEUS WITH NUCLEON CHARGE EXCHANGE REACTIONS

15M0 - IShBO TEE Portaal

S2

PLASWnSIKA

Vooraittar: Dr D Shtruall

IShZO - 2Sh4S CS

COLLISIONS EFFECTS ON THECURRENT-DRIVEN ION-IONHYBRID AND ION CYCLOTRONINSTABILITIES

D Johnston* and J£!J5T

S3

ASTROFISIKA EN ASTROKOHIE

Voorsitfr: Dr M W F*att

- moo re

PRESENTATION AND DISCUSSIONOF DATA OBTAINED FOR THESUPERNOVA 1 9 8 7 . AT THE SOUTHAFRICAN ASTRONOMICAL OBSER-VATORY

R H Catoknole (SAAOi

.S6TOEGEPASTE ENNYHERHEIDSFISIKA

Voortitttr: Dr A S M da Jamt*

IShiO - 1SM5 H?

NEUTRON ACTIVATION OF LARGESAMPLES USING A ONE MILLI-GRAM CALIFORNIUM 2S2 SOURCE

M Lyccudi and J I W Watter-JSnWJS)

S5TSORETIESE SEHINAAR

Voovti tfr: Prof C 3 van tj

lihiO - IShOO • I

QUANTIZATION IN AN ANGULARMOMENTUM BASIS : ALGEBRAICFORMULATION

C L de Umg* (UNP)

15h4S - 16W0 CS

THE ION ACOUSTIC INSTABILITYIN A MAGNETIZED TWO-IONPLASMA

J Govender and S Bharuthram)

IShiS - lthOO H8

REPORT ON PROMPT GAMMANEUTRON ACTIVATION ANALYSISAT SAFARI-1

C Boflntyr (AEC)

tehoo - iskis aELECTROSTATIC WAVES IN ANION-BEAM MAGNETIZED PLASMASYSTEM

K Saidu and J P MaKenzisItino)

2ShOO - lShlS F3

1 3 CM VERY LONG BASELINEINTERFEROMETRIC OBSERVATIONSOF THE SUPERNOVA SN I987A

A Kenball (HRAO) at al.

IShOO - lShli B9

DIE GEBRUIK VAN OUTOREGRES-SIEWE METODES BY DIE RUIS-ANALISE VAN 'N NAVORSINGS-KERNREAKTOR

J ff Conradi* en F van!tiek*rk(AEKI

IShOO - ieh30 IIFACTORIZATIONS OF TWO VECTOOPERATORS FOR THE COULOMBPROBLEM

Old* hang* and R E Raab(VHP)

18hlS - lSh3O CS

ANISOTROPIC ION BEAM-PLASMAINSTABILITIES

P Sinah and R Bharuthram

- 17HCO F«

DWARF NOVAE, NOVAE, BUT NOTSUPERNOVAS

S Warner (UCT)

ISMS - IShiO BIO

STAND VAN DIE NVS SE EtADIO-ISOTOOPPRODUKSIEPROGRAH TEFAURE

s j mil*

ishzo - ishis ceNUMERICAL CONSTRUCTION OFTHE SAGDEEV POTENTIAL ANDASSOCIATED SOLITONS ANDDOUBLE LAYERS I S A WARMMULTI-FLUID PLASMA

S Baboolal (UDW), R Bharuth-ram and M A Bellberg

ieh4S - C?

MODULATIONAL INSTABILITY OFSTRONG ELECTROMAGNETIC WAVESIN A MAGNETIZED PLASMA

S Sharuthram (WU), P Singhand P K Shukla

IShiO - IShiS Bll

FRODUKIE VAN l I 3 I BY DIENVS - EERSTE ERVARINGS

P H SortUr (SVS1, 0 F Steyn«n V L Rauttnbaah

IShiS - IThOO H12

PRODUKSIE VAN 5 2 F « UIT MnMET 6 6 MtV PROTONS

G F Steyn, F M Nortier en

16h30 - l?teC II.

GFSUyn,S J Mitla mvs)

HOE OM FERMI ENERGIES UITTHOMAS-FERMI TEORIE TE VOOR-SPEL

J H Brink an F i Kok (UP)

17H00

17h30

19K30

- VhlO

- lBhOC

vir 20hC0

PLAKKAATSESSIE: ALL£ SROEPE BEHALWE VASTETOESTAfOFISIKA

SJERRIE

KONFERENSIEOINEE

(Pi-pie) Soportaal

Portaal

'Great TLanga' ilangeni Hotel

53

THURSDAY 16 JULY HORNING

S7

SOIID STATE PHYSICS 1Chairman; 5r C I Chv: •"»

S9SOLID STATE PHYSICS 2

Chaiman: Prof H I Albtrta

NUCLEAR AND PARTICLE PHYSICS

SISOUR-TERRESTRIAL PHYSICS

Chairman: Mi 5 Lcmbtrt

ShOO -

LASER EPITAXY OF DEPOSITEDSILICON THIN • FILMS :CHANNELING AND ELECTRONMICROSCOPY MEASUREMENTS

J Adam (UHC), 0 Knoesanand H ?r*toriue

$h00 - ShlS All

BEHAVIOUR OP THE TURNANCLBOF DYSPROSIUM NEAR THEIC •* C PHASE TRANSITION

f P"de tHAV) andF Brit$

ehoo - skisA UNIFIED TRIMT OF OIFPUUAnOHS

A DH Ualktr and JF(UNO)

n

ShlS - 3h33 AS3 8hlS - 8h30 Ait

DOPING OF SILICON BY LASER-INDUCED DIFFUSION

T K Maraia MC), » S Allisand S ppetoriue

3h3C - 8h4S ASS

BURIED ANTIMONY PROFILES INSILICON FORMED SY LASERDOPING

.? Caroliaaen (SAC),0 Knotaen, H J "4cGttrick andH PretoriuB

3k4S - ShOO A2?

EVIDENCE OF MULTILAYERSTRUCTURE IN AMORPHOUSSILICON

•/ Auc<m and .? SiiXtnepoel

3hCC - ihlS A29

EFFECTS OF RE-SPUTTESISCPROCESS PARAMETERS OK MEOPTICAL CONSTANTS OF a - S i : H

J Ausars -2nd R Suanevoel(SAS!

ShlS - 9h30 A31

ELERTRIESE GELEIDING EN FOTO-GETEIDINr VAN AHORFE SILIKON

J J ? Priralco en R Suane-noel i'MV)

CRITICAL BEHAVIOUR OF THESINUSOIDAL — PARAMAGNETICPHASE TRANSITION TN

\CB F Brita (AEC) andI Pd»V_ du ~

8h30 - 8h4S AZ6

ELECTRICAL RESISTIVITY OF

DILUTE (Cr^AI^gjHOj

ALLOYS

P Smit and S I Alberta (RAU)

8h4S - 9hOO AS8

STUDIES OF ELASTIC CONSTANTSOF LaF 3 AT HIGH TEMPERATURES

P S Bgovx (VST), J D Cominasnd A J Every

ShOO - 9hlS A30

THERMOLUKINESCENCE <TL) INROOM TEMPERATURE (RT)IRRADIATED KCl: N» CRYSTALS

A M Mdebuka and J 8 SeretloTUFHI

9hlS - 3h30 432

THE THERMAL STABILITY OFSOME LANTHANIDE NITRATES

C Strudom and C P J vanVuuren TV?)

ShiO - 9h30

SPECIALIST GROUP MEETING

NUCLEAR AND PARTICLE PHYSICS* * * * * * *

SPESIALISGROEPVERGADERINGKERN- EN OEELTJ1EFISIKA

ShlS ' ShJO E»

THE STXUCTUU OF COUPLEDMACKETOSONIC A » ALFVENHAVES AT PCS FREQUENCIES

B p * ! a ~ : d * i a n d A D M V a V t m v7MT)

8h30 - 3h4S BIO

DAMN PeS PULSATIONS

H S Barter (USD)

BhiS - ShOO Ell

IONOSPHERIC PULSATION FIELDSAND MECHANISMS FOR OBSERVEDDOPPLER VELOCITY OSCTIXA-TIONS

A W V Pool? (RU), P S Sut-oliff* and A D H Walter

9h00 - 9hlS BIZ

THE RELATIONSHIP BETWEENLATITUDE AND THE IIGZRPERIODOF Fe3 PULSATIONS

S K ? Sattingh and P H Sut-aliffe

ihlS - 9h30 £13

RESOLUTION OP TEMPORAL AMDSPATIAL AMBIGUITIES IIIPULSATSIC AURORA

H J Koaah and M W J Seour-IUHU)

9H3C - 10h30S8

OR E NIELSEN

Chairman: Profeaaor J A CltdkCll

:Ch30 - lOhSO TEA Poyir

54

DONDERDAG 16 JULIE 06GEND

S2

OPTICS AND SPECT8O3COPY

Chairmani Be 8 H van Btrgmtm

ShOO - MS P

FOCUSING OF LASER IEAKS WITHA CAS U N SK Itotautt, » H Ntohatli* and? F tunniisghan (UHB)

3hlS - 8k30 24

C.A.R.S . TECHNIQUES FOR COM-BUSTION AND CHEMtCAl REACTORDIAGNOSTICS

D Ball. 8 S T OrCvtr, R, JHutehton and G H RobertsonCJCT)

ehio - iha ssMINIATURE CO2 WAVEGUIDELASER0 Sahneder (NPSl),C 8 Diakerton md D Preuei-Ur

3h4S - 9h00 Pe

THE USE Of A WAVEGUIDE ASRAKAN CELL FOR CEMERATION OFIR LASER LIGHT

.f Budtinaki and D «T Brink(NPBL)

3HC0 - ah3O 2 '

STUDENT SESSIONOPTICS AHD SPeCTHOSCOPY

MOK-LUEAR OPTICS : SOMEPRINCIPLES AND APPLICATIONS

0 J Brink tSFPX)

S3

EDUCATIONChairman; M* H Stanven

8hiS - ShlS a:

THE TASK OF THE UNIVERSITY

U de Baa* (VSO)

S6APPLIED HMD INOUSTK1AI PHYSICS

Chairman: Dr S tuyokx

thOO - this HISAEROSOL ADVKJROMS - UCENTRESULTS FROM FIXE ANALYSISQF AIRBORNE PAKTICOLAnS

B J Annsgem (WITS), A Zuoh-ohiatti and J P F Stlliohop

Shli - BhSO 81

F O B ANALYSIS OF MINERALHATTER IN THIN SECTIONS OFBIHAR LUNG

A S Pillay, B J Anntgarn(HITS), D Faurt and J C ADavit*

BhlO - SH4S BIS

A VERSATILE UHV APPARATUSFOl SU1FAC I PHTSICS ANDCHEMISTRY

TEDjnm, R G Copptrth-uaitt, P H Loggtnbti\ . V SBrook* and J P F S*lliehap(WITS)

Sh4S - ShOO BIS

THE REDUCTION AND SUBSEQUENT^CARJURIZATTON OF AN I N D U S ^ ^TRIAL CO-HYDROGENATHUKtATA-LYST : AH XPS AHg^rffS STUDY

p H U>qg*nbf#Q. R J Copptrth-xxtitt cnt'J P F Selliohop(WIIST

S5THEORETICAL SEMWH

Chairman! Or I I Sty*.

ShOO - thOO

OOHIFMK TAN OIK OIHI

w iwsomoonS B Otyr «n £ A it tot(US)

ShOO - 9hlS 81?

k STODT OF THE FORMATION OFZIRCONIUM SUICIDE ONSILICON (100) SUBSTRATES

US 3rvo_k* (VIIS), t XutM-lan, ASK lAtteh, T E Dtrryand fl G Copptrthxritt

a- A-

ShOC - 9h3:

CAVITY QUANTM CKROHOOT!!MICS TO ORDER o j

A J Stoddart md r iViollitr ;VCT!

9hlS - 9h30 02

HUMirOIE OR DISCOMTORI INDEX,D . I .

X D 9ark*r (UNO)

9hlS - 9hZ0 ?78

RAPID COMPUTER-CONTROLLEDCAPACITAIICE TRAHSIENT CRARAC-TERIZATIOir OF DEEP-LEVELCENTERS

B a Haguir* (7>*nt Polyttehnie, ilk), A Horthall andJ P F Stlltohop

ShSO - lOhZO CURRENTS AND ELECTRIC FIELDS IN THE EARTH'S MAGNETOSPHERE AND IONOSPHERE

lOHZO - lOhSO T E E Portaal

SS

THURSDAY 16 JULY MORNING

$7SOLID STATE PHYSICS 1

Chairman; DP S Bart

llhOO - UhlS A3!

GRONTH OP G*Al EPITAXIALLAYERS USING CURRENT CON-TROLLED LIQUID PHASE EPITAXY

V J Wtrtt*ra, J S Vemaakand A W S Uitah (VPE)

llhlS - Uh30 A3S

AN INVESTIGATION INTO THEMECHANISM OF FORMATION OF

C >i Coirrit fVCT), J C Uuand J 'it Mayer

Zlh33 - Uh4S A3?

HIGH TEMPERATURE APPLICATIONOF SCHOTTKY CONTACTS TO GaAl

S Felling IHIMR), A P Bothaand 3 Pretorius

Hh4S - 12HO0 A39

Co- AND Ni-SILICIDE FORMA-TION IN THE PRESENCE OF GOLD

3 A Has rsfflffj, J J Cruy-*jagen and H Pretorius

ZZWO ~ IShlS A41

THE EFFECT OF OXYGEN IMPURI-TIES ON THE SOLID STATEINTERACTION BETVEEN THIN ? t -FILMS AND SILICON

.V A i/andt and R Pretoriua

IShlS - 1BH30 A43

N i - S i SOLID-STATE REACTION :FORMATION OF SILICON-RICHLAYER WITHIN N i S i 2 IN THEPRESENCE OF EXCESS AMORPHOUSSILICON

J I toslesd (SAC), 3 A ROB•md ?. Prezoriua

S9SOLID STATE PHYSICS Z

Chairman; DP R Pratcriu*

UhOO - :iMS AH

MAGHETIC EFFECTS IN DILUTEC r - S i ALLOYS

B L Albarta and J AJ Zourant(RAO)

JIMS - IIMO AleTHE EFFECTS OF PLASTIC DEFOR-KATION ON THE ANNEALING OFINTERSTITIALS PRODUCED BY RTIRRADIATION

P M M,TOara (WITS), JR Sexvtloand AM Hdebuka

WHO - Hh4S A3S

KKCDIUESS FRACTION STUDIESOF SUPERCONDUCTING NIOBIIM-TIN ALLOTS

G R Baame and B Xolk (WITS)

Uh4S - IShOO A40

PHONON FOCUSING IN PIEZO-ELECTRIC CYSTALS

A a Every (WITS) and

12h00 - 12hlS AiZ

RAMAN STUDIES OF IRRADIATEDtl AND K I ( S r )

A M T Allen, C E AllenspaoHand J D Camins (WITS)

mis - zzhzo PDl

SYNTHESIS AND CHARACTERIZA-TION OF SOME HIGH-TEMPERA-TURE SUPERCONDUCTORS

? R Clayton, A van Zyl,X Sioalaa and S Janteky(tiMR), D S MaCachlan

NUCLEAR AW) PARTICLE PHYSICSChaiiTnan; DP W R HoHavay

UhOQ - llhiO BIS

STUDENT SESSION

NUCLEAR AND PARTICLE PHYSICS

SOME CORHNT CHALLENGES INNUCLEAR PHYSICS t ITS FIELDSOF APPLICATION

J P P Stlltahop (WITS)

HMO - llhii B16

NUCLEAR PHYSICS DATA ACQUISI-TION WITH A PERSONAL COMPUTER

fi U Ptarisk (WITS)

11H4S 12hOO B17

POSITRON PRODUCTION INNUCLEAR COLLISIONS

B Spoalstra (HZ), J P P Stll-eahop and U Von Wirmersperg

IZhQO - lthli BIS

OBSERVATION OP A DEVIATIONFROM BHABBA SCATTERING HITHE ELECTRON-POSITRON SYSTEM

!) Don Wirntrsptrg, S B Con-ntll, R P A Hoernle andE Sidtraa-Baddad (WITS)

- 12h30 B19

TDPAD MEASUREMENTS OF IMPLAN-TATION TEMPERATURE DEPENDENCEIK 1 ? F UFLANTED DIAMOND

S Connall (WITS), IP? Stll-aahop, H S Stvmtt, B Apptland K Bharuth-Ram

SIEDUCATION

Chairman: Prof P B Stoktr

UhOO ' IShOO

SPECIALIST GROUP MEETING

EOUCATION

SPESIALISGR0EPVERQADERIN6

OPLEIDING

IZhOO - 12h30

STUDEHT SESSION

EDUCATION

WILL COMPUTERS REPLACEPHYSICS PROFESSORS?

G E ObtPtm (RV)

G3

12H3C - 13hOC POSTER SESSION : SOLID STATE PHYSICS (P17-P30) upper Foyer

a: - :3Hso LUNCH Charl*B Smith Dining Sail

THURSDAY

ZihCC - lihOC

S3

16 JULY

j DR G D NICOLSON ^ -i '/ooreitter: Dr H W Feaat C^*

AFTERNOON

:s-.oc - :s TEA Foyer

:sh33 S8 ANNUAL GENERAL MEETING S A I P

MAYORAL COCKTAIL PARTY Durban City Sail

OONDERDAG 16 JULIE OGGEND

S2PLASM* PHYSICS

Chairman: Hr P H Krwm

UhOO - UhlS C3DESIGN OF HELICAL MAGNETICCOILS FOR THE AEC TOKAMAK

D P Cottar, J A » daHlliara, J D Fletehtr,G Sothnasel, D E Robert« andD Shemell (AEC)

S3ASTROPHYSICS AMD ASTRONOMY

Chairman; Prof B Warmr

UhOO - Uh30 Fi

THE AGING OF OLD DEGENERATES:ASTEROSEISMDLOGY OF WHITEDWARF STARS

D O'Donoghue (UCT)

S6APPLIED AND INDUSTRIAL PHYSICS

Chairman: Dr B J Annagam

UhOO " UhlS HIS

AANWENDING VAN TITAANNITRIED<TiN)-DEKLAGIES DEUK IOONPLA-TEKING a DIE INVLOED VANPROSESVERAHDEKLIKES OP DIEEtENSKAPPE VAN DIE DEKLACIESD PUUvttn. I A Kottf »nP U da Lang* (AEKI

ssTHEORETICAL SEMINAR

Chairman! Dr R Ttgtn

UhOO - UhSO ZZZLEE-YANG TEORIE V M FASE-OORGANGE

Cecn.lt Thorn (US)

UhlS - llk30 C9

MAGNETIC FIELD MEASUREMENTSOF RESONANT HELICAL WINDINGSON THE AEC TOKAMAK

D P Coater, J A M deVilliara, J D Pletoher,0 Sothnagal, D E Roberta andD Shenxll

llhlS - UhiO 320

DIE VERSICYNSEL VAN RESSPAN-NING EN DIE METING DAARVANMET BEHULP VAN X-STRAAL-DIFFRAXSIE

y B du Pree* en G Ifieuuoudt(AEK)

Uh30 - 11H4S CIO

REPAIR AND BE-ASSEMBLY OFTOKOLOSHE

J R O'Hahcny (AEC)

Un30 - Uh4S F6

IMPLICATIONS OF RAPID STELLARROTATION FOR NONRADUL PULSA-TION HOD'S IDENTIFICATION

C A Engalbreeht (UNISA)

UhSO - IMS H21

DIE METING VAN RESSFANNINGSIN HETAALKOHPONENTE MET BE-HULP VAN X-STRAALDIFFRAKSIE

g Sieuuoudt an U B du PreezTASK)

UhiO - 12hZO I2S

NON-O(6) RELATED DYNAMICALSYMMETRIES OF THE INTERACT-ING BOSON MODEL

B g Gayer, F J U Safma andF G Seholta (US)

Uh4S - IZhCO

RESONANCE STREAMING INTOKAMAKS

D Sherwell (AEC)

CU Uh4S - IZhOO F?

OBSERVATIONS OF SHORT PERIODBe STARS IN THE YOUNG GALAC-TIC CLUSTER NGC3766

WITHDRAWN

Uh4S - IZhOO RZZ

WEAR MECHANISMS MODIFICATIONINDUCED BT ION IMPLANTATIONIN WC-Co.

S a Cuyakx. 1 Caaeuto andJ P F Sallsahop (WITS)

IZhOO - 12hlS

ENERGY TRANSPORT IN ANERGODIC MAGNETIC LIMITER

•V A Hellberg (UND) andW Feneberg

CIZ IZhOO - IZhlS F8

SOME QUESTIONS ABOUT THEHYDRODYNAMICS OF'ACCRETIONDISKS

C Kotn (imiBO)

IZhOO - IZhlS SS3

EFFECT OF VARYING SHEETTHICKNESS ON THE FRACTURETOUGHNESS OF HIGH STRENGTHSTEEL

g Protopappat, J Nieuumeijerand W B du Praez (AEC)

12hlS - IZhZO

PROBE MEASUREMENTS IN ASTEADY-STATE TOKAMAK D I S -CHARGE PLASMA

P J Barrett (UND), M Ono,V Darrou and G J Greene

C13 IZhlS - IZhZO F3

PROPERTIES OF ALFV& WAVEDRIVEN STELLAR WINDS

11 K Dougherty and J F Ha-Xenzie (USD)

IZhlS - 12h3O HZ 4

ELECTRON PROBE MICRO-ANALYSIS(EPMA) OF IRON IN GALVANIZEDCOATINGS PRODUCED ON LOWSILICON STEELS

A It Kirkbrid* and A Wells(Sim)

IZhiO

llhOO

IShOO

UhSO

lBhOO

- IZhOO

- IZhSO

DONDERDAG

- IShiO

ss

16 JULIERECENT ADVANCES IN

AND

PLAKKAATSESSIE : VASTETOESTANDFISIKA (P17-P30)

HIODAGETE

THE TECHNIQUES OF VERY LONG BASELINE INTERFEROHETRYITS APPLICATIONS IN ASTRONOMY ANO GEOPHYSICS

TEE

JAARVERGADERING S A I F

SKEHERONTHAAL OEUR BURGEMEESTER

3oportaal

Charles Smith Eetsaal

MIDDAG(VI.BI)

Portaal

Durbante Stadeaal

57

FRIDAY 17 JULY MORNING

S7SOLID STATE PHYSICS 1Chairman: Prof P dt 7 du

Pl**til

ShOO - ShlS A1S

"N STUDIE VAN DIE P t / S iDONLAGIE SISTEEM TUSSEN7SO*C «D lOOO'C

G I P Btrnina tn t W LoxaiWOVS)

BUS - BhSO A4?

DIE EPITAKSIALE GROB1 VAN CrOP Ag(ni) SUBSTRATE

H 0 van dmr B»ra «ng I Oaiqher (UP)

S9SOLID STATE PHYSICS 2

Chairman: Dr 3 Sooytnt

ShOO - this AM

ATOMIC SITE LOCATION OFDOPANTS IK CaAa BY ELECTRONCHANNELING

E H Ghtnn*, R C Snymxn,CAB Ball and B Smith (UPE)

BhlS - 8h30 A4S

A TEM STUDY OF THE STRUCTUREOF ANNEALED NITROGEN -IMPLANTED SILICON

B C Snuaan, B P Zetlie andJ S Itttthlina (UPE)

NUCLEAR AWD PARTICLE PHYSICS

Chairman: Prof W J RauM

SISOLAR-TERRESTRIAL PHYSICS

Chaiman: Dr A W V PooU

ShOO - ShlS I

A SOURCE r « 3 Hx AURORALPULSATIONS

g J Banitn. E Hravlag andHV J SoemrfUld (USD)

BhlS - BhSO BIS

AURORAL PULSATIONS ANDASSOCIATED CHORUS

g J Ban$en and M W J Soour-fUld (USD)

Sh30 - 3H4S A49IDENTIFICATION OF DEFECTS BTMEASURING THE IN-PHASE (I)AND QUADRATURE (0) DLTSSPECTRA DURING A SINGLETEMPERATURE SCAN (IQ-DLTS)

f D Ata-et and H Hal (UPE)

Bh4S - ShOO AS1

IMPROVEMENT OF SEMICONDUCTORMATERIALS BY MEANS OF DEFECTENGINEERINGL W Snurm (UPE)

9k00 - ShlS ASSPROBLEMS EXPERIENCED WITHOPTICAL FTIR CHARACTERIZA-TION OF C«A»

J A A Engelbrveht, I J leeand A Botha (UPS)

8h30 - SMS A4B

DEEP RADIATION DAMAGE INMETALS AFTER ION IMPLANTA-TION

E Friedland and B V Albert*(UP)

8h4S - 9h00 ASO

I0ONINPLANTERING IN A l : S i -KONTAKTE

S A Carr, J B Malherbe «nB Fi-iedlmd (UP)

ShOO - 9hlS AS2

DIE MODIFTKASIE VAN N i - S iSCROTTKYKONTAKTE MET BERULPVAN IOONBUNDELVERMENGING

C Muburg, J B Malhtrb* tnE Fntdland (UP)

9hlS - 9h30 AS4

IMPLANTED FLUORINE PROFILESIN DIAMOND

J F Print, T S D»ny. C C PMadiba and I P ? Salltehop(WITS)

BhSO - Sh4S BIO

SOEXXOG VAN DIE WAARNEMUIGVAN SONVLAMIEDTRONE IN DIEVTFMOIUTEDATA VAN DIENEUTRONMOHITOR IE TSUMEB

P 8 Stoltar (PI/)

Bh4S - ihOO BS1

KARAKTERISTIEKE VAN SEKOND-SRE-EIEKTRON ENERGIESPEKTRA'

C Dtdnan, 1 van Waart »nW Hingay Oiffl

Jd L

3h00 - ShlS B22STROamiGTHEtD EFFERTE INSEKONDtRE ELEKTRON ENSRGIE-

C Dtdnam tn J van Vaart 79MS - 9h30 823

LEEFTTD VAN DIE Oj TOE STAND

V H Pro*»skf4 *n D W MingaytAEK)

BhSO - ShiS

AN INTERPRETATION OF SO-CALLED 'DRIFTING DARKAURORA'

g SehouU-yanntek, H W JScour field and £ Hravlag(»

ShiS - ShOO Zl?

THE RELATIONSHIP BETWEEN THEPLASMASPHERE AND AURORALOVALJ Stepfwnem and M U J Scour-fitla (Cimi

ShOO - this SIBEXIT-POINTS OF WHISTLERS HITHE REGION OF SANAE -ANTARCTICA

J HLa&tig and A R U Ought*(HUD)

ShlS - 9H30 E19

RAY-TRACING STUDIES OF THEPROPAGATION PATHS OF VLFSIGNALS ORIGINATING NEAR THEEQUATOR

Praveth Ranlall and A D !4Walker (UNO)

9hS0 - JOhlO

S8PROFESSOR R K LEfflER

Chairman: Profttsor C A Sngtlbrtaht

lOhZC - lOhSO T E A Foyer

& ^

VRYDAG 17 JULIE OGGEND

S2 S3OPTICS AMO SPECTROSCOPY EDUCATION

Chairman: Dr F J Co*t*»r Chairman: Prof B SpotUtra

S6APPLIED AHD INDUSTRIAL PHYSICSChairman: Dr T E Dtrry

S5THEORETICAL SEMINAR

Chairman Prof R D ViollUr

ShOO - BhlS B2S

PASSIVE SINGLE-PASS SOLARWATER BEATERS

T B Sah»:Stadin ffir and J C van

ShOO - ShiO 124ACOUSTIC CHERENKOV RADIATIONBT SUPERSONIC HEUTROHS

0 Tmxr (UCT)

ShlS - ShSO SB

OPTICAL FIBRE COMMUNICATION

S Gunn (AbarSare Group)

8hlS - 8h30 04

SIMPLE ELECTRICAL CIRCUITSA PRACTICAL TUTORIAL APPROACH

M S Alii* and J E King (VCD

BhlS - BhSO

OPTIMAL FLOW IN A SOLARWATER HEATER

T B SaheffUr (UP)

B28

8hS0 - 8MB D9

COUPLED-MODE THEORY FOR THEACOUSTC-ELECTRO-OPTICEFFECT I S SAW DEVICES

A V Soholtz (UP)

Sh30 - 9h00 GS

CONCEPTUAL PROBLEMS INSIMPLE DC CIRCUITS: INSIGHTSGAINED FROM STUDENT RESPONSESIN EXAMINATIONS

H Stanton WITS)

8h30 - 8h4S B27

DEVELOPMENT OF HIGHLY EFFICI-ENT, LOW COST THERMAL INSULA-TIONS FOR USE IR THE100-400'C RANGE

B Potgitttr, P R Clayton,I Sigalas and R J Gumow(MM)

8hSO - 9h30

SUPERNOVA MODELS

C A Engelbreoht (US)

12 S

- 9h00 D10

DIE CEBRUIK VAN APODISASIEIN DIE ONTWERP VAN b AKOESTO-OPTIESE SPEKTRUMANALISEERDER

£ de Koker (UP)

ShtS - 3h00 B28C . A . R . S . TEMPERATURE MEASURE-MENTS IN A RUNNING INTERNALCOMBUSTION ENGINE

D Ball, B S T Driver, R J But-ohecn, G 8 Robtrtacm (UCT),K P Btnnttt, R K Dutkitoicz,R Sattt and A rates

9h00 - 9hlS Dll

AKALISE VAN NIE-LINEARITEITEIN AKOESTO-OPTIESE INTER-AKSIES

A J Boffman (UP)

9hlS - 9h30 D12

EVALOASIE VAN KODERIKGS-TEGNIEKE VIS REKENAAR-GEGENEREERDE-HOLOGRAHME

PSRoux (UP)

9hOO - 9hS0 Gt

THE SIMPLE ELECTRIC CIRCUITAS AM ENERGY SYSTEM: SOMECDNCE»TDAL DIFFICULTIESWHICH CONFRONT STUDENTS INSIMPLE CIRCUIT TEEORY

Z Jiya (UPB)

9h00 - 9h30 829

STUDENT SESSION

APPLIED AND INDUSTRIALPHYSICS

SOME RESULTS OF UITERGOLD'SRESEARCH PROGRAM

G Gafner (ISTERGOLD)

THE STRUCTURE OF MATTER AT HIGH ENERGIES

lOhSO - lOhSO T E E Portaal

59

FRIDAY 17 JULY HORNING

$7SOLID STATE PHYSICS 1

Chairman: Nt'at J Auoam?

llhOO - UhlS ASS

THE APPLICATION OF REAL TIMEFAST FOURIER TRANSFORMATIONSIN EDS ELECTRON MICROSCOPY

D R Scalding and £ ttaiatzy(USD) ""

UhlS - Uh30 AS?

CORE-EXCITATION EDGE AND EX-TENDED ELECTRON LOSS SPECTRAFROM VARIOUS CARBON SURFACESUSING LOU ENERGY REFLECTEDELECTRONSB G Maguire (Trent Polyteeh-nio, UK) and J P F Sellaehop

llhSO - Uh4S A5S

LINEAR AND PARABOLIC REAC-TION KINETICS IN BINARYCOUPLES

S C Zingu (MEDUNSA)

Uh4S - IZhOO A61

CORRUGATED GLIDE SURFACESAND THE ORIGIN OF EARTH-QUAKES

P J Jaakaon (UffP)

12hO0 - 12hlS AB2

'M KOHSISTENTE HERANALISEVAN DIE TEORIE VAN OPPERVLAK-SEGREGASIE IN MJLTI1COMPONENT-ALLOOIE : EWEWKSEGREGASIE

J du Plesaia en G H van Wyk(UOVS)

12hlS - IZhZO ASS

'N KONSISTENTE HERANALISEVAN D?E TEORIE VAN OPPERVLAK-SEGREGASIE IN MULTIKOMPONENT-ALLOOIE : KRITIEK OP ANDERTEORIEJ du Pleasis en 0 H -Jan ifyk(UOVS)

12h30 - 13hOO At?

APPLICATION OF SPACE GROUPTHEORY TO SECOND ORDER PHASETRANSITION IN CRYSTALS

3 W Xunert I UP)

S9SOLID STATE PHtSICS 2

Chaimm: Dr 1/ 8 du Prvc«

UhOO - UhlS ASt

GEPDLSEERDE EL3RW>NBUNDEL-vatRiTnxc (PEV), LASER EHTEMPERATUURUITGLOeiWC VANCEfHPLANTEEW)!! InSbS WAlUrti «n R CillUn7BP7

llhlS - UhlO ASS

STRALINGSKADE VANWE LIGTEIONE IN InSb

5 J E van Sonder tn E Fritd-land (UP)

llhiO - 11H4S

DIE GEStfJIK VAN LAE ENERGIEIOONVERSTROOIING VIR DIBONDER5O1EX VANKANGSKIOCINGS

C H van (UOVS)

JZhiS - IZhOO

'N STODIE VAN DIE ADSORPSIEVAN l; 20 OP POLIKRISTALLYNEVLET/RK STAAL MET BEHOIP VANEDELGAS IOONVERSTROOLN3

G n van Wyk (UOVS), U Sng-lert «n E Taglauer

WiOO - 12hlS A64

DIE ONDERSOEK VAN VERIIKIL-LENDE TIPES AMORFE KOOLSTOFH.B.V. X-STRAALDIFFRJUCSIE

M P/ifk (AEK) <m P /? ISchoning

12hlS - IZhSO ASS

TRANSMISSION ELECTRO* DIF-FRACTION PATTEBK ANALYSISUSING mCRODENSITOMETRY

C I Churns (UHC) and S Xrit-zinger

12hS0 - 12h4S A68

SEGREGASIE VAN TITANIUM INGOUD

P g 7iljom, J P0 Holtzhauaen (UOVS)

SONUCLEAR AND PARTiaE PHYSICS

Chairman; Prof J P IRtimokt

UhOO ' UhlS B24

ANOMALOUS RESPONSE OF THINFILM PLASTIC SCWTTLLATOI TOHEAVY IONS

B Fronklyn (ABcTl

UhlS - Uh30 B2S

PROMPT GAMMA-RAYS FROM THER-MAL NEUTRON CAPTURE INNATORAL Oi AND Ct

C B Fmnklyn (ABC)

UhiO - Uh4S BBS

Kg /K EMISSION RATES FORX-RAY PRODUCTION BY PROTONS,DEUTERONS, AND ALPHA PARTI-CLES

P B Kottt and 0 V HingayJAEC)

Uh4S - IZhOO 827

K X-RAY SPECTRA PRODUCED BYNITROGEN IONS HI Ti AND V

P B Kotzt and D V Mingay7SEC1

12HO0 - 12hlS B28

MICRODOSTMEnSY - CONCEPTSAND QDAHTOIES

J B Hough and P J Sinna(SAC)

i2his - nhio mMEASUREMENT OF SINGLE EVERTSPECTRA IN A HIGH LET RADIA-TION FIELD

P J Binnt and J B Bough

SISOLAR-TERRESTRIAL PHYSICS

Chairmn: He 8 Haggard

UhOO - UhlS IZO

tflHD PATTERNS IN THE METEORREGION

L H G PooU (W>

UhlS - Uh30

GEOMAGNETIC INDUCTION

EFFECTS

0 I H Sohfptrt (HOB)

UhlO - Hh4S E22

PLASMA SIMULATION ON AMASSIVELY PARALLEL PROCESSOR

I HA OUdhill, 0 Buntmanand t R0 Stormy (STARLab,Stanford Vnivrtity, USA)

12H4S - 13hOO A?0

DTE ROL VAN KLEIN PERSENTA-SIES Pt-METAALTOEVOEGINGSIN Fe40Cr STAAL

J ? Roux, D J Holtzhaueen tnH 'J •Jcni Stadtn (UOVS)

- :3hs: L U N C H Chart** Smith Dining Ball

60

VRYDAS JULIE 0G6END

S2PLASHA PHYSICS

Chaimms Mr J 0 Ft*tah*r

llhOO -IMS CU

OBSERVATIONS Of THE ION-IONIWO-STIEAM INSTABILITY

p J Barrett and R 0 Grtav**

UhlS - Hh30 CIS

SPATIAL CHARACTERISTICS OFaOSSFTELD ION ACOUSTICTURBULENCE

R 0 Greaves and P J Barrett(tm>

S3ASTROPHYSICS AND ASTROHOHY

Chairman: Prof P H Stoktr

llhOO - UhlS P10

A T«V TRIPLE PEAK FROMPSR 1509-587

0 C da Jqgtr, B C Rauban-h*inar, A R north, a I da

and G van Urk (PU)

UhlS - llh30 F2

THE EA¥El"m> TcV GAMMA-RAYFLUX FROM ISOLATED PULSARS

0 C de Jager, Bid* Jagtrand B C Raubenhrimtr (PU)

S6APPLIED AND INDUSTRIAL PHYSICS

Chairman: Dr D T I Jon**

llhOO - llhlS B30

THE APPLICATION OF THE RADIALDiFFusmrr EQUATION TO THEPETROLEUM INDUSTRY, El PARTI-CULAR WITH RESPECT TO WELLTEST ANALYSIS

P Stligmann (SOEKOR)

IMS - Uh4S B31

SIKLOONSKEIERNAVORSING

P A KareUn (AEK)

THEORETICAL SEMINAR

Chairman: Prof C A Engtl-brtoht

llhOO - IZhOO Ite

STUDENT SESSION

THEORETICAL PHYSICS

ON THE CREATION OF MATTER VITHE UNIVERSE

R 0 VioUier (VCT)

UhiO - 21h4S CIS Uh30 - Hh4S P12

CURRENT RESULTS FROM THELASER SECTION OF THE PLASMAPHYSICS RESEARCH INSTITUTE,UNIVERSITY OF NATAL

J A Waltham, P F Cunninghamet at. (USD)

Uh4S - IShOO Cl?

DRIFT IN A MAGNETIC FIELDWITH UNLIMITED GRADIENTS

' and B Moraal (PU)

A SEARCH FOR SOURCES OFULTRA HIGH ENERGY GAHKA-RATSWITH THE POTCHEFSTROOM EXTEN-SIVE AIR SHOWER KRRAT

0 C de Jagtr, A R north *tal. (PU)

22*45 - IZhOO F13

FURTHER RESULTS FROM THERHODES 2 . 3 GHz SURVEY

3 Woermann and J Jonas (RU1

- moo pi4COKING COAL CONTROL BYAUTOMATED IMAGE ANALYSIS

L E Konrin-Kottakouski(NICR) and a Roux

i2hoo - izhis as

PLASMA ROSSBY WAVES

M K Dougherty and J F UaKen-zie (USD)

IZhOO - IShlS F14

OB MASERS IN SOUTHERN IRASSOURCES

M S Dollery (BSAO), H J Gay-lard, P n f/hitelock and R JCohen

IZhOO - 13h00 12?

NUCLEOH-ANTINUCLEON ANNIHILA-TION IN RELATIVISTIC QUARKMODELS

R Tegen (VCT)

IZhlS - 12k3C C19

PHASE MEASUREMENTS OF THEION CYCLOTRON INSTABILITY

W J Alvort and E 0 vanSi»T<ark (USD)

22*25 - 12h30 F1S

OH MASERS IN OBJECTS SHOWING10 MICRON ABSORPTION

M J aavlaed (IBUO), M E Dol-lery arut P A Whit* look

12h30 - 12H4S C20

MAPPING THE FREQUENCY DETER-MINING REGIONS OF THE ELEC-TROSTATIC ION CYCLOTRONINSTABILITY

P Krurni and R Sehrittuieaer

turn)12h4S - IZhOO CZl

A SIMPLE METHOD TO DETERMINEABSOLOTE VALUES OF SPACEPOTENTIAI.

g Hraulaa and P Knmm (USD)

IShOO - 13hS0 HIDDAGETE Charles Snith Eattaal

P O S T E R S FOYER/BOPORTAAL P L A K K A T E

ON TIHE-DBFBNDENT POTENTIALSpie

H VKfcmOld (ABC)

VOORXEURVBRSTUIWING VAN VERBINDINGSPI?

J B Halherbe {Uf->

DIFFUSIESTUDIES VAN Si IN F«-CEBASEERDE AMORFE ALLOOIEPIS

W D Roos en 0 X van Vyk (UOVS)

HAGNETIC PROPERTIES OF AMORPHOUS (METALLIC GLASS)Fe.n N i , 0 BPIS m * •

M D Rang. T B Doyle and D R Spalding (UND)

A M5SSBAUER STUDY OF THE MAGNETIC HYPERFINE FIELD DISTRIBUTION IN AMORPHOUS F e , ^ N i 4 Q B 2 Q

A Maekenjee, H Sdxirds and K Sharutk-Ram (VW)

NEUTRON DIFFRACTION EXPERIMENTS OF SOME RARE-EARTH INDIUM COMPOUNDSP21

) f l G B o o y s e n (RAH), P d e V d u P l e a e i s a n d G B P B r i t s

ELASTIC BEHAVIOUR OF MOLYBDENUM PHOSPHATE GLASSESPSS

J D Comins (WITS), J E Maadonald, F F lambeon and G A Sounders

ON SURFACE DAMAGE TO (100) CdTeP23

M E Lee, E 0 de Neijs (VST), A H Leteoalo and R J Muller

BROMINE-METHANOL ETCHING OF ( 1 0 0 ) CADMIUM TELLURIDE SURFACESPZ4

M E lee, A M letaoalo (UNT) and il 0 Barnard

!| THE OXYGEN COVERAGE ON DIAMOND SURFACESP25

T E Perry (WITS), J 0 Sanaen, P E Harris, R G Copperthjaite and J P F Sellachop

INFLUENCE OF TEM GRIDS ON AMORPHOUS SILICON DURING IN SITU SILICIOE FORMATIONP26

S Kritzinger, C J Bedehsr and J C Lombaard (US)

OPTICAL BIREFRINCENCE STUDIES OF DEFECTS IN GaAsP27

E E van 3yk, J S Ver->aak -2nd A V R Zeitah !VPE>

HALL PROFILING OF CaAs EPITAXIAL LAYERS

J A Goodman, A U P teitah and «.' 5 Vermaak 'VPS)

EFFECTS OF PEBA ON GaAsP2$

H W Alberts (UP), ? D Auret (UPE), H Wei and H le Roux

DETECTION OF ELECTRON AND HOLE TRAPS BY DLTS IN PROTON IMPLANTED VPE GROWN n-GaAs USING SBD'SP30

M Sel and F D Auret (VPE)

DEVELOPMENT OF AN IMPROVED ITERATION SCHEME FOR LARGE DIMENSIONAL PROBLEMS

<aH&^H^° •%**>*

s»t»«

Flights, Cruises, Package Tours, Charters, MotorCoach Tours, Car Hire, Hotels, Passports, Visas,

Travel Insurance, etc,

DURBAN® 289151RIDGE LEVEL

OVERPORTCITY

PINETOWN © 7010201NORLAINE CENTRE

OLD MAIN ROAD

i

GRUnDIGoteot ron ic GRUNDIG OSCILLOSCOPES PROMOTION

MO 20:20 MHz Dual-Channel Oscilloscope of the low-cost Category.

MO 20

QUANTITY1 - R1 995,00 each

10-R1 490,00 each

MO 22:20 MHz Dual-Channel Oscilloscope with Automatic Time Range.

MO 22

QUANTITY1 - R2 725,00 each

10 - R2 075,00 each

MO 53:50 MHz Dual-Channel Oscilloscope.

MO 53

QUANTITY1 - R6 075,00 each

10 -R4 050,00 each

WILLISTON ELINBox 39481 Bramlay 2018 South AfricaT»l. (011) 702-2227/8/9 T«lm 4-24206 S A

Abstracts Opsommings

SOLID STATE PHYSICS VASTETOESTANDFISIKA

A1 THE STABILITY OF CERTAIN INSTRUMENTSWHICH ARE ESSENTIALOF AN OMVPE REACTOR

IN THE FUNCTIONING

0 j LombardNational Institute for Materials Research

Stability of certain instruments in m OMVPE reactor,/or- example the mass flow controllers, pressurecontrollers, etc., are essential to obtain reproduce-able results. This Mill be discussed along withresults wnich were obtained from calibrations done onthese instruments which are used to control the OMVPEreactor in operation at the N1MR.

A2 USING ACRT FOR THE GROWTH OF CdHgTe

J H S Roodt. M A Marais and R J MullerNational Institute for Materials Research, CSIR

Buules of cad«*lum mercury telluride produced by theBridgman method suffer from radial and axial lnhomo-geneity due to the orcnounced segregation of HgTe andCdTe during such equilibrium type growth techniques.The Accelerated Crucible Rotation Technique (ACRT)applied to Bridgraan growth will be discussed as amethod to improve the radial homogeneity and to in-crease yield. Recent results obtained at the NIMR, CSIRusing this technique will be presented.

M THE DESIGN OF AN OVERALL SAFETY SYSTEMFOR THE SAFE OPERATION OF AN OHVPE REACTOR

A P Uys, A P Botha, 0 J Lombard and J C Q FletcherNational Institute for Materials Research, CSIR

Organometallic Vapour Phase Epitaxy (OMVPE) is a keymaterials technology for advanced high-frequencyoptical and microwave devices. The purpose of thispresentation is to profile the hazardous propertiesof gasses being used on a research reactor, anddescribes an OMVPE-reactor safety interlock andautomatic shutdown system now being used at the NIMR.Some specific features employed are reactor over-pressure detection, susceptor overheating detectionand toxic gas exposure control. This presentationwill also deal with the technique used to remove Asand AsH from the reactor exhaust.

A4 CORRELATION BETWEEN CARRIER CONCENTRATIONIN HgCdTe AND CHLORINE DENSITY AS DETER-MINEO BY SIMS AND FAB

H J Strydom, M A Marais, D E C Rogers and J H BassonNational Institute for Materials Research, CSIR

In order to produce (HgCd)Te for photoconductivedetector applications, near-intrinsic material withfew residual impurities is required. Material withhigh carrier concentration has been found to containlarge amounts of chlorine using SIMS. A direct cor-relation between the Cl concentration and the carrierconcentration were found. The sources of Cl contamina-tion have been found to be the Cd starting material(as determined by FAB). Chemicals used to clean thestarting Materials as well as the silica ampoulesused during growth. The powerful combination ofmagnetic sector SIMS, quadruple SIMS and FAB massspectrometry is unequalled in the field of ppm to ppbconcentration levels.

AS A SIMPLE FAT-FET GROWN BY OMVPE

Jack C Q FletcherNational Institute for Materials Research. CSIR

A simple, large gate length (FAT) FET nas been grownby Organometallic Vapour Phase Epitaxy. Conditionsgoverning the growth of both buffer and active layerswill be presented as will various aspects of materialsconsistency over large deposition areas. Deviceprocessing and performance charactaristies will bediscussed briefly.

A6 ANOMALOUS HALL EFFECT ON n-TYPEH30 gCdfl 2Te GROWN BY THE SOLID STATERECRYSTALLIZATION TECHNIQUE

J H Basson and H BooyensNational Institute for Materials Research, CSIR

Anomalous Hall curves have been obtained for thicklow-doped n-type Hg o.sCd 0.2 Te samples grown by thesolid state recrystallization technique. These curvesare of such a shape that the 77 K value of Hallcoefficient is significantly lower than that at verylow temperature, contrary to theoretical predictions.These results are explained in terms of a p-type coresandwiched between two n-type surface regions.

67

A T TH« GROWTH OF AlGaAa BY MOVPE

D Raubanhaimer. A W R I*itch and J S Vtnutk

University ofPhysic* DepartmentElizabeth

Port

Th« presentation reports on the MOVPE growthof AlGaAs from trimethyl gallium (TMG),triaethyl aluminium (TMA). and AsH,. The mostcritical growth parameters appear to besubstrate temperature, and the ratio of inputpartial pressures of AsH, to TMG plus TMA,i.e. the V/III ratio. Doping techniquesutilizing dimethyl zinc (DM!) and H.Se willalso be discussed. The properties of theepitaxial layers were characterized by Hallmeasurements, photoluminescence and opticalmicroscopy. The variation of these propertiesas function of growth parameters will bediscussed.

A8 SURFACE LAYERS OH f t FORMED DURING PLASMA

W1TRIDIHG STUDIED BY XPS ANO EELS.

M i l l Strydon - NINR, CSIR.

AnoMlous compound surface 1ay*r growth Is observedduring plasma nitriding of ferrous materials undtrcertain operating conditions. The formation of an Ironoxy-nitride laytr by the redeposition of sputttrtdcathode material was found to Influence the growthkinetics of the ?'-Fe,,N layer which forms during theplasma nitriding of a-Fe to the extent where the v'-Ft.Nsurface layer In i t ia l ly increases and subsequentlydecreases in thickness after deposition of the Iron oxy-nitride layer. The nature of these layers were studiedby XPS and reflection EELS to elucidate the electronstructure of the valence bands of these compounds.Results are shown which explain the thermodynamicstability of the iron oxy-nitride layer and the apparentde-nitriding effect that this layer formation has on theunderlying Y'-FeHN layer.

A9 THE GROWTH OF AlGaAs-GaAs QUANTUMWELL LAYERS BY MOVPE

A W R Leitch and J S Vermaak

Physics Department,Elizabeth

University of Port

Metal-organic vapour phase epitaxy (MOVPE) hasin recent years proved to be a techniquecapable of the growth of layers havingthicknesses of atomic dimensions. The growthby MOVPE and the characterization of suchquantum well layers, using the AlGaAs-GaAssystem, will be discussed.

A10 THE ROLE OF AH INTERFACIAL LAYER OF Ni INAuGe OHMIC CONTACTS TO GaAs

A P Botha*. E Relling*. and R G Capperthwaite*"National Institute for Materials Research, CSJR•Schonland Centre, University of the HltwctersrandThe quality and electrical behaviour of AuGe olaticcontacts to GaAs depend critically on the role Ni playsas a wetting agent. The atomic ratio of Ni to Ge In-fluences the distribution of the Ga in the alloyedcontact layers. It is well accepted that the Ge plays amajor role in the lowering of the contact resistance.Not only does the relative amount of ¥.1 that is presentin the metallization, determine the ohmicit.y, but alsothe initial position of the Ni layer is critical to tnefinal state in which the Ge is available. In soae casesa nickel germanide forms in such a way that Ge is beingtrapped away from the interface where it is needed toinitiate one of the possible mechanisms in lowering thecontact resistance.

In this investigation the Ni/AuGe/Ni/GaAs system wasstudied as a function of interfacial Ni layer thicknessand the contact resistance was correlated with theatomic distribution of the Ge.

All EFFECT OF ANNEALING ON THE1.49 eV BAND IN SEMI-INSULATINGLEC GaAs

H L Ehlers, J S Vermaak and A W R Leitch

Physics Department,Elizabeth

University of Port

In this paper the influence of rapid thermalannealing on the dominant residual acceptor,carbon (1,49 ev) in undoped semi-insulatingliquid encapsulated Czochralski (LEC) GaAs isreported.

50 mm Diameter undoped 1100) GaAs wafers fromtwo different vendors were examined andcompared. Annealing was carried out at 650#Cfor 2 sec in an argon ambient. The radialdistribution of the 1.49 eV band was determin-ed using a 10 K scanning photoluminencesystem.

A12W 0 Barnard

METALLURGICAL AND ELECTRICAL INVESTI-GATIONS OF Au-Ge 8ASED OHHIC CONTACTSTO n-TYPE GaAs

J B Malherbe* and A J Willis*•National Institute for Materials Research, CSIR•Department of Physics, University of Pretoria

Metallization systems based on Au-Ge have been usedextensively to form ohmic contacts to n-type GaAs.Different fabrication techniques are being used inpresent day contact formation such as furnace alloy-ing, sintering, ion beam mixing etc. fn this investi-gation furnace alloying and ion beam mixing were usedto form Au-Ge based ohmic contacts to n-type GaAs.The contacts faoricated in this way were both studiedby means of Auger electron spectroscopy and ion beametching, while current voltage measurements were alsoperformed on these contacts. The results obtainedfrom the above measurements will be given and dis-cussed.

68

SOLID STATE PHYSICS ANO MICROELECTRONICS

H Booytns, NIMR/CSIR

Tht phrast "high technology" has become practicallysynonamous with tht fitid of microelectronics. While It1s popular to vitw microelectronics as tht domain oftht electronics tflg1nt«r. Solid Statt Physics Is thtcrucial undariying science that makes It all possible.Tht history of microelectronics-related solid stattphysics will bt nrtstnttd. S O M of tht excitingdevelopments art discussed and some views vtnturad onthe futurt.

A13 HALL MEASUREMENTS ON UNOOPED 0MVPE-6R0WNGaAs

R ThavarNational Institute for Materials Research, CSIR

Fro* the Hall analysis of a semiconductor Material,the carrier concentration and mobility may be deter-mined at various temperatures. For this purpose astaple and efficient Hall system is used to charac-terize OMVPE grown GaAs at the NIMR. Tht system iscapable of both 30UK and 77K measurements of the GaAssample on which annealed tin dots »rt used for onmiccontacts. Results show that high purity OMVPE layersgrown under identical conditions have differingmobilities and carrier concentrations for differentepilayer thicknesses. The accuracy of results forthicknesses below S microns is also questionable,however, the system shows excellent reproducibilityof results. These characteristics and limitationswill be discussed.

THE GROWTH OF PORXFIBD POLYCRYSTAL-LINE SILICON IN GRAPHITE

CRUCIBLESMELee*, A M Letsoalo*. J G Jantsky1 and S Hart*•Electron Microscope Unit, University of the North+ Physics Department, University of the North• NIMR, CSIRThe use of polycrystalline silicon as a photovoltaicmaterial is well known. Firstly, in the growth ofsilicon the choice of crucible material is criticalwith respect to tht chemical reactivity and therelative thermal expansion coefficient. Secondly,it is essential to characterize this material in termsof it's crystalline structure, optical and electronicproperties and Impurity concentration.In this paper the recasting of purified metallurgicalgrade silicon in graphite crucibles will bt described.This will bt followed by the presentation of resultsfor the characterization of this material.

A15 SKUIFSLYTASIE EIEHSKAPPE VAN VERSTUIWINGS-1OONPLATEERDE PLATINUM LA6IES

D J dt wet tn A Hells, NIMN, VMNR

Tydens vtrstuiwingsioonpiatering word 1> eenvoudige ge-lykstroom gloei-ontladina In argon-gas gtbrulk omplatinum vanaf "n katode (skyf) deur d1t prosts van loonbombardtment (verstuiwing) oor te dra na "n substraat1n D sagte vakuuM kamer. Ioonplatering word gewoonlikgebrulk om goele adhesie tussen die lagie en die sub-straat te verkry.

ti Klein verstuiwingsioonplatering-sisteem Is ontwerp enself vervaardig om dun platinum lagits teen it lae kosteen relatiewe lae tegnoiogie te vervaardig. Die wry-wings- en slytas1e-e1enskappe van hierdie platinum ge-plateerde opperviakke Is bestudeer tydens skuifsiyt-toetse met keramiek-, metail- en Pt-geplateerde balleonder droe en gesmeerde toestande. Die slytasie-groewe1s gekarakteriseer met behuip van SEM- en AES-tegnicke.

A 4 C DETERMINATION OF IMPURITY CONCENTRATIONSM i l l IN POLYCRYSTALLINE SILICON BY MASS

SPECTROMETRYO.E. Rogers*. M.E. Lee*, O.A.A. Engelbrecht0

* NIMR. CSIR* Electron Microscope Unit, University of the North0 Physics Department, University of Port ElizabethThe major difficulty encountered during the purificationand growth of polycrystalline silicon is the determina-tion of the impurity concentrations in the ppma range.

In this paper the technique of nass spectrometry usinga glow discharge source for the analysis of impurityconcentrations in polycrystalline silicon will bediscussed. This will be followed by the presentationof results for the analysis of metallurgical gradesilicon, purified silicon and recast polycrystallinesilicon in various crucible materials.

A17 ELECTRICAL ASSESSHEHT OF SIN LAYERS OH

c » milsNational Institute for Materials Research, CSIR

SIN is used extensively In the GaAs Industry as anencapsulant and dielectric overcoat. It Is Importantto know what the electrical properties of a depositedSIN layer art in order to model the fabricateddevice/circuit properly. The work done here was donewith this aim in mind. Capacitance - voltage (C-V)V M ) thermally stimulated capacitance (TSCAP) measure-ments were made in order to characterize the SINlayer and the GaAs/SIN interface.

A18R J Gu—ow and I SigaiasNational Institute for Materials Research, CSIRPyrophylHte and t»lc are widely used as pressuretransmitting and gasket materials In high pressuresynthesis and related techniques. For the thermalmodelling of such processes, the high pressure, hightemperature thermal conductivity 1s an Important Inputparameter. Results arc presented for both pyrophylHtcand talc e. a function of temperature and pressure Inthe ranges 0-2.5 GPa and 300-850 K, which .were obtainedby using the hot-wire technique. The trends observed arcdiscussed In the light of the current understanding ofthe structure and chemistry of tftse materials.

A19 THE PASSIVATION OF (HgCd)Te SURFACES

C J Botha. M A Marais. R J MullerNational Institute for Materials Research, CSIR

The semiconductor material (HgCd)Te is widely usedfor the production of infrared detectors operating ineither the photoconductive or photovoltaic mode.However, as a result of the reactive nature of-itssurface, the cerformance and long-term stability ofsuch devices are severely limited by surface relatedphenoaency. The development of a suitable passivantfor the (HgCd)Te surface is thus of great technologi-cal importance to device performance.

Preliminary work as regards the passivation of'HgC<)Te material produced at the NIMR has been doneand will be discussed briefly.

A20 ELASTIC CONSTANTS OF ONE GLASS AND ON|GLASS CERAMIC

S Gravett, I Sigaias and P R ClaytonNational institute for Materials Research, CSIRThe elastic moduli of one glass, Photogrcy, and oneglass ceramic, Zerodur, have been measured as a functionof pressure. An ultrasonic pulse echo overlap techniquewas used up to 2 GPa. The glass shows an unusualbehaviour due to Its chemical composition. Thelongitudinal modulus and the shear modulus decrease withpressure, but the bulk modulus increases. The glassceramic shows a phase transition at l.S GPa.

A21 LASER EPITAXY OF DEPOSITED SILICONTHIN - FILMS ; CHANNELING AMDELECTRON MICROSCOPY MEASUREMENTS

D. A<Um»*. D. KnocMtn* and R. Pretorius** Physic* Department, University of the- Western Cap*,

Bellville.* Ion-solid Interaction Division, National Accelerator

Centre, Faure.

Pulsed laser irradiation (Ruby laser - pulsewidth 30ns)of amorphous silicon films deposited onto single-crystalsilicon substrates was carried out in an attempt to obtainepitaxial growth of the amorphous silicon. For good epitaxyit is necessary that complete melting of the amorphoussilicon layer and some of the underlying single crystal silicontakes place. Channeling and electron microscopymeasurements were carried out to test the crystallinityof the deposited silicon layer before and after laserirradiation.

A22 BEHAVIOUK OF THE TUIUIAHCLE OT PTSHOSIPHNEAR M I C * * C PHASE niAWSlTl0s7

f de ? du rlassis. «AO, G I T Brits, A K

The lubject of iacoasMnsurata (IC) «-> cosBMnsurace (C)phase transitions has, sines the pioneering work ofFrank and Van der Herve, been actively studied (or adiversity of physical systems. Fisher and Tithaiusing Man-field theory predicted that the deviationof the IC wave vector from Che wave vector in thecoaaensurate phase has a logarithaic dependence on thereduced Ceaperacure t • (J-Tc)/?c. Theodorou question-ed Che validity of this logarichaic behaviour andshowed chat che experimental result« for Ho racherobey a 8-exponenc power law. Neutron scatceringnejsureaents of che helical incerlayer Curnangle ofDy near chc IC (helical) ~ C (ferroaagnccic) phasecransicion were performed and che results vill be cost-pared with the preceding prediccions.

70

A23 DOPING OF SIUCON BY LASER-INDUCEDDIFFUSION

frfr Marata, M.S. AUI«« and R. Pmtoriua

to»>totld Int«racttoB Division, Van de Gruff Croup, NAC.Paw*,•Dtpt. of PayaJlci, Univeriity of Cape Town.Very ahafl> "•* *»»Uow dopant profUit can be obtained byutilising 1*MT doping of semiconductor*. Such profile* aredesirable fcr producing solar cells and special typei ofmicroelectronic device* such aa IMPATT diode*. Thin antimoaylayers fc 50A thick) were evaporated onto single crystal siliconsample* aad irradiated with a pulled ruby laaar (wavelength• 6940A, pulMwidtb « 3 0 M ) . During melting of toe Mrfacai-egion interdiffwion tftkai place with the Sb being trappedin Uw silicon (attic* upon solidification. B«cauM of thenon-equilibrium nature of the proc«M, dopant conccntratiouZ to 3 orden of magnitude greater ;han the normal valuecan be obtained. Channeling of charged nuclear particle*,show that nearly all the dopantt occupy subatituiional sites.Tncs* result* are compared with theoretical modelling oflaaer doping.

A24a H F Hrlta. AtC, t d ¥ du rlaaat*, UU

The critical behaviour of the alowoldal —paramagnetic phaae tranaltloa aa eihlbltrt by tx atTH - W.OR baa until now attracted only Unite*theoretical and experimental acttntloa. Hlgoraaolutlon peak atutxoa Maaurewata takes abascycling up and down In temperature through IVIndicate a contlnoua tranaltlov without anynyatereala. Integrated neutron a«s«u;«a«ot« pertenwdbetween 90.9K and 8».5K give a critical eipoamt v •l .a aad a 9-espoaent that cshlbtta a crossover ttom •value of 0.37 when only •eaaureaenta near TJJ aseIncluded In the analyala to a value of 0.4& for Checoaplet* teaperature range studied. The lnveatlgatlonof the critical behaviour waa further auppleawnted byultrasonic velocity and attenuation Maaurcacats.

A2S BURIED ANTIMONY PROFILES IN SILICONFORMED BY LASER DOPING

a. Carollasen. D. Knoesen*, M.J. McG«trick* and R. Pretorius

Ion-solid Interaction Division, Van de Graaff Grctm, NAC,Faure.•Physica Department, University of the Western Cape, Bellville.

To obtain buried dopant layers in semiconductors, it U usuallynecessary to grow an epitaxial layer of the semiconductormaterial after doping. By irradiating a Si < 100> /Sb (50A/S1-amorphous (2000A) structure with a pulsed ruby later, it isenvisaged to carry out the doping and epitaxy process in asingle step. Theoretical heat-flow calculations have beencarried out far this structure, in order to determine thetemperature profiles in the sample during pulsed laserannealing. ThU information enabled us to determine themelt-depths a* a function of laser energy and the, solidificationvelocity. The dopant profiles were measured by RutherfordBackscattering Spectrometry of charged nuclear particles,while the quality of the epitaxial layer has been determinedby using the channeling effect as well as electron microscopy.

A27 EVIDENCE OF MULTILAYER STRUCTURE INAMORPHOUS SILICONJ.Aucaap and R. "Swantpoel, RAU.

In the literature it is generally itsuocd that a-Si:Hi* a homogeneous material. Very tittle research hasbeen done on the effect that variation in thickness ofthe thin films has on the optical and electrical pro-perties. By investigating the electrical conductivityand other physical characteristics, especially at thesubstrate-fila interface, it is reported in the litera-ture that the possibility of an intermediate layer atsubstrate-fila interface does exist.

The effect of film thickness has been studied by growinga-Si:H thin films of various thicknesses and characteri-sing them by scans of ellipsometry. It was found thatthe results could only be satisfactorily explainedusing a two layer model for the a-Si:H film. Approxima-tely the first 1000A of the fila was found to consistof one type of material while the bulk of the filmconsists of a second type of material. These resultswill be discussed for Corning 70S9 as well as c-Sisubstrates.

A26 ELECTRICAL RESISTIVITY OF DILUTE(Cr,-xAtx)95Mos ALLOYS ~

P. Sait and H.L. AlbertsDepartment of Physic*, Rand Afrikaans UniversityThe temperature dependence of the electrical resistivity(0) of (Cr.__A«x)9cHoe alloys with x • 0.113, 0.441,O.77Z, 1.492, 2.07Z, 3.111, 4.841, 7.312 and 1O.63Z,wa* measured in the temperature range (4-500) K. Aremarkable phenomenon wa* observed, namely that theaddition of SZ Mo to Cr-A< completely supresses anti-ferromagnctism for ZZ < x •€ 62. The non-magneticbehaviour of o of the antiferromagnetic alloys (x«0.11Z,0.44Z, O.77Z, 1.492, 7.312 and 10.632) wa* determinedby using the temperature dependence of the alloys withx • 2.O7Z, 3.112 and 4.842 that remain paramagnetic atall temperatures, as a model. This allowed ui toanalyses the data in terms of existing theories. Rela-tive good fits were obtained with theories for both thelow and high temperature behaviour as well as for themagnetic contribution to o.

A28••o

STUDIES OF ELASTIC CONSTANTS OfAT HIGH TEMPERATURESJ.D. Comins0 and A.G. Every0P.E. Sgoepe

+ department of Physics, University of the (northo Department of Physics, University of the WitwatersrarW

Brillouin scattering studies of the fast-ion conductorLaF, have been carried out in the temperature range

300-1400 K. The frequency shifts associated withmodes in the various phonon propagation directionsshow a linear decrease below 1100 K, followed by anarked reduction above this temperature. Significantchanges in the frequencies related to separateelastic constants are also noted around the sametemperature. The results are discussed in terms ofanharmonic effects and the cooperative generationof disorder.

71

EFFECTS OF RF-SgyTTERHIC PROCESS PARA-METERS ON tiiE OPTICAL CONSTANTS OF

J.Aucaap and K. Swanepoel, RAU

IC i* wall known from tha literature chat Cha opticaland alactrical characteristics of a-Si:H thin filae araaffected by a change in eh* praparacion condition*. Tooptically charactaria* a-Si;H thin filat a* a functionof thickness and rf-sputt«ring power, tha followingpreparation condition! wara leapt constant: Growth pro-cess (rf-sputtering), chamber geometry, Ar-Hj ga< ratio,gas flow rate and substrata temperature.Through calibration of tha system, it was found thatother preparation conditions also affacts tha charac-teristics of the thin films. The effects on film growthwill be discussed with respect to the "gas flow effect",the geoaetrical form of the substrate, the geometry ofthe chamber and the type of substrate used. The opticalcharacteristics will be discussed as a function of filathickness and rf-sputtering power.

From these results it can be seen that correlating re-sults between two or more different laboratories teadsto a difficult task with many factors affecting results.

A31 ELEKTRIESE GELEIDING EN FOTQGELEIDXNGVAN AMORFE SILIKON

J.J.R. Prinsloo en R. Swanepoel, RAU

Die elektriese eienskappe van a-Si:H is iterk afhank-lik van die bereidingaparameters. Verder verander dieeienskappe mec uitgloeiing na bereiding, hoofsaaklikas gevolg van verli.es aan H, en to mate van kristal-lisering.

Die elektriese geleiding sowel as foto-geleiding vanrf-verstuifde silikon is as funksie van temperatuurgtaeet. Die effek van uitgloeiing en lagiedikte isook ondersoek. Die verandering in elektriese gelei-dingsvermoe en bandgaping sal bespreek word. Eksperi™aentele bepalir.g van die werklike temperatuur van dielagie op die verhitte substraat sal ook toegelig word.

A30 soon>RTt iKRADIATEU KC<: Na CRYSTALS

A.M. Mdnbuka and J. I. Seratlo, Departaetit of PhvslcsUNIVERSITY Of FORT HARE.

n In 8T A- *na JF> irradiated iCi: Na O25U f>wn> ha*sten examine J. Tha orocaxsas involved durini. lu roilot.:irst-oruer kinetics. It is suggested that the<t«0 na band oaak found in oura vaaplas is rasoivedoartiallv Into 300 na and 430 na band oeeks InN«-doo«d samples. Tha frequency factor

H O S* ) obtained favours recombination via theconduction band.

A32 THE THERMAL STABILITY OF SOME IANTHANIDENITRATES

C. Strydom, C.P.J.van Vuureo,

Department of Chemistry, University of Pretoria.

The temperature where decomposition starts when usinga heating rate of 5'C.min"1 is used as a relativemeasure of the thermal stability of tore lanthanidenitrates.. The reaction enthalpy values at atmosphericpressure and a pressure of 5 x 10' kPa showedremarkable differences, due to reversible processes,occurring during the decomposition reactions. Thenumber of temperature dependent reversible processesare determined using the kinetic rate constants forthe isothermal reactions in Arrhenius plots. Anincrease in the number of temperature dependentreversible processes, as well as the increasinginstability, when moving down the lanthanide series,could be due to the lanthanide contraction.

A33 GROWTH OF GaAs EPITAXIAL LAYERSUSING CURRENT CONTROLLED LIQUIDPHASE EPITAXY

V J Watters, J S Vermaak and A W R Leitch

Physics Department,Elizabeth

University of Port

Control of the growth rate for submicronlayers using conventional liquid phase epitaxy(LPE) has been a persistent problem in thepast. This paper reports on liquid phaseelectro epitaxy (LPEE] where an electriccurrent across the solid-liquid interfaceinduces Peltier cooling (or heating) at theinterface. Because c; the localised nature ofthis coding (heating) effert at theinterface, much more accurate control of thegrowth rate to produce submicron layers can beachieved. The design and construction of sucha system and the initial results obtained withthe LPEE reactor will be discussed.

A34 MAGNETIC EFFECTS IN DILUTE Cr-Si ALLOYS

H.L. Alberts and J.A.J. LourensDepartment of Physics, Rand Afrikaans University

Measurements have been made of the thermal expansionand elastic constants of seven Cr-Si alloys in the con-centration range from 0 to 3.A2 at.X Si. The resultspoint to the absence of a re-entrant feature in thevicinity of the triple point where the paramagnetic (P),commensurate (C) spin density wave and incommensurate(1) spin density wave states coexist, favouring thesequence of phase changes from P to C to I. The firstorder C-P transitions are marked by discontinuities inChe thermal expansion and by large ultrasonic attenua-tion near TN. Calculated latent heats associated withthe first order transitions compare uel} with directmeasurements. Application of existing itinerant elec-tron theories to the magnetoelastic iaca does not givethe correct concentration dependence of the magneticmo&ent and Nee I temperatures.

72

;*««:r

A35 r pwMTIGATIOH INTO TW MICHAWiaw OfgnwftflOM OF IPITAXIAL Pd,Sl

J.C. Liut and J.M. Hayart

•J ii which has t haxagonal cloaa packed structura,• M O T * " ' 1 ' 1 ^ o n S i * u l > substratas bat not on tlM

5 h M S e w •* tilicon. Thtn Ta and Ti fllaa hava been• * T M inert aarker» to aonitor tha growth process of

itaxial Pd»Si. It « u found that SI Is tha dominant2 . U K • p a d " d« l n» «Pit*xlal »iUeid« growth. It2 , i3«o found that polycrystalline Pd,Sl will re-orderITbacoae epitaxial during slllcida growth. Thi»M-ordaring is due to th« growth process alona and ianot dwa to tharaal effects, indicating that Si ia vary•nfcila during alllcida growth. Sinca only Si vacancydiffusion would result In high Si aobility it is arguadthat the findinga atrongly auggaat that Si dlffusaa by» vacancy machanlia during epitaxial Pd,Sl formation.

A36 TION

t. M. Miwarat. J. R. Saretlo anda. H. Mdabuka*

t Now in tha DspartMnt of Physics, University of thaVltvatararasd

* University of Fort Rara

Tha annealing of intaratltlala In XC2 cryatala doped withdivalent and aonovalent iapurlty atoas (Ca and Na re-spectively) has baas invastlgatad by various worker*.Froa tha activation anargy spactra obtained by Hdabuka,two additional paaks aaaoeiatad with lntriaslc trapsaawrgad. In this papar an attaapt is Mda to undarstandwhich of tha two paaka ia affactad by plastic datama-tion, and why. This was aehlavad by calculating acti-vation anariy spactra on plastically daforswd undopad KC1crystals. Tha rasults ara axplainad in tana of a pref-arantial trapping aodal.

A37 HIGH TEMPERATURE APPUCATIONSCHOTTKY CONTACTS TO GaAa

OF

»• ReUing, A.P. Botha and R. Pretoriua*

National Institute for Materials Research, CSIR, PRETORIA*Ion-aolid Interaction Division, Van de Graaff Group, NAC,FAURE

To integrate G»A» MESFETi on a very Urge scale, aMlf-alignment fabrication technology has been developedahica involves a high dosage implantation through a gatemetallisation. Annealing temperatures >800*C are requiredto activate implanted dopanta. Since GaAs degradation occur*above 600* C, annealing muit occur using a suitable encapaulantto prevent arsenic evaporation. The excellent stabilityexhibited by metal filicide* at high temperatures makes themauitable to form Scaottky contacts on GaAs. In this study,ire used cobalt filicide for the gate metallisation with Sias an encapiulant. Rutherford Backacattering Spectroacopywas used to study the chemical atability of this system. Someof the problems encountered as well as the electricalcharacteristics of the contact will be discussed.

A38 £11ACTION STUDIES OF

MDUCT1NG KIOHUM-TIN ALliiVSHearne and 1. Kolk

Oapartasnt of Physics and Condensed Mattar PhysicsResearch Group, University of tha Vitwatararand

HSssbauer-affact (HE) aeaaureaents ware carried out onHbtSn and NbSn, at taaparaturas between 300 K and 4 K toexaalae anharaonlc effects in theaa interaatallic alloys.The aaaauraaeats were perforaed on superconducting tapecontaining both Nb-Sn alloys as well as pure tin. Thisallows us to coapare recoilleis fractions of tha "*Snatoas ia tha various Nb-Sn phases with those of "*Snatoas in Sn which are accurately known. In our previousanalysis of thlt data, tha recoilless fractions of the

Sn atoas In tha various tin phaaas were detcrained •-as Is often done •- froa the absorption areas of the HEspectra. Mere we report on an iaproved aethod of ana-lysing HE spectra which takes Into account saaple thick-ness affects. These effects, if Ignored, asy lead to anIncorrect estiaation of the recoilleas fractions. Ournew analy*is provides us with sore reliable values of theanharaonic Constanta of the lnteratoaic potentials in thevarious phase*.

*«A Co; AMD Ni-SILICIDE FORMATION INA " a ? 9 THE PRESENCE OF GOLD

H.A. Ras*. J.J. Crufwagen* and R. Pretorius 4

•National Institute for Materials Research, CSIR, Pretoria

'''Chemistry Department, University of Stellenboich4Ion-*olid Interaction Division, Van de Graaff Group, NAC,Faure

Although relatively inert in metal silicide matrices, goldcan be treated as a special type of impurity that affectssilicide formation through the very low Au-Si eutecticat 3?2*C. At temperatures close to and above this value,,the Si atoms are dislodged from the covaient Si-latticeto become "free" and highly mobile in the solid statestructure. Because of this increase of the effective Siconcentration, f'.e mechanism of Co-silicide formationchanges to operate in a lower temperature range and toproduce a different phase sequence, relative to the no-goldcase. No such drastic effects could be measured for thepresence of gold during Ni-silicide formation. An explanationfor this different behaviour, exhibited by the Co-Si andNi-Si systems, ia given in terms of the intrinsic diffusivitiesof the two systems.

A40 PHONON FOCUSING IN PIEZOELECTRIC CRYSTALSA.G.Every* and A.K.McCurdy*

*Physics Department, Witwatersrand University*E.E. Department, WPI, Worcester, Mass. U.S.A.

Striking changes are predicted in acoustic vavepropagation and the phonon focusing properties ofpiezoelectric crystals as a result of piezoelectricstiffening of the elastic constants. Monte Carlophonon focusing patterns are preserved for a number ofstrongly piezoelectric crystals. It is shown that thedegree of the equation of the slowness surface israised from 6 to 12, and that as a result, fast phononbranch focusing caustics are permitted.

73

A41 THE EFFECT OF OXYGEN IMPURITIESON THE SOUP STATE INTERACTIONBETWEEN THIN Pt-FILMS AND SILICON

M.A. Wandt and R. Prttorius

ton-tolid Interaction Division, Van de Graaff Group, NationalAccelerator Centre, FAURE.

Platinum lllicidet formed during the solid-state interactionbetween thin Pt-fllm* and silicon are important ai contact*in micro-electronic devices. The silicide phase which formsfirst is PtjSI, while PtSi forms at higher temperatures. Inthis study we have investigated the effect of oxygen impuritieson platinum silicide phase formation. Oxygen doping of thePt or Si films was carried out by introducing oxygen intothe ultra-high vacuum system during evaporation. The kineticsand sequence of phase formation upon subsequent heatingwas investigated by using Rutherford backscattering of chargednuclear particles. The observations were evaluated in termsof the effective heat of formation theory (1).

(1) R. P^itoriui, Material ResearchVol. 25 page 15-20 (1984).

Society Proceedings,

A42 RAMAN STUDIES OF IRRADIATED KI AND KI(Sr>

A.M.T. Allen, C. E Allenspach and J.D. ComlnsDepartment of Physics, University ofWitwatersrand, Johannesburg

the

Annealing experiment* have been carried out on KI andKKSr) after gamma-irradiation at room temperature.Studies of defect concentrations were made using bothRaman and optical absorption methods. The Ramanresults show that the trapped halogen interstitial*are in the form of large iodine aggregates. Thekinetics of the defect annealing behaviour is studiedin detail using various annealing routines andincluding a Primak-type analysis.

A43A44

Ni-Si SOLID-STATE REACTION : FORMATIONOF SILICON-RICH LAYER WITHIN NiSi;IN THE PRESENCE OF EXCESS AMORPHOUSSILICON

J.E. McLeod. H.A. Ras* and R. Pretorius

Ion-solid Interaction Division, Van de Graaff Group, NAC,Faure.'Electronic Materials Division, NIMR, CSIR, Pretoria.

Thin film structures with the configuration Si<100>/Ni/Si(a)were prepared and heated in a vacuum furnace at temperaturesranging up to 800* C. This enabled us to compare silicideformation with single crystal and amorphous silicon in thesame sample. It was found that if the amorphous siliconis present in excess amounts, the remaining surface silicondiffuse* through the nickel silicide to regrow on the Si <100 >substrate, as well aa forming a Si-rich layer within the silicide.Experiments, to account for this behaviour are described.

A45 •N STUDIE VW DIE Pt/Si DUNLAGIE SISTEEMTUSSEN 750"C EN 1000'C.

GLP Berning en CW LouwDepartement Fis ika, UOVS

pt/pol i -Si /SiO 2 /S i (100) monsters i s gebruiJc net d ie Ptlagie ICC run en die pol i -S i lagie 400 ran dik. Onder:000*C diffundeer nie Pt of Si deur die SiO2 lagie n ie .Monsters i s by vaste temperature tussen 750*C en 1000°Cjehcu vir 10 ram in 'n N2 atmosfeer. Auger dieptepro«r ie l e i s gemeet. 'n ?t /S i lagie groei by 7SC°C en i sstabie l tot omtrent SSO'c die laagste eutektiese tem«oeratuur van die Pt-Si bine're sisteem. Na verhittingby temperature tassen 33C°C en ongeveer 9508C verhoogi i e Si kcr.sentrasie op die opperviak terwyl die Ptkor.ser.trasie hoer i s naby i i e SiOj lag ie . sokant950°C i s i i e kor.sentrasie van die Si en die Pt (constantmet diepte tot by die SiO2 lagie . .Va verhifung by1300°C in Nj vir 5 ain is 'n 150 A0 SiO; lagie op iieoppervlak gevorm. 3y veraere c<sidis ie vortn suiwerS1O2. Indien die '.50 A° 3iOj lagie eers afge#':s wordvoor oksidasie bevat die SiOj lagie omtrent 2Z\ en 'noormaat suurstof.

L S_IT_E_L._QCATION..QF DOPANTS1_N .GAAS_ BY~ ELECTRON CHANNELING.

i---1-_Shenne, H.C Snyman, C . A . B . B a l l , and H.Smith.Department of Physics. Univers i ty of PortElisabeth.

The electrical activation of dopants in semi-conductors is determined Oy their incorpora-tion into substitutional and/or intersti t iallattice sites. In principle, measurements ofthe ratios of the matrix and impurity X-Rayelectron-induced yield at various crystalorientations lead to the determination of theimpurity concentration and its atomic site.This paper reports on the influence of theelectron beam, imaging and spectrometer para-meters on the sensitivity of the technique.Theoretical calculations of the transmittedelectron wave intensity with depth in thecrystal are also used to optimise the experi-mental conditions as far as specimen orienta-tion and thickness parameters are concerned.

\

A46 A TEM STUDY OF THE STRUCTURE OFANNEALED NITROGEN - IMPLANTEDSILICON

H C Snyman, B P Z e e l i e and J H Neethl ing

Department of Physics, University of Port Elizabeth

Nitrogen implantation of silicon is a prcmisir.gtechnique of forming bu'ied insulating layers. In this

paper we report on the structure of 150 keV, 10 N+

an' implanted layers as a function of laser, rapidthermal and conventional annealing paraneters. TEMshows that, depending on the annealing paraneters, therecrystallised zone may consist, frcm the surtaceinwards, of a single crystalline surface layer, a largepolycrystaliine, a macrocrystalline and an amorphouslayer. Various models are presented to describe therecrystailisation processes for different annealingconditions and i t i s ilc^n that twinning is dominantwhen melting does not jeeur.

74

A47 DIE EPITAKSIALE CROEI VAM Cr OP Ati111 )SUBSTRATE.

K.G. vao dar Barg «o H.L. Gaigher

Di« oriantatia an norfologia van opgcdaaptaCr(gaaiddtlda dikta 11.5 tot 20 na), gevora op Ag{ l l l }substrate in ultrahoë vakuua (~10"' torr) , i i daur•iddal van daurstraalalaktronmikroikopit tn elektron-diffrakaic ondersoek. Substraattanparatura waa in dieberaik 25 tot 290°C. Orientasie varwantikappa sal intaraa van suiwtr gaomttriesc modelie, an van dar KarueI« ccoric, wat a l a s t i s i t e i t van dia oproeisel in agoaaa» baapraak word.

A48 DEEP RAMATÏON DAMAGE IN META1.S AFTER IONIMPLANTATION

E. Friadland and H.H. Albert!

Dapt. of Physics, University of Pretoria

The depth of radiation damage in copper and platinuahas bean analyzed after implantation of different ionswith energies ranging bctwtep 50 keV and 150 keV atrooa 'emperaturc. Th* damage range entends ouch deeperthan the projected ion range and depend* primarily onthe ion energy. Possible reasons for deep radiationdamage will be discussed. '

A49 IDENTIFICATION OF DEFECTS BY MEASUR-ING THE IN-PHASE (I) AND QUADRATURE(Q) DLTS SPECTRA DURING A SINGLETEMPERATURE SCAN (IQ-DLTS).

f.D AURET and M. Nel, Physics Dept. UPE.

A simple method of analysing the transientsignal observed during deep level transientspectroscopy (DLTS) is presented. In thisMthod, IQ-DLTS, the transient is analysed byrecording its in-phase (I) and quadrature (Q)DLTS spectra by using the corresponding out-put of a two-phase lock-in amplifier with asine wave mixing function. Measurement of thepeak positions on the I- and Q-spectra, whichare simultaneously recorded during a singletemperature scan, facilitates the calculationof the defect activation energy and capturecross-section,which are required! for its iden-tification.

A50 IOONINPLANTERISC IN At:Si-KONTAKTE

B.A. Carr, J.3. Malherbe, E, FriedlandDepartement Fisika, Universiteit van Pretoria

OpgedampCe /iluminiumkoncakce op n-Si is met verski Uende

ione (Ar*, Xe*, Si*) geînplanteer. Elektriese (I-V)

metings voor en na inplantering is gedoen.

A51 IMPROVEMENT OF SEMICONDUCTORMATERIALS BY MEANS OF DEFECTENGINEERING

L W Snytnan

fhysics Départaient, University of Port Elizabeth

The thermo-dynamicai behaviour of defects during deviceprocessing has important implications In various fieldsof the semiconductor technology.

In the presentation the interaction mechanisms betweenextended detects (eg dislocations) and point defectswill be discussed. Experimental results obtained from arecent electron beam induced current (EBIC)investigation (which enables the high resolutioninaging of the electrical activity ir. a semiconductorcrystal) will be presented. Existing detectengineering techniques will be evaluated and new defectengineering techniques will be proposed to improve theelectrical activity in a semiconductor crystal.

A52 DIE MODIFIKASIE VAN Si-Si SCHOTTKV-

KONTAKTE MET BEHULP VAN IOONBUNDEL-

VERMENGING

G. Myburg, J.B. Malherbe, E. Friedland

Departement Fisika, Universiteit van Pretoria

Metaal-silikon tussenvlakke speel 'n belangrike rol indie elektroniese nywerheid en gevolglik is dieontwikkeling van metodes vir die vervaardiging vansulke kontakte met bepaalde elektriese eienskappe vantegnologiese belang. Iocnbundelvermenging, deur middelvan die inplantering van ione deur opgedampte Si-kontakte op enkelkristal silikon, is ondersoek. Dieeffek van inplanteringsdosis op die eienskappe vangenoemde kontakte sal met dié van ongeïnplanteerdekontakte vergelyk word.

75

A53 PROBLEMS EXPERIENCED WITH OPTICALFTIR CHARACTERIZATION OF GaAs ~

J A A gngelbrecht, I G Lee and A Botha

Physics Department, University ofElizabeth

Port

The determination of varioua electrical andphysical properties of semiconductor materialsby optical techniques has many advantages.Many methods are well established for silicon,but when some of these techniques are employedfor GaAs and related compounds in the infraredregion, problems are experienced. Theseinclude effects due to sample surfaces andcarrier concentrations. Results obtained forMOCVD grown samples will be discussed.

• P i IMPUKTEP nvonm w o r m s m DIAHOHPA 9 M V J.P.Print. T.E.Parry. CC.P.Hadiba,

J.P.r.Scllachop.Witi-CSIR Schonland Research Centra for Nuclear Sciences,University of Ch« Wicvatartrand, Johannesburg,South Africa.

StudU» of th« volume axpantion of diaaond ("mesagrowth") resulting from fluorin* ion irradiation ha*been reported previously by ui and explained in u n iof tha generation and notion of point defects. Themechanics of this notion will affect tha (hape andposition of the implanted fluorine profile*. Theseprofiles have now been measured directly, using theresonant "FC P . O Y ) 1 ' * ) nuclear reaction for different iondosas. The results were used to analyse tha possiblemechanisms responsible for the broadening of theinputted fluorine profile and to obtain information onthe vacancy density distribution.

THE APPLICATION OF BEJU. TIME FAST FOURIERTRANSFORMATIONS IN EDS ELECTRON MICROSCOPYD.R. SpaIding and L. Haiatry

Dept. of Physics, University of Natal, Durban.

A problea that often arises in energy dispersive spec-trometry (EDS) is the correlation of electron imagevariations with fine structure of the image generatedby means of an X-ray energy window. This paper dis-cusses the problem and shows how a personal computercan be hard wired to an EDS system to help facilitatedata interpretation.

CSPULSEERDE ELEKTRONBUNDELVERHITTING(PEV),LASER EH TEMPERATUURUITGLOEIISC VANGEfOTLANTEERDE InSb '

H W Alberts en R CilliersUniversiteit van PretoriaInSb-enkelkristalle is by 'n verskeidenheid energieeen temperature gelnplanteer met Be-ione. Dieinplanteringsdosis was cussen 5 * 10" tot 2 * 10"ione/cm2. Die anaiise is oet die RBS en kanaliserings-tegniek uitgevoer wiarin daar van 0,5 tot 2,5 HeVa-deeltjics gebruik gemaak ia. Die restourasieprosesvan die geinplanteerde enkelkristalle is ondersoekaan die hand van gepulseerde elektronbundelverhitcing(PEV), LASER en teoperatuurbehandelings daarvan.

A57 CORE-EXCITATION EDGE AND EXTENDED ELECTRONLOSS SPECTRA FROM VARIOUS CARBON SURFACESUSING LOW ENERGY REFLECTED ELECTRONS.

B.G.Maguire*, J.P.F.Sellschop*•Trent Polytechnic, Nottingham, United Kingdom.*Schonland Research Centre, University of the Witwater-srand, Johannesburg, South Africa.

The energy loss spectrum (ELS) obtained with low energyelectrons, <2 keV, reflected off clean atomicallyordered Diamond surfaces in Che near-elastic. It-edgeand extended K-edge energy regions reveals greaterstructural detail than that observed with high energyelectrons-80-100 keV-in transmission. These differingtechniques are compared and contrasted and possiblecauses for che dramatic differences observed arediscussed. Of particular significance in the loweredK-edge region are the possible diffraction effeccsencountered by these emerging secondaries. Similarresults are also presented for graphite and variouslyprepared amorphous carbon films.

A58 STRAL1NGSKADE VANWEE LIGTE IONE IM InSb

B J E van Tonder, E Friedland, Universiteit van Pretoria

Stralingskade veroorsaak deur alfadeeltjies in InSb isveral act behulp van kanalisering ondersoek.

Die invloed van die volgende fakcore op die omvang vandie stralingskade is bepaal: dosis, dosis tempo,inplantcemperacuur, isochroniese en elekcronbundel-uitgloeiing.

Die vervagce stralingskade is ook bereken deur dieTRIM- en MARLOWE-programoe Co gebruik.

'n Model vac die hoofcrekke van die resultace verklaarword aangebied.

76

AS9 L I WEAR ANO PARA80UC REACTION KINETICS INBINARY COUPLES

E C 2IM6U. M6DUNSA

Solid state reactions such «s thermal oxidation of s i l l -con and M t a i s , or mtal silicida formtion, involvtInterfacial reactions at tht phast boundaries anddiffusion of at least ont of tha rtactants through thtcompound layer.First order differential aquations ware usad to modeltht In t t r f ada l reactions whareas tha diffusion processMas modeled by a parabolic differential equation. Thefinite-difference approximation Mthod Mas used toobtain a solution to this moving boundary problem.The results suggest linear kinetics (compound layerthickness • reaction time t ) In the In i t ia l stage,followed by parabolic kinetics (thickness « t 1 ) .Th«$« predictions wil l be compared with those of similarmodels and with experimental results.

A60 Oil OEBBUHt VAH IMt P O O C H IQOWVtMTKOOI-IMG VI» O « OWOKMOeX VMI OPPEHVLAKATOOH-

GM van Wyk, Mputaitnt Plalka, UOVS, eloeBfonteinDi* verstrooling van la* energle (1 keV) edelgas- analkalie-ione word gebrulk am die lokal* rangwkiJtkingvan atom* op dla oppervlak te btpaal. Die uk»perlaen>tala op«tailing bastMn basic* ult 'n ioonbron, matta-•D enetgle-analiseardar an detektor in UHV, >«t dlafaallitelt am nagatlawa terugslagiona waar ta new.Kwantlflaerlng word bapazk daur nautrallaanle van ver«ttrooide lona. Dla toepasting van dia aetode It dlaondartoek van segregasia, vcork*urv*r*tuiwlng, gas*adaorbata an spreidlng In katallaatora. Gaordandaoppervlakstruktura kan kwantitatief waaxgeneaa word,ay laa atrooihoaka 1* dlt nodlg ca ta vargalyk netrekenaarsiaulaslas «oo» ARGUS an MARLOWE.

A61 COWUGATCT GLIPe SUM ACES AM) THE ORICIWOF EARTHQUAKES

T.J. Jackson, Physic* Department, Univers i ty o f Natal ,P ie teraar i tsburgI t haa baan known for many yaari that c r y t t a l * tkaar on• l i d a iurfaca* that art corrugated p a r a l l e l t o thad i r e c t i o n of shaar. Tha corrugation* do not run rightthrough tha Material , but and on i tep* where t a m i l aand eoapratt iva atraatea davalop p a r a l l e l t o the thaar-ing direction. In cryitela, glide occur* whan disloca-tion* tprted on cryatallographic planet. Corrugation*and ftapt for* at a reault of the crott-tlip of terewdi*location*. The propentity that glide ha* to deviateconaervativaly froa a plane i t howavar not peculiar tocrystalline tolida. Tha boundaritt of fault* can, «ndheva been, modelled with Voltarra ditlocetiona, and thel a r g f i o l * analogue of ditlocation croae>elip ihouldproduce corrugation* and (tap* on fault turfact*.Tha foratation by croaa-alip of *t*p* on corrugation*may explain tha origin of dil tional and antidilationalJogt on ttrika-alip fault*. Such jog* are thought toexert major control* on aarthquaka rupture in region*tuch a* Che San Aadrta* fault in California,

A62 'N STUDIE VAN DIE ADSOBPSIE VAN HaO OPPOLIKBISTALLYNE VLEKVOT STAAL MET BEHULPVAN EDELGAS IOONVERSTROOI ING.

GM van Wyk*, W Englart* an B Taglauar*

•Dapartaaant Fiaika, UOVS, Blowfontcin•Max Planck znstltuut vlr Plaaaafiaika, Garchlng

Ola adaorpala van vatar op poli*ristallyn« vlekvryataal It ondaraock mat bahulp van 1 kaV ioonvarstrooi>Ing by varsklllanda tamparatura tusaan 140 K an 500 K.Ola a* rujjicjttin an dia itrooistlr.e vanaf Fa tn 0i' • By laa taoparatura (<180 K) la sonolaagba>& ...... jrkry na ISO L. Hat vardar* blootatalling hat

<-. H" cit.n toaganatn tot 'n naksimuB by 550 L waarnatt. •- .- ->r hat. Laaaganoaada word varklaax daur•u: zqii iia. Bokant ISO K was vclladige bedak-king nla aoontllk n;i« an 'n toanaaa in die O/B-v«r»houding la gaaavt »«t to«namandc tanperatuur. Ioon-ga/tndussaarda dasorpala is gaoact an rasultata virdasorpaiadaursnitta word aangabiad an baspreck.

A63 •N KOM«I8T»MCT OTIvWAWSt VAH TtOBI"VAN OmXVXAXaSGMtGASIl INHMOXt i IMMIGHGM6A9X1.

3 4u Haasls an ON van wykDepartment Fiaika, uova, aioamfontein

'n Kon*ist*nt* en voUediga heranaiiaa va.n dia baskrywinq van oppervUksegregasie in aiUtikooponent sistaaeIn term* van makroakopiaaa temodinaaiesa aianakappeword be«pre«k, Dlt word aangatoon dat 'n analitiea*uitdrukking in 44-e appervl*ksp*nning varkry kan worden det die awewigaapparvlakkonaantraeias geldentiflsaerken word mat minima in hierdio funksia. oia Langauir-

, Rr^gg-'WilliM)*" en Guttman aegragaai* v«rge>wQr4 uit 4ic appervlakapanningsfunkala be-

reken d*W *e*iiit*te van dia gawona oploasingisoodel teaebrulk. T*Qretieaa en eksporiaentele reaultata,too* hl*«»r*al« effekt* an diakontlnus oorgang* in dieatfreeani* i»ot«m, wcrd varduidelik aan dia hand vanilt fedrae; van die oppervlakapanningafunktl*.

DIE OHPERSOEX VAN VCTSKILLPCE TIPES

AHOKTE KDOLSTOF M.B.V. X-STRAALPirFBAKSIE

N P FICX» «n r R L SCH6NIMG** Oapartaoant Matariaalwatanskap, AEX van SA Bpk• Fiaika Dapartaoant, Univarsitait van dia Witwat;arsrand

Varskillanda vorms van grafiat soot glasagtiqa koolstof .dun opgaaanc>ca laglas grafiat , ana., i« m.b.v. X-straal>diffrakaia ondarsoak. t)ia spaktra wat varkry i s , hetdia t ip iasa alanskappa van anorfa natcriala vartoon.

Siardia spaktra i s gabruik on radiala dis tr ibutee funk-siaa a .b .v . vinniga Fourier transforraasies te vertcry.Ult die funksies was d i t duidelik dat daar wel kort af>stand « 1 no) orda bestaan tussan die atome van diegrafiate wat ondersoak i s . Nia a l l tan kon die afstandetussen naaste bura betaken word nie , saar ook kon diaaantal atone op daardie afstand varkry word an varvol*(jen« dla struktuur van die oaterical bepaal word.

77

A65 'N KOHSISTEMTC H8WWM.ISE VAH 018 TBOHIEVAM OPPERVLAKSBJRIGASIE IB HULTIKOHPOWENT-AIXOOIB •- KKITIEK OP ANDEK TEOME.

J du P l e s s i » en GN van WykDepartment F i s ika , uovs , Bloemfontein

Die Guttman en under makroskoplese ternodineaieseana l iaea van oppervlaksegregasie word bespreek intern* van d i e neranal ise van du P l e s s i s en van Wyk.Verskcie gebreke en erns t iga foute in die ontwikke*l i n g van h i erd ie t e o r i t word u i tgevys .

A66 TKAMSHISMOH EUCTMH nimACTIOWUtkLYSI*

C.L. Ghana** «nd S. Krl winger*

"University of the Beseem CapeUniversity o£ Stellenbosch

Transalssion Electron Diffraction (TED) can be usedeffectively In the characterisation of -rystalllnespeclaens. However, the process can be tediouaespecially when only a ssull area of poly-crystallinespecloan Is available for analysis, and/or two or aorecoaplex diffraction patterns are superlitposed. Thisis especially trua In the ease of tnatnaenta on which•icro-dlffraction is noc possible.

A facility to simplify the analysis of TED alcrocraphsusing computer-controlled •icrodensicoaeery has beendeveloped, and la described alone with the generalprinciples on which the software is based. Theapplicability of the aystea in eh* handling of non-continuous diffraction rings and diffraction peakdeconvolutlon is also discussed.

Exaaples Illustrate that the systea, though relativelysiaple in design and operation, can obtain data froaotherwise unuseable TED micrographs.

A67 APPLICATION OF SPACE GROUP THEORY TO SE •COOT ORDER PHASE TRANSITIOW IK CRYSTALS

Herbert Wi l l i KunertDepartment of Physics.University of Pretoria.0002 Pretoria

In the Landau theory the symmetry change which takesplace at a continuous transi t ion i s related to the s y -mmetries of a certain act ive ,phys ica l ly i rreduc ib le rerepresentation of the high symwtry apace group. Thes e l e c t i o n of Che appropriate act ive irreducible repre -sentat ions of a space group i s discussed.In part icu larthe Real i ty Test and the Landau-Lifshier** c r i t e r i o nare analysed.

PD1 SYNTHESIS AMP CHARACTERIZATION Of SOMEHIGH-TEMPERATURE SUPERCONDUCTORS

P.R. Clayton, A. van Zyl, I. Slgalaa, G. Jantskyand O.S. .JfcLaehlan*. ~National Institute Tor Materials Research, CSIR•University of the Witviatersrand

Chemical synthesis techniques were employed to produceintimately mixed oxide precursor powders from whichdense ceramic superconductors were prepared.

This paper deals with the synthesis and process-ing of the oxiae precursors, as weii as the subsequentcharacterization of tfte materials with respect toresistivity. Xeissner effect, crystal structure andmicrostructures.

SEGREGASIE VAN TITmiUH IN GOUD

PE Viljoen, JP Roux en 0 Holtzhausen

Departement Flsika, oovs.

Die seqregasie van titaniua na die oppervlak van 'ngoucteonster vat 4 at. % Ti bevat, is ondersoek. Diesegregasieprose* vir Ti begin eers aeetbaar word bo-kant ongeveer 300*C. Koolstof wat aa 'n onsuiwcrheldin die allooi vecrkoa, segregeer self* by laer tenpera*ture sterk na die oppcrvlak waar dit in die voia vangrafiet verskyn. By ho«r temperature is dit in 'nchenies-gebonde of karbiedvorm op die oppervlak. By 'nbepaalde temperatuur is die Ti, C en 0 in 'n vastc v«r-houding ten opsigt* van mekaar teenwoordig in die oppepvlaklaag en word die afleiding gemaak dat die drie ele«mente <5f teen dieselfde tempo ko-segregeer na die oppepvlak iSf dat vast* chemiese verbindings tussen huilevora in die oppervlakgebied wat gemonitor word.Op hierdie stadiun is die proses of prosessc wat diesegregasietempo beheer nog nie bo alle twyfel vasgestelnie. Die segregasiegedrag van die allooi in 'n suur"stofaemoafeer word intussen ondersoek cm lig te werp opdie korrosieg«dr«g van di< komiersie<le goudmonster.

A70 DIE ROL VAN KLEIN PERSEKTASIES Pt-METAALTOEVOEGINGS IN Fe40Cr STAAL.

J.P. Roux O.J. Holtzhausen en M.J. v Staden

Dept. Fisika, UOVS, Sloemfonteia

Die invloed van Pd en Ru in kleinpersencasies aanwesig(o,5 - 3 %) in Fe 40Crvlekvry staal «ord bespreek. Die segregasieen oksidasiegedrag in UHV-toestande is onder-soek met behulp van AES en ESCA-tegnieke.

Die oppervlak van die monsters'is ookvertyk met Pd deur opdamping van • 600 A laagPd. ay verhitting blyk dit dat die Pd-laagCr selektief deurlaat wat 'n belangrike eien-skap is in die bevordering van korrosiebe-standheid. Die gedrag van Ru word vergelykmet die van Pd.

78

KERN-ENDEELTJIEFISIKA B NUCLEAR AND PARTICLE PHYS.

BI STATUS VAN DIE NASIONALE VERSNELLER-SENTRUM, .FAURE

n ».if arm en A H Both«Rationale Veranelleraentrum

Vordering »et die versnellers en ander fasiliteite vandl« NVS te Faure gedurende die afgelope jear aalbeapceek word met die klem op die inbedryfstelling vandie oopaektorsiklotron en toerusting vir die gebruikdaarvan. Vooruitsigte vir die voltooiing vanoorblywende take en die prosedure wat voornemendegebruikers moet volg aal ook toegelig word.

B4 12ÇUMETC

AT 66 HaVi EXPERIMENTAL11"DATA ANALYSIS

Pllcher3.3. Lawrle, A.A. Cowley, D.M. Whittal, 3.National Accelerator Centre

Coincidence data for the 12C(p,2p) knock-out reactionat a quaoi-free angle pair was obtained using a 66 MeVproton beam fro* the NAC cyclotron. The experimentalmethod and the method or data analysis, leading to thedetermination of a binding-energy spectrum in whichthe ground-' and first excited states of B areresolved and an energy-sharing distribution forknock-out to the ground state, will be discussed.Results compare well with previous experimental dataat SO and 100 MeV.

V

B2 OPWEKKING VAN REUSE MULTIPOOL RESONANSIES

W J Naudé*. D J Swanepoel*. W de K Loubser*. J A Stan-der*, J W Koen*»Universiteit van Stellenbosch•EVKOM

Die resultate van die nie-elastiese verstrooiing vanprotone vanaf atoomkerne in die massagebiedA « 58 - 197 en v i r laboratoriumhoeke e. = 8° - 35°,sal bespreek word.

B5 MODEL CALCULATIONS FOR THE l2C(p,2p)REACTION AT 66 MeV

P.M. Whittal, A.A. Cowley, 3.3. Lawrie and 3. PilcherNational Accelerator Centre

The experimental data are represented in the form ofan energy-sharing distribution (see preceedingpresentations). As is usual for this type of knockout experiment, model calculations are based on theDistorted Wave Impulse Approximation, but are insurprisingly poor agreement with the data. Attemptsto understand the discrepancies will be discussed,with particular reference to Optical Model parameters,the bound state wave function and off-shell effects.

B3 INTRODUCTION TO THE KNOCKOUT ANDCONTINUUM DECAY STUDIES WITH IHE NACSEPARATED SECTOR CYCLOTRON

A.A. CowleyNational Accelerator Centre

An introduction to knockout reactions pursued at thenew separated sector cyclotron will be presented, witha brief review of present knowledge regarding thereaction mechanism at 66 to ZOO MeV. The experimentaltechnique will be described, as well as the method torelate the measured quantities to physical propertiesof the scattering system.

I shall describe our research programme to evaluatethe role of an intra-nuclear nucleon-nucleoninteraction.

COINCIDENCE STUOY OF CONTINUUM DECAYINDUCED BY PROTONS OF 200 MeV ON U C

3. Pilcher. A.A. Cowley, 3.3. Lawrie, D.M. Whittal,S.3. MillsNational Accelerator Centre

An experimental study of coincident protons emitted inthe reaction p + C at 200 MeV has been carried out.Previous experiments on a single oiedium-mass nucleushave indicated that the reaction mechanism isdominated by an initial intranuclear nucleon-nucleoninteraction in the formation of continuum yields. Thecurrent experiment examines whether the target massdependence of the reaction follows the expectation.Results will be presented.

79

B7 EQJATE

EXCITATIONS

Oevid A»crwMn.University of Cape Town.

A Wlts-UCT experiment to study (p.?)reactions oo light nuclei at Intermediateenergies has begun taking data at thecyclotron at the National AcceleratorCentre. Giant dloole excitations of theground and excited states can be studied.as can the higher harmonics of the giantdloole states. Gassse rays mrm detected Ina large volume sodium. Iodide scintillationcounter with ant3-coincidence shield. Datataken with carbon-I2 and boron-tI targetswill be ©resented.

BIOV

THE 2HICU0M AS A COLOK HACSETIC SOLITOH

J M Crsbsn. Thsorscieal Physics Division,NMMS, csm

Th« QCD equations of notion for tha nucleon are solvedaiiag * seai-classical aneats for Ch« (luon fi«ld. Theansstz ii suggested by th« perturbacive solution of th«aquations of notion, uicb th« nucUon bains described Intanu of thraa valanca quarks. Tha f.luon sslf coupling,tens do not affact tha tiae component of tha gluon fiai<but hava a profound affact on tha space component* of thi«fitld. A non-trivial color-aaenetic vacuum solution isfound which can ba eonnactad to tha parturbativa vacuunby virtu* of tha quark-gluon intaraction, so that thsbaryon emerge* at a color-najnetic quantum soliton. Th*icala of tha solutions is fixad by tha nuclaon sass. u«•tudy tolutions for two valuas of tha strong coupling cocv>stant and give tha composition of tha nuclaon «ast in tarsof gluonic, quark sad spurious eantsr of t u n components.Wa also give results for tha static properties of thanuclaon, and discuss various properties of ths quarks(percentage saall component, asymptotic behaviour ate.)and the gluon fields.

B11TESTS Of NEUTRON DETECTORSFOR NEUTRON TlME-Of-f^IGHTSPECTROMETER FOR (o.n) STUDIESAT NAC CYCLOTRONOavld Aschman.University of Cape Town.

Large elastic scintillation counters forneutron detection have been tested In azero-degree neutron beam at the NACcyclotron. These will be used In a longftight oath time of flight spectrometer forstudying (p.n) reactions at Intermediateenergies, where Gamow-Teller nuclearexcitations have been observed.

OT OF M C O W a X W T MH>

CTOAfr fJ. Clsyaaaa, Mraltft ftr Miyslk, (Ntlvarat-

t i t , 0-4*00 atelefsU, IMcral Xssvelle of Oenwy aiMIInatituta of Thaovstieal fkysies vU Astrealqrsless Omi-Texsity at Case t m . Keaesseaek 7700, Ope, MA.K. ladliok, Dalvardtit, MeleCeM, fsd. Mpok. Oetassy.I . Cats, Delfwsisik, Slslsfsld, 9*4. Xepua. Oacaany.I . lahosee, Ofeivenitr, ir-tOHO Oaio, nalaad.tmtUGIi Ms eoswicsr S tHrse-sMse aodel of stroaflyiatwaotiaf aattor, tns t la f esefc snsse as am ideal «aamodtClea ky s slaele pliswaaeiioloeioal intaractiom faatnr*.For aoelxac matter, wa take lute aooowt tke baryoaierapolstear far tke ejsackf IUM plasaa, vm laoioda th»bmf pcassurai tke ssMtitnsat «jo*rk phase has a BOO-IMTO•ffaetlve sjssrk eass ss w»Xl es aa Udepamoast baf pew!•ore. ay statyiaf wklek stasasoainatM tketaa«ysaalcallyia unat reeiaa ef taaasratare awe keiyoa moaber aeaslty,urn eetela a passe dlafTsa far stxoaflr intuaetiaamatter aa< taia seas lastfkt oa the ralatiea batmaadeeeaCtaaasat sat eklrsl syaastry restoration.

'BE *C ELASTIC 3CATTERIMG REACTION.

E Sldaraa-Haddad. RU Fearlck and JPF Sellschop.WltJ-CSIR Schonland Research Centre for NuclearScience*, University of the Wltwatersrand,Johannesburg.

We have used a 4E-E detector telescope to measure the*Be • lJC elastic scattering excitation function inthe Cab energy range 11.5 MeV to 19 MeV, at two angles.Siallar structure to that seen by De Rosa et al (ref.l)h*s been observed. The data are presented here and weare proceeding with the theoretical analysis.

1. A De Rosa, G. Inglioa and H Sandoli, II NuovoCieento 65A (3) 1985.

B12 EMPIHICAL EFnCTIVt INTERACTIONS FOR SHELL-MODEL CALCULATIONS ABOUND MASS 40

B.J. COLE* and W.L. Oadinabokao*1

*Univereity of the Witwaterarand, Johannesburg'''University of Bophuthatewana

To perform nuclear structure calculations in thef, - d|. model space the effective Hainiltonian, com-

prising two single-particle energies and 1<1 two-bodymatrix elements, must be specified. tn the absence ofany reliable theoretical calculation of the two-bodyinteraction, these matrix elements must be extracted insome way from experimental spectra.

We have investigated several methods of obtaininginformation on matrix elements by computing configur-ation averages for the energies of states based on oneand two single-particle orbitals. Thia procedureprovides constraints on the values of two-body matrixelements.

60

B13 DINAHIESE S lHCTRie - n HUWE 6ES16SPUNT VAWDIE SKIlHQOg1 . A6TERCMM0 EM STRUKTUUR

B17 POSITRON PROOUCTION IN NUCISAK COLLISIONS

H I S«ytrInttituut v1r Ttortt1ts« Ktrnfiffkc, UhivtrsittUStellenbosch

01c GtnocclHo-model Mt aysijingj deur Feng, Vu e.a.bltd « nuwt kUs$1f1k«s1tsk«M van skilmodtitoestande.jUnntms soortgelyk u n di< van d1t wisstlwtrktndibosonmdti naak dit dan montUk on skUmdilbertkiningeanaltties binne *> groepttorttiest struktuur ult t« voer.Oft agtergrond en struktuur van hicrdit model wordkortUks geskcts.

B14 OINAHIESE SIWETRIE - Yi NUWE GSSIGSPUNT VAWPIE SKILHODEL

II. TOEPASSINGS EN RESULTATE

H-8 GcyerInstituut vir Teoretiese Kemfisika, Un1vers1teitStellenboschSpesifieke toepassings van die fermion-dinamiese*stmmetriemodel en vergelyking met eksperimenteleresultate word toegelig.

BIS "Some current challenges in nuclearphysics a i ts fields ofapplication"J.P.F. Sellschop

Wits-CSIR Schonland Research Centre forNuclear Sciences.University of the WitwatersraadJohannesburg. ______^_____^_^_____

A (small) selection is presented of recentdevelopments in the field of low energy nuclearphysics r heavy ion physics at low, medium andhigher energies, and from nuclear astrophysicsto illustrate the ongoing excitement andopen questions in the overall field.

In similar vein a survey of a few of the>current applications is explored to revealthe increasing extent and value thereof inan ever-widening variety of fields.

B16 NUCLEAR PHYSICS DATA ACQUISITION WITH APERSONAL COMPUTER

S U FearlckVlts-C3IR Schonland Research Centre for NuclearSciences, University of Wltwatersrand, Johannesburg.

Tha PC offers several capabilities which can usefullybe exploited for data acquisition in nuclear physics.Two applications will be discussed: using a PC tocontrol and display data froo a Nuclear Data HlcroMCA,and using a PC In a CAMAC-baaed aultiparameteracquisition systen. The performance of the lattersystem is enhanced by distributing part of theprocessing load to an ln-erate computer, thus allowingbuffering of data and the use of efficient blocktransfers.

8. Spoalatra*. J.P.F. Sellschop* end U Von Mi«ewraperg+•University"of Zululcnd.<tVUta«CSIR SchOnland Research Centre for NuclearSciences, University of the WitMtersrsnd.

The positrons produced in collision* of heavy nucleiyield important information about the reaction.However, recent measurement* of positron spectra forcollisions leading to a united nuclear charge Zu of180 or more, have shown peaks which could not be insterpreted satisfactorily [1]. The latest indicationsare that such peaks are also preser In the positronspectra for Zu « ISO. This paper is a report of ourinvestigation of the positron spectra generated in >2Cbombardment of nuclei.

Cl] U NUller U at. Z. Phys. A323 (1986) 261 ^

BHABHA

0 von Wimmersperg, 5H ConneU. REAJfoeralff 'andE Sideras-Haddad.Wits-CSIR Schonland Research Centre (or NuclearSciences, University of Hitwatersrand, Johannesburg.

Positrons froa a source .of " S i . obtained through thereaction >rAl(p,n)27Si, were scattered off electrons ina target of polyethylene, and e*o" coincidences weredetected in a pair of plastic scintlllators. Thedetector apertures were restricted to accept onlyevents corresponding to aaxiauB aosentua transfer atcentre of aass angle 90*. The variation with energy ofthe corresponding lab angle was utilized to obtair thescattering excitation function from the continuouspositron spectrua. Centre of aass kinetic energies inChe e*e~ system covered the range 342 to 845 keV. Adeviation froe Bhabha scattering of order 10* wasobserved at 720 keV. The possibility is considered thatthis phenomenon eight correspond to a scalar aagnetic(«*«') resonance of sass 1740 keV.

B19 TDPAfl MEASUREMENTS OF IMPLANTATIONTCEMPE1ATUM DEPEMDAHCE IM '^F UgUWTED

S. Conncll*. T.r.T.T?*!lichop*, H.S.SttH. App«l*, K. Bharuth-Ram*.*Wit*-CSIK Schooland Research Centre {or Nuclear Sciences

Univers i ty of the Witwatersrand, Johannesburg, S.Africa• U n i v e r t i t a t Karlsruhe, FR Germany.'Univers i ty of Durban-Hestvil le, South Afr i ca .' 9 F has been used to probe the s tructure of the diamondl a t t i c e . The oeasurenents were performed v ia the timed i f f e r e n t i a l perturbed angular d i s t r i b u t i o n (TDPAD)technique applied to the 197 keV scsce of I 9 F . The pre-inplanced probe nuclei were exc i ted using a(p,p'.gamnu)react ion i n i t i a t e d by a pulsed 6 HeV proton bean.

The one plane face of a type IIB Diaaond s lab wasimplanted a t 700*C and the other (oppos i te face) at nearLN temperatures. The residence s i c e s for Che probe ionswere determined. The hot implanted t ide had almosttwice the fract ion of probe ions at s unique s i c e as thecold implanted s i d e , *M expected in accordance with themobi l i ty of de fec t s above 600*C. The r e s u l t s are canparedto Measurements made at s imi lar temperatures by ther e c o i l implantation TDPAD technique.

81

TP.N:

B20P.H.

SOEKTOG VAN DIE WAAKHEHISG VA» SONVLAH-NEUTRONS IN DIE VYfMINUTEDATA VAN DIEKEUTRONMONITOR TE TSUMEB.

Stoker, PU vlr CHO

Die 18NM64 neutronaonltor te Tsuaeb (10*12'S, 17*35'E.hoogte (240 •) reglatreer kosaieae ttrale vlr 5 alnucavanaf Januarit 1978. Sonvlaaae gepubllaeer ulc ditwaarneainga van SUM (Solar Maxlaua Million) an In dl«lictratuur la gebrulk oa gclyktydige raglatraala vansonnautront deur dla neutronaonltor ee Tauaab caondersoek. Gaan atatlatlts-duldende gabaurcanla kongevlnd word nit. Ntutront la vanaf dla ionvlaa van3 Junla 1982 daur neutronmonitora op Aarda gcrcgl-atraar. Ook vlr hlardla gtbcurtenla waa dla eoenaoein ttlteapo van dl« neutronoonitor ca Tauaab nitatatistits duidtnd nit.

BAA LEEFTYD VAM P i t 0* TOISTAm TAW

V M Proieaky. 0 V Mlngays Atoo*esergl«-korporaala van Sold Airlka Bpk

'n GeraanluadttekCor vat as akjrf as dataktor gtbrulkla, It ate oeutrone van 'o -2*lA«(ia5-aroiigaboabardtar, co 41* 0J 691 kaV toaataad In 1*0*la daur oaclaatiaaa oaucroDvaratroollag opgawak. Dtalaaftyd van dla totatand la bapaal daus dlatydavarakll ta aaat tuaaan dia tamgakopatln van dla'*G«-k«ra an dla vaa dla volltdlga lnttrna sastctlngvan dla vlak. Dlt aaclnga It op twee dataktote(G«-Ll, ko-aka, dleptat 51 aa> dlaaatar: 4S,6 m) «&IG, vlak, dlapta: 5 aa dlaaatar: 10 aa) gtdoea as o.».varakllla In ladlngavaraaaallngatyd ta tdandflaaac.Ola gaaaca leeftydvaarde van 634 + 20 aa la vcxgelyk•at vorlga aetlnga. ~

B21C.C. 0cdaaa> J vaa Waart ta D.W. Mingty, AEX

<CAKAXTEBISTIEK£ VAH SEKOMDeRE-ELEKTRONEHERGIESPEKT8A

Sckoadcrt-tlcktrootaiaaic vanaf C- an Mylar*akyvca.g.v. invallanda awaarioonbundtla aec tnarglaatuaaaa 1 en 3.5 MtV, ia btatudacr. Met bahulp van 'nparallel plaat-anallieerdcr, la karakterlatleke venaekondcrt-elektros tnergittpektra waargeneea. Oaarla o.a. gekyk aa eindpunt tncrgiea konvool- enAugtr^tltkerouc. Die ladlogatoeacand afhanklikhcid,aowcl aa vergtlyklnga tusitn aolckultrt (Hj+) «oacoacra (U*) bundtla, la getraf.

D O 4 ANOMALOUS RESPOMSE OF THIS FILM PLASTIC

SCISTIUATOR TO HEA\nt IONS.

C B Franktyn. AEC

The intensity of scintillation light due to the passage

of fission fragments through ME102A thin fila plastic

scintillator has bean measured for fila thicknesses from

0.5 to 10 |ia>. As film thickness is increased up to 3 um

anci from S urn upwards the luminescence increases

gradually, however, from 3 to 5 um there is a rapid

increase in luminescence. A similar transition is

observed for 2.3 MeV He ions. Possible causes for

this effect are discussed.

B22 STKOOMDICTHEIP EFFEKTE IN SEKOSPeREELEKTROS ESERCIESPEKTRA ' ~

C Dednaw en J van Uaart, AEK

Die stroomdigtheid afhanklilcheid van sekondere-e lektron(SE) enereiespektra i s bestudeer in "n poging om u i t «s l u i t s e l ce verkry oor die rol vat skyfCenperatuur speelin die proses , "n Toe name in die oporencs van e lektronenet energiee "-I keV i s waar^eneem, v»t Ceenstrydij!i s net die welbekende gedra? van i i e Cotale opbrengsvan SE. Vecpelykings i s ook eecref tussen gepulseerdeen gelykstrootnbundels.n Stroordif theid afhankiike versktiwinf in die konvooi"pick enerf ie vind p l j j s vir ?eide koolstof en ee.ilu~•niniseerde Mylar f o e l i e s . Sic i s teens tr yd in met Viaanvaarde verklaring van die e'fek nl . ladin?sonbouinys*effekce op In skyf net hoe resi i t i w i t e i t .

BAB PROMPT GAMMA-RAYS FROM THERMAL MEUTROS

^ CAPTURE IN NATURAL Os AND Ce

C B Franklyn. AEC

D i s c r e p a n c i e s have been found between standard t a b l e s

of prompt V-ray e n e r g i e s from < n c h , V ) r e a c t i o n s for the

natura l e l ements Os and Ce and standard c a b l e s of T-ray

energies from (nc h iV) reaccions in their isotopes. The

results of new (n,V) measurements are presented and

indicate chat the standard tables of energy and

absolute intensity of prompt Y-rays from thermal neutron

capture in natural Os and Ce require drastic revision.

DM A Lone. R A Leavitc, 0 A Harrison Atomic Data and

Nuclear Data Tables 26(1981)511-559

\

82

• t t f t a S * « * ' IC- EMISSION MJES FOR X-fAYBZO HHiBPHflbH IT PROTONS. DEUTaOMS.w m AMD ALPHA PARTICLES

Kotaa and 0 W Hlngayl c Phyaica, AEC, PrtcorU

» • Kotaa anjjuclaar aod

m* rtlatlvt transition probabilities ofeharacttristlc K X-raya were measured in thintargets of X, Ca, Sc, Tl. V, Cr. to. Ft. Co. Ml., a CJ, Ga. and Sr rttultlng froa bombardment by•roton, dtuttron, and alpha particle beams. Theexperimental valuta art compared with Hartrce-Fockcalculation* aa well at the theoretical valuta ofScofield. The proton - and alpha particle Inducedcalsalon ratta compart favourably with photonloductd data, with minor anomalies at Cr, and Cu,but the anomaloua behaviour of tha deuteron datacannot be explained. The Influence of projectileenergy on the KA I K, ratio* waa alao Investigatedbetween 0.6 Mev and 2.* Hev. No direct velocitydependence could be obaerved In the present data.

B27 K X-RAY SPECTRA PRODUCED BYNITROGEN IONS IN Tl AND V

P B Katie and D V KlngayNuclear and Atomic Physic*, AEC, Pretoria

K X-ray spectra aa produced by nitrogen Ion impacton Tl and V are compared with proton-Inducedspectra at 2.4 (lev. The K ^ and K« lines fromnitrogen bombardment are found to be shiftedapproximately 45 and 90 eV, respectively, relativeto the proton-induced spec.tra. Hartrtt-Fockcalculations show that the obaerved ahifta are m*expected from atoms with two or more additionallneer-shell vacancies. Double K-shell lonlzatloncan be ruled out in these cases.

HICKODOSIMETRV - CONCEPTS AND QUANTITIES

J.H. Houth and P.J. Biunf, Nationrl Accelerator Centre,CSIR, Pretoria

la contrast to conventional dosiaetry where the absorbeddose D*dT/dm is clearly a macroscopic quantity, aicro-dosimatric data reflects the pattern or distribution ofenergy depositions along track lengths of the order ofM micron. These dimension* are relevant to radiationaction at a cellular level and a tissue-equivelcnt pro-portional counter can be used to evaluate lineal energyspectra for simulated track lengths in the range 0,25 -10um. Probability distribution function* and meanvalues for aicrodosimatric quantities will be discussed,in particular single event spectra which are ocacuredexperimentally and are usually displayed as a functionof lineal energy.

B29 MiASUKtrtENT"Ut SINGLE" tVLfli irtHKA in A

HIGH LET RADIATION FIELDP.J. Binns and J.H. Hough, NAC, CSIR, Pta

The quality of a fast neutron bean intended for medicalor biological application can be determined vith varyingdegrees of exactness. In routine dosimetry the totalabsorbed dose is stated with acceptable accuracy in termsof the constituent neutron and photon components. Thisaccuracy is improved if the spectral distribution of theincident neutron flux is known. Of more fundamental in-terest is microdosimetry which provides a fuller discri-ption of beam quality as related to the event sizespectra of recoil electrons, protons, a-particles andheavy nuclei, as measured M a microscopic level (ie1-2 urn). Track lengths of these dimensions are simulatedin a tissue-equivalent proportional counter filled withtissue-equivalent gas at the appropriate pressure. Thedetector pulses are processed using NIM electronics andpulse height spectra accumulated in a oulti channelanalyser. From this data, single event spectra are cal-culated and probability distributions expressed as afunction of lineal energy. Spectra obtained undervarying physical conditions in a d(16) + Be fast neutron

m!ffo&Hme1r?J*plS?a£eltel?s.discus»ed in teras of various

PLASMA PHYSICS PLASMAFISIKA

A . PLASMA WAVES IN LABORATORY AND SPACE

V I P.J. BarrettPlasma Physics Research Institute,university of Natal, Durban.

A description of the wide variety of plasma waves willbe given in terms of two-fluid theory. Laboratoryexperiments on some of these will be described and re-lated to observatior.s in the Magnetosphere andionosphere. The significance of wave studies for thefusion programme will be discussed briefly.

A A COLLISIONAL EFFECTS OH THE CURREMT-DRIVENC 2 ION-ION HYBRID AND ION CYCL0T3CN

INSTABILITIES

D. Johnstone and M.A. Hellbcrg, University of Natal,Durban.

Numerical and analytic analyses of the growth rate oftne ion-ion hybrid mode (IIH) as a function ofelectron-ion collision frequency (w ) are presented.

Linearity is lost Tor ̂ fl > h R - K ^ l . A parameter

survey of the IIH mode ha3 been carried out. as well ass study of the effects or M?h « g l on the lignt ion

and heavy ion cyclotron modes. The transition diagramof Sharuthram and Hellberg is found to be Inappropriatefor high vel.

83

C3 THE ION ACOUSTIC INSTABILITY IN AMAGNETIZED TWO-ION PLASMA

J. Govender and R. BharuthranUniversity of Durban-WestviUe and Plasm* PhysicsResearch Institutt, Univarsity of Natal, Durban.

The behaviour of the crossfield current-driven ionacoustic instability in a magnetized plasma containingtwo ion species is theoretically examined. Thedependence of the critical drift speed forinstability (VQ C) on several plasma parameters isstudied. These include the heavy to light ion massratio, fraction of light ions, magnetic field strengthand the propagation angle.

C4 ELECTROSTATIC WAVgS IK AN ION-BEAMMAGNETIZED PLASMA SYSTEM

K. Naidu and J.F. McKenzieDepartment of Mathematics andApplied MathematicsUnivarsity of Natal, Durban.

In this papar, a multi-fluid approach is used toobtain the electrostatic ion-cyclotron acoustic wavein a plasma syst«a consisting of hot, massless elec-trons and cold ions. The properties of the dispersionrelation in different frequency regime* is investi-gated using the wave number surfaces.

The generalized wave aquation for a plasma consistingof a stationary magnetized background plasmarelative to which an ion bean drifts with velocity u Dperpendicular to the magnetic field is also obtained.The properties of the dispersion relation for this ionbean systea are investigated in the V.L.F. regimefor instabilities.

^Modulatlona! Instability of StrongElectromagnetic Haves In a HagnetnedPlasms

». Bharuthran*. P. Singh* and P.K. Shukla*•University of Durban-Westville, DurbanRuhr-Universltat Bochum, Fed. Rep. of Germany

Accounting for the relatlvistlc electron quiver velocityand the relativiatic pondcronotlve force, thenodulational instability of an arbitrarily largeamplitude electromagnetic wave in a magnetized plasma isInvestigated for three type* of plasma slow responses.A parameter study of the instability growth rates ispresented.

'Also at Plasma Physics Research Institute,University of Natal, Durban.

C8 DESIGN OF HELICAL MAGNETIC COILS FORTHE AEC IOKAMAK

D P Coster, J A M de ViUiers, J B Fletcher, £Nothnagel, D E Roberta, 0 Shervell ~

Fusion Studies DivisionAtomic Energy Corporation of South Africa

Three sets of helical colls (I - 1,2 and 3) havebeen Installed on Tokoloshe for the purpose ofstudying their effects on disruptions. A particulargoal of the coll design has been the achievement ofas pure a magnetic island structure as possible.

The design philosophy la outlined while computedIsland alzes and their Importance for futurestudies arc discussed.

C5 ANISOTROPIC ION BEAM - PLASMA INSTABILITIES

P. Singh and R. Bharuthram

University of Durban-Westville and Plasma PhysicsResearch Institute, University of Natal, Durban.

Using kinetic theory, the dispersion relation forelectrostatic instabilities arising from theinteraction of an anisotropic ion beam and a backgroundplasma is established. Solutions of the dispersionrelation are presented for varying plasma parameters.

C6 S j « 6 f l I C < l :OBSTRO:7IO» Of THE S*GD££V 9QTENTUL AND

OUTCHS A*0 JOuBU L

PLASM

ana

* 3eoa*t«en; of Applied «itne»ati•• D«3*-;»en: of 'hysics

j n w e s i t y of 3ur&an-eiest*i] le

C9 MACNCTIC FIELD MEASUREMENTSRESONANT HELICAL WIMP DIGS ON THE AECTOKAMAK

D P C o s t e r , J A M de V i U i « r « , J 0 F l e t c h e r . CNothnagc l , D E R o b e r t s , D Sherwe l lFusion Studies DivisionAtoaic Energy Corporation of South Africa

Observation ports and engineering constraints re*ultin deviations of tha helical vladlage from theirtheoretical path on Che surface of the vacuumchamber. These deviations must be such' that theperturbation of the resultant field la small.

Measurements of the radial field due to thesewindings, without plasma, at different alnor radiiand toroidal positions are compared vlth theory.

C10 REPAIR AND Jt£-ASSEM6LV OF TOKOLSSHE

entei for canst'jct;rtq :*)f:onsisting of :«o iotzifi

for «n

*«p*it-fle ion-»c3ustic loliton iia :ouble-'.a««r potentialat 33£a.*c4 without the usual cold *on or \aail aiplitude

J R O'Mahony Atomic Energy corporation

An arc which developed between the ohalc heatiag iadtoroidal f i e ld c o l l s of TaKoloshe necess i tated acomplete disassembly of tne tokamak. This paperdeta i l s the damage caused, I t s repair and there-asseably of Tokoloshe unlch Is now In progress.

84

en nsramci STtmmw 01 tomwa

r«y Corporatloa

nin atnuiai don aoa-lUaar Itlaad coctowa•" - tlapla w y of rlauallsia^ uaufott Mchaaleaa*" >ir-fc« It ak l C 4

t l p y ^ ft0>ir-fc«- It aakaa elaar, Cor *Maa4a, to*

* r1 . . .<g*l procoea and cm U aaafully ap*Ua4 to- i ^ - Mgtielaa In a fuelo* reactor. Iba Cbaory baaZ M T stopond oaly Cos regular lelaada but caa ba! i y artawlad to atochaatlc orbtca vfaara tagulw

ovarlap.

or m IOH.IOM

and K.c. Graavaayaios Raaaarch Xnatltute, 'Jntvaralty of

Xatal, OurMn.*arlou» typo* et bawgantrcced inatabUltlaa hav*baan studied In tha Dovbla FUana davlce. Moat orthess ara kinetic Instabilities, drlvan by raaonantpartlolaa, with a relatively broad frequency apactrua.In tlM praaant axparlaant Ma »c» darting with ahydrodynaalc inetablllty <*rlv«n by tha ralatlva <irlftof baaa lona and baekcround iorti, occurring at aalnjla aharply doflnad fraquaiwy. Obaarvad rraqutnela*and growth rataa ara eoaparad with thaory and Indleatathat obllqua propagation la Important. Tha eorraa-pondlng »otIon of lona In valrelty apaca la praaantad.

C12Duroan.

EHERGY TRANSPORT IH AH EHGODIC MAGNETICLIHITER

and W. P*n*b*rg , University of Haul,

A 3-dioansional numarieal aodtl for tnargy tranaport Inai.> tr«o<Sic aagnatle Xlalfcar la dcseribad. Radial htattrans?ortad aa? ba doainatad by conduotlon along thatrgodle field llnita which have s saali ceaponcnt normalto th* oagnatle aurfacaa. tha haat conduction aquationla solvad, naklng a Fourier anaatz in both poloidal andtoroidal angla. Raaliatie boundary condltlona ara uaadand nonlinaar and toroidal affaeta lneludad. Unaar-lxatlon is affactad by introducing two tlaa-acalaa,r«lat«d to th* p a r a l l « l and parpcndlcular tharaa lconduct lv i t l«B, r a a p a c t i v a l y . Tha aodal aay baapplied to Tora Supra, Taxt and Tokoloaha.

(•>! far Plaaaaphyalk, Garching, U. Germany.

PROBE MEASUMCHTS IH A STEADY-STATETOKAMAK DISCHARGE PLASHAP . J . B a r p a t f . M. Coo, 0 . Darrow and G.J.

Graana, Princaton Plaaaa Phyaica Laboratory, PrJr.caton,«J 0«5M, U.S.A.

Tha Cjrrant Drlva Exparlaant (CDX) at' Princaton i n -volvaa "Hal le l ty i n j a c t i o n " In tha fora of a lov-anargyMgh«currant a l a c t r o n b«aa which antara tha plaaaaalong dlvartar fiald linaa. This eonatitutaa a jurfactcurrant which gats transferred acro«s tha aagnatle fialdto fora toroidal current throughout tha plaaaa voXuaa,thertby ionizing th* (heliua) g*M and aalntalning atokaaak fi«ld configuration. Typical paraaatara aretoroidal Held 5 kG,T 25 aV, T, 15 aV, i

central density 3 x 10*J ca "",lajor radius 60 ca, ainor radius

(of plasaa) * ca. Diagnostics includa and caJsilv*electrostatic probe, to ba used to aap out tha electro-static potential and to observe electric fiald fluct-uations. Tha exptriaent will be described briefly andprellalnary results frcaj the ealsslva prob* will bapraaantad.'On iMve froa Oapt. of Physics, U. of Natal, Durban.Expariaant supported by US D0£ contract Ho. DE-AC02-76CHO-3073.

CIS SPATIAL CHARACTERISTICS OF CBOS5FIELOION ACOUSTIC TUBFUIEKCE.

R.G. Crtivti mi P.J. BimttDtftfim4nt of Pkfiiei, Uttiurtilf oj Nttst, Dnin.

TM cnMslfeM to* tcouttii iniMbJIity occurs whtn there Is rditiv* drift be-tweui unm»|fHt?iMd I M * and ftiifnttlied titttiont tent* » mignctic Md(w^ « w « v n ) . Cbsarv«tlon* of the twbutane* Mwcitted wli* this initibtHty*n prtstntad kaf*. Tttt spatial prapcrtto of the thra»dlmMiioritl k-tpKtramwarn Inrotif(1*4 by applying convwitkMal ticJinlqiitt of digiul fpaetrvm anal-ysls to tlmcaanis datf obtained (ram two-probe tnd thrat-proae arrays. TherewHt «ara roa*4 ta t* l i tgrsameat wftk tufler oe*«.-vaUo«« oetsIiMa' «*!»(analog comlatle» m*awr«m*rit». Obt«rntJ<»» of partide htatinf by crou**WtwrbHlenu ire aito prutnted.

CUHBEHT RESULTS PROH THE LASEK SECTIOHOF THE PLASMA PHYSICS RESEARCH INSTITUTE,UNIVERSITf Of KATAL

J.A. Halthaa. P.P. Cunnlnchu, P.. Cazalat,A. Chaaberlain, H.M. Mlchaalla and H. Hoteutt, PlaaaaPhyaica Research Institute, University of Hatal. Durban

Up to 300 MM of Ruby laser light la focuaeed on solidplanar targets under vacuua. Tha plaaaa la diagnosedwith an N2*laaar proba beta, X-i-ay diagnostics and

charga collecting Paraday cupa. Lataat raaulta regard-ing ion-flows and X-ray characterisation will bepraaantad.

Ct7 IH A, MACHETIC FIELD WITH UNLIHITEPGKADIEHTS

R.A. Burter and H. MortalPU/CSIR Cosalc Kay Research Unit, Potchefstrooa

The slaplc drift cxprcsalon

xv^j, - (p v/3<j) I x (B/BJ)

for a naar-lsotroplc particle distribution, is generall)said to ba valid only if the ratio of particle gyro-radlua/acale length of variations in B (R/L) is muchl than 1. ~

We show that th» aaxlnua value of Ch« spatial averageof thla quantity la (*/4) v, and us* a siatple oagneclcfield to Illustrate the physical reason for tha break*down of this expresalon in situations where R/L £ 1.

85

C18 tlASHA KQSSWt VkVtS

U.K. fotthatty and J.F. McKensUDepartment of t.r>O)ea»atics andApplied Natheaatica,University of Natal. Durban.

Th« latitudinal variation of th« vertical componentof the aarth's rotational frequency gives rl«a tolarge-scale incompressible ahoar waves in tha earth'sataoephere/ocean • known aa Rosaby wavea. In amagnetized pUsaa a slallar type of vava (electroata-tie in nature) arises whan tha background Mfnetlcfiald varlaa In a direction perpendicular to It. Forsimplicity, in thia paper, we assume that tha plaaaaconsists of cold ion* and hot ttasslass electron*.Tha low frequency llalt (i.e. u « Q.) yield*"RoMby" type shear vavaa M wall as acoustic wavesModified by thla "0" affect. The properties ofthese vtvea are discussed in detail in teras of thegeoaetry of their wave normal iurfaces.

C19 PHASE MEASUREMENTS OF THE ION CYCLOTSOHINSTABILITY

M.J. Alport and E.G. van NlekerkPlaaaa Physics Research Institute, University of Natal,Durban.Phase measurements of the lor cyclotron instabilitydriven by an electron drift are presented. Tha experi-aent waa perforaed in a Q-aachine (n "*• 10 1 0 eaT^T, = T s 0.2 eV, B "* 0.27} and the measurements oade

using signal processing techniques. The propagationcharacteristics of the ion cyclotron waves weredetermined by making measurements in the radial, axialand azimuthal directions. The effect of plasaa density,aagnetic field and electron drift velocity on the phaseof the waves was Investigated. We analyze the data inthe light of the Druaaond-Rosenbluth theory and sakeeewparisons with an alternative "2-0 potential drivenaodel".

C20Dtsarfcatai •/ Mfmi , (M««rnrf t/Xelef, Oerlaa.

Electrostatic tea CydMroa Waits an netiatly dettabfliaed by drawiai acarnal to a dak f battoa*) isuatrttd ia a •Mfutiiea' plasm colmau. Tatfraqaeacy dttarmiaiai ttfioa of tkt iattabilky caa bt Mapped by awnac. tktbattoa aloM tkt axa of a Q-meekiae ia a tpallaUy varyisi aarattic ttldaad aoaitoriag tkt frtqatacy at a faactioa of battoa positioa. Uadar ctrlaiacoaditioat two ptakt an obttnrtd ia tkt aoiat tptctraa ef tke battoa camat.Wt tetablitk tkai tktat an die to iattabilitke wkick an excited ia diftrtal•patial rtfioa* ia Eroat of tkt battoa.

T i w i f i l tiilraM Tmill.K fm Tk«ei«tictl Pbgnia, tfalmnlir tt UMtrak, loa*.

A SIMPLE M E T H O D TOC21E.MrarlaiDtttrttiuni

ABSOLUTE VALUES Ot SPACE POTENTIAL

aad P. Xnmnnet, Vttiwiitf af NtUt, Dwivi *

Pmbwd tnuanvt probtt, at sppottd to cold Ltafmmir probtt, «llow for tktdinet, aaarabi(aomf dtttnniastioe ot tfc* tpta poUalial ia a planaa. Uafor-tnaattly, tkk nctthod nqairtt a fairly complex electronic circaitry, aad ktactit aot oaly itiiau but alto proa* to dutarbiaf ialatactt.CoatUaoaaly optrated tmiattrt probtt, oa tkt otktr kaad, providt aa tqaalljaccaratt aad mmca aiapkr way to dtt tmiat tat ebtcfat* valw of tkt (pactpoUatUL previdad tat tltctroa tatoratioa c u n a t b tqaal to C< maraudtketraa aniorioa emmat. Tkt potaatial ia tkta t m a by tkt mtanrtd vala<ot tkt loatiaf pottatiil akifttd by kalf tbt poUatial drop acroat tkt probe tipFor a Q-mackiat platma tkt ralata of tkt «p#- pottatisl dtttrmistd in tkirway utiaf aa «mi»«v« probe operated ia tke coatinaooa moJe an computewith tkt Ttlaat determined ia the palted modi. Wt Sad txcelkat airtamta!witkia tkt experimeatal actor of tkt emutehw probt mttkod.

TUt wttt ••• «ip«u(t«lbr t]» Autrlaa KaMank Find umhr Onsa N*. Ptiri. Thel o« the Q-««calm a/ U» toUltuM far T)ao»««kii ftriici tf

OPTICS ANDSPECTROSCOPYDOPTIKA EN SPEKTROSKOPIE

D1 S15TEMAT1ESE NEIGIWgS IN DIE LEEFTYE VAWVLAKkE 13 DIE KOOLSTOF EH STIKSTQF I S 0 -ELEKTR1E5E k E I

F J Coetzer , F 0 Mostert* en P van der Westhuiren

*Universiteit Steilenbosch, 7600Somchem, Somerset-West 7130

Die bepaling van die vtrloop van leeftye in isogiektro-niese raeksekan bydra tot die afskatting van diekaskadebydrae as gevoig van repopuiasie van energie-vlakke. tn hierdie ondersoek word Yi peg ing aangewendom die verloop van die viatcleeftye yan die kooistof- enStikstof-isoe*lektroniese reekse te verkry dear r. ver-geiyking van eStsperimentele en teoretiese viakieeftyevan C, N, 0, F en Ne. Besondere aandag word gegee aanafwykings vanaf die algemene leeftydverlcop as gevolgvan Qie inaqneming van kaskade-effekte.

D2 LEEFTYO-ANALISE VAH DIE 3p ' D " ENERRIE-VIAKKE IN 0 I I I

T C Kotz< , F J Coetzer* en P van der Westhuizen*

Straiingsbeheer

•Universiteit van Steilenbosch

Leeftye van die 3p 50° energievlakke in 0 111 soos qe-meet in bundeifoelie-eksperimente is onderhewig aanfoute as gevolg van kaskade-repopulasie vanaf hoe"r-liggende vlakke, YI Uitvoeriqe studie van die verval-wyse en kaskade-bydraes van die 3p 5D° tenne is metbehuip van statistiese metodes op die leeftyddata uitge-voer. Die gekorrigeerde waardes toon goeie ooreenstem-ming met teoretiese en arder eksperimentele waardes.

86

D3focuamc of LASER BEAMS WITH A GAS LEWSM. Wotoutt. H.H. MchaeUs and P.F.Cunnlnchaa Plato* Phrslee Reeearch

institute, University of Natal, Durban.

. M a itM it ua«d to rocua the focal length and spot•lfe are investigated for different gases and varyingflow rates. A hole la drilled in a iheet of alualniuBwhich cannot be done by a coaparable glass convex lena

D4 C.A.R.S. TECHNIQUES FOR COMBUSTION ANDCHH1ICAll<EACT0R DIAGNOSTICSffi

0 BalK H.S.T.Driver, R.J.Hutcheon and G.N.RobertsonJ H S t of Physics, University of Cape Town

We discuss the general principles of Coherent Anti-StoUes Raman Scattering (CARS) spectroscopy and itsadvantages over other non-intrusive optical techniquesfor combustion diagnostics and for the investigationo f gas-phase catalytic chemical reactors. In particular,nitrogen thermometry and gas concentration measurementsare described.

We present preliminary results on flame temperaturemeasurements and on the diagnostics of a tubularcatalytic chemical reactor (CO • H • huH«w*rhnnO.

• k B MINIATURE CO? WAVEGUIDE LASER

D. Schaieder. C.B. Dickerson and 0 Preussler

Optical Science! Division, NPBL/CSIE

CO, waveguide later* can be exciterd in the DC and BF•ode. They find applications at later radar transmitterand in laser eoaaunication systeas. Mt report hereabout our effort to build « CO^ DC excited waveguidelaser and give aore details about electrode construc-tion, cooling and stabilization problems. In a firstattempt ve achieved an output power of 4 Watt in a 450•a long device.

D6 THE USE OF A WAVEGUIDE AS RAMAN CELL FORGENERATION OF IR LASER LIGHT

M Budzinski and D J Brink

Generation of far infrared laser light by Raman scatter-ing can be substantially enhanced by confining theinteracting beams in a low-loss waveguide. The paperwill discuss che construction and characteristics ofsuch a waveguide cell.

D7 BOH-LIMEA* OPTICS: SOME PRINCIPLES AMP

D. J. Irink. C3»

(ton-linear interactions of light waves aaong themselvesand with the aediua they pats through encompass a viderang* of interesting and often useful phenomena. These,however, usually only occur at such high intentitiet thatpowerful later beau are a prerequisite for practicalutilization. Consequently the field of non-linear op-tics it s t i l l relatively new with large scope for futuredevelopments. The lecture will outline tli* main prin-ciples at well as some applications and future trends inthis field.

OPTICAL FIBRE COMMUNICATIONS

S Our , Aberdare Group

Optical f ibre has grown exp los ive ly from theore t i ca lconcept to large scale installation within the lastIS years. This paper will discuss this fast growingtechnology and its applicability in today's comsunica-tion networks both for long distance and intra-officeapplications.

D9/».¥. SCHCLT2Carl Md Billy Fuchs Institute for Micro Electronics,University of Pretoria.

Aco ito-opt1c (AD) and electro-optic (E0) Interactioncan be levieMnttd siauUtneously 1n a surface-acoustic-nave (SAM) device. The resulting acousto-electro-optic (AEO) Interaction can be used to givethe designer of optical signal processing devices aoref lex ib i l i ty than the c u t «h«re to or CO Interaction1i ased jeperately. This paptr wi l l discuss thecoup1ed-e»rfe theory that has been developed todescribe this Interaction, as M i l as practicalresults obtained wUh Raun-Nath diffraction.

D10 on ciinom VM Afoonxan IMOil OHTWiKP V3MI '» aKOMTO-

OrTllSt

In die ontworp van 'n akoeste-optiea*

•p«ktruaanalla««rd<ir epacl tw*e>

paraaetera nl reeoluale en dlnealeae

becaik balangrlka rolle. In hlecdla

rafaraat sal aangetoon word hoadat

apodlaaalm "jmbrulk kan word oa bei.de

hlerdle paraaatare ta opttmaar. Raaultate

van *n alaulaala eal beapreek an eovar

aoontllk a«t praktleae raaultate vergelyk

word*

87

D11 KlUIHEAMTEITE IN AKKST9-

A.J.HOFFHMICarl tn Gaily Fucnsinstituut v1r Mkrolitktronika,Univtrsittit van Pretoria.

'n Fundwtnttit btptrking wort op dta dinwitt i btrtikvan 'n tkotsto-opttm prostssttrdtr gaplaas dtur ditopwtkiring van inttmodutuitproduktt. Oit twtt bt-lanarikstt ananisats vir dit opwtkfcing van Inttrwdu-lasitproduktt Is akotsto-optitst ftstmdulasit tn nit-I int t r t akotstitst voortpianting. 'n Viskundigt lodtiwat hitrdit t f f tktt btskryf, word aangabitd. Oitttndiatnsiontlt anal l i t vir dit voortpianting vanakotstitst goiwt In n1t«11nttrt Md1a, wat rttds voor-hatn dturgtvotr Is, word ultgtbrti na twtt of dritdiuwnsits. D1t twtt MgaMsnts word vtrgtiyk In tera*van dit dcgradering In wtrkvtrrigting van dit Sragg-st l . Voorwaardts wat dit don1nans1t van ttn van dittwtt meganisMs sal bapaal, word btsprttk.

012 u:u;r.\i.uuu;'i.UJC~Kxr;- <•• i v

F. $ . RONSCarl a* brily Fwh» InatUutit vir HUrMiaktrmiUaUnivtrsittit van Pretoria

Vtrsktit kodtringsttgnttk* Is voorgutti v1r ditkodtring van rtktnaar-gtgtntrttdt-ho1ograt»t ( MH). 'n itiangrika totpasiirtg van MHi Is waar ditgtbruik word as tangtpasdt nilnU'lkt filters inoptitM korrtiasit tttistTs. '» StHdit Is gtdotn Mdit vtrskilitndt kodtringstwnitkt In hitrdittotpassing t t tvaiuttr. 01t tvaluasit is s»t bthulpvan 'n rt«ks »lau)as1ts uttgtvotr. Ott btvtntftnfsvan hitrdit studit tn d1t siswlasits wat ultgtvotrIs sal btspratk word.

Oit tfftktitwa gtbruik van optitst drywing 1s 'nbaUngrikt asptk In dit ontwtrp van aangtpasdtru1itt?<kt f i i t t rs . H1erd!t asptk tn dit Inviotd watfast tn uplitudt daarop iitt sal totgtUg word.

SOLAR-TERRESTRIAL PHYSICS E SON-AARDFISIKA

El SOUR-JERRESTRIM^HYSICS^THEIONOSPHERE AND THE MIDOLE ATMOSPHERE

J A Gledhill, Hermann Ohlthaver Institute forAercnamy, Rhodes University, Grahamstown

The effects af solar ultraviolet and X-ray photonsand charged particles on the upper atmosphere arediscussed. The formation of the Ionosphere and itseffects on redio waves and the emission of airglowand the aurora are described. In the middleatmosphere the emphasis is on the formation of ozoneand its destruction by chlorofluorocarbons and otherminor constituents.

E3 DATAVERWERKINGliMETODES VIR KLEINABSORPSlESNORMAALVER<IORI

SERFON

N RIOMETERDATA MET NIE

• n P . H . STOKEIN (PU v i r CHO)

(PU v i r CHO)

Riometardata i» by SANAE*Ba»i t Antarkt ika( L M )v*r»am«l. D i * doal van d i * «k*perim«nt is omrcsonanspratipitasi* van * t ra l inggord* i -• l «k t ron« , d t u r fluit«rmod*-go!tv« in diaBLF-radiogtbiad( 2-6 kHz), t* vtrifieer. Dietftktront word in di* ionotfnr g*presipite*r•n veroortaak ionisasia, wat wa«rhoogfrikwant* radiogolw«( 20 MHZ) absorbesr.Hicrdi* «biorpti*s is bar. '-l«in( «0.2 dB) ankan wtens impulsitws •t«aring» in diadat»( totnamts in intantitait), baia mocilikin dia data ondertkai word. Hierdi* steuringtword varwydar m.b.v. *n filtar wat stark stem?op die fisiki van dia ionosf«er.

E2 AURORAGEBEURTENIS VAN 27 JUNIE 1982

P.H. Stoker en A.G. CoeC2er, PU vir CHO

HoogteproJleLe vlr energleverlies van elektrone enhulle X-scrale Is met behulp van Mono Carlo-meCodesdeur Berger et al. (J.A.T.P. 35, 591, 1974) b«rek*n.Hierdle berekenlnge is gebruik on die absorpsie vankosmiese radioruis van 20, 30 en 31.4 MHz vir eksponen.-siSle elektronspektra met vouenergie 10, SO en 200 keVC* bereken. Hierdie berekeninge is gebruik om dieabsorpsiegebeurtenls wat gedurende die vroei oggendurevan 27 Junie 1982 ce Sanae waargeneem is, te oneleed.Aanduldlngs is verkry dac golflengteverstrooiing vanafdie helderder dele van die radlo-hemelruim volgens dieBragg-voorwaarde voorgekom het.

E4 EJ^CTRONPRECIPn^ONEFfECTSINTHEDAYTIME E-RE6I0N IN THE SOUTH ATLANTICSNDMALT

R Haggard and J A Gledhi11Hermann onlthaver Institute for Aeronomy, RhodesUniversity, Grahamstown, 6140, South AfricaAnalysis of the diurnal variation of foE during theInternational South Atlantic Anomaly Campaign(ISAAC), an a cruise from Cape Town via Gough Islandto 30°S 45°w and back, shows that an extra source ofionization in addition to solar photoionization ispresent. The magnitude and variation of this extrasource in the South Atlantic Anomaly agree remarkablywell with the ionization that would be produced byprecipitating electrons measured by AtmosphereExplorer C.

AW tVALUATIOM Of COWPOCTRIUPMITHODS FOR HF MUF PWEDICTIOW

3. Lambert. KITH, Johannesburg

computer programs are available for-Tedlctlng Haxiaua Oaeable Frequencies forE* coaaiunlcations. Agreement between thePredictions and experimental Kaxiaua Observedfrequanciaa ia oftan disappointing, evenwhen vertical-incidence critical frequencleamatch closely.

Syt arrora axpactad froa coaaonlyua«d pradictlon programs axa outllnad. Raytracing through aora raalistic ionoapharic•odeIs makas quantitaciva arror estiaateepossible. Results are presented and eoapantdwith experimental data where possible.

E6 OBSEBVATIOHS OP GRAVIT* WAVES AT DURBANM.B. Barker. Physic* Dept. Univarsity ofNatal, Durban.

Observations of cloud patterns provide evidence fortha presence of gravity waves In the high altitudewesterly wind* prevailing over Durban. Thecharacteristics of these gravity wave* will bediscussed.

UL OF COUPLEDSMrrOSOMC AKO ALFVtH WAVE3 AT

-S§S"gg«B*. ttkddu andDepartment of Phyaica,Univeraity of Natal,Durban, 4001A sat of coupled aquations describinghydroaagnetic wavas with short asiauthalwavelength has bean developed. This iaexpected, to be useful in the atudy of PcSpulsations near geostationary orbit.Computations have bean carried out to find tftecharacteristic pariods and polarisationstructure of such waves. The results arecompared with obeervatione. Some features ofthe calculations are that tha coapraasionaland Meridional coapononts of tha acgneticfield perturbation are of opposite ayaoMtrieaabout the equator. Tha oscillation for higherkaraonics can be confinad to a region quitecloae to tha equator.

E10 DAWK Pc5 PULSATIOHSH.D. Barker. Physics Dept.iatal, Durban.

University of

Clear PcS pulsations of period approximately 300aeconds are observed infrequently at SANAZ over anuaber of daya. Coaparison of results of spectralanalysis of dawn pulsations observed during 12th-27thDoceaber 1970 and 8th-l«th Moveaber 1972 are presented.

E7 1KCLPSIOH OP A WAVT BEOTIAL SHEET IH ATWO-DIMENSIONAL DRIFT MODEL

•..A. Burger. M.S.* Potg later and B. MoraalPU/CSIR Coiaic Ray Research Unit, Poechefstrooa

Two e x i s t i n g aechods for the Incorporation of neutralsheet drift In tm-dlaensloiial drift aodels are evalua-ted and coopered to a aodel which uses the actualneutral sheet drift velocity field. We show "^*t thecornea denominator between physically correct t«tbodsIs a-spatially averaged neutral sheet drift of •agnltudcv/6> end that It Is possible to elaulate the (fleet ofe vavy neutral aheet by decreasing this quantity.

A IfNIFTEl? 1TL9 PtTLflA.

A. P. M. WaJfcet* and J. F. McKeniie*.Vnivtrntif of Natal, Dvrlan.A unified theory of standing hydromagnctie oscillations in a re-alistic magnetic field geometry is developed. The theory allowsfor two plasma ipeciss, one hot and one cold and can thus beUKd for modelling pulsations in a region of ring current.' Whilecylindrical symmetry is assumed the theory is otherwise applica-ble to an arbitrary geometry. An important feature of the theoryis that cut-off frequencies are displayed explicitly. These cut-offfrcqnencks arise from the geometry and the inhomogeneitiai inthe medium. Furthermore, in appropriate circumstances, some ofthese cut-off frequencies may be imaginary, allowing the possibil-ity of instabilities. In this paper some examples of the applicationof the theory are given.

*D«p*rtm«*t of T jwics*D«p*rtmmt of Miiatmatks aad Applitd MatfctnUka

Ell IONOSPHERIC PUISATIOH flElDS AMDUR UB5fcCTH> WUPKLtK VELOCITYTKClUATlOHS

A H V Pooltf, P R Sutclifft* «nd A 0 M Milker*» H*n*m cnlthaver Institute for Aarooosy, Rhodes

University* Magnetic Observatory, Herainus> Oepartatftt of •ftyilci. University of Natal. DurbanGrovxi basad Mgrwtlc pulsation •NSunaants ftavti*jA sham to be «ccosp*nisd by oscillations In theDappler velocity of ionospheric echoes recorded by •co-located digital lonosonde. By calculating thecosplex amplitude of the electric and Magnetic fieldsIn the ionosphere. It Is possible to quantify therelative contriiHitlons of the various sscfcanlsssHhlch give rise to the Ooppler pulsations.Indications are that the sost isportant are:(i) bodily vertical aoveaent of the Ionosphere underthe action of the eastward directed electric fieldand (11) Increases of plasaa density along the raypath proportional to tha field aligned component ofthe pulsation sjgnetic field.

E12 VO. IP^TIOMSHIP BETMIEM LATITUDEAMD THE EISEH?ESIOD OF Pc3POXSATIOHS

S K P Hattlnah and P B Sutdlff*. HagnetlcObaervatory, BerBanua

A distinct latitude dependence is evident In theelgeaperlod of Pc3 pulsations recorded during 1982 ata nuaber of altea lying along a coeBon geoaagnetlcaerldlan la Southern Africa. Hodel calculationsbased oa the assumption that pulsations recorded onthe ground arise froa standing Alfvln waves ongeoaagnetlc field lines support these obsarvatlona.Data collected during subsequeae »utvy» (19S6 sad19S7), however, show no latitude dependence In thedoalaanc period. lesults froa the varloua aurveysare presented and possible ressons for thadifferences discussed.

89

E13 RESOLUTION Of TEMPORAL ANP gPATIALAMBIGUITIES IN PULSATING AURORAn.J. Koict, and M.W.J. Scourfleldpnyaiea Dept., Uni varsity of Natal, Durban.

Th« detailed «volution or an auroral fora In apaea andtin« has an Important Input to understanding th«associated electron precipitation Mchanlaa. TV iaagaaof aurora racorded at SANAE, Antarctica, ara analytadusing advanced digital laag« processing tachniquaa.w« show that such techniques »vav« r«v«al«d that it isessential to unravel any spatial-teaporal aabilgultlea.

El 4 A SOURCE FOB 3 Hi AURORAL PULSATIONSH.J. Hansen, E. Hravlag and M.H.J.Scourf i e l i , Dept. of Physics, University

of Natal, Durban.

Correlated auroral and VLF taissiona hav« been Identi -fied at L : 1 during simultaneous recordings of 'TVauroral images as>ä broadband VLF. Coaaon per iodic i t i e sof 1.5 * 0.3 Hz and 3.0 ± 0.1 Hz occur in the powerspectra of both the VLF and the optical intensity vari-a t ions . These are shown to be consistent with anexternal o sc i l l a tor source driving at a frequency ofaoout 3 Hz with varying amplitude. The externalsource induces wave growth and strong pitch anglescattering via the cyclotron resonance interactionwhan the electron pitch angle distribution functioni s such that the f lux l eve l s exceed the flux trappingliait.

E17 THE RELATIONSHIP BETVllM THE PLASHA3PHES»AND AURORAL OVALJ. Stephenaon and M.W.J. Scourfield

Th* poaition of auroral torn», observed at SAJIAE by alight level TV ay«tea, la uaed to define th« poaitionof th« auroral oval. Simultaneous whiatlerobservations *p» ua«d to demarcate th« position ofth« plasaaaphcr«. A eooparlaon of th« spatial re-lationship between th« plasaasphere and oval can beused to gain an insight Into th« relativ« raapons« ofthese two région« to changing magnetic conditions.Indirectly it is also possible to answer th« questionof whether auroral precipitation occurs on closedmagnetic field Unas.

E18 OF WHISTLERS IN THEKEG ION OF SANAE -ANTARCTICA

J.M. Ludwig ud A.K.W. Huf hw.DtpêttmtiU of Pkfrict, Ihnwtnitf of S*t*i, Dtrttn.

Ova 1300 Wkiitlen *n toUywd from VLF d>U »corded durinf 1985. Exit*point« «r» dcttnnintd vine tkt L-vtlne ud (he uimutb of tm'vtL Tktdutibation of tket* poiai* à duciund.

E15 AURORAL PULSATIONS AND ASSOCIATED CHORUSH.J. Hansen and M.W.J. Scourfield.Oept. of Physics, University of Natal,Durban.

Images of pulsating aurorae and correlated chorus ele-•ents have been observed in television and broad-bandVLP recordings' at Sanaa (L : 4).

Peaks in auroral-light intensity are displaced In timeby -400 to 4-400 as from the associated chrous ale-•ents. On frequency versus tlae spectrograms theslopes of successive chorus groups change in s randommanner.

These results are compatible with a gyroresonanceinteraction between VLF waves and 50 to 200 keVelectrons. The source Is randomly located withina region extending from the equatorial plane to aposition 8000 km beyond it. A relaxation oscillatorBOdel (G.T. Davidson, J. Geophys. Res., 81, 6517-6523, 1979) is suggested as the modulation source.

El 9 RAY-TRACING STUDIES OF THEPROPAGATION PATHS OF VLF SIGNALSORIGINATING HEAR THE EQUATOR

Pravsh RamlalJ and A. D.M. WalkerDepartment of Phymics,University of Natal,Durban, 4001A ray tracing program ha» b««n developed tostudy the propagation of radio waves in r.magneto-ionic aediua. In this paper we use itto study the patlis of vl? »ignäls originatingin various parts of the aagnetosphere,particularly near the equatorial plane in thepresence and absence of ducts. The resultsare applied to aid the understanding of thepropagation path of waves which arise froacyclotron resonance with energetic particles.

E16 AH INTERPRETATION OF SO-CALLED 'DRIFTINGDARK AURORA'H. Schoute-Vanneck M.W.J. Scourfield andE. Mravlag, Physics Dept., University ofNatal, Durban.

A comprehensive data set has been assembled on thephenomena of 'dark aurora' from observations made atSkibotn, Noruay (L : 6,6). The set consists of lowlight level TV observations, electric fields fromSTARE and particle data from GEOS.

We will show that the 'drifting dark aurora' couldoccur as the result of luminous regions moving throughstable dark channels embedded in the background aurora.The auroral precipitation is of limited verticalextent and the movement of luminous regions is anapparent effect resulting from the localized fieldaligned extension of the auroral precipitation.

E20 WINO PATTERNS IN THE METEOR REGION

L.M.G. POOtE Rhodes University

A coherent wave ireteor radar system has been inoperation near Grahamstown for the past year.Ooppier shifts in radio echoes from ionized meteortrains enable drifts due to motion of the neutralatmosphere at meteor heights (winds) to be determined.Some results obtained to date will be presentedand discussed with particular reference to diurnaland other periodicities found cy spectral analysisof the data.

90

E21lay***

t

CEOHACMTIC IWWCTIO1I tTPICTSC I M 3 d W M t > . KiWtlC Obaarratory

curreata flowlag la tb« lemoaphara aaaladuca eurrwca la tha eoaductlag

•*• Earca. Tha aatura of Che Inducedearr dependa on tha ccadacdvlty la thaMi(ltbouraood of tha obatrraeloa polat. LateralHacoaclaaldaa la tha conducting layera will producelaoar*— varlttloaa la tha vartlcal coapoaaac of Chegeoaataeclc field. Tha affact la lUuaeratad by thabehaviour of tha Z variation* recorded to thariclaity of Baraaaua. A battar understanding ofInduction aooaallaa la Important for various(«caagnatlc application*.

SIMULATION ON A HASSIVEIY PARALLEL

l.M.A. fiUdhlll. o. Bunwun and L.R.O. StoreyS I M L M , Stanford University

Parallel computers Kith large nuaiMrs of proc«»ingtl«wnts art toslymd for highly r tp t t l t i v * sets ofcalculations, such is tho*t for ttcii partlcl« andgrid point In • P U S M sisuUtion. W* dtscribt asiMlation for NASA's MPP (Sassivtly ParallelProcessor), Mtiich consists of 16384 proctssingelajMitts, each with local maory. conntctsd In atMo-dlwnstonal atsh, and operating in locksttp.Tht mdt l Is ful ly electromagnetic and re lat iv lst lc ,and eaploy? 2k diaensions (two spatial and threevelocity). The sipping of particle and f ie ld dataand corresponding choice of algorithm depend on bothhardware architecture and the problwi in hand, andnew algorithms have been developed accordingly.TlRing results show that under optiMl conditionsthe MPP competes with conventional supercomputers.

ASTROPHYSICS ANDASTRONOMY

ASTROFISIKA ENSTERREKUNOE

F1 SDPERHOVAE

H.V. F«««t. SAAO

Our currant understanding of suparaova t i p l o s i o n s w i l lba o u t l i n a d . Tha iaportanca of thata avants i n a s t r o -physics and co«nology w i l l ba s t r a s s a d . Sooe coaoantson tha 1987 suparnova i n tha Large Hagal lanic Cloudw i l l ba aada as a background t o papara in s a c t i o n F.

PRESENTATION AND DISCUSSION OF DATAOBTAINED FOR THE SUPERNOVA 1987a ATTHE SOUTH AFRICAN ASTRONOMICALOBSERVATORY

R.M. CATCHPOLE SAAO

The b r i g h t e s t supernovc observed in 300 years occurredon February 23 1937 in the Large Magellanic Cloud.The South African Astronomical Observatory, i d e a l l yplaced to observe this event, has obtained excellentphotometric and spectrosc.opic data coverage. Thesedata, obtained by many members of staff, will bepresented and discussed.

The supernova is of type II but is atypical in thatafter the init ia l decline in brightness over the first5 days the supernova started to brighten exceeding i tsinitial luminosity within 30 days.

W 13 CM VERY LONC BASELINE INTERFER-OMETRIC OBSERVATIONS OF THE SUPER-

. HOVA SN 1987A.A. Cuba.:1", at al .

'Hartebees"hoek Radio Aatronoay Observatory

During tha period Fab 28 to Mar 2 1987 i n t e r -f e r o a e t r i c obaarvatlona at 13 ca wavelengthwere carr i ed out of the supernova SN 1987Ain chs Large Megellanlc Cloud using tha longb t a a l l n a between the Hartebecsthoak RadioAatronoay Obaarvatory (Johannesburg) and DSS42, a radio telescope at Tldblnbllla, Australia.Tha ala of tha experiment waa the determinat-ion of tha angular siza of the supernovashall during tha early stages of expansion.Prallaloary result* ara reported.

M DWARF NOVAE, NOVAE, BUT NOT SUPER-

NOVAEBrian Warner, Department of Astronomy,Umutpaity of Cave TownA review of some of the research on cataclysmicvariable stars being undertaken at the Univer-s i ty of Cape Town.

F5 THE AGING OF OLD DEGENERATES : ASTERO-

SEISH0L06Y OF WHITE DWARF STARS

D. O'Danoqhue. Department of AstronomyUniversity of Cape Town

The use of pulsations as seismic probes of the structureof white dwarf stars is reviewed and a description ofwork in this area being carried out at the "niversityof Cape Town given.

91

P6 IKrUCATIOHS O F » » »NOtfRn.DIAL PULSAIIOH MODE

C A BngalbrechtDepartaent of Phys ic* . University of South Afr ica

Rapid stellar rotation and ii.j concoadtant distortionof th* spherical gtoaatry of a star My have aataeurable effect on th« shapes of the radial velocitycurve and th<> light curve. An investigation of thiseffect ic discussed and implications for pulsation•ode identification are considered.

F7 OBSERVATIONS OF SHORT PERIOD Be STABS INTHE YOUNG GALACTIC CLUSTER HGC3T66

F10 A TeV TRIPLE PEAK FROM P$ftt9Ot>Mr

0* Jaqar.O.C., Raubenhahner,6.C., Nerth.A.R., 0 *jager, H. I . and van Urk.C.

PU/CSIR Cosmic Ray Research Unit, PotchefstroomUniversity

Vary high energy I-ray (VHE) observations ofPSR1509-S8 with the Potchafftroom Carankov telescopeproduced positive results which indicate that the lightcurve hat a tripla p«ak with phase conservation for atleast eievan days, whilst the I-ray output was steadyfrom night to night. Tha significance of tha third

harmonic alone ia 6*10 . A naw tast was developed toidentify this pulsar at a final confidence level of 99.92%.

Tha VHE luminosity of this pulsar is 3«HT* erg s"1 atan energy threshold Ej>2 TaV. This luminosity is in

accordance with calculationsT-ray production models.

from existing outar gap

WITHDRAWN

W SOME QUESTIONS ABOUT THEHYDRODYNAMICS OF ACCRSTION DISKS

Chris Koen, University of Bophuthatswana.

Two alternatives to the standard -modelof disk accretion, namely semi-radial andpressure driven accretion, are discussed. Anumber of questions regarding the possibilityand nature of turbulence and turbulentstresses in disks are raised.

F11 THE EXPECTED TaV GAMMA-RAY FLUXFROM ISOLATED PULSARS.,

O.C. da Jager, H. I . da Jager and B.C. Raubanhaimar.

PU/CSIR Cosmic Ray Research Unit, PotchefstroomUniversity

Evaluating existing models for isolated pulsars, wefound that both tha polar cap and outer gap models canproduce TeV gamma-ray emission, but from differentpopulations of pulsars. The outer gap modal explainsthe radiation from all five known TeV gamma-raypulsars successfully and identifies a number of candi-date sources.

FS PROPERTIES OF AL^VEM WAVE DRIVEN STELLARWINDS

U.K. Dougherty and J.F. McKenzie

Department of Mathematics andApplied Mathematics,University of Natal, Durban.

The equations of conservation of mass, momentum andenergy in a one-fluid theory vhich describe thesteady, spherically synnetric outflow of a plasmafrom a gravitating point mass, Ms, art generalized toinclude the effects of Alfven waves propagatingradially outward. The critical point requirementswhich ensure a snooth subsonic - supersonic flowtogether with the Bernoulli - fom oi Che energyequation are used to determine tha mass flux andultimate speed of the wind. The results for variousvalues of adiabatic index, r and wave pressure arediscussed. In particular, it is shown that Alfvenwaves can have a dramatic effect on the properties ofthe wind.

F12 A SEARCH FOR SOURCES OF UL7 ^HIGH ENERGY GAMMA-RAYS WITH THEPOTCHEFSTROOM EXTENSIVE AIRSHOWER ARRAY.

D.J.Van Oar Walt, B.C.Raubenheimer, 0 .0 .De Jager,A.R.North, C.Van Urk and E.J.De Villiers.

PU/CSIR Cosmic Ray Research Unit. PotchefstroomUniversity

Results are presented which confirm that Vela X-1 isa PcV gamma-ray emitter. As in the case of Cyg X-3this effect was only found for showers with large ageparameters. The light curve may indicate that PeVgamma-rays are emitted by a particle beam interactingwith the limb of tha companion star.

92

F13 FURTHER RESULTS FROM THE RHODES j.3 GHzSURVEY. ""

S.University

During March and Apri1 1986 we observed an area ofthe southern sky, S hrs to 12 hrsM -24s to -63s Dec, at 2.3 GHz using themrtrteesthoek radio telescope. This paperreports on a number of interesting features visiblein the data.

F14 OH MASERS IN SODTHERN IRAS SOURCES

M E Dollery •. fH J Gaylard•ad ft J Cohen

P A Whitelock

•Hartebeesthoek Radio Astronomy Observatory•South African Astronomical Observatoryfjoarell Bank, UK

A set of UU southern IRAS sources were•elected as being possible OH/IR stars on thebads of their infrared colours. Ten of thesewere already known OH/IR stars. Of the 34unknown sources about one third showed 1612 MHsOH maser emission with the characteristicdouble-peaked spectrum. Some of them alsoshowed 166S and 1667 MHz OH user emission.JHKL photometry has been done on most of thesources and the infrared spectra of the maserand non-maser sources are compared. The lowresolution spectra of the sources are alsocompared, where available.

F15 OH MASSES IN OBJECTS SHOWISC 10 MICRON

ABSORPTION

M J Caylard . H E Dolltry , P A Whltslock

* Hartebeesthoek Radio Astrouoay Obsirvatory

+ South African Astronomical Observatory

The infra-rtd spectra of OH/IR stars, which posses*dense, cool, oxygen-rich dust shells, often exhibita strong absorption feature attributed to silicates,at a wavelength of 10 microns. Ten southern infra-redsources showing such a feature were selected froa theIRAS Atlas of Low Resolution Spcctr*. They wereobservti at 18 ca wavelength using the Hartebeesthoekantenna. The characteristic double-peaked OH maseremission at 1612 MHz was detected in eight of the ten.None showed detectable main line emission at 1665 or1657 MHz.

EDUCATION OPLEIDING

G1 THE TASK OF THE UNIVERSITY

W. de Haas - University of the North, Qwaqva Branch

With the independence of the Qwaqwa Branch of the

University of the North just around the corner, it

seems an opportunity to reflect upon the task of a

university arl to attempt an answer to the question:

what is a university?

G2 HUMITURE OR DISCOMFORT INDEX, D.I.M.D. Barker. Physics Dept. University ofNatal, Durban.

During the months December to March, the high air temp-erature and high humidity conditions along the Natalcoast result in discomfort for humans and animals.

Oiinatoiugical records for the period January to March1987 will be presented, illustrating the unusuallyhigh occurrence of days and nights of extreme discom-fort during these months. The physiological effectsof conditions of high Discomfort Index will bediscussed.

93

G3 HILL COMPUTERS REPLACE PHYSICSPROFESSORS?

6 E Oberew, Rhodes UniversityComputer-assisted instruction (CA1) is being used to* limited extent by several Physics Departments inSouth Africa. In this paper, S O M of the questionsfrequently asked about CAI by persons new to thisarea of Physics Education will be addressed, forexample ."can computers really teach Physics and if sowhat do they do best?" A brief review of some of theprograms available will be presented together with anindication of where the future emphasis Bight lit.

GS CONCEPTUAL PROBLEMS IX SIMPLE PC CIRCUIT*.

thWtarUnafcS

H. Stanton University of the MittatersrandAn In-depth study has bc«n M d e of the responsesoffered by students to two questions on series andparallel resistors In 1986 exMinations at the Uni-versity of the Witwatersrand. The students concernedC U M mainly from academically disedvantaged back-grounds.It Is clear that a number of misconceptions concerningelectric current and PO are very prevalent and persis-tent; these will be described and discussed. Thestudy also attempts to show the timilarttii* anddiffcvnot* that exist between the Alternative con-ceptual frameworks exhibited by these students tn4comparative studies made In Israel and the USA.

G4 SIMPLE ELECTSICM. CIRCUITSA PRACTICAL TUTORIAL

U.S. AlIle and J.E. KingUniversity of Cape Town

First year students often experience problemsin trying to reconcile the symbolicrepresentation of electrical circuits with thepractical realisations thereof. The result ofthis is that many baste circuit laws are notreally understood In practice and curiousmisconceptions arise. In the case of Physicsstudents on our Academic Support ProgrammeScience Foundation Year the problem Is moreacute owIng to genera11y dIsadvantagedbackgrounds. A simple laboratory practical onelectrical circuits was developed with the aimof addressing the problems described. Basicconcepts such as res I si tors In series and Inparallel are covered.

G6 THE SIMPLE ELECTMC CIRCUIT AS AW ENEKCYSYSTEM: SOME CONCEPTUAL DimCULTIESWHICH CONFRONT STUDENTS IB SIMPLE CIRCUITTHEORY

Z JIYA: UNIVERSITY OP FORT HARE

Conceptions of students about tl» electric circuit asan energy systesi 4T« established and discus tad. Thaninappropriata conceptions ara justified in tana ofth« atomistic approach to reaaonln| about naturalphanoaana, which accepts that a physical problaat isunderstood, at least in principle, If it ts explainedin aechanical tenac. An argument ia put forwardagainst accepting that an energy system may be satis-factorily understood without using the approach toenergy genarallv used in thers»dvna*ics and quantumtheory.The difficulties with conceptualization in tens ofthe frjaevork of eaf, potential, potential!energy)difference are highlighted and the influence of noe»nclature on the understanding of the theory is analy-sed. Certain guidelines towards resolution of theseproblem* ara proposed.

APPLIED ANDINDUSTRIAL PHYSICS H

TOEGEPASTE- ENNYWERHEIDSFISIKA

HI\ Strtdcat. A H Lauacbnar

Atoo««Q«riUROrpora«l« vao SA apk

Dla tocaU bavolklat oaxvaaa. 'a srotar doala loasaaraada atrallng wmindM»sl|srodiikta aa i m f alia «ait«r aroaoa taaaa*. I t d H ta ' • adalfaavac me radluadraaada u c a r u l t aatanaa. jUnoival dla frakalooalaradltiakoaairacrislaa la utuurllka iioad aal< ' laa| l a , la dlt i l lradloloilea nalaacbaar o n . !laaallka aitlvltalc* aaea waou U i <U<radlaaKocavatxaalta ta aia o«atvlog varaoof «a aodoaodt ook 'aradio:jaltaa lapaL *t 41a bcvol«lax -if* Xadowtiaacocrialva varlaar cuaaaa'o paar H"3 ">' lu>od>rda H/s 3 . ladon la 'a b«»«««H«« taa an ayradlolojUM • I fat «otd Wpaai daur a; »ol|»toduktt. Ola aatlag van radoe<a «aa a; radloloalaaa lapaa barua op dla attla* «aa »r <ol(>roduata.Da*r baatua 'a varakfldaoftald vao aaattagalata vtr radoa aa ay<ol|oridti*u. Ola AB la die «f»«lcpt M l jaar Ma l i att 'oradou«ltaclli<|>ra|raa oat dla oct«l«k«Llm >u Mt law aa paaalamradoo«acca(t>ltk> loslult. Hlardla casiuia It oorxlkul oaradoakooaaat?aalaa al&aaaahvla io«*l «a 1ft dla aaiaavlat ca aaaaal.

H2 CHARACTERISATION OF THE WAC NEUTRONTHERAPY g

O.T.L. Jones*, H. Yudelev* end W.L.J. Hendrikse*•National Accelerator Centre•Faure Hospital

The neutron therapy facility at the NationalAccelerator Centre has been operational since February1987. A baas» of 66 MeV protons is used to produceneutrons fro* a beryllium target.. The target islocated in en isocentric gantry which is capable of±185° rotation. Neutron fields fro* 5 ct > J d to30 c« * 30 c" are defined by a rotatable continuouslyvariable "book-end" collimator. A manually activatedmoving floor has been constructed to permit fullrotation of the gantry. Preliminary measurements ofthe beam characteristics hsve been wade. A fulldescription of the Facility will be given and Sdetailed analysis of the neutron bees properties willbe presented.

H3* . a al«tttaaatrall*| w< niaietkd »|r laaaaralfla q i

***Trf.i.i««aUalt tttallaetataaattatio* (UnU. Me nKHlfiwr*J* £ T » »MtlllM«H »aa aadltaa atatakta Ml aalu katualart ti* * " * anaatl«ta< iwtri. M* *rlt ilpa* •»•)!•* Mi tJt takan

_ • banal t "•» «taaaaattattakaala»t I t 'a Mafia »aa rawalJIaaaaZH^m .an -a laaaJt-aO taal l t ia l t aaawt. •araklJlaaaa

faftacadlM la* tana «aa akaaaala at daalaaalfataitait ia aaa aat. a * aarakaaiaaa vlr 41a gakaaa aacwara gadaaa. Oltalaaa)ik la

[jajattla ratal u ta tackri vac ta«radtf*ad eat aarakatet caaultaia

H4H4a I l u l K l * ! * T t v l W , C I H l a a r * . G Da Lacaf

*t

skialdlis • ' aaciaar >SMC raaccota ia aa iaaattaat aaaact af cba

t i , laartctt ' Miclaaf Sociaty Staadataa Caaaictaa 4.1.1.taaat t< ctlltasrttora fton tha la t tmt ioaa l aclaatlftc

•It. aalTa tba atokUaa tialat Uffaraac eoaauutlaaat tacaai«uat aad,ru«4act laa data kaaaa. Tka ratalta tktalaad ia tall "»T aca coaparadlITcaaclytlaaa CM U «raaa aa tka Uiamcj af tka cnta-aactloa tetaZ t a aaad aad caaa»tatlaaal tacbkl«uaa. laaattaat itaat paraaatart caaJT-. M avalaHad la tana af accuracy aad acaaiaj »t caaaatat kacdmrenaviraaaata. Ika tatulu «1U alae aa coaaawa «ltk aiparlantal dataif tatf aaceaa avallaUa. . . . * .

n a anMaat da*c<lkad kava a caaaaa oaJacciT. af calcalatlas t^*ndUtiaa imU at aaactflc lacattaaa U a aaa-dlatultaal U»ke uatac•aactar raarataatatlaa at c a n aldalaaa. lack anklaa aaa datlaad «itkmt rttkoat tkt ccacrata aklald aad lU«t ta aldar ta aataralaa tkalautat fratawa vaaaal. Uakaaa. Tha raaulta too. tka chaa«aa ia aavccsaa>j akatoa daaa ratat aad tka cattaapaadlas aaataj aatctta at oartowa

-. dlataacaiat tka eota r ' - - 1 —

H5 jlMO VAX 'N TtLClOMtTKItSSMT1WC VAN»f -II 5AMMA1KO

[ Cr..ff an J a Vantar, AIK van SA

'a Studia batraffanda dia ultstraling van Co«ptonalaktrona uit'a fotonba-atraalda 7at*rakjf« >a fadoan. *n Kobalt-SO-»untbrondian aa bron van

Itt osiiaua dikta van dia akrf t«t opai(t* van di«.laktroauitatraling it «kss«ria«nta*l ta tooratlaa bapaal.y.rakllland. diktaa van *n yatarakjf it ia dia aktpariaanttakrulk. an di* oatisua dikta it bapaal dtur di* aantalcl.ilrona n t uit dia akyf vrrlaata) "ord, ta lat.

Dia iaeraticaa to«rakanlng b*hala di* nabootainc van dia proaaaaat 'n Horn. Carlo-aetod*.

H7 HEUTMM ACTIVAT1OH OF LA«CE SAWLES U8IHCA OWE HUXICHAH CALironwiuti T51 souicE

M. lycoudi **& J.I-W.tfaccanonWiti-CSH School and Kaitarch Cantr* for Nuclaar Sci«nc«»,Univariicy of th« Uicvatarirand, Johannaaburc> S. Africa.

A n«w oachod for analysing oras and ainaralf ia iotro-ducad uaing iiotopt-tourca nautron accivacioiuNautrontand (atjau-raya ara highly panacracing radiationa and thaaachod ia uaad ee analyta taaplas in bulk. This ovarcoaatinhoaoganaity and saapling preblaaa and iaprovaa tha aan-•it ivUy of eha aathod. laotop* aourea nautron activationhaa baan vidaly appliad to avail aaaplaadaa* than 50 g)and thia, togathar with tha low intanaity of tha aourca*haa providad inadaquata aanaicivity. Containing tha larganautron fluxaa available with an intanta Cf-2S2 nautrontourca and a aaopla aiza of tha ordar of a tbouaand eiaaatha sita practieabla for raactor irradiation, tha graataanaitivitiaa characteriatic of raactor nautron activat-ion analysis ara approached. The aethod i i non-destruct-ive but i t doea require a detailed study of the effectsof aeutren abd gaaaa-ray absorption.

Initial results comparing this aethod and conventionalreactor activation will be presented ud discussed inthe context of thil aooroach.

H8 REPORT ON PROMPT GAMMA NEUTXDS

ACTIVATION ANALYSIS AT SAFAU-1

C Hofmeyr, AEC

In-bcaa proatpt gaauu analysis utlllctag thenal-

aautroo capture foraa a part of neutron b«aa

utilization at the SAFARI-1 reactor. Progreaa will

be reported and dlacueaed. Reference will b* aade

to eleaental differentiation aa a function of

specific gravity In carboniferous eedlaeotary

deposits froa three locallty-apeciflc atrata. The

occurrence of coapound-deptndent variation In

•leaeatal aenaltlvity In aaall aaaplea will be

substantiated.

THE SMALL ANGLE NEUTRON SCATTERIWC

FACILITY AT PELISDABA

C B franklvn. AEC

It has become increasingly recognized chat neutron

scattering and especially small angle neutron scattering

(SANS) is * powerful and in some cases unique cool in

aaterials science studies. A review of the capabilities

of the SANS facility at Pelindaba, in che basic and

applied research field, will be given.

H9 DIE GEBRlTK VAK OITOR£GRESSIE»E METOPES »Y DIEU S t VA*» '.< SAVORS 1-SCSKERSREAKTOR

J N Conradi« *n f van Nickcrk. AEK van SA.

P J # a>nBliai* v»n n»ut.ronrui» by ti«rnr>*litorc OB b»si«acr*aktorhin«i i««« par«actcr» t» b»p»«1, i t r»eds 'n bekendetcrrc in van r * » h t o r f . a i k t . "n Rftdvl.lt onl»ngie ont**tklt«ling iaOB outor#^r#«*i*?™ t * o n • ta? t#bruik v t r di * b#r*k*ftiB# vanoutoMorr*lasi«t «n ipektra.

Oi* b*>»i«a* t«or i« v*n outor«ar*>«t««>e actod** Sftl bcaprttfc•ord , asook vo^rlop.ge r e s u l t a t * van d i * l o c p a s u n l nivrvan opb*ak*kbarw nvutronrui idata.

95

H10 RADIOISOTOOPPROOUK-SIEPROGHAH TE FAURE

H14 PIXB ANALYSIS OP.HINntAL MATTfB JN

S.3. HlllaNaelonaie""Veranellaraentrua

•n Ooralg M l gsgee word van die vordering wet geaaekla M t die beplanda aanvanklike radioisotoopprodukaie-pcogrtM by did NVS a* oopaektoralklotronfaailiteit taFaura. Baplartde an andar aoontlika to«ko«atlgaultbraiding tot hlerdie prograa aal ook kortlikaoeapreek word.

H11 PRODUKSIE VAN 1 2 3I BY DIE NVS - EERSTEERVARINGS

F.H. Nortier*. G.F. Steyn*, S.O. Hills* enW.I. Rautenbaeh**Naaionale Versnellersentrun•Universiteit van Stellenbosch

1 2 3I ia een van die eerate radiolsotope vir aediesetoepasaings wat by die NVS, Faure se isotoopprodukaie-raailiteit geproduseer gaan word. Mat die beaklkbaar-heid van 66 MeV protonbundels vanaf die oopaektor-siklotron, is voorlopige U3I-produksielopiea by laebundelatroae gedoen. Die aerate ervaringa met dieaanvanklike produksieproaea word beapreek.

H12 PRODOKSIE VAN 52Fe PIT Mn HET 66 MeVPROTONE

G.F. Steyn. F.M. Nortier, S.J. Mi l laNasionale Veranelleraentrue

Opwekkingakraaaes is geaeet aet die foel ieatapel -aetode oa dla S2Fe-opbrenga sowel aa die opbrengatevan die gelyktydig-geproduaeerde kontaainante tabapaal. Hlerdia infornaale kan gebruik word OM diegeakikata produksieparaMtera te verfcry. Anderaapekta van Fe-produkaia sal ook beaproak word.

AEROSOL ADVENTURES -__RBC8NTRBSULTS FROM PI IB ANALYSES OPAIRBORNB PARTICULATBS.*

HJ Annecarn, A Zuchchiat t i • and JPF Se l l s chopWita-CStR Schonland Research Centre forNuclear S c i e n c e s , Univers i ty of Witwatersrand,Johannesburg and *Isr.ituto Sazionale diF i s i c i Sue 1 eare , Cenova, I t a l y .A number of environaental and i n d u s t r i a lhygiene related studies of airborne particlesare in progress at the SCRNS. The coaaon themelinking these projects is the use of ParticleInduced X-ray Emission for saaple analysis .Results will be reported froa studies inunderground gold nines, where io ie unexpectedelemental components were encountered, in thevicinity of surface gold mining and of coal-fired power stations. The well matchedprotocol of tine-sequence saapling, PIXEanalysis and s ta t i s t i ca l interpretations willbe emphasised.

TU. J0J.^_y_W!!gAl Pi l lar, HJ Annegarn. D Fayra* & JCA 0»viaa*Wits-CSIR Sohonland Raaaaroh Centra forNuclaar 3oianc«a, Univeralty of Witwatararand,and 'National Centra for Occupational Health,Dapartaant of National Haalth and PopulationDevelopaent, Johannaaburg.The NCOH, aa a aatter of routine, receivea theheart and lunga froa a l l daceeaed, ainara.Saaplea of tissue fro* each autopay,"1000 aia>, are preaerved in wax for archivalpurpoaea. The NCOH now haa aeveral thouaandauch aaaples. Aa part of a propoaed api-deaiological survey of duat-induced lungdiseaaea, a rapid, inatruaental technique iarequired to aeaaure the aineral content ofthese aaaplea. Particle Induced X-ray Eaisaion(PIXE) haa been Investigated aa a auitablemethod. Methoda of thin aection preparationhave been evaluated. Suitable irradiationconditions have been developed, including theirradiation of samples in a He ataoaphere.Preliainary results show that PIXE ia auitablefor thia application.

A VERSATILE UHV APPARATUS FOR SURFACEPHYSICS AMD CHEMISTRY.T.E.Parry*. R.G.Copp«rtbvi»it«+,

P.M.Logg«nb«rgr, W.S.Brooks*, J .P .F.ScUschop*.* Schonland Research Centre for Nuclear Sc iences ,+ Deportment of Cheaiscry,

University of the Uitvaterarand, Johannesburg.South Africa.

Surface physics and cheai i try experiaenta are performedat the Schonliod Research Centre on a modifiedconaercial UHV system containing the fol lowingf a c i l i t i e s : XPS, icanning Auger, LEED, Ar* sputtering,MBE, pure gas admisiion and quadrupola a n a l y s i s .Connection Co two accelerators v i a d i f f e r e n t i a l l ypunped baaaliaaa enables RBS or implantation to becarried out *t 1O~" abar. Saaplea can be transportedinto UHV without breaking vacuum, i f desired v i a ahigh-pretiurc react ion chamber operating to IS bar.Once i a UHV they are transferred to a universal aani-pulator where they can be heated to 1200*C or cooled toU>2 teapcratura before or during analys i s . Exaaplaa ofthe uae of t h i s unique apparatus are presented insubsequent papers.

II4 C THE REDUCTION AMD SUBSEQUENT C A R B U R I Z A T I O NII IW OF AS INDUSTRIAL CO-HYDROGENAIION CATALYST:

AM XPS AND AES STUDY.P.M.Loggenbera*. R.G.Copperthwtice*. J .P .F .Se l l schop** Oept of Chemistry, University of the Witwatersrand.* Schonland Research Centre, University of the 'Jitwaters-

rand, Johannesburg, South Africa.

The reduction of an industr ia l CO-hydrogenation cata lys tat 400*C changes the surface composition d r a s t i c a l l y .As che dif ferenc structural and chemical promoters playa v i t a l role during synthes is , eha surface compositionis important for an act ive CO-hydrogenation c a t a l y s t .The build up of surtace-carbon during carburization withcarbon monoxide sheds some l ight on the act ive phases for^O-hydrogenation. We have found evidence which stronglysuggests chat carbon i s deposited on potassium richs i t e s . These carbon species are removed by H^O creac-aent at 320*C enriching potassium ac che surface .

96

HI 7 A STUOY Or ftC FOKHATIOH Of 2IRCOWIUMSUICIDE ON SILICON (100) SUBSTRATES H20

A.C.K. Lutch , T.E. D«rvyU.S. Brook* , I . KusttelanR.G. Copp«rthv«itt* Chemistry Department, University of the

Witwatersrand** Schonland Research Centre, University of the

Witwtterarand+ NEERt, CSIRZirconium Silicide contacts have been produced onSilicon (100) surfaces by deposition of Zr metal andsubsequent annealing in vacuum. The lilicidationprocess was monitored, in situ, by Rutherford Back-scattering and X-Ray Photoclectron Spectroscopy. Thecurrent/voltage characteristics of the annealed con-tacts w«r* determined.

H18 RAPID COMPUTER-CONTROLLED CAPACITANCETRANSIENT CHARACTERIZATION OF DEEP-LEVEL

H-CMaguire*. A.Marshall*. J.P.F.SeXlschop** Trent Polytechnic, Nottingham, United Kingdom.* Texas Instruments Ltd., United Kingdom.* Schonland Research Centre, University of the Witwaters-

rand, Johannesburg, South Africa.A computer-basad deep-level capacitance transient spec-trometer is described which was designed and constructedas a result of the inadequacy of present commerciallyavailable deep-level transient spectroaetcrs. Deep-levelactivation energies and trap concentrations arc hereobtained in a single-temperature scan. Unlike conventiontal systems, which "contour" predetermined emission ratesby viewing a rate window, giving only one point per level;,thermal emission rates are here directly determined.Thisretains more information and reduces the redundancy ofconventional methods by obtaining all information neces-sary to construct an Arrhenlus plot in a single-temper-ature ramp. The method requires fewer coaputer calcul-ations compared with systems using Fast Fourier Analysis,and displays improved signal-to-noise ratios.

H19 AANWENDINC VAN TITAANNITRIED (TIN) -DEKLA-

GIES DEOR IPONPLATERIHG EM DIE INVLOEP VAN

PROSESVERANDERLIKES OP DIE EIENSKAPPE VAN

DIE Df AGIES

D P ie tersen . I A Kotztf en P H de LangeOepartenent Materiaalwetenskap, AEK van 5A Bpk

TiN-deiclagi.es word i n die nywerheid veral op mas?ir.eer»gereedskap qebruik. Dlt verskaf ft ba ie harde, slyt.asie>werende en chemies s t a b i e l e l a g i e , wat d ie l e e f t y d vandie gereedskap aans ienl ik verleng.

TiN-deklagies i s op sag te - en ho*spoedstaal aangebringdeur "n ioonp l a t e r ing stegniek wat gebruik maak van hol«katode-ontlading in "n sc iks tof -argon a t a o s f e e r . Metdie oog op d ie op t ioer ing van d ie l a g i e s se eienskappei s verske ie eienskappe van die l a g i e s as Vt funksie vanst ikscofdee ldruk, substraattesiperatuur en negatiewevoorspanning op d i e substraat gemeet. Die r e s u l t a t avan h i c r d i e ondersoek sa l bespreek word en daar s a laangetoon word wat d i e optimum eienskappe i s wat nage*

word.

DIB VEKSKVNSEL VAN RESSPAHNING EH DIE

METING DAARVAH MET BEBULP VAN X-STKAAL*

DinrmnsieW B du Pro i en G NisuwoudtDeparteaont Materiaalwetanskap, AEK van SA> Bpk

Met die geveldige tegnologiese voorultgang van die af»"•lope dekades, hat dlt noodsaaklik geword on betrou*bare kwantltatiewe metings van resspannings in metaal*komponente te kan doen. Waar hoe-graadse tegnologieter sprake i s en komponente aan uitcrste bedryfstot-stande onderwerp word, kan dlt ultcrs riskant wee* omdie moontllk* teenwoordlgheid van resspannings te ig»norcer. Indien resspannings van h spesiflckc aard engrootte beheerd gctnduseer kan word, kan dit egter ookcot voordeel in 'n komponent aangewend word.

Die aard en oorsprong van resspannings, die invloeddaarvan op materiaalclenskappc en die beskikbare oeet>tegnleke sal bespreek word. Hierna word die beginselswaarop die X-straaldiffraksiemeetcegniek berus, behan*del en die voordele van die tegniek uitgelig.

DIE METING VAN RESSPANNINGS IN METAAL*

KOMPONENTE MET BEHULP VAN X-STRAALDIFFRAK'

SIE

G Nieuwoudt en W B du PreezDepartement Materiaalwetenskap, AEK van SA Bpk

Die s in 1 ijMnetoda word hoofsaak l ik aangewend v i r die me*t i n g van makro-resspannings m.b.v. ta X - s t r a a l d i f f r a k t o -meter. X-straaldiffraksie is tans ook een van dieenigste eksperimentele tegnieke wat aangewend kan wordvir die meting van mikrovervormings in metale.

Na ~n kort vcrduideliking van die meettegniek, sal fakto-re soos die monstergrootte wat hanteer kan word en diediepte van resspanningneting onder die oppervlak van "nmetaalkooponent, bespreek word.

Die eksperimentele gemete spanningstoestand in ioonpla«teerde TIN-deklagies, asook die invloed van voorkeur*oriintasie op hicrdie tipe resspanningmetings, sal be<spreek word.

H22 WEAR MECHANISMS MODIFICATION ISPUCEP BYION IMPLANTATION IN UC-Co.

Y. Cassuto , J . P . F . S e U s c h o pWits-CSIR Schonland Research Centre, Universi tv of theUitvatersrand, Johannesburg, South Africa.

Scratching and rubbing t e s t s were carried jut on S*implanted and non-implanted HC-6Z Co samples. Thescratching t e s t s were carr ied out bv applying a 100 eload to a diamond microindenter. These revealed chatior. implantation i n h i b i t s the extrusion of coba l t ,which is the f i r s t s t ep in the abrasive wear process ofUC-Co.

The rubbing cescs were carr ied out by rubbinz a brassball on th« surface of the sample under control ledconditions. By means of scanning electron microscopyit was established that less brass adhered to theimplanted surface than to the non-implanted one.

97

H23 ?TT«CT OP VAKYIHC ««CTT CTIOOIt OM W

Towamm or •ic» inuuwrn ITCTL

tuganla frotopappaa. J HleuwNljer and w • du PreecMaterials Science Department, « K « ( M Ltd

h w t t w n (and oftan costly) component failure My InMny Instances be avoided by th« appropriate use offracture Mchanlca analyiwa. The application of frac-ture aachtnlcs In engineering design of crit ical coapo-nant* for fractura control and fatlgua Ufa predictionla vail aatabllahad. Flana-straln (Ktc) fracture tough*naaa tasting uaually antftlle tha uaa of thick enoughspecluans to yield representative reaulte. aovever,different tasting techniques, tuch aa J-lntagral Mic)and crack growth raalatanca curve* (R-curvas) are ra»quired for tasting of thin coaponents, or whera planaatraaa condition* pravail.

Tha affect of varying tha shaat thlcknaaa from 0,4 aai to16 aai on tha fractura toughnass of high atrangth stealusing J i c . R-curvas and Klc tast methods will be dlscus»sad. Fractographs of tha assoclatad fallura surfacaswill also ba prasantad.

H26I I Icktditr, rvtut Mat, Prttsrlt

Ftr tttt iHttn It ••• |Htr i l l * tallt*** tktl te sttlsli* tfctkttt ctlltcttt I* i u l i r atttr ktattr, M I kis la aaiitlit tktMaarata • t» H W I UrkcliMt M M m* Milslia ta*a-»t»»attrkilt tratt'tr »» krittlns I m Ut ittMMt tMiftrr t«»ar. ewa«ar, tlMlt calcalitlwf tkM tktt ft tkt I M kcit traatftr rattatr MM craa at « l ltt Plata Kite ctlltttw, tkik Ik lk»lkkifi-cMt< liitrisMt tk«*» that iktratwikMlkt i f t ttt* iMlckM«r«tt M tkl I I H ^iMif lk •• CMITKtlM (t«t I* • ( IM IM*><in* aklck »ir» r§rr I M flmrttM) cMtlttMtlf mAfmim* klak• It irtti t*»t»t •«•(••• - k» *H«t U • in.Ir ipplrl"! Ik* I»l»r-».«ir««|t rtrUHMil cilc*la* It tk* tlM-itrt •<«>tit« 4tr tkt kttt 4tll«trM kr i (kl«r ct l l«tw, Ml*rl<t tkt tkt Mtlttl tMtriir Melalilt|> 4cfMM*ct t< tktU«r«tt t« UttlatlM. H O1IM tkt Itttar is « stMtr tkitlaclalti it l i t prlMfy C I H H H I Ikt c«l*f lrra<lM» Mtt tktetlUcttr, kit < l» tkt t«tct i U tkt ctlltcttr l»ti C M M U I -Mt, *M ti tkt laltt aaf tatlMt ttaatratortti

•• alia <«ri«t t»» tatlaal rtlatit* tttatto Dtaratt »»# Ml lac-ttr tttatrtttrt lacraktRti •»< tktrtftr( M t«lltct«f Ni l t ttt«»tr»"ur». vail iktvt tkratkaK, tklt <aaan*a<ca *»pcta'*ai allattr fart. Tkaaa ratttla»a art %ii»t. kf aia?!* analyticUnttlim, an« ha»t alaala tcall*« pratcrtita altk raapact talaOpa*<a»t ^aantitlaa (laaalatla* ft t»paratura l t

H24 ELECTRON PROBE MICRO-ANALYSIS (EPHA) OftON IN GALVANIZED COATINGS PRODUCED

ON LOW SILiCOH STEELS

A H Kirkbride. A Wells - Nation*} Institute forMaterials Research - CSIR

Hot-dip galvanizing of certain low silicon contentsteels (semi-killed steels) is known to result Inexcessively thick and br i t t le corrosion resistantcoatings (termed the Sandelin ef fect) .

A series of galvanized layers produced on a rangeof binary Fe-SI alloys were examined using electronprobe «icro~ana1ysis. Studies have shown the Sandelineffect to be associated with the absence of the6i Fe-Zn intermetallic phase. The analytical sethoddeveloped &nd the results obtained wi l l be presentedand discussed.

H25 PASSIVE »iweLc-»>Ae» SOCAW W>TM HSATITO

T 1 lcka««lar mi l C »«• Hai fa , (aft a«Uatvertlt? al Prataria

I tv t r t l Kwikara kavt racnt lr iktm, k« aaaaaraaatti aa« ataaU-tiaat *t-» tkaraal ktat l i t t a< » M f l a a " . AccardUf ta Haitaaa'a[ I t IS] "•*•» a talar kat aatar tr«tt* . . liat kaaa ra-*nf!aatratf ttrla> Ut» , i t i t aiicft flaplar ta inttali •** caataiaa ttrit, laaatiptnilirt caapanant* than th> carrtttanaini ki|k Han tritaa*. Lt«Brtiaurt (ariai-ianiiictar lnen-rtclrcgl»tli>|) tyttaas t l lar IvrtkarHtntiitti hifkar ateraia tMleitucy tn« «iapiilla< |UaklR|.

Far a %\»%\t-ntt <*ltr w t i r lisstar I t la latartaat ta aptiaallyithat i t , m • aaanar that ai l i aaiiaiia eallactaf haat) aatcki

Hi iK-ctantanaaua Haxrttt to iniaUtiam tut(kl tally callacter Moa ( I .a. I t i lv praluctua a» hat aattrl

t t faily caatuaptian • ta altki* iktvt JOJ.

T« titffy li>, tkt l l u r i l i autt an i | ) ' t « 4tr ftllam ana •» tkaaptiatl Mo* curvat. Tha cnaica e< Maacurva i t ta • • tuch at ta•atlKy i l l . Sanaltlvtty afialytn mtlcataa titat nalthar nttt atta t t t l l t t ta Hl|h accuracy ta t t tna in aJHciaacv sail ikavi actfl'tntlenal puapat lyttta.

(a fatcriit t tiaplt fur i t i t tyttia tha( tchltytt tkt t t ikjtc-t l > « t 4*4 proaiaaa ta tiaultanatutly lacraaaa parf;raaact tafttcrtasa inatallat coit.

H27 DEVELOPMENT OF HIGHLY EFP1CIEMT. LOWTHERMAL INSULATIONS FOR USE IN100

RMAL-400*C RANGE

EHze Potaieter, P R Clayton. I Sigalas and R J GusnwRational Institute for Materials Research, CSIR

Effective thermal mnagenent of temperature-sensitive systems or equipment Is highly Important, andt'.«e thermel Insulations employed should have thefollowing characteristics: possess very low totalthermal conductivities (a few nW/n.K) with smalltemperature dependences, be easily fabricated from cheapand re«v'n,w available materials, be Inert and stable forextended periods.

Various materials combinations are suggested whichnay satisfy the above requirements, showing how theirspecifications are derived from the necessity ofminimizing the Joint contributions of solid-phase,gas-phase and radiative thermal conductivities.

Our guarded hot-plate apparatus capable of measuringthe performance of Insulations at different gaspressures Is described, together with results obtainedfor some thermal Insulators which were designed 1naccordance with the relevant physical cr i ter ia .

H28 C.A.R.S. TEMPSRATURUNWIN6

D.Ball*,H.S.T.Driver*.R.J.Hutcheon*. G.W.Robertson*,K.F.Bennett+, R.K. Dutkiewiczf. R.N«tesT, and A.Yates

* Department of Physics, University of Cape Town* Energy Research Institute, University of Cape Town

The onset of "knock" in a spark-ignition engine Unitsthe usable compression ratio and hence the thermodynamicefficiency. The synthetic fuels in use in SouthAfrica differ chemically from the natural petroleumfuels for which the engines were designed. Fundamentalstudies of the chmical kineties of autoignition ofthe engines in synthetically-fuelled engines areneed.

Coherent Anti-Stokes Raman Scattering (CARS) is themost advanced optical technique for temperature measure-ments in an engine. The experiments being set up atUCT are described. The results will be used as inputdata for chemical kinetic modelling of engine knock.

98

H29 SOME Msurrs OF IHTEKOOLP'S RESEARCHPROGIUttMB

a. Gafnar. International Gold Corporation,JohannesburgTha objectivaa of Xntergold't research prograsae ar«eh* davalopsent of new products relevaut t o tha goldindustry and thair c o e a m c i a l i s a t i o n . An out Una w i l lbe given of how tha toopa of tha p r o g r a m la ta i loradt o au i t tha naada of tha industry. Successfulprojects w i l l ba dascribad which re lata to high caratjewel lery a l loy* , n«v e lec tro -p la t ing procaasaa andeoin-and-bar authanticators. Saaplea of tha product!w i l l ba Mda avai labla for viewing.

H31 SIX1.0OHSKXISKHAVOHSIHC

P.A. Karitcn, AtooMnat | iakorporuia f ValindabaDla gaoMtria an karaktariatiaka vloaipatroon varbondaaao Vi tonvansionele aikloontkaiar word kort l iksbespreak. Enkala toapaaaing la dia nyverheid sa lu i tga l ig word tasaaa mat dia voor- an nadala varbondaaan hierdie altaraatiava skaidingtkonaap. Diabaeadarioi to dia navorsing sat spai i f iaka varvysingna fiodaaaota la vloaivaldondarsoaka a . b . v , IDA, asookskaidingswarkavaluasia ondar badryfstoastanda antaoratiasa aodal laring s a l kort l iks toaga l ig word oat

rasul tata .

CTB APPtlCATIOM OF THE itADIAL OltrvSIVlTYEQUATION TO THE PETROLEUM IHDUSTY. 1MPABTICUIAR WITH RESPECT TO WELL TEST ANA-LYSIS.

P. SELIGMAMHSOEKOR (PTY) LTDIn p«trol«ua anginaaring tba rasarvoir Is oftanidaaltaad by considering it to b« » right circularcylinder of constant thicknasa, with a wall opanadovar tha cntira thicknaas. Plow is consldarad totaka placa in th« radial direction only. This flowaodai in thapatrolaua industry is ganarally rafarradto aa radial flow. In this papar solutiona to thisaquation ara praaantad and co»parad to solutions forunataady stata haat conduction through a cylindricalcora. Tha uaa of a Kirchof intigral transform tolinaarisa tha aquation for tha flow of r«al gasasthrough* porous madiun is shown.

In conclusion i«pl«»ant»tion of tha solutions to tharadial diffusivity aquation to calculata variouareservoir parastatras is prasantad.

THEORETICAL SEMINAR I TEORETIESE SEMINAAR

II A SEMICLASSICAL CALCUtATIOH OF THE STATICPROPERTIES OF KUCLEI AT FINITE TEMPERATURE

H G Millar. C J Vright - ThaoraticalPhysics Division, NRIMS.H Kohl, Institute da Sciences NucKaires,Grenoble, France

Semi-classical calculations of the static proparcies ofnuclear systems at finite temperatures have been per-formed. The effects of the continuum states can beincluded. Results for liquid to gas ohase transitionshave been obtained.

12 ENTROPY CALCULATIOHS IN CHAOTIC SYSTEMS

J.A. Louw and W.-H. SteebDepartment of Physics, Rand Afrikaans University

An atteapc is made to quantify quantum chaos byconparing numerical entropy calculations to othercriteria for chaos in classical systems which showchaos. The results arc then conpared to the behaviourof quantum mechanical counterparts of the classicalsystems.

99

13 PHASE TRANSITIONS AMD EXCEPTIONALPOINTS Of A MANY-BODY HAMUTONIAN

A.A. Hot««; W.O. HtiiiCentre for nonlinear studies and department of PhyaicsUniversity of th« Witvatararand.

For a typical many-body Hamiltoni«n which givaa ria«to a phaee tranaition it la shown that this tranaitlonla aaeociated with an accumulation of exceptionalpointa of th« Haniltonian. Th« sudden chang« of th«ground stata atructur« la explained by thia pattaro.Using in particular th« Lipkin modal it is shown thata mean, fiald approximation parforma badly in th«vicinity of th«a« singularities, while th« nor«expensive Generator Coordinate Mthod reproduces th«aod«l exactly.

T A A CHIRAl SOL1TOH HOOEl C0H5TRAIHE0 BY gfl/qv* " E.J.O. Gavin, R. T>q«n, In«.of Theoretic«!

Physic», UCT; 1 P. !<Mk, In«, für Physik,Universität Basel, CH-4052 Basel, Schweiz.

Wt present on« example of • smooth chirai confinementmodel of the nucléon constrained (within a mean-fieldtheory) by the measured g./ov of th« neutron. The result-ing confining sealer potential for the quarks Inside thenucléon has a max1nun In the surface and approaches Itsasymptotic value from above. LOM energy properties ofthe nucléon (3 quarks in their g.s.) arc not spoiled bythis peculiar surface behaviour. The "hellcity argument"(only spin carrying fields Inside the nucléon contributeto 9A/9V) we employed here further, sheds new light onthe modelling of the htdrons in terns of hybrid skyrmionsand on the description of the Nil decay ««ode of excitedbaryon states.

14 TOESTANOVERGEIYKINGS BY UITERSTE TOESTANDE

J R Engelbrecht en C A Engel brechtInstituut v i r Teoretiese KernfisikaUniversiteit Stell erbosen

By hoe temperatuur en digtheid word daar tërwieseewewig tussen gebonde nukieone en ti gas van vryenukieone verwag. Hierdie ewewig kan beskryf wordmov die Saha-vergelyking of mbv tt grootkanonieseformalisme. Vergelykings tussen hierdie metodesword bespreek.

17 FINITE TEMPERATURE BEHAVIOUR OF LICHTNVCLEI

R M Quick', B J Col«+ and H G Miller*

Theoretical Physics Division

'University of ch« Witvaccrsrand

la relativistic heavy ion collisions, nuclear natter isehernally «xciced and aay undergo "phase transition".Although few experioents are available, a nuober oftheoretical predictions exist. At present, finitetemperature calculations consist of finite temperacureextensions of variational aechods used ia nuclearstructure calculations at zero temperature. In thepresent work we compare these results with the resultsof exact canonical averages.

15 THE RPA AS A GROUP CONTRACTION AHO THE

IMPLICATIONS TOR SYMMETRIES.

F.G.Schom and F.J.W.Hahne

Inst i tute of Theoretical Nuclear Physics, Universityof Stellenbosch

Using the concept of group contractions, we discuss

the implications of the RPA for the dynamical as well as

Symmetry groups of f i n i t e boson systems. In particular

i t is snewn that i f the Hartree-Bose ground-state

breaks the symmetry, the RPA contracts the Symmetry

group onto a non-semi simple grouo which is a symmetry

group of the RPA Hamiltonian. This group contains a l l

Subgroups of the original symmetry group which are not

Sroken 3y the ground-state, " e abelian invariant sub-

algebra of the contracted alaebra contains the excita-

tion operators of the spurious

18 HUBBAM MODEL FOK THE BCf LATTICE

C M . VilletDepartment of Physics, RAU.

A variational method is used to find approximativesolutions of the Hubbard model for the ground state ofth« bec lattice in Che weak and strong coupling limits.The neucral case (a half-filled band) is found to beantiferrooagnetic for all values of the coupling con-stant. However, (or other choices of Che band-fillingsecond order phase transitions between different mag-netic structures are found if Che coupling constantis varied.

:ioo

19 FLAP* fLeXTRONlC *N*> STKUCTUMtCALCULATION! FOR •OitCONOUCTOftt.

W. 3. Vervoerd. Dept. of Physic*. Uni»«.

The FLAP* (Fully s«Ifconsistent LinearisedAugmented Plans Wave) method for calculatingcrystal band structures Is discussed.]Uthough derived from the long-standing andnt first not very successful APW approach,this method is in ita present form one of themost accurate available ab initio methods. Aparticular advantage of this approach is thedirect way in which aspherical and warpedmuffin tin effects can be incorporated. Thiscan be expected to be particularly importantIn the open crystal structure ofsemiconductors. Considerable restructuring ofthe method used for metals is required, butloads to an efficient algorithm of whichapplication to silicon is shown.

112 STUOIEg VAN DIE EHC-SFFEXS C H»r»1» «n C A EngelbrtchtInstituMt vir Ttortt1*st KtrnfijiksUhlv t r j iU i t Sttlianbosch

01c iwontlikheid 1s ondersoek dat d1t EMC-effek by died1epon*last1est verstrooiing van leptone dcur ktrnc « nnorna! t karnfisitst tienskappa toegeskryf kin word. DieiMMntuMvcrdtling «n die binding v»n nukleone v t rk in rdie EMC-verhouding in brtt trekke. Dit Is igter nood«saaklik d»t die teenwoordigheid van pione in die kernook In ag gencem word.

110 OB THE MOLECULAR CLUSTERS MODELLINGDIAMOHD UID SILlCOtt SURFACES

prora BAPZIACDepartaent of Phy»ic», Unlaa, P 0 Box 393, Pretoria,0001 U.S.A.

Molecular cluster* aodelllnt diaaond and silicon(til) surface reconstructions arc analyzed by swans ofseal-eaplrical quantum chemistry MIDO and MIflDO/3 pro-cedures. The analysis focuses on the <2xl) reconstruc-tion of the diaaond surface and on the (7x7) recon-struction of the silicon surface.

It Is shown bow by a proper choice of differentclusters and then by a careful analysis of the resultsone can do the following:

1) coapare the enersies of surface structures withdifferent chemical bond patterns

11) draw conclusions about surface band structuresill) Investigate structures with surface unit cells

containing aore stoat than the bluest msMrtca' -ly sanageable clusters.

The results of noaerical calculations are finallypresented and discussed.

113 ELECTROMAGNETIC NEUTRON STRUCTUREFUNCTION

Kouichi NakanoInstitute of Theoretical Physics i AstrophysicUCT, Rondebosch 7700New methods of extracting the electromagneticneutron structure function are proposed viathe quark parton model and by combining themuon and neutrino data only on the hydrogentarget. Firs*., the proton and neutron struct-ure functions are expressed in terms of the nonon-singlet structure function of the differe-nce between proton and neutron. Then an iter-ation procedure in this difference structurefunction is carried out. An additional struc-ture function involving the strange and charmquarks is constructed from neutrino and anti-neutrino induced experiment*. The small xbehavior of the new calculation is much small-er than the usual model.

111 FO8MELE UIDRUXKINGS VIR DIE TOESTAND-VERGELYKINGS VAN CASSE

J . J . Kenning, AEK

Die v i r i a a l k o e f f i i i e n t e word bepaal met behulp vanClus teru i tbrc id ing* . Die i d e n t i t e i t wac gebruik word,i s ook handig om die samehang cussen d i e versk i l l endeGreense funksies in Vi kvanttx&veldeteofie, neer bepaaldv i r d ie Chrooodinamika, af te l e i .

114 EMC EFFECT AT SMALL X REGIONKouichi Nakano

Institute of Theoretical Physics C AstrophysicUCT, Rondebosch 7700The method of equivalent quark approximationof virtual photons is applied to explain thesmall x behavior of the EMC effect by incorp-orating the qq component of virtual photons.This procedures takes into account the spacetime behavior of virtual photons in the forw-ard Compton scattering amplitude. The quarknucleon interaction is estimated by the addi-tive quark model. In order to incorporatethe fini-.e size effect of the target, the pro-bability of qq pair propagation through thenuclear medium is multiplied to the structurefunction due to the new mechanism, which is lranalogy with the concept of the mean free path

101

| J m PECULIARITIES ASSOCIATED WITH THE HIGHER

* " ^ JOTATCW

C.». Van Wyk

Univers i ty o£ the OFS

Th* product of two pur* Lorentz transformations i s

•xpressad In tha fora

where L is a pure Lorcntz transformation and R ia a

pur* rotation. For given u , v , $, , $2 w* hava to

solv* for the unknowns n , 8t , 92 , w and

properties of the solution are discussed.

Th«

118 ?ACTOM2ATI0HS OP TWO VECTOK OfpATOM FOKTHE COULOMB PROBLEM

O . L da Lang* ancl R.E. Raab, P h y s i c s D e p a r t m n t ,University of Natal, Pieteraaritcburg.

Tha Coulomb potential has b«*n shown to po«|a** twoadditional vector constant* of tha motion C~, which arequantwaechaiiical analogue* of eH classical cons«rvadvector* (1 + iL) * A<., where L is tha orbital angularnoaentxa anil Jc the Laplace-ffungs-Leni vector. £ arashift operator* which transfon between all kat* |ni»>of a given energy. It ia shown that C~ caa be f»c-_torized in two different way* to yield operators which,apart from their dependence on constants of the action(H and L2), arc linear in either p or r. In this way16 abttract ladder operator* are obtained. Theproperties of these operator* and their relationship Cothe Factorization Method of Schrodjoger, Infeld andBull are discussed. Because the C~ are representation-independent, the factorisations allow ladder operatorsto be found in both the co-ordinate and momentumrepresentations of wave mechanics.

116 SYMMETRY VECTOR FIELDS AMD SIMILARITYSOLUTIONS OF A NONLINEAR FIELD EQUATIONDESCRIBING THE RELAXATION TO A MAXWELLDISTRIBUTION

N, Euler and W.-H. Steeb

Department of Physics, Rand Afrikaans University,

Johannesburg 2000, South Africa

In the study of the Formation of Maxvelliaa tailsthe nonlinear partial differential equation

2 23 u/3x3t + 3u/3x • u • 0

arises. We determine the Lie point symmetry vectorfields and calculate the similarity ansatze. Thenwe discuss the resulting ordinary differential equa-tion. Finally the existence of the Lie Backlundvector fields is studied and a Painleve analysis isperformed.

119 HOE OM FERMI ENERGIEe PIT TKOMAS-fERMITEORIE TE VOORSPELJ.B. Brink en F J Kok (Departement Fis ikaUnivers i t e i t van Pretoria)

Met 'n voor die hand liggende wysiging van die ThoaasFarai teor ie i s d i t aooutl ik cm taamlik akkuxatatiindingsenergiei van atooe te bareken. As tomji-Cvarkry ons ook Fermi *nergie< ("gemiddel" oor 'nperiod* in Mendeleev se tabel) van die regte ordegroot te .

117 Q0ANTI2ATI0H IN AH ANGULAR MOMENTUMBASIS : ALGEBRAIC FORMULATION

O.L. de Lange , P h y s i c s Department, U n i v e r s i t y o f N a t a l ,Pieteroaritzburg

A prescription is given for constructing classicaldynamical variables which, for certain sphericallysymmetric, nonrelativistic potentials, can be quantizedto yield an Hennitian basis for a representation-'independent, spectrum-generating algebra in an angularaomentun basis. To illustrate the procedure, thethree-dimensional, isotropic harmonic oscillator in anangular momentum basis is considered and the knownspectrum-generating algebra S0(2,1) ®SO(3,2) isderived. The special cases of wave mechanics in thecoordinate and momentum representations are discussed.

120 OOgSPRONG VAN P I EgTERH IW PIE WISSELHEPKEWDE FERMIQN-B050NM0DEL

H B Geyer en £ A de Kock

instituut vir Teoretiese Kernfisika, UniversiteitStellenbosch

Alhoewei daar in beginsel ti hete aantal moontlikefemrion-boson wisselwerkings in die wisseiwerkendefermion-bosonmodel kan voorkom, blyk dit empiries datdie uitruilvrisselwerkingsterm Ti kardinale rot speel.Hikroskopiese oorwegings vtr hierdie situa^ie wordbesoreek.

102

121 CAVITY QUANTUM CHR0M00YNAM1CS TO ORDER ajA.J. Stoddart <nd R.D. VioUitrInstitute of Theoretical Physics «ndAstrophysics, University of Cape Town

Recently Cavity Quantum Chromodynamics Mas reformulatedIn the Feynman gauge Including the unphysical gluon andghost terms. Particular care has been devoted toensuring that the boundary conditions for the quark-,gluon- and ghost fields preserve the Beccnt-Rouet-Storasymmetry of the theory which ultimately guarantees therenoraalliability via the Ward-Slavnov Identities.Here we have calculated, for the two-quark and quark-antiquark systems, all non-diverging graphs to order a|which do not Involve additional quark-antiquark pairsin the intermediate states. Using these two-body Inter-actions which Include the two-gluon exchange and two-giuon-annihiiation graphs, we obtain a satisfactory fitto the experimental meson and baryon spectra. Asexpected the two-gluon annihilation diagram splits themasses of the it- and n-mesons while it retains thedegeneracy of p- and w-mesons.

124 ncaomc crounraov BAPHVUOW n axnauumtc

Institute or Theoretical Physics and Astrophysics,University of Cap* Town

Abatract

Tb« occurrence of Ctoraokov-lik* acoustic radiationwhen tha neutron velocity exceeds tas speed of soundin a solid ia investigated. Altbougb tha affaet iafound to exist theoretically, U w aaar^y loss par unitpath length ia so aaall aa to praclnda its observation.

125 SUPERNOVA MODELSC A EngetbrechtInstitute of Theoretical Nuclear PhysicsUniversity of Stelienoosch

A short survey is presented of the rtost promisingtheoretical models of type I and type 11 supernovae.Possible interpretations of the supernova LMC 1987Aare briefly discussed.

122Cecile Thorn

LEE-YANG TEORIE VIP FASE-00R6ANGE

Oepartement Fisika, Universiteit van Stellenbosch

I f ' « w CN Yang het t\ statistiese teorie ontwikkelwa< beide fases betrokke by n fase-oorgang sowelas ji<i oorgangsgebied beskryf word. Hulle het aange-toon dat Vi enkele stel vergelykings die toestandverge-lyking van sowel die gasfase as die gekondenseerdefase volledig beskryf. Verder is aangetoon dat diebestudering van toestandvergelykings en fase-oorgangegereduseer kan word tot 1\ ondersoek na die grootkanoniese toestandsom se wortels in die komplekse vlak.Hierdie teorie sal volledig bespreek word, met spesi-fieke verwysing na sekere Teoremas wat die wiskundigegrondslag ddarvan vorm.

123 NON-U(6) RELATED DYNAMICAL SYMMETRIES OFTHE INTERACTING BOSON MODEL

H 8 Geyer, F J W Hahne and F G ScholtzInstitute of Theoretical Nuclear Physics, University ofStellenbosch

The traditional view of the interacting boson modelreveals three dynamical symmetry limits. Furtherdynamical symmetries within the model have recentlybeen identified and we discuss this aspect and someof its implications.

126 ON THE CREATION OF MATTER IN THE UNIVERSER.O. Viollier. Inst. of Theoretical Physic*and Astrophysics, University of Cape Town

Matter in our Universe is structured : in fact, in themicrocosm and macrocosm we can observe a great varietyof objects with characteristic sizes and masses. Thescales are determined by the presently known four funda-mental interactions : gravitation, electromagnetism,weak and strong interactions. Matter in our Universealso evolves : from galactic redshifts and the microwavebackground radiation we can conclude that the Universeand with It matter has been created some 10 to 20billion years ago in the hot Big-Bang, presumably as aresult of the Laws of Nature.We will speculate on what could have caused this Big-Bang, what drives the expansion, where the energy forthe Big-Bang comes from and why the Universe is souniform, flat and long-lived. We will also address thequestions why there is a matter-antimatter asymmetry inour Universe today and when the light elements and themicrowave background radiation were formed. Finally wewill discuss how the heavy elements were and still arebeing cooked up in stars and supemovae explosions.

127 NUCLEON-ANTINUCLEON ANNIHILATION INRELATIVISTIC QUARK MODELS

R. Tegen, Inst. of Theoretical Physics and Astrophysics,University of Cape TownI review recent relativistic quark-gluon model descrip-tions of the Nfl annihilation mechanism. A comparison torecent pp elastic and charge exchange date at the sameenergies allows for an independent constraint on boththe annihilation range and strength. The size parametercorresponds to a quark core size of 0.60fm which agreeswell with independent information from the axial-vectorform factor of the nucieon. The annihilation strength(% -2GeV) is much smaller than earlier models foundwhich used a phenomenoiogical Wood-Saxon r-dependence.Specific annihilation channels NfJ •• MiMj (M « «r,K,p,p,u,*) are discussed in view of a new relativistic quark-model description which consistently incorporatesinitial and final state interactions.

103

128 AVERAGE HAORONIC MULTIPLICITIES IN THETUS) UEWM IH qCO

C O , N a U u , Inst. of Theoretical Physicsand Astrophysics, University of Cape Town

The average hadronic multiplicity for the bound quark-antiquark state whose decay mode 1s via three gluons,which then fragment into observable hadrons, iscalculated within tht framework of perturbative QCD.The summation of the leading and next-to-leadinginfra-red effects to all orders of perturbation theoryresults in the treatment of the perturbative phase ofj«*t development in terms of perturbative expansions inthe parameter /as. Me work to 0(/a$) and makepredictions for the ground state T(1S), JPC * 1 " ,neglecting the soft effects which result from the non-perturbative mechanism for the conversion of partonsinto hadrons.

129 OCD CCMUaCTIOM TOW* I*t •J B • Y

laatitate of Theoretical Physics and JUtropbyeic*.VaJvfitf of Cap* Town.

Mtaeaact

m * proposal toiMttit radiatioa «aro la tha dacayW • J«t • J«t + y to aaaaora tbm W aaammloOM aaonatic•o—nt is asaainad in viev of tb« Otas) QCD correctionsto this process. Hotklng in etia partial fractioaad Jat-draaeing achaaa It ia found that tba QCD corractiooe totha Dalits plot ara aaall, Imariag a claar signal oftlta claasieal radiation M T O .

POSTERS PLAKKATE

PI DIE EERSTE KERNFISIESE METINGE MET PIESIKLOTRON BY DIE NASIONALE VERSWELLER'SfcNTRUM, PCTRE

W J Naude , J A Stander

Universiteit van Stellenbosch

Gamastraal en gelaaide deeltjie enkel en koTnsidensspektra is met die beskikbare 66 NeV protonbundel opdie gamma bundeilyn (bundellyn 6) waargeneen on dieoplyning van die bundellyn te toets. die gamma enneutron aktiwiteit in kluis nomer 3 te bepaal, diekwaliteit van kemdata te toets deur van standaardskywe gebruik te m a k en on die data versameiing enanalisesisteen van die NVS omvattend te toets en tegebruik.

P3 DIE AANWEKDING VAN TiAKSIE vtR PIE Qf7, ISTRUKTUURSTUDIE w T

EFFEKTIEWE INTERSHODELRUInrE EN W

U A Richter*. M Q van der Merwe*. W J Maud6«,J A Stander*, B A Brown*

'Universiteit van Stellenbosch•Departement van Gesondheid^Michigan Staat Universiteit, East Lansing, Michigan

Die suksesvolle aanwending van t\ nuwe semi-empirfeseeffektiewe interaksie1) in die Qs-Id s k i l , is opgevolgnet berekeninge vir die 0f-1p s k i l . Die energie*vlakskema van "V asook oorgangsterktes in hierdieatoomkern, word uitgesonder in die aanbieding.

'J'Effektiewe interaksies in die Os-Id s k i l " .

B A Brown, U A Richter, R E Jul ies, B H Wildenthal(in voorbereiding vir publikasie)

P2 EIENSXAPPE VAN VLAKKE IN "Ne, "A< EW " V

L D Olivier*, R E Julies**, D M van Rooyen*.H_J_Naud§*. J W Koen*. J A Stander* en S Froneman

* EVKOM** universiteit van Wes-Kaapiand* Nasionale VersneHersentrum* Universiteit van Stellenbosch +*Unisa

Energievlakke in " N e , J'A1 en n V is met (a, py)reaksies by E a - 12 MeV opgewek. Gammastr«,Hng is inkoTnsidens met geassosieerde protone, met ti multipara=meter data versaroelingsisteem waargeneem. Resultatesal vertoon word.

P4 Energievlakke van "°C«J. Schoenan, J.P.L. Reinecke, J.J.A.P.U. vir CHO

Salt,

Die 39K(p, ^"Ca-reaksie word aangevend om die energie*toestand van "0Ca te bestudeer. 'n 4arieal SS'-spektrais reeds opgeneem en geanaliseer. Voorlopige rcsul*tate oor die gamsavervalle van ongebonde en gebondetoestanda in "°Ca word aangebied.

104

P5 STERKTES VAH >0A.r(p.Y)-HESONANSlESÏ.H.J. fretoriue, J.J.A. Salt. J.f.t.Kaiaecke, F.B. Kundere au J. K* lootten

Absolute sterktes »«n reeonaaelea u t L. • 1087, 1102•n 1109 keV vsn dl« *<)Ar(p,Y)-raakste II bepaal. D Uabsolute «eerkce* van 39 andar reaonanalas la uithi*rdie résultats affalai. Uit Valsskopf-ekattintsla spinne en parie«ltt van resonanevlakke beperk.

P6 INTERNATIONAL COMPARISON OF CO-109

ACTiyifV HEASUSOCNTSB.lt.S. Slapaon and flTft. MeyerNational Accelerator Cantra

During 1986 the radioactivity laboratory of U M NACparticipated in an international comparison ofactivity aeaaureaent* of a solution of l Cd. Theactivity waa asasured using two aethoda, neaiely

(i) liquid scintillation counting of the internalconversion elactrona (4ne - 4IIe coincidencecounting); and

(11) coincidence counting of internal conversionelectrons and K X-rays.

A description is given of the upgraded countingsyatea which was used. This systeai incorporatesa aultiple-channel coincidence unit which allowsfor up to 15 data points to be Measured simulta-neously. The results of the NAC activity aaasureaentsare coapared with those of the other nationallaboratoriea who participated in the coapariaon.

D T POLARIZATION IN NEUTRON-PROTON ELASTICr I SCATTERING AT 21 .< fiëv"

B.R.5. Slapson* and F.D. Brooks»• National Accelerator Centre• University of Cape Town

The polarization in n-p scattering has been «assuredat 21.6 NaV using polarized neutrons fro« theT(d,n) He reaction. The aeasuring inatrviaent was ananthracene scintillation polarlaeter. The results arecoapared with earlier aeeaureaents aads at siailarenergies, with the phase shift analyses of Arndt stal. and Bohawion et si., and »ith predictions baaed onthe Paris potential. The experimental data are foundto bs consistent with the Perls potential.

THE *>Ir(n.d)MT »«0 KCKItOaS AT

< Wurufi-awT • * »eüurrtfi » C taaa'and A » «*id«o*•PXytics Oeoirtaent, university of Ourt>tn-«»»tvil It.

•Van di Urttft Group, »itjonjl tccelertcor Cancrt.

The 902r(n,d)8 T m d »»(n.a) ag rtactitns h»»t bid in«t>tifaCtd itln • 22 Ht« «ith t détection lyste« etntittinq of tl>r«< propsrtionilcounter» follo»«d by > curven pUitic icjntil ! Jtion detector.>irticle di»cri»in«tion is icnie»ed »icli t»o proportional countersacting at "££' de tec to'i and the icintillator as an energy " C detectorT"t spactroacter alloMs the siaultaneout accuaulation of data over anangle range af 80*.

OHBA analysts of the deuter-on angular distrifrutiofts from t*e tworeactions nave bctn carried out ̂ ith the tode OUUC!1 &. andisectroscopic factors obtained For transitions to states in f ana•g. the rtsults are coapared .ith other single-proton transfer

tcasurtaents. and aodtl predictions. Single particle Itrengtnj ofso«e transitions art deduced.

P9 FO» THf MAC.

JC Cognai1National Accelerator Centre, CSIR

A beaa aulnçer la described which will peraltthe anyle of Incidence of particle beaas ontoa target to be varied fora O» to O0o. Forsyasetry cheek«, the beau can also bs swungto approxlaataly -So. Neutron detector« at0», 30«, 60S and 90» will then peralt angulardistributions of nautron* froa reactions tobe studied using conventional tlaa-of-flight•ethods, but without changing datactor angle.

P10 REKEHAAR8EHBERDE INSTELLING VANSTUORMAGHETE BY D U NVS

JL Conradle, DT Four le un JC Corn«11Nasional« Versnellerseatru», WNNR

Vir die badryf van die NVS oopsektorslklotronword 'n seai-autoaatlese rekenaarbeheerdeclsteea vlr die Instelling van sekere bundel-tr*nsparteleaent* ln die voorultslg gastel.

Ervaring is rtcdt opgedoen aet 'n Interak-tiewe stelsel van stuuraagnete aet behulp vanrekenaarprocjrama«. Data vanaf drie profiel-»onitorc word ingelees, «n stuurnagnest-insttlwaardtt word daarvan bereken om diegalaalde-deeltjiebundsl prvsles op diebundellyn-as te centreer.

P11 BOMDItCTITTAMaiBMITIMC HIT ,IHDLPVAM PROFI1LIIOMITOR3 BY DI» MV3.

DT Fourle, JL Conradle an JC Corna11Naelonale Versnellersentrua, UMNR

'n Metode uord beckryf waaott elunskappe vandie eketerne deeltjiebundel. vanuit die oop-sektorslklotron bepaal kan word. Orlc pro-flelaonltorc wet die v- en y-groottec van diebundel aantoon, varskaf data vat ln 'n reken*aarprograa lngevoar word oa die bundel seealttanele en begtnwydtes (due horlcontaal envertikaal ) en -dlvergensies to bereken.

Fokuctiering deur vletpoolaagnete uit tussendie profielaonltorc lé. uord ook in eg geneesln die berekening, en nuwj lnctelllngc virdié aagnete word terselfdertyd bereken om diebundel beter by die einde van die bundellynte fokusceer

105

IQNUATION IN A GLOW DISCHARGE MASS SPEC-TROHETER ION SOURCE

D E C Rogers,National Institute for Materials Research, CS1R

Glow Discharge Mass Spectrometrytrace analysts of solids by MS.

(GDMS) is used for

Sensitivity is limited by the intensity of the ion beamleaving the source. It is related to the dischargecurrent, discharge voltage, gas pressure, type of gas,source geometry and the materials used in the source.

Multiply charged and molecular ions can be formed inthe plasma. Candidate mechanisms are electron impact,Penning ionization and change transfer ionization. Ion-iiation will be discussed in terms of these ions.

Ferreira N P, Strauss J A and Human H G H. SpectrochimictActa. 1984. 37 b, pp 273.

PI 5 OH THE UNIQUENESS OF AW UHCatTAlNTV

H 0 KxtBOld, A1C

It 1« shown that subject to general conditions «ncluncertainty relation between angular noMOtua andthe ilnut of th« angular displacement relative tothe txpectad angular displacement i t vmlqui.

P1 A OH TIME-PEPEMDEMT POTENTIALS

H U Kranold, KEC

Certain problems Involving time-dependent potentialscan be solved by groups of coordinate and timetransformations.

PI 3 TRANSMISSIE EN REFLEKSIE VAN 'N PUSABSORBERENDE LAGIE OP 'N DIK ABSORBERENDESUBSTRAAT

R. Swanepoel, RAU

to Algemene sisteem in opcika en opto-elektronika isdie van ta dun unifonne lagie op fc dik nie-uni formesubstraat. In hierdie geval kombineer die veelvuldigevecrkaacsings vanaf die agterste vlzk van die substraatnie koherent nia.

Die geval van "n uniforme lagie op to uniforme substraatkan numeries met die matriksformalisme hanteer word enwaardet van T en R kan bereken word. Die formalistaeis egter nie geldig vir die geval van inkoherente kom-binasie van refleksies nie. In die liferatuur is dieeenvoudige sisteem nog slegs deur (soms foutiews!)benaderings opgelos, aeestsl vir die geval van In dear-sigtige substraat.

Die sisteem is veer vahuit eerste beginsels beskou eneksakte uitdrukkings vir T en R is afgelei. Die fonnu-les is geldig vir alle invalshoeke en ook alia waardesvan n en I' van die lagie of die substraat:

P17 VOORKEURVERSTUiWING VAN VERBINDINGS

J.B. MalherbeUniversiteit van PretoriaEksperimentele metings uit die literatuur is set

teoretiese voorspellings vergelyk. Sigmund se

voorkeurverstuiwingsnodel is gebruik om 'n geskikte

keuse vir die oppervlakbindingsenergie ce verkrv.

P14 COKING COAL CONTROt BY AUTOMATED IMAGEANALYSIS

L,E•Korwin-Kossakowski. HICR, CSIR, H.ROUX, ISCOR

Coals vary widely in their ability to form coke and itis customary to blend them before carbonization in or-der to produce the type of coke required.

.Petrographic analysis is now widely used for predictingcoking properties of coal and developing coal blendingprocedures. The analysis of coal blends is difficultby conventional optical microscopy.

The HICR of the CSIR has started a comprehensive studyin order to develop a method, for the analysis and con-trol of coal blends, by utilizing automated image analy-sis using suitable software.

A number of blends including the coals of origin wereprepared, polished and measured. In this paper theinstrumental and experimental conditions as veil aspreliminary results are reported. The results obtainedby image analysis are compared with conventional pecro-graphic techniques and discussed.

PI 8 DIFFUSIESTODIES VAN SI IN Fc-GEBASEERDEAMORFE ALLOOIE

WD Roos en OH van HykDeparteaent Fisika, UOVS, Bloemfontein

Die aktiveringsenergie Q vir diffusie van Si in Fe-gebaseerde amorfe allooie is met behulp van segrega*siekinetika-metodes bepaal by temperature onderkantdie kristallisasieteoperatuur van die amorfe allooi.Die gemete Q-waardes is laer as in voorafgekristal»liseerde allooie. Die metings is in allooie net ver»skillende Si-konsentrasies gedoen en die aanduidingsis dat bogenoeode effek minder prominent by ho£r Si-konsentrasies is. Die resultate wora bespreek interae van moontlike interaksies tussen segregante endie eliminasie van oorversadigde defekkonsentrasies.

106

PI 9 IWMTIC norms or AMORPHOUS(KTALLIC GLASS)fa.. « ! „ • _ .

K.O. R«n«V, T.B. Doyla , D.D. Spaldlng•University of Dvirban-Wtstville•University of Natal, Durban

Aaocphous (natallie glaaa) rtbbona of Ni4 Q

th

<HC>

^ 4Qwar* pu'iae annealed by pasting a current through theribbon.

Tht KH bahavlour was racorded for the various•peclmens and the following measurements war« nada:

1. Coercltivltjr

2. Anisotrophy

These aaaauremants were made as £ function of pulaelength (tlaa), pulae height (current density) andmechanical streaa (weights).

A significant reduction in H and K were obaervedfor the first few pulse anneals but wi\£h subsequentpulsing, these parameters increased. Pulsing underlongitudinal mechanical stress prevented an increase inHc and Ku.

P22 ELASTIC BEHAVIOUR OF HOLYBPEHUM PHOSPHATEGLASSES

J.D. Comina* J.E. Nacdonald* f.T. L»mb»on* and G.A.

Saundera *1 Phytlcs D*p«rti«ent, University of the Mttwatarsrand•School of Physics, University of Bi»th, ClavertonDown, Bath, United Kingdom

Hydroatatic pressure and temperature dependences ofultrasonic wave velocities have been meaaured Inmolybdenum phosphate glasses over a wide compositionrange. Marked discontinultiea In elastic propertiesoccur with compoaltion and result from differences inthe structure and bonding. The effects ofvibrational anharmonicity are examined •_.• determiningthe appropriate QrUneisen parameters. Lowtemperature measurements of elaatic constantsindicate the interaction of the phonons withtwo-level systems.

P20 » « 5 S » « U » STUDY Qf THE MtGHETtC HYPERFIWE flELOOIStRIBUTIOl III »»0«PHOUS ft Hi 8

*. Bactitnjtt. H. Edtaards and «. Bharuth-fta*.Physics Otpartttnt, Unintrsity of Ourban-Mtitvillt.

•Stibautr jptctra of pulst-inntaltd suplts of letiUic glassFt li J atrt invtstigattd •> a function of pulling tiat.

lnsttad of the sharp sii-lint sptctrua typical of iron ab>orb«ri,tha sptctra ihOM broad absorption linti Mhich rtfltct a distributionof hyptrfint aagnttic fitlds at iron sitts. Tht lint widths incrtastfro* tha insidt pair (3,4) to tht outsidt pair (1,6). Crystallitatioasat* in at a pulsing tin of about 90 as, at ahicli point tht sptctruachangts to a tort coapltx fora.

Tht nariatian of th< sptctral paraatttrs (isoatr tkift,quadrupoU splitting, lint nidth and arta ratio) art in«tstigattd asa function of aulsing tiat. Inttrpritation of tha rtsults in ttras oftht aagnttic hyptrfint fitld and tht aagnttic atatnt directions in thtribbon art offtrtd.

P23 ON SURFACE OAMAGE TO (100) CdTe

M E Lee*. E 0 de Neijs*. A M Letsoalo+ and R J Muller** Electron Microscope Unit, University of the North+ Physics Department, University of the North• N1MR, CSIRCadmium telluride is an extremely soft and brittlematerial and is therefore easily damaged and readilycleaves along (110) planes during routine surfacepreparation techniques such as lapping, dimpling andmechanical polishing.

In this paper the observation of the damage to (100)cadmium telluride surfaces caused by 6 urn, 3 urn, 1 urnand 0,3 um alumina abrasives respectively will bereported.

The damaged CdTe surfaces were observed by means ofX-ray topography and scannino electron microscopy.

P21 NEUTROW DIFFRACTION EXPERIMENTS OF SOMERARE-EAKTH INDIUM COMPOUNDS.

E.G. Booysen*. P. de V. du Plessis* and G.H.F. Brits'

* Sand Afrikaans University, Johannesburg." AEC, Pclindaba.

RIn compounds (P • Tb, Er, Ho) have been investigatedby neutron diffraction. These compounds exhibit ananciferromagnetic structure and the temperaturedependence of the sublattice magnetization as obtainedfrou powder scans will be presented.

P24 BRONINE-METHMtOL ETCHING OF (100) CADMIUMTELLURIOE SURFACES

M E Lee*. AM Letsoalo* and W 0 Barnard** Electron Microscope Unit, University of the North+ Physics Department, University of the North* NIMR, CSIRThe aromine-methanol etch r^ien is well known in thepreparation of semiconductor surfaces. The use of thisetchant for (100) CdTe surfaces has been ssown to beselective for solutions of compositions less than 5%and non-selective (polisning) for solutions above thiscomposition.The stoichiometry of (100) CdTe surfaces after applica-tion of the bromine-methanol etchant has to date notbeen investigated.In this paper the stoichiometry of (100) CdTe surfacesetched in bromine-methanol solutions will be investi-gated. The results for the Auger spectroscopic analysesof these surfaces will be presented.

107

BAJB THE OXYGEH COVERAGE ON DIAHOHP SURFACESremît T.B.Dacry. J.O.Hansan*. P.t.Harris.

lUG.Coppetthwaite, J.P.F.Sellichop.Hits-CSIR Schonland Research Centre for Nuclear Science«,University of the Witwatersrand,Johannesburg,South Africa* &«B*tr» Diamond Research Laboratory,

Diaaond surface* prtparad by polishing or cleaning Inaqueous stadia and esaainad by RBS or XPS show afractional aooolayer coverage of oxygen i c o n , whichaay ba dua to hydroxyl group» replacing hydro Ran on tiha"dangling bond*". Staric hindranca batvaan cha largaoxygen atoas should l i a i t covaragat on (111), (110) and(100) aurfacas to one-chird, ona-third, and one-halfmonolayer» raspactivaly, and valuas cloa« to thesa araaeasured by RBS.

Tha oxygen daaorbs slowly in UHV or rapidly on waning,with an activation anargy (M«V) comparable with C-0bond-strengths measured in organic oolecule*.

P28 HALL PROFILING OF GaAs EPITAXIAt

S A Goodman. A W R Leiten and J S Vei/mat*

Physics Department, University of PortElizabeth

Traditional Hall affect measurements are usedto characterize an epitaxial layer in terms ofits carrier concentration and nobility. Suchmeasurements will give the averag* propertiesof a layer, being unable to detect localvariations in the electrical properties. Forthis reason a chemical Hall profiling systemhas been developed, capable of profilingthrough several epitaxial layers of differentdoping levels. The construction of such asystem with preliminary results, will bepresented.

P26 INFLUENCE OF TEM GRIDS OS AMORPHOUSSILICON DURING IN SITU SILICIDE FORMATION

S Kritzinger, C.J Bedetcer and J C LombaardPhysics Department, University of Stellenbosch

The usa of salf-supporting thin filas for in situstudies of suicide formation has various advantagesover tha use of traditional single crystal silicon sub»strates. However, during investigations of silicidaformation, using vscuum deposited bilayars of chromiumand aaorphous silicon, wa observed that tha supportingcopper and nickel TEM grids caused extensive whisker andhillock formation upon annealing above SOO'C. X-rayanalysas showed the presence of Cu and Ni at the affec-ted areas, indicating that the grid material underwentinterdiffusion with the aaorphous silicon layer. Thisraactioo complicated tha SAD patterns of tha expectedchrcaiusi suicides. Oxidation of the Cu grids prior touse iaproved the results below 600*C. By using pre-oxidised Ni grids the interaction could be prevented atteaperatures up to 750*C.

P29 EFFECTS OF PEBA ON GaAs

H.W.Alberts*. F.D. Auret*. M. Nel+andH. le Roux*

'University of PretoriaUniversity of Port Elizabeth

Tha influence of pulsed electron beaa annealing(PEBA) was studied on both Cr implanted and unioplantedGaAs.

GaAs single crystals were implanted with 150 k*V Crions at doses ranging between 1 * 10 u to 5 * IOU ions/cm?The radiation damage was analyzed with the RBS techni-que, using 1,5 MeV a-particles. The restoration processof the implanted crystals was studied as a function ofthe energy obtained from the PEBA process up to 0,4J/cB2.

On tha other hand DLTS-maasureoents indicated thattha PEBA process in itsalf created electrically activedefects (traps) in consentrations as high as lO^ca"1.Tha properties of soae of these dafects closely resembleChose präsent in electron and proton implanted GaAs.

P27 OPTICAL BIREFRINGENCE STUDIES OFDEFECTS IN GaAs

E E van Dyk, J S Vermaak, A W R Leitch

Physics Department, University of PortElizabeth

Infrared (IR) birefringence technique has beenused to observe induced defects in GaAs.

Sixty degree dislocations were induced by theplastic deformation of n-type (001) orientatedGaAs, about one of the <110> axes at 550°C inan Argon atmosphere. The IR biretringenceimages of these defects will be discussed.

P30 DETECTION OF ELECTRON AND BOLE

TRAPS BY DLTS IN PROTON IMPLANTED

VPE GROWN n-GaAa USING SBD'S .

M. MEL and F.D Auret, Physics Dept. OPE.

Schottky Barrier Diodes (SBD's) were used for

DLTS characterization of electrically active

defects in proton implanted n-GaAs. The use

of lowly doped <1x10 /cm ) VPE grown n-GaAs

in conjunction with a forward bias DLTS fill-

ing pulse enabled the detection of majority

and minority carrier defects in n-GaAs. The

results showed the presence of at least S majot

electron and 5 hole traps. With the aid of IQ-

DLTS another electron trap EO, of which the

DLTS peak usually coincides with that of the

El, could also ba detected.

108