Physics Today David Powell ShoemakerKenneth Hedberg and Verner Schomaker Citation: Physics Today 49(7), 85 (1996); doi: 10.1063/1.2807706 View online: http://dx.doi.org/10.1063/1.2807706 View Table of Contents: http://scitation.aip.org/content/aip/magazine/physicstoday/49/7?ver=pdfcov Published by the AIP Publishing

Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions. Download to IP: 131.215.225.131 On: Mon,

17 Oct 2016 18:15:26

GEORGE BEKEFI

nonlinear wave propagation in hotplasmas and the various emission proc-esses from this novel medium. Thework culminated in his classic mono-graph, Radiation Processes in Plasmas(Wiley, 1966).

In the mid-1970s, George was readyto explore new fields. Earlier, duringa 1966 Ford Foundation visiting fel-lowship at the University of Oxford, hehad worked with Hans Motz, a pioneerof free-electron lasers. Thus beganGeorge's love affair with relativisticelectron beams, an affair that flour-ished until his very last days. In ad-dition to his research at MIT's RLEand Plasma Fusion Center, he was anactive participant in experiments atBrookhaven National Laboratory andthe CERN Linear Collider.

Also in the 1970s, together withMiklos Porkolab, George conceived thehighly original Versator II tokamakresearch program at MIT. It was thefirst tokamak to demonstrate the fea-sibility of driving substantial plasmacurrent with plasma waves, a step thatwas crucial to the development of thesteady-state tokamak reactor concept.In 1972-73, George traveled on a Gug-genheim fellowship to the Universityof Paris in Orsay and to the HebrewUniversity of Jerusalem. In 1978, heserved as chairman of the division ofplasma physics of the American Physi-cal Society. During his career, Georgereceived seven patents.

George was an enthusiastic andpopular teacher with a particular lovefor the freshman and sophomore phys-ics courses at MIT. He and Alan Bar-rett were coauthors of the text Electro-magnetic Vibrations, Waves and Radia-tion (MIT Press, 1977). In 1976, incollaboration with Abe Bers, Georgerestructured the MIT interdepartmen-tal graduate plasma physics course,

which has been successfully taughtsince then.

George was much loved for his readywit and engaging manner. No matterwhat the subject, a conversation withGeorge was always interesting and joy-ful. His early life experience, his broadeducation and his love of physics com-bined to create a personality that wasthoughtful and sympathetic. His pass-ing leaves a great void among his col-leagues and many friends.

ABRAHAM BERSBRUNO COPPI

DANIEL KLEPPNERMIKLOS PORKOLAB

Massachusetts Institute of TechnologyCambridge, Massachusetts

Joseph MurrayJoseph J. Murray, a world-renownedI leader in the design, construction

and operation of electromagneticbeams for the transport of high-energyparticles from accelerators, and a long-time member of the Stanford LinearAccelerator Center faculty, died on 29January 1996 at the age of 72.

After receiving his PhD in physicsin 1954 at Caltech, working on /3-ringspectroscopy, Joe Murray joined theaccelerator group under Ed Lofgren atwhat is now the Lawrence BerkeleyNational Laboratory There he begana series of designs for a crossed electricand magnetic field particle separator,which led eventually to his major in-novation, the use of heated glass platesto maintain gradients as high as 200kV/cm. The plates were used in almostall of the experiments run by LuisAlvarez's group using the largeBerkeley bubble chamber and sepa-rated beams of kaons, pions and pro-tons up to energies of 1 GeV.

Joe joined SLAC in 1967, along withthe team that had operated the Alvarez72-inch chamber. In a short time, hedesigned and installed a single-stageseparated beam, based on the radiofre-quency structure of the SLAC beam,for the 82-inch chamber and designedthe two-stage beam separator for thelarge-angle solenoid spectrometer. Inthis work, Joe demonstrated his out-standing ability to combine an intui-tive, analytical and practical approachwith a deep understanding of the phys-ics principles involved.

He then turned his attention to pro-ducing high-energy quasimonochro-matic gamma-ray beams by backscat-tering visible high-intensity laser lightoff the main electron beam. Thisgamma-ray beam led to a whole rangeof succesful gamma-ray induced parti-cle experiments. The techniques andanalysis developed for this beam have

JOSEPH MURRAY

led recently to a highly successfulCompton polarimeter used to measurethe longitudinal polarization of themain electron beam from the StanfordLinear Collider (SLC).

In the later stages of his career, Joeapplied his knowledge to the beamproblems associated with the SLC andhis contributions were essential to itssuccess. He also found time to pursuehis own ideas and experiments, notablyon gamma rays radiated by positronschanneled in crystals.

He spent most of his free time withhis family. He loved the sea and wasan accomplished diver and sailor.

Joe will be remembered for the pre-cision and completeness of his work andfor his willingness to provide guidanceto anyone requesting it. His contribu-tions to SLAC and to beam physics ingeneral will benefit many laboratoriesworldwide for a long time to come.

WOLFGANG K. H. PANOFSKYJOSEPH BALLAM

Stanford Linear Accelerator CenterStanford, California

David PowellShoemakerDavid Powell Shoemaker died sud-

denly on 24 August 1995 in Albany,Oregon. He was bom in Kooskia,Idaho, on 12 May 1920 and received aBA in 1942 from Reed College, and aPhD in 1947 from Caltech, both inchemistry. Following a fellowship yearabroad, he returned to Caltech as asenior research fellow (1948-51) beforegoing on to MIT as an assistant pro-fessor. He moved to Corvallis in 1970as chairman of the chemistry depart-ment of Oregon State University andretired there in 1984.

As a graduate student, David was

JULY 1996 PHYSICS TODAY 85 Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions. Download to IP: 131.215.225.131 On: Mon,

17 Oct 2016 18:15:26

first involved in a number of war-related projects, directed largely byLinus Pauling. When he was a seniorresearch fellow, he and B. GunnarBergman worked out the structure ofthe sigma-phase of the Fe-Cr system,a study that marked the beginning ofhis main research career, the struc-tures of transition-metal phases. AtMIT and later at Oregon State, he andhis wife Clara, together with their as-sociates, worked out the structures ofa very long list of transition-metal com-plexes. Many of the binary and terti-ary alloy phases (often containing sil-con or aluminum) have large unit cellsand are very complex, but a commonfeature is that their interstices aredistorted tetrahedra, whence the name"tetrahedrally close packed'1 ("tcp").Some representives of this group ofcompounds later became important aspossible storage materials for hydro-gen. Following the discovery of quasi-crystals in 1984, the building principlesof tcp phases were used in the deriva-tion of models of their structures.David was able to make importantcontributions to this field, and his in-sight and critical sense were muchappreciated.

Early in his MIT career, David alsobegan a notably productive researcheffort on the structure of zeolites, whichincluded derivation of the structures ofthe commercially most important zeo-lites, A and X/Y-Faujasite. He alsofound time to write (with Carl W. Gar-land, Jeffrey I. Steinfeld and laterJoseph W. Nibler) a widely used labo-ratory text Experiments in PhysicalChemistry, (first published in 1962 byMcGraw-Hill and now in its sixth edi-tion). Among David's professionalservices were 15 years on the US Na-tional Committee for Crystallography,including 3 years as secretary-treas-urer and 3 as chairman (1967-69);organizing chairman of the Eighth In-ternational Congress and General As-sembly of the International Union(1969); chairman of the American Crys-tallographic Association (1970); mem-ber of the executive committee of theInternational Union of Crystallogra-phy (1972-78); and regional coeditor ofAda Crystallographica.

After his retirement, David contin-ued to be active in science despite hisfailing health. At the regular luncheonmeetings of the physical chemists atOregon State, he contributed his cus-tomary insights to the discussions untilthe last week of his life.

KENNETH HEDBERGOregon State University

Corvallis, OregonVERNER SCHOMAKER

California Institute of TechnologyPasadena, California

Gianni Ascarelliianni Ascarelli, a member of the

vJTPurdue University physics depart-ment for over 30 years, passed away inWest Lafayette, Indiana, on 24 Septem-ber 1995, after a four-year struggle withcancer.

Ascarelli was born in Rome, Italy, on25 October 1931. In 1938, the familyresettled in Sao Paulo, Brazil, but re-turned to Italy in 1948. Ascarelli, whohad received a BS degree in physics fromthe University of Sao Paulo, enrolled atthe University of Rome and obtained aphysics degree ("Laurea") in 1954.

Ascarelli worked for a short period atthe Italian equivalent of the NationalInstitutes of Health. In 1955, he sailedto the US and enrolled as a physicsgraduate student at MIT. After obtain-ing his PhD in 1959, he spent two yearsas a postdoc at the University of Illinois.

In 1961, Ascarelli returned to Italyto assume the positions of group leaderwith the Italian National ResearchCouncil and lecturer at the Universityof Rome. In 1964, he joined the facultyof Purdue University as an associateprofessor and was promoted to profes-sor in 1970. Subsequently, he spentseveral years as a visiting scientist invarious places in Europe.

Ascarelli's research interests wereinitially focused on solid-state physics,with emphasis on the properties ofsemiconductors and ionic crystals. Inthe early 1960s, he made several pio-neering contributions to solid-statespectroscopy through the innovativeuse of the modulation techniques heinvented. He studied recombination,and low field breakdown processes, aswell as nuclear magnetic resonancephenomena in doped semiconductors.By employing optical absorption tech-niques, Ascarelli established at Purduea strong effort to explore the physicsof excitons and the electron-phononcoupling in semiconductors.

Along with his work on semiconduc-tors, Ascarelli developed a keen inter-est in the optical properties of biologi-cally relevant materials. He used far-infrared techniques to establish thevibrational spectrum of a number ofbiological systems. To this end, hebegan to utilize submillimeter cyclo-tron resonance with suitable lasers.He also explored the effects of the appli-cation of relatively high magnetic fieldson biological systems. Having dealt ex-tensively with aqueous solutions, As-carelli became interested in the intrigu-ing, fundamental problems associatedwith the mobility and the transport prop-erties of electrons in liquids.

During Ascarelli's last fifteen yearsor so, his main field of research wasthe exploration of electron energy levels

and electron transport in some non-polar dielectric liquids, mainly those ofthe rare gases. He also succeeded inmeasuring indirectly the exciton effectivemass in liquid xenon, in cooperation witha group from the universities of Jerusa-lem and Hamburg. While measuringelectron mobility, he also found an ap-parent discontinuity in the density ofliquid argon along isobars slightly abovethe critical temperature, and the possi-bility of a surface phase transition caughthis attention. Later on, he was able toresolve this mystery by estimating theeffects of capillary condensation.

His last effort was the direct meas-urement of the effective electron massin liquid rare gases, using cyclotronresonance.

Ascarelli's research was characterizedby an attempt to identify an issue onwhich there might be a conceptual or anexperimental difficulty, and then designan experiment to resolve the question.

He also made important theoreticalcontributions, such as his model of theelectron mobility in rare-gas liquids.From a comparison of the model cal-culations and experiment, he was ableto evaluate the density dependence ofthe effective mass of electrons in liquidargon and xenon. He continued hisexperimental work even when his lastillness made it very difficult.

He was an outstanding experimen-talist. Always full of ideas and plans,he was meticulous in the execution ofhis projects, being involved in everydetail. His very fruitful and imagina-tive experimental work was based ona deep and thorough understanding ofthe relevant theories. He was alwaysopen to new ideas and developments,and by giving advice and engaging indiscussion he contributed to the researchof many people who consulted with him.

Fluent in French, English, Italianand Portuguese, Ascarelli was able togive physics lectures in all these lan-guages. He was a rigorous person,demanding much from his studentsand colleagues alike. This trait, alongwith his urge to firmly uphold his moralprinciples and opinions, caused attimes disagreements and misunder-standings. He was a loyal, pleasantand helpful colleague and friend. Hewill be missed by many.

ROBERTO COLELLAGABRIELE F. GIULIANI

HISAO NAKANISHIPurdue University

West Lafayette, IndianaJEAN-PAUL JAST-GERIN

University of SherbrookeSherbrooke, Quebec, Canada

ITZHAK T. STEINBERGERHebrew University of Jerusalem

Jerusalem, Israel B

86 JULY 1996 PHYSICS TODAY Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions. Download to IP: 131.215.225.131 On: Mon,

17 Oct 2016 18:15:26