8th topical seminar on innovative particle and radiation detectors siena, 21 – 24 october 2002

1

8th Topical Seminar on Innovative Particle and Radiation Detectors

Siena, 21 – 24 October 2002

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SIENASIENA is located in Tuscany about 50km south of Florence

Ancient Etruscan settlement, became Roman colony under the name of Sena Julia

Its importance grew in Middle Ages until became a municipality in 12th century: flourished in XIV century

Frequent confrontations with neighbouring towns: taken over by Florence in 16th century

Still retains an authentic medieval atmosphere

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Piazza del Campo 14th century, is the heart of the city

Location of the ancient roman forum, boasts 14th century gothic buildings

Palazzo pubblico e Torre del mangia Fonte Gaia by Jacopo della QuerciaThe horse race (Palio) is held here, 2nd of July and 16th of AugustOf medieval origin, sees the 10 of the 17 contrade competing against each other: the winner gets the Palio (banner)

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The Dome,XIV century: one of the best roman-gothic architectural examplesMasterpieces by Nicola Pisano, Donatello,Pinturicchio

Floor consisting of 56 different mosaics, depicting sacred scenes, required more than 150 years to be completed

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High Energy High Energy Neutrino AstronomyNeutrino Astronomy

Christian Spiering, Siena, October 2002

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Physics Goals

A. High Energy Neutrino AstrophysicsWeakly interacting neutrinos reach us from very distant sources:

possible invaluable instrument for high-energy astrophysicspossible invaluable instrument for high-energy astrophysics B. Particle Physics

Magnetic Monopoles, Oscillations, Neutrino Mass ...

C. Others Supernova Bursts, CR composition,

Black Holes, ...

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Cosmic Rays

1 TeV

GZK cut-off

8

Supernova shocksexpanding in

interstellar medium

Crab nebula

up to 1-10 PeV

9

Active Galaxies: accretion disk and jets

VLA image of Cygnus A

up to 1020 eV

10

log(

E2

Flu

x)

log(E/GeV)TeV PeV EeV

3 6 9

pp core AGN p blazar jet

Top-down

GRB (W&B)

WIMPsWIMPsOscillationsOscillations

UndergroundUnderground

UnderwaterUnderwaterRadio,AcousticRadio,Acoustic

Air showersAir showers

Microquasars etc.

GZK

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1 pp core AGN (Nellen)2 p core AGN Stecker & Salomon)3 p „maximum model“ (Mannheim et al.)4 p blazar jets (Mannh)5 p AGN (Rachen & Biermann)6 pp AGN (Mannheim)7 GRB (Waxman & Bahcall)8 TD (Sigl)9 GZK

Diffuse Fluxes: Predictions and Bounds

Mannheim & Learned,2000

MacroBaikalAmanda

9

12

Detection Methodsand Projects

Detection by Air Showers

Underwater/Ice Cerenkov Telescopes

Acoustic Detection

Radio Detection

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Underwater/Ice Cerenkov Telescopes

4-string stage (1996)

Strings of widely spaced PMT put in deep water

AMANDA: Antarctic Muon And Neutrino Detector Array

14

cascademuon

Cerenkov radiation in H2O : v0.75c, = tg-1[(n2 v2/c2-1)1/2] High-energy neutrinos through the earth may

interact and create muons which emit Cherenkov light

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1 km

2 km

SPASE air shower arrays

resolution Amanda-B10 ~ 3.5°

results in ~ 3° for upward moving muons

(Amanda-II: < 2°)

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AMANDA-II

AMANDA

Super-K

DUMAND Amanda-II:677 PMTsat 19 strings

(1996-2000)

80PMTs

302PMTs

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Preliminary limits (in units of 10-15 muons cm-2 s-1): Cas A: 0.6 Mk421: 1.4 Mk501: 0.8 Crab: 6.8 SS433: 10.5

Point Sources Amanda II (2000)

1328 events

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Expected sensitivity AMANDA 97-02 data

4 years Super-Kamiokande

8 years MACRO

170 days AMANDA-B10

-90 0-45 9045

10-15

10-14

cm-2 s

-1

declination (degrees)

southern sky

northern sky

SS-433

Mk-421 / ~ 1

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IceCube

1400 m

2400 m

AMANDA

South Pole

IceTop

- 80 Strings- 4800 PMT - Instrumented

volume: 1 km3

- Installation: 2004-2010

~ 80.000 atm. per year

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mediterraneum

Mediterranean Projects

4100m

2400m

3400mANTARESNEMO NESTOR

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Site: Pylos (Greece), 3800m depth towers of 12 titanium floors each supporting 12 PMTs

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-2400m

40 km

Submarine cable

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ANTARES Design

2500m2500m

300m300mactiveactive

Electro-opticElectro-opticsubmarine cablesubmarine cable ~40km~40km

Junction boxJunction box

Readout cablesReadout cables

Shore stationShore station

anchoranchor

floatfloat

Electronics containersElectronics containers

~60m~60mCompass,Compass,tilt metertilt meter

hydrophonehydrophone

Optical moduleOptical module

Acoustic beaconAcoustic beacon

~100m

10 strings12 m between storeys

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abs. length ~70 m80 km from coast 3400 m deep

NEMO Neutrino Mediterranean

Observatory

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NEMO 1999 - 2001 Site selection and R&D

2002 - 2004 Prototyping at Catania Test Site 2005 - ? Construction of km3 Detector

ANTARES 1996 - 2000 R&D, Site Evaluation 2000 Demonstrator line 2001 Start Construction

September 2002 Deploy prototype line December 2004 10 (12?) line detector complete 2005 - ? Construction of km3 Detector

NESTOR 1991 - 2000 R & D, Site Evaluation Summer 2002 Deployment 2 floors Winter 2003 Recovery & re-deployment with 4 floors Autumn 2003 Full Tower deployment 2004 Add 3 DUMAND strings around tower 2005 - ? Deployment of 7 NESTOR towers

26

d

R

ACOUSTIC DETECTION•Suitable for UHE Threshold > 10 PeV•Particle shower ionization heat perpendicular pressure wave

P

t

50s

Attenuation of sea water → given a large initial signal, huge detection volumes

can be achieved.

Maximum of emission at ~ 20 kHz

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AUTEC array in Atlanticexisting sonar array for submarine detection

Atlantic Undersea Test and Evaluation Center

52 sensors on 2.5 km lattice (250 km2) 4.5 m above surface 1-50 kHz !

Threshold ~ 100 EeV

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RADIO DETECTION: Askaryan process

Interaction in ice:e + n p + e-

e- ... cascade

relativist. pancake ~ 1cm thick, ~10cm

each particle emits Cherenkov radiation

C signal is resultant of overlapping Cherenkov cones

Coherent Cherenkov signal for >> 10 cm (radio)

C-signal ~ E2

nsec

Compton scattered electrons shower develops negative net charge Qnet ~ 0.25 Ecascade (GeV).

Threshold > 10 PeV

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Showers in RF-transparent media (ice, rock salt)

RICE Radio Ice Cherenkov Experiment

firn layer (to 120 m depth)

UHE NEUTRINO DIRECTION

300 METER DEPTH

E 2 · dN/dE < 10-4 GeV · cm-2 · s-1 · sr-1

20 receivers + transmitters

at 100 PeV

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AntarcticImpulsiveTransientArray

Flight in 2006

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el.-magn.cascade

from e

hardmuons

from CR

EExtensive Air Showersxtensive Air Showersfor E > 10 EeV produce Ionization trails

Far inclined showers ( thousand per year)

Hard s

Atm

osphere

• Flat and thin shower front• Narrow signals• Time alignment

Deep inclined showers (~ one per year?)

Atm

osphere

Soft s + e.m.

• Curved and thick shower front• Broad signals

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Observation of upward going optical Cherenkov radiation emitted by tau neutrino -induced air-showers

Need an observation from above (satellite)

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Horizontal Air Showers seen by Satellite

500 km

60 °

E > 1019 eV

Area upto 106 km2

Mass upto 10Tera-tons

Horizontal air shower initiated deep in atmosphere

1 - 20 GZK ev./y

34 Orbiting Wide-angle Light-collectors

OWL

Extreme Universe Space Observatory

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RICE AGASA

Amanda, Baikal2002

2004

2007

AUGER Anita

AABN

2012

km3

EUSOAugerSalsa

GLUE

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0.1 km3 and 1 km3 detectors underwater and ice

Conclusions

Contacts: Christian Spiering csspier@ifh.de

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P.G. PelferUniversity of Florence and INFN, Firenze, Italy

F. DubeckyInstitute of Electrical Engineering, Slovak Academy of

SciencesBratislava, Slovakia

A.OwensESA/ESTEC

Noordwijk,Netherland

P.G. PelferUniversity of Florence and INFN, Firenze, Italy

F. DubeckyInstitute of Electrical Engineering, Slovak Academy of

SciencesBratislava, Slovakia

A.OwensESA/ESTEC

Noordwijk,Netherland

Solar Neutrino Solar Neutrino Spectrometer Spectrometer with with InP InP DetectorsDetectors

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Why InP Solar Neutrino Experiment ?

Why InP Solar Neutrino Experiment ?

Semi Insulating InP Material

base material for:

Hard X-Ray Detectors

Fast Electronics and Optoelectronics

InP Spectrometer,

the Smallest, Real Time, Lower Energy

pp Solar Neutrino Spectrometer

The Solar Neutrino Spectrometer from/for R&D on InP X-Ray Detectors ?

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• BASIC KNOWLEDGE

• Solar Neutrino Physics• X-ray astronomy

• X-ray physics

• MEDICINE• Digital X-ray radiology (stomatology, mammography, ...)

• Positron emission tomography• Dosimetry

• NONDESTRUCTIVE ON-LINE PROCESS CONTROL• Material defectoscopy

• MONITORING• Environmental control

• Radioactive waste management• Metrology (testing of radioactive sources, spectrometry...)

• NATIONAL SECURITY• Contraband inspections: cargo control

• Detection of drugs and plastic explosives • Cultural heritage study

DETECTOR APPLICATIONS

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• Room temperature (RT) operation• Portability• Fast reaction rate• Universal detection ability• Good detection parameters: CCE, FWHM,

DE• Radiation hardness• Well established material technology • Well established device technology (10 m)

• FE Electronics and Optoelectronics integration on the Detector

• LOW COST

RT OPERATION: EG > 1.2 eV POLARISATION EFFECT: EG < 2.5 eV HIGH ENERGY RESOLUTION: EG small HIGH STOPPING POWER: Z > 30 HIGH CARRIER MOBILITY: > 2000 cm2/Vs

CANDIDATES

CdTe, HgI2, GaAs, InP

Requirements for Hard X-Ray Detectors of the New

Generation>10keV

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Attenuation and mobility

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Neutrino from the Sun

Neutrino from the Sun

ChlorineHomestakee + 37Cl 37Ar + e-

GalliumSAGE, Gallex, GNOe + 71Ga 71Ge + e-

WaterKamioka, SuperKx + e- x + e- (ES)

D2OSNOx + e- x + e- (ES)e + d p + p + e-

(CC)x + d n + p + e-

(NC)

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Requirements for Indium Solar Neutrino Spectrometer

Requirements for Indium Solar Neutrino Spectrometer

1. Indium incorporated into the detector

2. Energy resolution ∆E/E of the order of 25% at 600 keV. Important for spectrometry as well as background reduction.

3. Time resolution of the order of 100 ns for ~ 100 keV radiations.

4. Position resolution ∆V/V 10-7 at a reasonable cost. Very important for background reduction

5. Good energy resolution for low energy radiations ( ~ 50 keV )

6. Made with materials of high radiactive purity

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497.33 keV

E e(E - 118 keV ) + 115 Sn*

Delay = 4.76 sec

115Sn* 115Sn + e-(88 112 keV)/1 (115.6 keV) +

2(497.33 keV)

1/2= 4.76 sec

-

e

115In (95.7%)

1/2=6x1014 y

115Sn

612.81 keV9/2+

7/2+

1/2+

3/2+1

2

0

Neutrino Detection by In Target

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" prompt event “ in a “1 cm3

cell”

“ delayed event “ in a 27 cm3 macrocell

12

3 4 5

6

789

12

3 4 5

6

789

e

1

2

10 s

time

Solar Neutrino Eventin InP Detector

Solar Neutrino Eventin InP Detector

Calorimeter Module

1 cm3 cell

106 InP “1 cm3 cell”

Detector made up of many ‘basic cells’

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100 mm 200 mm

Spectrometer Module

Spectrometer Building Block

Pad Detectors

V microcell 1 mm3

N microcell /cm3

1000

FULL NEUTRINO SPECTROMETERFULL NEUTRINO SPECTROMETER

Nmodules 125

1 neutrino event once a day for 1011 background events

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SemiInsulating InP Wafer6” 6” diameter, diameter, 1 mm1 mm thick

Pad Detectors

Basic Component ofNeutrino

Spectrometer

Present InP Material and Detector Technology

Present InP Material and Detector Technology

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SI InP Material and Detector Technology

SI InP Material and Detector Technology

Original BUFFERS realised using ion implantation in backside (PATENTED)

Symmetrical circular contact configuration, 2mm , using both-sided photolithography

Final metallisation: TiPtAu on top and AuGeNi on backside

Surface passivation by Silicon Nitride

Producer:

JAPAN ENERGY Co., Japan

Growth Technique:

LECHigh-Temperature Wafer Annealing

Resistivity (300 K): 4.9x107

cm

Hall Mobility (300K): 4410 cm2/Vs

Fe Content: 2x1015 cm-3

Orientation: <100>

Final Wafer Thickness: ~ 200 m

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3.142 mm2 x 200 m

InP Detector Test Setup

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E=2.4 keV at 5.9 keV : 8.5 keV at 59.54 keV

Energy Resolution vs Shaping Time andSpectral Response in InP Laboratory Measurements

Energy Resolution vs Shaping Time andSpectral Response in InP Laboratory Measurements

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2

12355.2/355.2

a

EaeEFE

Linearity and Resolution vs X Ray Energyin InP Laboratory Measurements

Linearity and Resolution vs X Ray Energyin InP Laboratory Measurements

53

InP Spatial DistributionsInP Spatial Distributions

Count rate

Peak centroid

Resolvingpower

contact

bond wire

The detectors spatial response measured at HASYLAB using a 50 50 m2, 15 keV

X-ray beam.

54Contacts: Pier Giovanni.Pelfer pelfer@fi.infn.it

Present Radiation Detectors based on Bulk SI InP Fe doped have very good Detection Parameters

for the X ray Detection

from HASYLAB SR FaciltyFWHM from 2.5 KeV at 5.9 KeV to 5.5 KeV at 100 KeV

DE 10% at 100 KeV for 200 m thick Detector

dueto Better Material from Japan Energyand to Improved Interface Technology

Some Problems for Detector Polarisation

Detectors performances good for Solar Neutrino Spectrometer

Optimisation is our next research goal

Summary and ConclusionsSummary and Conclusions

55

A.Montanari, F.Odorici

INFN Bologna & Bologna University Italy

Application of Application of nanotechnologiesnanotechnologies in High Energy Physicsin High Energy Physics

56

•Nanotechnologies characteristics•Technologies for processing material on a nanometric

scale: 1-100nm•Interests in many field of research: biology,

chemistry, nanoelectronic,science of material

Nano-objects very attractive also in terms of application to a

new generation of position particle detectorsNano-holes, nanochannelsNano-wires, nanotubes

Mask, dies

Contacts, probes

57

•Single-Wall Carbon Nanotubes (SWNT) discovered in 1991

•Essentially long thin cylinders of carbon

Nanotubes introduction

58

•Single-wall nanotubes are formed in a carbon arc in the presence of a metal catalyst.  The tubes are found in the matted soot deposited on the reaction chamber wall  low yield

•The As-Produced Soot contains tubes that are 0.7-1.2 nm in diameter and 2-20 µm in length.  The product contains 10-40% tubes, the remainder is carbon-coated metal nanoparticles and amorphous and carbon nanoparticles

price list from Bucky USA websitebuckyusa@flash.net

59

•NT can have very broad range of electrical, optical, mechanical, thermal characteristics depending on their geometrical properties (diameter, length and chirality)

•SWNT are truly 1D objects

•Beside SWNT it is possible to grow Multiple Walls Nano Tubes (MWNT)

Energy gap dependency

on diameter and chirality

Quantum conductance of

MWNT G0 = 2e2/h 1/12.9 k -1

60

•Nanotransistor FET using NT as channel

Microphotograph from IBM website

•At low temperature, it becomes a Single Electron Transistor (SET)

NT applications

61

FIELD EMISSION FROM ARRAYS OF CARBON NANOTUBES

The aligned Nanotube field emitter are grown on a silicon substrate, by CVD

Nanotubes array grown by CVD

20 left 2 right 1 separation min

from NanoLab website

62

•Peculiar properties expected by the nanodimensions associated with NT filling:

•Superconductive phenomena (reported for K,Rb,Cs) at rel. high temp 50K

TEM image of KI@SWNT hybrid material

2 atoms crystal KI within 1.4nm SWNT

63

•New concept: bundles of NT used for position detectors

Readout electronics

Radiation

•Filling of nanotubes already possible

Nanopixel detector

64

•Require uniform and reproducible structure: using catalysts in chemical vapour deposition straight nanotubes are possible

Anodization of iperpure Aluminumsheets (100-300 mm thick ) undercontrolled conditions produces anoxide (Al2 O3 , Alumina) withself-organized regular honeycombstructure

The size and pitch of nanochannelsdepend on the parameters of theprocess (voltage, acid type,acid concentration, temperature): Pitch: 40 -> 400 nm

65

    Alumina nanochannels used to grow nanotubes

Alumina nanochannels can be used to grow CNs, after thedeposition of the catalyst (Ni, Fe, Co) at the bottom of each single pore

Growth of CN by Chemical Vapor Deposition of a hydrocarbur at 600- 800 o C

Temperature, gas concentration and duration of theprocess determine the CN structure (SWNT or MWNT, metallic or semiconductor)

66

Alumina nanochannels growing

67

NANO CHANNEL ACTIVE LAYER DETECTOR CONCEPT

68

Conclusions   

    NanoChant project (INFN & CNR) started as an R&D study aimed at improving by one order of magnitude the spatial resolution of position particle detectors, by using nanotechnologies (Carbon Nanotubes grown inside Alumina Nanochannels)•Present state: building of the Alumina Nanochannels pore size 40nm pitch 100nm•Immediate next step: growing of CN inside Nanochannels •Future step: study of properties of CN, to optimise their use as charge collectors and their coupling to active medium   

Contacts: Alessandro.Montanari@bo.infn.it

69

DIAMINE CollaborationWP-2 BARI, Italy

M. Abbrescia, G. Iaselli, T. Mongelli, A. Ranieri, R. Trentadue, V. Paticchio

Resistive Plate Chambers Resistive Plate Chambers as thermal neutron as thermal neutron

detectorsdetectors

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Reasons for new thermal neutron detectors

The humanitarian demining problem

Neutron Backscattering

Technique (NBT)

Metal Detectors not effective against anti- personnel mines:

•Neutron backscattering method: moderation of high-energy neutrons produced by radio-isotopic source or generator

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•Low (thermal) energy neutrons reflected from the soil is a direct indication of the amount of hydrogen •The amount of hydrogen in a plastic landmine is much higher (40-65%) than that of the surrounding soil even in case this is wet • A thermal neutron detector in combination with a neutron source is scanned across the soil, the presence of a landmine will be indicated by an increase in the number of thermal neutrons  

GroundLandmine

252Cf source

Cosmics

and “fast” n RPC

Thermal n

72

RPCs for thermal neutron detection

1) Bakelite electrodes2) Gap: 2 mm3) HV electrodes: graphite 100 m 4) High resistivity layer 5) Pick-up strips6)&7) readout electronicsOperating pressure: ~ 1 Atm

bakelite resistivity 10 10- 10 12 cm electrodes treated with linseed oil

RPCs are easy to build, mechanically robust, light-weighted, cheap, can cover large surfaces, are adapt for industrial production, etc.

particularly suitable for “on-field” applications

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Neutron Detection

Neutrons can be revealed only

after the interaction in a

suitable material

Production of secondary

ionising particles

The choice of the converter is crucial for the performance

of the detector

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Choice of the converterGd

• Natural Gd is characterized by a thermal neutron (50 kbarn) 12 times larger than 10B (3840 barn) • Produced electron range (15-30 m) is >than ’s (3-4 m)• Beyond E=100 meV, Gd cross section decreases much more rapidly than the one of 10B E1 eV it is smaller than the one of 10B.

For application concerning only thermal neutron detection Gd is preferable to 10B

75

HV

•Layer of the converter consists of Gd2O3 mixed with linseed oil; the mixture is sprayed onto the bakelite electrodes, which are used to build standard RPC  • It is possible to obtain extremely uniform layers, with very constant thickness and density 

The electric properties (surface resistivity) of bakelite electrodes are not altered

Gas

•RPCs 10x10 cm2 in dimensions one without Gd2O3, used as a reference and two with a different concentration of the oil Gd2 O3 mixture •Signal readout: copper pad Signal input to: NIM discriminator, Vthr=30

•Operating voltage 10-11kV (streamer mode) gas mixture 

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RPC with Gd-oil

TDC2

2 layers of 10B 0.35μm

U

e-

RPC

CI

TDC1

t0 start DAQ

tn stop to a multihit TDC

Schematic diagram of test system

TOA of e- plus delay start signal for two multihit TDC Neutron energy computed

77

     ‘raw’ data show already the higher efficiency achieved using this method  •Background noise (of the chamber, out of

time neutrons) to be taken into account

Relative efficiency of conversion:

CI

RPC

rel N

N around 2.5-3

times better

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Conclusions

•Demonstrated the feasibility of this approach to build Gd-RPC for thermal neutrons •Both detectors have an efficiency > 2.5 eff. CI ( 6%) 

•RPC-Gd experimental efficiency is > 10B theoretical maximum efficiency >> 10B-RPC experimental efficiency

•Coupling two of these detectors together efficiency reaches about 3.5-4 eff. CI (analysis in progress)

Contacts: marcello.abbrescia@ba.infn.it

•Performances of various types of detectors have been evaluated by a technical board of EC together with Monte Carlo analysis of the signal generated by a APL.

•Decision on when and how to really test a device is being under consideration.

79

Cinzia Da Via’

Brunel University, London, UK

ADVANCES IN SEMICONDUCTOR DETECTORS ADVANCES IN SEMICONDUCTOR DETECTORS FOR PARTICLE TRACKING IN EXTREME FOR PARTICLE TRACKING IN EXTREME

RADIATION ENVIRONMENTSRADIATION ENVIRONMENTS

80

PHYSICS REQUIREMENTS AT LHC AND SHLC (1035 cm2s-1)

p p

Hb

b

SUCCESS OF THE EXPERIMENTSREQUIRE PRECISE MEASUREMENT OF

•MOMENTUM RESOLUTION•TRACK RECONSTRUCTION•B-TAGGING EFFICIENCY

POSSIBLE WITH SILICON, HOWEVER…

Higgs channel

INTRODUCTION

81

RADIATION ENVIRONMENT AT LHC ANDEXPECTED AT SLHC

5*1015 5*1014

82

SILICON DETECTORS NORMALLY USED IN HEP

PRESENT STATUS OF RAD HARD

83

EFFECTS OF RADIATION DAMAGE IN SILICON DETECTORS

•Generation of charge traps by displacement damage of bulk silicon (interstitials and vacancies)

•Nuclear interactions

•Secondary processes from energetic displaced lattice atoms

Non Ionizing Energy Loss:Energy loss due to collision with lattice nuclei• depends on mass of the particle

84

RADIATION INDUCED BULK DAMAGE

85

RADIATION DEFECTS AND MACROSCOPIC EFFECTS

V,I mobile migrate until meet impurities and dopantsto form stable defects:

•Charge defects: Neff,Vbias

•Deep traps, recombination centers: signal charge loss

•Generation centers: Ileak noise

Oxygen-Vacancy complex forms an acceptor state in the upper half of band-gap (acts as a trapping center)

Neff

86

MACROSCOPIC PARAMETERS CHANGES AT 1015 n/cm2

87

SPACE CHARGE AFTER IRRADIATION

88

COLLECTION DISTANCE DETERMINED BY DRIFT LENGTH

Leff= t*Vdrift

•Also effect of charge sharing due to low field region after type inversion

89

MAIN DETECTORS STRATEGIES FOR SURVIVAL BEYOND 1015 n/cm2

90

OXYGEN AND STANDARD SILICON

•Vfd reduced 3 times

•No improvements for neutrons

•Defect engineering:influence the defect kinetics by incorporation of impurities•Higher O content: less donor removal

VO

P

VO not harmful @ room T

VP donor removal

91

SHORT DRIFT LENGTH USING 3D DETECTOR

92

3D VERSUS PLANAR APPROACH

93

CONCLUSIONS:

Contacts: Cinzia.DaVia@brunel.ac.uk

94

E.Giulio Villani, Renato Turchetta, Mike Tyndel 

Rutherford Appleton Laboratory

Analysis and Simulation of Charge Analysis and Simulation of Charge Collection in Collection in

Monolithic Active Pixel Sensors Monolithic Active Pixel Sensors (MAPS)(MAPS)

95

Reset

Column line

Row sel

Column parallel ADCs

R C e oa n

d to ru ot l

Data processing – output stage

I2 C

•Charge generated by impinging radiation in sensitive element D diffuses towards the cathode.The related voltage variation is buffered by the source follower and transmitted further down the line once the row is selected. One row at a time is readout

MAPS CONCEPTS AND MAPS CONCEPTS AND CHARACTERISTICSCHARACTERISTICS

96

P+ P+

P Sensitive volume(2 – 20 μm thick)

P++ Substrate(300 – 500 μm thick)

N+electronics

•Ionisation- generated charge remains confined within the potential well in the epitaxial layer and moves by thermal diffusion towards the cathode

97

•Typical diffusion time for 5m active area is about 20ns, with 600e- collected (simulation performed with ISE-TCAD on device with 5m epitaxial thickness >10m substrate 2V bias)Sufficiently fast for Linear Collider: however, LHC would require faster and more Sufficiently fast for Linear Collider: however, LHC would require faster and more radiation tolerant deviceradiation tolerant device

F 20ns

Typical results

98

New concept design and analysis: introduction of N-layer to extend electric field into active region

nRnGnnDtn 2

oSiz

2

2

KTFpEFiE

inKT

FiEFnEinANDNqz expexp)(

To be solved within the regions of the

device

N layer

Cathode

Active area

99

DEVICE DESIGN

Simulation results: Electric field comparisonNEW STANDARD

100

Superposition of voltage variations at the collecting cathode: new structure shows smaller swing than the standard structure but is faster regardless of the hit point

Fall time τF (0 to 90% of full swing) approximately 8.5 times smaller

τF 17ns

τF 2ns

101

Charge collection time shows the same fast behavior with fall time τF 2ns

Total capacitance C 6.63fF 

τF 2ns

NEW STANDARD

102

CONCLUSIONS

• Results of 2D simulations on standard MAPS compare favorably with what amply reported in literature   •      New structure proposal: analysis suggests the possibility of performances improvements  •       Design and simulation: results show shorter collection time and better efficiency which pave the way for improved radiation tolerance    Next steps:o     Full 3D simulation of a device with side implantso     Fabrication and testo     Implementation of readout electronics

103

PWy

PWx

DNWy

X

Y

Z

DSUB

New device structureNew device structure