2002-6-24 여름학교

Scintillation Detectors and it’s Application

2002 년 6 월 24 일 , KNU Summer school

김 홍주 , 연세대학교

1) Particle interaction in matter2) Scintillation mechanism3) Inorganic scintillation detector4) Organic scintillation detector5) Light Sensor6) Application a) Nuclear, High energy, Astroparticle physics b) Astrophysics c) Bio-, Medical physics

2002-6-24 여름학교

How to detect Quark to Cosmos

Cosmos -connection- Quark

2002-6-24 여름학교

Detectors use characteristic effects from interaction of particle with

matter to detect, identify and/or measure properties of particle; has “transducer” to translate direct effect into observable/recordable (e.g. electrical) signal

example: our eye is a photon detector; (photons = light “quanta” = packets of light)

“seeing” is performing a photon scattering experiment: light source provides photons photons hit object of our interest -- some absorbed, some

scattered, reflected some of scattered/reflected photons make it into eye; focused onto

retina; photons detected by sensors in retina (photoreceptors -- rods and

cones) transduced into electrical signal (nerve pulse) amplified when needed transmitted to brain for processing and interpretation

2002-6-24 여름학교

Overview of Experiment

detector signal processing

data handling

analysis&

control

01011101

computersimulation

PhysicsPhysics

origininteraction

2002-6-24 여름학교

Particle energy loss in matter

X rays

gamma rays

PE

CS

PP

electron(s)

dE/dx loss

charged particle

thermal neutronsnuclear reaction

energetic neutrons

proton

scintillator

dE/dx loss

dE/dx loss

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Dependence ofType of interaction

Energy

Zcm2/atom

Zcm2/g

Photoelectric Effect E-3.5 Z4 to Z5 Z3 to Z4

Compton Effect E-0.5 to E-1 Z independentPair Production E1 to ln E Z2 Z

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Interactions of photons with water and lead

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Gamma interaction

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Particle Detection Principle

2002-6-24 여름학교

Scintillation detectors and sensors

Scintillators Light sensors

inorganic crystals organic plastics/liquid glass gas

PhotomultiplierMicrochannel platesilicon diodesCCDsAvalanch photo diodehybrid photo diode

In radiation detectionin solid state physics: luminescencefast < 1 ms: fluorescenceslow > 1 ms: phosphorescence

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2002-6-24 여름학교

Scintillator

• Light emitted from ionisation in transport material( dE/dx loss)

a) I(t) = I0e-t/decay time, several component possible

b) s -> count rate<< MHz, ns -> count rate>> MHz, c) Wavelength of emission determine photosensor

• Two main material types of scintillators a) Inorganic scintillator b) Organic scintillator

2002-6-24 여름학교

Scintillator charasteristics• Inorganic scintillators a) Result of crystalline structure b) Large band gap, insulators c) High light output but relatively slow (~sec) d) Rather expensive, moderate size (~kg)

• Organic scintillators a) Molecular property of hidrocarbons b) Moderate light output but fast (~ns) c) Cheap, large size (~ton) d) Liquid scintillator (LSC) Plastic scintillator (PSC) Crystal (ex:anthracene, stibulene)

2002-6-24 여름학교

Inorganic Scintillator

• Ionisation excites electron conduction band de-excitation via photoemisson or radiationless

transition

• Large bandgap => slow process

• Impurities add centres (traps) in band gap Increase transition rate Suitable doping can also increase light output ( ex: CsI(tl), CsI(Na) Hols trapped at activate site -> recombination with e- -> emits photon

2002-6-24 여름학교

Inorganic Scintillator examples

2002-6-24 여름학교

Organic Scintillator

• Based on excited states of carbon atom (benzene ring : C=C bonds) Quasi-free electrons confined to molecule Complex vibration stats gives fine structure Range of singlet and triplet stats gives both long and short time structure => neutron and gamma separation capability

• Chemical Mixing Solvent : Medium for absorbing the energy of nuclear recoil Energy transferred to 1st solute moleculs 1st Solute: highly efficient fluors (efficient scintillator) Very short wavelength 2nd Solute: Wavelength shifter to match with bi-alkali photo sensor

2002-6-24 여름학교

Organic solvent

Band gap structure Energy transfer mechanism

ns ms solute 1st solvent 2nd solvent

2002-6-24 여름학교

Organic scintillator Solvents• Solute

a) Liquid Scintillator 1,2,4-Trimethylbenzene (Pseudocumene) p-,m-,o-Xylene, Toluene, Benzene, MN…

a) Plastic Scintillator Polystyrene (Polyvinylbenzene, PS) Polyvinyltolunen (PVT) • 1st Solvent PPO, p-Terphenyl, PBD, Naphthalene..• 2nd Solvent POPOP, M2-POPOP, bis-MSB….

• Standard Liquid Scintillator : PC + PPO(1.5-4g/l) +POPOP(10-50mg) 65% of anthrecene, safe, Pulse shape discrimination of n/gamma

2002-6-24 여름학교

ZEUS 실험

2002-6-24 여름학교Photomultiplier tube (PM or PMT)

generates electric signal

Light guide transmits light

to photodetector

Passage ofcharged particle generates lightin scintillator

Charged particle

Basic principles of operation

Scintillator light output readout

2002-6-24 여름학교

Light transmission

• Total reflection sin> next/n,

sin> 1/n, next = air

• Light guide• Optical grease (optical cement) • Light reflector Teflon, Al, white paint

2002-6-24 여름학교

PMT

PMTreflector

scintillator optical coupling

dynodes

photo cathode

electron multiplication

N

1

2

3 nNel

ideal case: Nel = N

Light detection

Photomultiplier Tube

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Light Quantum efficiencyof PMT photocathode

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PMT types

Venetian blind (old)

Box-and-grid

Focused linear structure

Circular grid

Gains - 107

PMTS

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Detection principle

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Detected Energy

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Typical signals from CsI(Tl)

660 keV

660 keV 10 keV

Oscilloscope signal

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CsI crystal R&D

Co57 source Am alpha source

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Neutron gamma separation with BC501A

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Neutron gamma seperation with BC501A

PartialTotal

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Energy spectrum in LSC with gamma, n

Cs137 in LSC 2.24MeV neutron in LSC

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Difference between Crystal & LSC

Cs137 source(661 keV) to detector (GEANT4 simulation)

CsI crystal BC501A LSC

Quiz : Why different response?

2002-6-24 여름학교

Scintillator Application

• High energy physics BELLE, BES, CDF, L3, Phenix, CMS, LC, Focus … Many more!

• Astro-particle physics Neutrino ( LSND, Super-K, Kamland..), Underground( Darkmatter, neutrino,

double beta), Ground array ( HE neutrino, UHE cosmic ray, HE gamma)

• Nuclear Physics, Nuclear engineering. Neutron, Radioactive decay, heavy ion, radioactive beam. ; Power reactor

monitoring

• Astrophysics, Astronomy Balloon (ATIC, IMAX..), Satellite (GLAST, INTEGRAL..), Space station (AMS..)

• Bio-science: Track radioisotopes in biology sample, Quantifying DNA and RNA

• Medical science: PET, CT, Track radioisotopes in human body, medicine

• Environmental science: Monitoring of radioactivity, nuclear waste, Radon

• More :Safety inspection, Military …..

2002-6-24 여름학교

Identifying particles

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What is happening in detector (Simulation)

1GeV gamma

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ZEUS detector at HERA(ep)

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The BELLE Detector (B physics)

Charged particle tracking and vertexing

–SVD: 3 layer DSSD silicon microstrip –CDC: 50 layer drift chamber (50/50 He-C2H2)

• p = 0.46 % @ pt = 1.0 GeV/c

Particle identification

–Hadron ID•CDC: dE/dx in central drift chamber•TOF: Time-of-flight system•ACC: Cherenkov light threshold counters

–Electrons•ECL : E&M calorimeter E/p•CDC: dE/dx

–Muons•KLM: RPCs in magnetic return yoke

Neutral particle detection•Photons: E&M calorimeter•8800 CsI(tl) : 40ton•KL : direction in the KLM

2002-6-24 여름학교

AGASA ( UHE cosmic shower)

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LSND (neutrino oscillation)

Mineral Oil +

LSC

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R&D of mineral oil loading

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KAMLAND (neutrino osc.)

2002-6-24 여름학교

DAMA experiment

DAMA NaI(Tl) crystal ~100 kg Gran sasso underground lab. Low threshold ~ 2keV Low background ~ 1/kg/kev/day Annual modulation method Found a evidence of WIMP

2002-6-24 여름학교

KIMS experiment Detector & Shielding Design(Dark matter Search experiment)

100kg 5 ton

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ATIC Ballon (HE cosmic ray)

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GLAST Sattelate (HE gamma)

2002-6-24 여름학교

Radioisotope imaging:Planar scintigraphy

Radiopharmaceutical

2D position sensitive detector:Gamma camera + motion

Multihole collimatorcrucial for image formation

emission

Radiation in Medical science

2002-6-24 여름학교

PET Scans(Positron Emission Tomography)

Scintillating crystal detectorand photomultiplier

3-D image

CrossSection

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Radioisotope imaging:Planar scintigraphy

Phosphonate tagged with 99mTc,injected into the blood stream,is mainly transported to bones,producing a view of theskeletal systemThe method is e.g. used to determinewhether or not cancer has metastized

From: National Geographic 171/1(1987)2-41

Radiation Technology

2002-6-24 여름학교

1D position sensitiveX-ray detector

X-ray tubepoint source

transmission

Radiation in Aviation Security X-ray Application

Conveyor

Fan beam

1D + motion 2D

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Radiation in Aviation Security X-ray Application

From: Heimann Systems, Wiesbaden, Germany

Advanced Multi X-ray Energy Method

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Fan beam

Gamma-ray source

Moving truck or container

1D PSD

CsI(Tl) crystals integrating

Radiation in Border Control Gamma-ray Application

transmission

1D + motion 2D

2002-6-24 여름학교

Radiation in Border Control Gamma-ray Application

From: NRC Handelsblad