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ɣ-Ray Induced Radiation Damagein PWO and LSO/LYSO<strong>Rihua</strong> <strong>Mao</strong>, Liyuan Zhang, Ren-yuan ZhuCalifornia Institute of TechnologyOctober 28, 2009Paper N32-5, 2009 NSS/MIC at Orlando, USA

Introduction‣ Crystal scintillators suffer from radiation damageoriginated from electromagnetic energy deposition (ɣrays),neutrons and charged hadrons. This papercompares ɣ-ray induced radiation damage effects intwo heavy crystal scintillators: PWO and LSO/LYSO.‣ Possible effects of ɣ-ray induced radiation damageinclude (1) damage to the scintillation mechanism; (2)radiation induced absorption; and (3) radiation inducedphosphorescence (afterglow), which would cause anincrease of the electronic readout noise.‣ Photo-luminescence and transmission spectra, lightoutput and response uniformity, ɣ-ray inducedphosphorescence are measured.10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech2

SamplesLSO/LYSO samples: 2 x 2 x 20 cmPWO samples: 2.85 2 x 22 x 3 2 cmLSOLYSOPWO10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech3

Instruments Used in This StudyTransmittancePhoto-luminescenceLight yield <strong>by</strong> 137 CsLight Yield <strong>by</strong> 22 Na10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech4

No Damage on Photo-luminescenceNo difference was found between spectra measured beforeand after irradiations for both PWO and LSO/LYSO10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech5

Very Different Damage RecoveryPWO: 3 components: a few tens hours, a few thousand hours and a longerone equivalent to no recovery. LSO/LYSO: no recovery at room temperature.Dose rate dependent damageNo dose rate dependence10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech6

Damage may Depend on Dose RateA simple model waspublished in NIM A 332(1993) 113-120 for thekinetics of radiationinduced color centerdensities in crystalscintillators. It was used toexplain the dose ratedependent damage forPWO crystals in a paperpresented in NSS96 andpublished in IEEE Trans.Nucl. Sci., Vol. 44 (1997)468-476.10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech7

Damage on Optical Transmission-1PWO: dose rate dependent damage; LSO/LYSO: No dose rate dependence.Thermal annealing was found effective to remove ɣ-ray induced damages.10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech8

Damage on Optical Transmission-2Emission weighted longitudinal transmittance:10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech9

Damage on Optical Transmission-38-21% loss after 10 5 rad @9 krad/h5-9% loss after 10 6 rad10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech10

Damage of Light Output-1PWO: dose rate dependent damage; LSO/LYSO: No dose rate dependence10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech11

Damage of Light Output-222-35% loss after 10 4 rad @400 rad/h About 10% loss after 10 6 rad10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech12

Damage of Light Output-325.6% loss after 10 4 rad @400 rad/h 12.4% loss after 10 6 rad10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech13

No Damage in LRU if μ < 1 m -1Unchanged LRU maintains the constant term in resolution10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech14

ɣ-ray Induced PhosphorescencePWO and BGOhave small (10 -5 )afterglow.Afterglow forLSO/LYSO variesbetween 10 -3 to10 -4 . LYSO fromSaint-Gobain hasthe lowestafterglow.10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech15

ɣ-ray Induced Readout Noise-1ɣ-ray induced anode current was measured for samples at different dose rate10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech16

ɣ-ray Induced Readout Noise-2ɣ-ray Induced Readout Noise in PbWO 4 CrystalsSample L.Y. F Q bar Q end σ bar σ endp.e./MeV µA rad -1 h p.e. p.e. MeV MeVSIC-S392 7.13 97.9 290.7 9690 2.39 13.8SIC-S411 6.70 89.2 264.7 8822 2.43 14.0BTCP-2133 5.79 82.1 243.6 8119 2.69 15.6BTCP-2162 7.12 95.7 283.9 9466 2.37 13.710/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech17

ɣ-ray Induced Readout Noise-3ɣ-ray Induced Readout Noise in LSO/LYSO CrystalsSample L.Y. F Q bar Q end σ bar σ endp.e./MeV µA rad -1 h p.e. p.e. MeV MeVCPI-LYSO-L 2606 4.8 3.44x10 4 1.15x10 6 0.13 0.74SG-LYSO-L 2305 4.9 3.51x10 4 1.17x10 6 0.12 0.67CTI-LSO-L 2020 5.2 3.75x10 4 1.25x10 6 0.14 0.79SIPAT-LYSO-L 2155 4.9 3.56x10 4 1.18x10 6 0.12 0.7210/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech18

Summary‣ ɣ-ray induced radiation damage in large size PWO andLSO/LYSO crystals are evaluated. No damage in thescintillation mechanism was observed in both crystals.While PWO crystals recover at room temperature, leadingto a dose rate dependent damage, LSO/LYSO shows norecovery so no dose rate dependence.‣ Light output loss was found 26% after 10 4 rad @400 rad/hfor PWO, and 12.4% after 10 6 rad for LSO/LYSO.‣ ɣ-ray induced phosphorescence was found at 10 -5 level forPWO, and was between 10 -3 to 10 -4 for LSO/LYSO. Saint-Gobain LYSO has the lowest afterglow.‣ The equivalent readout noise induced <strong>by</strong> ɣ-ray dose atCMS Barrel and Endcap are about 2.5 MeV and 15 MeV,respectively, for PWO. The corresponding numbers forLSO/LYSO are 0.15 MeV and 0.8 MeV.10/28/2009 NSS09 Paper N32-5, <strong>Rihua</strong> <strong>Mao</strong>, Caltech19