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Absolute light output determination of crystal scintillators

Absolute light output determination of crystal scintillators. Presented by Min Jeong Kim. Contents. Large Area Avalanche Photodiode Experimental Setup APD Optimization Test CsI(Tl) and newly developed crystal test Conclusion. Large Area Avalanche photodiode.

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Absolute light output determination of crystal scintillators

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  1. Absolute light output determination of crystal scintillators Presented by Min Jeong Kim

  2. Contents • Large Area Avalanche Photodiode • Experimental Setup • APD Optimization Test • CsI(Tl) and newly developed crystal test • Conclusion

  3. Large Area Avalanche photodiode • The quantum efficiency close to the 80% in the visible and near infra-red. (PMT ~20%) • Gain of up to several hundred in the total collected charge is possible. (Photodiode doesn’t have internal gain) <Windowless LAAPD>

  4. FADC FADC FADC PreAmp Amplifier crystal APD PreAmp PreAmp Amplifier Amplifier crystal crystal APD APD 25MHz 25MHz 25MHz property value HV HV HV Light output (Photons/MeV) 40000~60000 PC PC PC (1800V) (1800V) (1800V) Density (g/cm3) 4.53 Decay Time (ns) ~1050 Peak Emission (nm) 550 Hygroscopicity slight <Properties of CsI(Tl) made by Bicron> CsI(Tl) & Experimental setup

  5. APD optimization test • Energy resolution from different gain by changing high voltage. • The best resolution is obtained between 1780V and 1820V.

  6. APD optimization test • Energy resolution from different shaping time. • The best resolution is obtained with 3~4μs shaping time.

  7. Energy resolution of CsI(Tl) • Energy resolution (FWHM) :4.7% • If we use PMT, energy resolution is about 7% 662 keV <HV:1800, gain:20 and shaping time:4us in amplifier>

  8. Calibration • The number of e-h pairs : 37,000 e-h/MeV • The absolute light output : 52,000 ph/MeV <HV:1800, gain:100 and shaping time:4us in amplifier>

  9. CsI(Tl)_1 CsI(Tl)_2 CsI(Tl) from Yangyang 47,000 ph/MeV 73,000 ph/MeV

  10. 662 keV SrCl2 crystal test • Energy resolution (FWHM) : 9.6% • The number of e-h pair : 14,000 e-h/MeV • The absolute light output : 20,000 ph/MeV

  11. Ba0.20Sr0.80Cl2 crystal test 662 keV • Energy resolution (FWHM) : 5.4% • The number of e-h pair : 16,500 e-h/MeV • The absolute light output : 23,000 ph/MeV

  12. Conclusion • The best resolution of CsI(Tl) is obtained with 3~4 μs shaping time, and with 1800V high voltage of LAAPD. • We can measure the number of e-h pairs and the absolute light yield of scintillation crystals with LAAPD. • The number of e-h pair of CsI(Tl) is obtained to be about 37,000 e-h/MeV and the absolute light output is obtained to be about 52,000 ph/MeV for 662 keV 137Cs γ-ray source. • We estimate the relative light output of newly developed SrCl2 crystal to be about 40% of CsI(Tl) and Ba0.20Sr0.80Cl2 crystal to be about 45% of that. • We measured the absolute light yield of ZnSe(O), CeBr3 and other scintillation crystals.

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