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
Model
Diameter
16mm
window
Windowless
Enhancement UV
Gain
130 at 2600 V
Dark current
110 nA
Capacitance
110 pF
<Windowless LAAPD>
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)

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

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

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

10. SrCl2 crystal test Energy resolution (FWHM) : 9.6%
662 keV
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 Energy resolution (FWHM) : 5.4%
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.