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
<Windowless LAAPD>
Model 630-70-73-510
Diameter 16mm
window Windowless
Enhancement UV
Gain 130 at 2600 V
Dark current 110 nA
Capacitance 110 pF
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)
CsI(Tl) & Experimental setup
slightHygroscopicity
550Peak Emission (nm)
~1050Decay Time (ns)
4.53Density (g/cm3)
40000~60000Light output (Photons/MeV)
valueproperty
<Properties of CsI(Tl) made by Bicron>
PreAmp Amplifier FADC 25MHz
PC
HV
(1800V)
APDcrystal PreAmpPreAmp AmplifierAmplifierFADC
25MHzFADC
25MHz
PCPCHV
(1800V)
HV
(1800V)
APDcrystalAPDcrystal
APD optimization test
Energy resolution from different gain by changing high voltage.
The best resolution is obtained between 1780V and 1820V.
APD optimization test
Energy resolution from different shaping time.
The best resolution is obtained with 3~4μs shaping time.
Energy resolution of CsI(Tl)
Energy resolution (FWHM)
:4.7%
If we use PMT, energy resolution is about 7%
<HV:1800, gain:20 and shaping time:4us in amplifier>
662 keV
Calibration
EE
E
P
PY
ion
rayX
rayX
peakhe
1
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>
EQR
YY
PTFE
heAPDph .
1,
CsI(Tl) from Yangyang
CsI(Tl)_1
CsI(Tl)_2
47,000 ph/MeV73,000 ph/MeV
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
662 keV
Ba0.20Sr0.80Cl2 crystal test
Energy resolution (FWHM) : 5.4% The number of e-h pair : 16,500 e-h/MeV The absolute light output : 23,000 ph/MeV
662 keV
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.
