Transcript A Study of CsI(Tl) Scintillator with Optimized Condition

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 infrared. (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
property
value
Light output (Photons/MeV)
40000~60000
Density (g/cm3)
4.53
Decay Time (ns)
~1050
Peak Emission (nm)
550
Hygroscopicity
slight
<Properties of CsI(Tl) made by Bicron>
crystal APD
APD
PreAmp
Amplifier
FADC
FADC
25MHz
25MHz
HV
(1800V)
PC
PC
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)
662 keV
<HV:1800, gain:20 and shaping time:4us in amplifier>

Energy resolution
(FWHM)
:4.7%

If we use PMT,
energy resolution
is about 7%
Calibration
Ppeak E X ray 1
Yeh 
PX ray Eion E
Yeh 1
Yph , APD 
RPTFE Q.E
<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
CsI(Tl) from Yangyang
CsI(Tl)_1
CsI(Tl)_2
47,000 ph/MeV
73,000 ph/MeV
SrCl2 crystal test
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
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
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.