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.