Compton imaging with thePorGamRays Detector

D S Judson

Imaging 2010, Stockholm, 8th-11th June 2010

Outline

PorGamRays project outline

Detector description

Spectroscopic performance

GEANT simulations

Experimental Compton imaging performance

Summary

PorGamRays: AimsPortable Gamma-Ray Spectrometer

The project aims to develop a gamma-ray spectrometer that is

Handheld and battery operated

Able to work at room temperature

Capable of providingIsotope identificationImaging

Potential applications for this sensor include:

decommissioning, security and

safety monitoring

6 CZT detectors

Modular design

Energy range:

60 – 2000 keV

PorGamRays: Schematic

gamma

Pixelated CZT

ASICDaughter board

MotherboardLaptop

PorGamRays: CZT detectors

Dimensions of 20 x 20 x 2 mm

Pixelated (10 x 10)

2 x 2 x 2 mm voxels

PorGamRays: CZT detectors

Dimensions of 20 x 20 x 2 mm

Pixelated (10 x 10)

2 x 2 x 2 mm voxels

Detector wire bonded

to daughter board

Data read out through

custom built ASICs

The PorGamRays demonstrator

Two CZT detectors

5 mm separation

Running from external

power supplies

NUCAM II ASICS [1]

Energy range of up to 350 keV

[1] P Seller et. al., IEEE Nuclear Symposium Conf. Rec., V6, 3786, ‘06

Spectroscopic performance of CZT

At 60 keV (241Am), FWHM ~ 6 keV, noise ~ 20 keV

Geant4 simulations

Simulated data used to evaluated the effects of the 20 keV noise level and 350 keV energy limit

Simulated two CZT detectors in PorGamRays configuration

Two different gamma-ray energies were used: 121 and 356 keV

Geant4 simulations

121 keV γ-rays deposit little energy in the scatter detector

Scatterer

Absorber

Eγ (keV)0 20 40 60 80 100 120 140 160 180 200

Eγ (keV)

Geant4 simulations

356 keV γ-rays deposit 140-220 keV in each detector

Scatterer

Absorber

0 50 100 150 200 250 300 350 400

Eγ (keV)

Source located at

x = y = 100 mm

z = 40 mm

x (mm)

y (m

m)

FWHM ~ 20 mm

120

120

100

100

y (mm)

x (mm)

Compton images – 133Ba – 356 keV

Compton images – 133Ba – 356 keV

x (mm)

y (m

m)

FWHM ~ 20 mm

Source located at

x = 105mm y = 115 mm

z = 40 mm

120

120

100

100

y (mm)

x (mm)

Possible to resolve changes in source position of only a few mms

x position (mm)

x = 95 mm

x = 115 mm

Compton images – 133Ba – 356 keV

Multi-spectral imaging

133Ba (356 keV) 57Co (121 keV)

x = 110, y = 120 mm x = 130 mm, y =85 mm

Conclusions

A CZT based Compton camera has been developed

Energy resolution of ~ 10 % at 60 keV

Position resolution of ~ 20 mm FWHM has been demonstrated

Changes in position of ~ 10 mm can easily be resolved

Simultaneous measurement of 2 different source demonstrated

CollaboratorsA J Boston1, P J Coleman-Smith2, D M Cullen3,

A Hardie4, L J Harkness1, L L Jones4, M Jones1,

I Lazarus2, P J Nolan1, V Pucknell2, S V Rigby1, D P Scraggs1,

P Seller4, J Simpson2, M Slee1, A Sweeney1

and the PorGamRays collaboration.

1 The University of Liverpool

2 STFC Daresbury Laboratory

3 The University of Manchester

4 STFC Rutherford Appleton Laboratory

Funded jointly by the EPSRC and TSB