Compton imaging with the PorGamRays Detector D S Judson Imaging 2010, Stockholm, 8 th -11 th June 2010

Outline PorGamRays project outline Detector description Spectroscopic performance GEANT simulations Experimental Compton imaging performance Summary

PorGamRays: Aims Portable 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 providing Isotope identification Imaging 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 ASIC Daughter board Motherboard Laptop

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 ( 241 Am), 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) Eγ (keV)

Geant4 simulations 356 keV γ -rays deposit keV in each detector Scatterer Absorber Eγ (keV)

Source located at x = y = 100 mm z = 40 mm x (mm) y (mm) FWHM ~ 20 mm y (mm) x (mm) Compton images – 133 Ba – 356 keV

x (mm) y (mm) FWHM ~ 20 mm Source located at x = 105mm y = 115 mm z = 40 mm 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 – 133 Ba – 356 keV

Multi-spectral imaging 133 Ba (356 keV) 57 Co (121 keV) x = 110, y = 120 mmx = 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

Collaborators A J Boston 1, P J Coleman-Smith 2, D M Cullen 3, A Hardie 4, L J Harkness 1, L L Jones 4, M Jones 1, I Lazarus 2, P J Nolan 1, V Pucknell 2, S V Rigby 1, D P Scraggs 1, P Seller 4, J Simpson 2, M Slee 1, A Sweeney 1 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