First images from a CeBr 3 /LYSO:Ce Temporal Imaging portable Compton camera at 1.3 MeV
Résumé
During nuclear decommissioning or waste management operations, there is a need for imaging the contamination field while identifying and quantifying the contaminants. Our objective is to test a Compton camera within the energy range 300 keV-2 MeV that uses both light and timing distribution of fast scintillating monolithic crystals. In this experiment we use a 5 mm thick CeBr3 scatterer plate and a 20 mm thick LYSO absorber plate. Our algorithms record for each scintillation event the full position and energy of the event including DOI, even in the thin plate and the relative timing between the detection in the two plate. Our CRT was measured at 293 ps FWHM in coincidence mode without DOI correction. This good time resolution allows for a stringent veto on real Compton event that must be recorded simultaneously in both the scatterer and the absorber plates, thus reducing background very efficiently. Acquisitions were performed with a Phillips Digital Photon Counter SiPM 3200 matrix with a delay-time correction map applied pixel by pixel. After accurate detection of gamma interaction coordinates (x,y,z) and energy in each plate, a list-mode maximum likelihood iterative reconstruction algorithm is applied to better estimate the gamma source activity distribution. Our Compton camera is a promising device for imaging high energy gamma rays, moreover, it can be also suitable for on-line monitoring due to its timing performance. The project TEMPORAL is funded by the ANDRA/PAI under the grant No. RTSCNADAA160019.