A study of the effects of position resolution and energy resolution on Compton imaging using a single planar strip detector

The feasibility of single element Compton imaging using a Double Sided Germanium Strip Detector (DSGSD) has been investigated, with potential use in assisting particle identification as part of Phase III DEGAS at DESPEC in mind. DEGAS is a proposed high-purity germanium tracking array for use in the DEcay SPECtroscopy (DESPEC) experiment at FAIR. The concept of γ-ray tracking within a DSGSD has been proved viable, with Compton images reconstructed from partial energy depositions within the detector volume. Using the raw positional information provided by the segmentation of the detector, initial source locations were unable to be resolved, with the resulting image displaying multiple ‘hotspots’ resulting from the selection criteria imposed. The causes of these features have been explored and explained in terms of scattering angles using the simulation package GAMOS. The effects of Pulse Shape Analysis, as a means of improving position sensitivity, have also been investigated, using a simulated database in con- junction with a grid search algorithm. Detailed electric field simulations were created, enabling a simulated pulse shape database to be generated using the ADL software package. Experimental data were sorted to locate potential Compton events, with charge pulses for each events stored using a digital electronics setup. Experimental pulses were compared to pulses from the simulated database using a FoM minimisation grid search algorithm. This improved the position resolution of interactions within the detector, thus improving the effectiveness of the resulting Compton reconstructions. With the application of PSA, initial source positions were located to within ∼ 10 mm, with the image resolution found to be of the order ∼ 100 mm for a range of initial γ-ray energies. Initial results appear promising, with future work required to improve the efficiency of the method. Additionally, Monte Carlo simulations have been performed to study the individual contributions of both energy and position resolution on the final reconstructed Compton image. Simulations were performed for three energy resolutions; 0, 3 and 50 keV, with a fixed position resolution of 2 × 2 × 10 mm, in addition to three position resolutions; 1, 2 and 5 mm3, with a fixed energy resolution of 5 keV. The results of these showed that the position sensitivity of the detector has a much more significant impact of both the location and resolution of the reconstructed Compton image.