Experimental Benchmark of Electron Trajectory Reconstruction Algorithm for Advanced Compton Imaging

Electron-tracking-based Compton imaging of gamma rays reduces the background level of the backprojected Compton image through the additional measurement of the initial momentum vector of the Compton electron. This reduction in image background has the potential for the detection of weaker sources in a complex background radiation field. Electron-tracking-based Compton imaging was demonstrated recently in solid-state detectors through the use of scientific Si charge-coupled devices (CCDs) with excellent position and energy resolution characteristics. In addition, the sensitivity of the electron track reconstruction algorithm has been evaluated extensively on the modeled detector response to Monte-Carlo electron tracks. We have now benchmarked the modeled algorithm sensitivity with our experimentally observed algorithm sensitivity, by measuring CCD electron tracks from a collimated 662 keV gamma-ray source in coincidence with a position-sensitive HPGe detector. For all coincident events the electron momentum vector deduced by the reconstruction algorithm is compared to the electron momentum vector calculated from the measured positions. This measured distribution of angular error of the algorithm agrees well with the angular error distribution calculated from our electron transport and detector models.