Polarization sensitivity and efficiency for a planar-type segmented germanium detector as a Compton polarimeter

We have investigated performance of a planar-type germanium detector with 25 segments as a Compton polarimeter to measure the linear polarization of gamma rays. We considered three different configurations in sampling horizontal and vertical Compton-scattering events for linearly polarized gamma rays incident on the detector. The experimental polarization sensitivity Q, coincidence efficiency ϵcoin, and figure of merit F for each configuration have been extracted for gamma rays of interest below 600 keV found in our previous in-beam spectroscopy on 155Gd. We also obtained theoretical values for these three quantities through a Monte Carlo simulation. Experimental values were in good accord with simulation results for all the three configurations. The third configuration, sampling pairs between the segment of incidence and any off-diagonal segments in coincidence, turned out to have the largest Q as well as ϵcoin value of all the three configurations, thereby resulting in the best figure of merit F.