Measurements of charge sharing in small pixel CdTe detectors

CdTe detectors with a thickness of 1 mm and a pixel pitch of 250 µm have been flip-chip-bonded to the HEXITEC read-out ASIC. The detectors record both the position and energy of X-ray interactions producing an X-ray spectrum for each of the 6400 pixels in the energy range 2-200 keV. In this arrangement, detectors have been shown to produce excellent spectroscopy with FWHM better than 1.2 keV at an interaction energy of 59.5 keV. Due to the use of small pixels, a significant number of events experience charge sharing where the total energy of the event is distributed between multiple pixels. Under normal operating conditions, the proportion of events that experience charge sharing was measured to be 36.4%. Without correction these events lead to a reduction in the spectroscopic performance of the detector, the production of pronounced fluorescence and X-ray escape peaks, and the detection sensitivity. In this paper, the effect of different correction algorithms and operating conditions on the detector performance is presented.