CZT performance for different anode pixel geometries and data corrections
We have investigated the energy resolution and absolute photopeak efficiency of CZT detectors with three anode pixel geometries after three data correction steps. Before data corrections, the energy resolution is 4–5% at 122 keV, and the efficiency is 46–70% for a 21 keV photopeak window. Charge sharing events, which make up 10–25% of all events, are a significant cause of the poor efficiency. We discovered that large gaps between anode pixels have a strong negative impact on both charge sharing and absolute photopeak efficiency. Using three-dimensional position-dependent energy corrections, we were able to compensate for some of this reduced sensitivity, increasing the efficiency by up to 35% to a final efficiency of 62–80% of incoming gamma events.
Fig. 1. For two-pixel events, anode signals for pixel 1 versus pixel 2. Curvature in the distribution for Design C indicates electron loss.