Performance and simulation of CdZnTe strip detectors as sub-millimeter resolution imaging gamma radiation spectrometers

We report gamma-ray detection performance measurements and computer simulations of a sub-millimeter pitch CdZnTe strip detector. The detector is a prototype for gamma-ray astronomy measurements in the range of 20-200 keV. The prototype is a 1.5 mm thick, 64 x 64 orthogonal stripe CdZnTe detector of 0.375 mm pitch in both dimensions, with approximately one square inch of sensitive area. Using discrete laboratory electronics to process signals from an 8 x 8 strip region of the prototype we measured good spectroscopic uniformity and sub-pitch (similar to 0.2 mm) spatial resolution in both x and y dimensions. We present below measurements of the spatial uniformity, relative timing and pulse height of the anode and cathode signals, and the photon detection efficiency. We simulated the photon interactions and signal generation in the strip detector and the test electronics and we compare these results to the data. The data indicate that the cathode signal-as well as the anode signal-arises primarily from the conduction electrons rather than the holes. This presents a detection efficiency limitation which must be considered in the design of strip detector systems.