Edge and corner effects on spectra of segmented CdZnTe detectors

We present a theoretical and experimental study on the effect of detector edges on the performance of coarsely segmented CdZnTe pad detectors. We performed an analytical 3 dimensional calculation of the weighting potential of a finite size detector and studied the induced charge profile on central, edge and corner pads. The calculation involves a closed form solution of the 3 dimensional Laplace equation inside a rectangular detector. The edge effects are introduced via the boundary conditions at the detector edges. We compare our calculations to experimental results and show that they are both qualitatively and quantitatively consistent. We show that the spectra in edge and corner pads are inherently inferior with respect to the central pads. We discuss a novel electrode configuration that can overcome this problem and provide excellent uniform spectra from the entire detector.