Preliminary performance of CdZnTe imaging detector prototypes

The promise of good energy and spatial resolution coupled with high efficiency and near-room-temperature operation has fuelled a large international effort to develop cadmium-zinc-telluride (CdZnTe) for the hard-X-ray region. We present, here, preliminary results from our development of small-pixel imaging arrays fabricated on 5 x 5 x l-mm and 5 x 5 x 2-mm spectroscopy and discriminator-grade material. Each array has 16 (4 x 4) 0.65-mm gold readout pads on a 0.75-mm pitch, with each pad connected to a discrete preamplifier via a pulse-welded gold wire. Each array is mounted on a three-stage Peltier cooler and housed in an ion-pump-evacuated housing which also contains a hybrid micro-assembly for the 16 channels of electronics. We have investigated the energy resolution and approximate photopeak efficiency for each pixel at several energies and have used an ultra-fine beam X-ray generator to probe the performance at the pixel boundaries. Both arrays gave similar results and at an optimum temperature of - 20 degreesC we achieved between 2% and 3% full-width at half-maximum energy resolution at 60 keV and around 15% at 5.9 keV. We found that all the charge was contained within one pixel except very close to the pixels edge, where it would start to be shared with its neighbor. Even between pixels, all the charge would be appropriately shared with no apparently loss of efficiency or resolution. Full details of these measurements will be presented, together with their implications for future imaging-spectroscopy applications. (C) 2001 Elsevier Science B.V. All rights reserved.