CdZnTe arrays for astrophysics applications

The scientific objectives, status, and future instrumental requirements of high energy X-ray astronomy (similar to 20 to 200 keV) are discussed. Two particularly compelling requirements are: (1) an improvement in sensitivity to a level of similar to 5 microCrab (5 x 10(-6) of the flux from the Crab Nebula), which is a factor of 100 improvement over the next-generation spare instruments now in development and will make several hundred thousand X-ray sources accessible to observation; and (2) a survey of the sky at a sensitivity of similar to 0.1 milliCrab, which will discover and characterize similar to 10,000 new sources. The, first requirement can be fulfilled by imaging telescopes that use large-area focusing X-ray mirrors, which are effective over similar to 5 similar to 30 are minute fields, and the second requirement can be met by arrays of large area coded mask imagers with wide fields, similar to 50 degrees. Multilayer mirror and CdZnTe detector technology now in development offer the potential to meet these objectives. Position-sensitive CdZnTe detectors are well-suited to both of these imaging techniques and instrument concepts that use these detectors are described. Detectors with pixel readout are better suited for focusing telescopes and those with crossed-strip readout is better suited for coded mask imagers. Technical aspects of these detectors are discussed. Recent work at UCSD and WU on CdZnTe strip detectors is described in detail. Here studies with small, similar to 40 micron, X-ray beams have mapped a crossed-strip detector's spatial response with fine spatial resolution. The results demonstrate that crossed strip detectors have many desirable properties for both spatial and spectral measurements. They also show there are irregularities in the spatial properties which may limit detector performance on small scales.