Development of high spectral resolution CdZnTe pixel detectors for astronomical hard X-ray telescopes

Cadmium zinc telluride detectors (CdZnTe) offer the possibility of achievin g excellent spectral and spatial resolution for compact hard X-ray sensors operated without cryogenics. These characteristics make these detectors ide al for several astrophysical applications, including focal plane sensors fo r multilayer hard X-ray telescopes, and in the image plane of coded-apertur e imagers. We are developing a CdZnTe pixel detector and low-noise VLSI rea dout for use at the focal plane of the balloon-borne High Energy Focusing T elescope (HEFT). In particular, we have concentrated on achieving excellent spectral resolution in a device with 600 mum pixels. Here we report result s from the testing of our fully functional prototype hybrid detector. The d etector (an 8 x 7 x 2 mm(3) single crystal of CdZnTe with an 8 x 8 pattern of platinum contacts on one side and a monolithic contact on the other) is indium bump-bonded to our 64-channel readout chip, which contains a charge- sensitive preamplifier, shaping amplifier, and combination peak stretcher/d iscriminator for each pixel. In this paper, we present results taken at roo m temperature, demonstrating a low-energy threshold near 5 keV and electron ic noise of 1.5 keV FWHM at 60keV. Subsequent testing of this detector at - 10 degreesC, reported in Cook et al. [Proc. SPIE 3769 (1999) 92], achieved 670eV FWHM resolution at 60 keV, with electronic noise of 340 eV. (C) 2001 Elsevier Science B.V. All rights reserved.