High resolution CdZnTe pixel detectors with VLSI readout

CdZnTe pixel detectors with a custom VLSI readout, are being developed at Caltech/JPL for use in focusing hard X-ray telescopes. We have recently tested several prototype detector assemblies, each consisting of a 2 mm thick CdZnTe pixel detector indium bump bonded to our VLSI readout chip. A complete pulse height analysis chain is located directly below each 680 by 650 mu m pixel and includes a preamplifier, shaping amplifiers, and a peak stretcher/discriminator. Here we report on the first fully functional operation of these detector/VLSI hybrids. Using an Am-241 source, collimated to illuminate a single pixel, excellent energy resolution of 670 eV FWHM was measured for the 59.5 keV line at -10C, with electronic noise of only 340 eV FWHM. Illumination with an uncollimated Am-241 source was performed to assess the uniformity of pixel response and to exercise the readout chip's ability to process multiple pixel events arising from X-rays interacting above pixel boundaries. The imaging capability of the detector was demonstrated using a tungsten slit mask.