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Session 43 - HST Instruments & Other Missions.
Display session, Tuesday, January 14
Detectors based on CZT, a room-temperature semiconductor, have many desirable properties for high energy X-ray astronomy. They can obtain sub-keV energy resolution, sub-mm spatial resolution, and operate from <10 keV to >200 keV. Thus they are attractive for future balloon and space instruments using coded masks to image wide fields, >10^\circ, as well as focusing optics for small fields, <1 ^\circ. We report recent progress and future plans for these detectors by a collaboration of UCSD and WU. Linearity of energy response has been measured with monochromatic X-rays. One-dimensional, strip readout, detectors with resolutions as small as 100 microns and a two-dimensional, crossed-strip readout, detector have been fabricated and tested. Charge collection and charge sharing among electrodes has been studied in detail. Charge is typically shared by 2 or more electrodes, but the full energy signal is obtained by summing the electrodes which have significant signal. Accurate measurements of the spatial response of the 25 x 25 x 1.4 mm thick 2-D detector were made with a precision x-y stage that carried a narrow, \sim50 micron beam. X-rays entered the cathode side of the detector. The selectivity between cathode strips was very sharp; the strip-to-strip transition required \sim75 microns including the effects of the beam size. The strip-to-strip transitions occurred at the nominal 375 micron pitch. The anode strip selectivity was similar, but the strip-to-strip transitions varied \pm140 microns from the nominal 375 microns. The latter effect is under further study. These results show that crossed strip readout is feasible for spatial resolutions of \sim500 microns, but the ability to obtain reliable resolution at much smaller scales, e.g., 100 microns is uncertain.
Program listing for Tuesday