High Altitude Balloon Flight Of Cdznte Detectors For High Energy X-Ray Astronomy

CdZnTe (CZT) is a room-temperature semiconductor well suited for high energy X-ray astronomy. Knowledge of its background properties is essential for optimizing CZT based instruments. To study its background, we flew two CZT detectors on dedicated high altitude balloon flights from Fort Sumner, NM, the first in October 1997 and the second in May 1998. The first detector is a 12 x 12 x 2 mm(3) detector with orthogonal crossed strips and the second is a standard 12 x 12 x 2 mm(3) planar detector. The cross strip detector has 500 micron pitched electrodes plus anode "steering electrodes" to improve the anode charge collection. The energy range for these flights was 20 to similar to 350 keV. We have found a preliminary background level in 20 - 40 keV of 8.6 x 10(-3) cts/cm(2)-s-kev using passive 2 mm PbSnCu shielding and 6 x 10(-4) cts/cm(2)-s-keV using active collimated shielding. We present preliminary energy resolution and background spectra with several passive and active shielding schemes for the first position-sensitive CZT detector at balloon altitudes.