IMPROVING CDZNTE X-RAY-DETECTOR PERFORMANCE BY COOLING AND RISE-TIME DISCRIMINATION

We have studied several methods for improving CdZnTe detector performa nce, especially energy resolution and charge collection properties. En ergy resolution can be greatly improved by cooling the detector to abo ut -30 degrees C [1-3] which reduces the detector leakage current enab ling the use of low-noise, pulsed-optical feedback preamplifiers and h igher bias voltages. High bias voltages are necessary for more efficie nt charge collection which reduces spectrum background and peak tailin g. Applying rise time discrimination circuitry to the linear amplifier reduces the tailing effect even further, especially at higher energie s. Combining all these methods we tested a 16-mm(2), 3-mm thick Cd0.9Z n0.1Te detector crystal at -30 degrees C, and obtained energy resoluti ons of 292 eV at the 5.9-keV line of Fe-55, 600 eV at the 59.5-keV lin e of Am-241, and 780 eV at the 88-keV line of Cd-109. Another 9-mm(2), 3-mm thick Cd0.9Zn0.1Te detector crystal showed a charge collection p roblem at -30 degrees C which caused all spectrum peaks to be doublets . However, the rise time discriminator removed the ghost peaks form th e spectrum almost completely, and improved the energy resolution and b ackground.