Large area high temperature hard X-ray spectroscopy detectors for space experiments

High quantum efficiency, good energy resolution and room temperature operation make Cadmium Zinc Telluride (CZT) pixel detector an unique advantage for space experiments. We present here the results of two large area CZT detector systems; one with external ADC (Analog-to-Digital Converter) and high power Application-Specific Integrated Circuits (ASICs)(Ideas) having faster parallel readout system and the other with on-pixel ADC and low power ASICs (OrboTech) having slower serial readout system. We have studied background, energy resolution and detection efficiency of these detectors between 20 and 100 keV. For Ideas detectors, large power dissipation in ASICs increases the detector temperature (upto 70 °C) and the thermal background. This rise in temperature increases thermal noise sharply which drastically affects both the energy resolution as well as the detection efficiency. The low energy dissipation in OrboTech ASICs keeps the detector temperature low & constant, making thermal background stable. We find that OrboTech resolution & efficiency are far better than that of Ideas detector in spite of slower readout system. We further discuss the use of these detectors in space experiments.