Development of uniform CdTe pixel detectors based on Caltech ASIC

We have developed a large CdTe pixel detector with dimensions of 23.7 x 13.0 mm2 and a pixel size of 448 x 448 μm2. The detector is based on recent technologies of an uniform CdTe single crystal, a two-dimensional ASIC, and stud bump-bonding to connect pixel electrodes on the CdTe surface to the ASIC. Good spectra are obtained from 1051 pixels out of total 1056 pixels. When we operate the detector at -50°C, the energy resolution is 0.67 keV and 0.99 keV at 14 keV and 60 keV, respectively. Week-long stability of the detector is confirmed at operating temperatures of both -50°C and -20°C. The detector also shows high uniformity: the peak positions for all pixels agree to within 0.82%, and the average of the energy resolution is 1.04 keV at a temperature of -50°C. When we normalized the peak area by the total counts detected by each pixel, a variation of 2.1% is obtained.