Development of Uniform CdTe Pixel Detectors Based on Caltech ASIC

We have developed a large CdTe pixel detector with dimensions of 23.7 × 13.0 mm and a pixel size of 448 × 448 μm. 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.