We have developed a large CdTe pixel detector with dimensions of 23.7 \times 13.0 mm ^ { 2 } and a pixel size of 448 \times 448 \mu m ^ { 2 } .
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 ^ { \circ } 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 ^ { \circ } C and –20 ^ { \circ } 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 ^ { \circ } C. When we normalized the peak area by the total counts detected by each pixel , a variation of 2.1 % is obtained .