We have developed CdTe double-sided strip detectors (CdTe-DSDs) for the ASTRO-H mission and other future missions. We designed and assembled the CdTe-DSDs for ASTRO-H. These CdTe-DSDs have a strip pitch of 0.25 mm, an imaging area of 3.2 cm$¥times$3.2 cm and a thickness of 0.75 mm. The double-sided strip electrode configuration enables us to achieve a fine position resolution and a large detection area at the same time with a relatively small number of readout channels. Moreover, the double-sided readout provides high spectral resolution of 1.7–2.0 keV(FWHM) at 60 keV, and additional sensitivity to the interaction depth by comparing the anode signal with the cathode signal.
However, the hard X-ray and gamma-ray response of CdTe-DSD becomes complex because of the small mobility-lifetime product of holes in CdTe semiconductor. Therefore, one of the important issues for the accurate observations is to investigate the response of the CdTe-DSD.
In order to obtain information on the response corresponding to interaction positions and depths,
we performed scanning experiments at a synchrotron radiation facility SPring-8. By using a 30 keV monochromic X-ray beam with a size of about 6 um, we scanned both sides of the detector along two axises, and successfully obtained the response dependence on three-dimensional interaction position.
In this paper, we will present the imaging and spectral performance of the ASTRO-H CdTe-DSDs based on the results of scanning experiment.