Investigation on the performances of multiple microstrip CdTe detectors

A study of the spectroscopic response of several large-size CdTe detectors equipped with a conventional cathode and a multi-microstrip anode (15 strips, each 150 μm wide, 500 μm pitch) was carried out. Measurements were performed scanning the detector across the strips, by means of a narrow rectangular photon beam (57Co and 109Cd sources), with its longer side oriented parallel to the strip direction, at normal incidence, in order to evaluate the detector behavior when the photon beam impinges at the strip position and at different positions inside the gaps. The detectors were also irradiated changing the value of the angle θ between the photon beam direction and the normal to the cathode surface in the range 0°<θ<70°. The behaviors of the 14, 22, 88 and 122 keV energy peaks have been analyzed. From the scanning along and across the strips some degree of spatial non-uniformity has been observed. As expected, the spectroscopic performance of microstrip detectors is only slightly dependent on the angle, i.e. our strip design is working well. Further measurements are in progress to study the observed charge sharing between adjacent strips, in order to understand if these detectors are suitable to be used as position sensitive devices with spectroscopic capabilities to build up focal planes of X-ray telescopes for astrophysics applications.