CZT drift strip detectors for high energy astrophysics

Requirements for X- and gamma ray detectors for future High Energy Astrophysics missions include high detection efficiency and good energy resolution as well as fine position sensitivity even in three dimensions.We report on experimental investigations on the CZT drift detector developed DTU Space. It is operated in the planar transverse field (PTF) mode, with the purpose of demonstrating that the good energy resolution of the CZT drift detector can be combined with the high efficiency of the PTF configuration. Furthermore, we demonstrated and characterized the 3D sensing capabilities of this detector configuration.The CZT drift strip detector (10mm×10mm×2.5mm) was characterized in both standard illumination geometry, Photon Parallel Field (PPF) configuration and in PTF configuration. The detection efficiency and energy resolution are compared for both configurations . The PTF configuration provided a higher efficiency in agreement with calculations. The detector energy resolution was found to be the same (3keV FWHM at 122keV) in both in PPF and PTF .The depth sensing capabilities offered by drift strip detectors was investigated by illuminating the detector using a collimated photon beam of 57Co radiation in PTF configuration. The width (300μm FWHM at 122keV) of the measured depth distributions was almost equal to the finite beam size. However, the data indicate that the best achievable depth resolution for the CZT drift detector is 90μm FWHM at 122keV and that it is determined by the electronic noise from the setup.