Charge collection and depth sensing investigation on CZT drift strip detectors

CZT drift strip detectors with Planar Transverse Field (PTF) configuration are suitable for high energy astrophysics instrumentation, where high efficiency, high energy and position resolution are required from the sensors. We report on experimental investigations on the DTU Space developed CZT drift detector operated in PTF configuration 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. A CZT drift strip detector (10 mm x 10 mm x 2.5 mm) was characterized in PTF configuration at European Synchrotron Radiation Facility (ESRF) using ID 15A beam with its very fine collimations (beam spot size typically of 50μm and energies up to 500 keV). The depth resolution is measured to be 100μm FWHM @150keV and 200μm FWHM@500keV. These are well agree with the theoretical values. With these measurements, we demonstrated to achieve high efficiency due to large effective thickness, high energy resolution due to small electron drift lengths and sub mm position resolution using depth information using CZT drift strip detectors with N+1 readout channels in PTF configuration.