Study of 5 and 10 mm thick CZT strip detectors

We report progress in the study of 5 and 10 mm thick CdZnTe strip detectors featuring orthogonal coplanar anode contacts. This novel anode geometry combines the advantages of pixel detectors with those of double-sided strip detectors. Like pixel detectors. these are electron-only devices that perform well as hard X-ray and γ-ray spectrometers and imagers even in the thicker configurations required for reasonable detection efficiency at 1 MeV. Like double-sided strip detectors in an N×N configuration, these detectors require only 2N readout channels to form N² "pixels". Unlike double-sided strip detectors, all signal contacts for spectroscopy and 3-d imaging are formed on one detector surface. Polymer flip chip bonding to a ceramic substrate is employed resulting in a rugged and compact detector assembly. Prototype detector modules 5 mm thick have been fabricated and tested. Prototype modules, 10 mm thick, are currently in procurement. Measurements confirm these devices are efficient detectors throughout their volume. Sub-millimeter position resolution and energy resolution (FWHM) better than 3% at 662 keV and 15% at 60 keV throughout the detector volume are demonstrated. Options for processing the signals from the non-collecting anode strip contacts are discussed. Results from tests of one prototype circuit are presented. We also report on detector simulation studies aimed at defining an optimum geometry for the anode contacts and at determining optimum operating conditions and the requirements of the signal processing electronics