Development of CdZnTe detector systems for space applications

This work covers a comprehensive investigation of the issues confronting radiation damage in CdZnTe drift strip detectors planned for use as space instrumentation. Five main problems requiring investigation are identified and addressed including requirement specification with particular emphasis on device material properties, particle induced radiation damage, energy resolution improvement, noise minimization, and electron sensitive detector geometry. This thesis reports on experimental studies of the radiation damage effects of a 2.7 mm thick CdZnTe drift strip detector exposed to 30 MeV protons in order to describe the effect on the electron trapping characteristic of the material. The experimental studies, reported on this thesis, have been performed at DSRI, in collaboration with the cyclotron facility at Copenhagen University Hospital. The detector characteristics were evaluated after exposure to a number of fluences in the range from 2 × 10⁸ to 60 × 10⁸p⁺/cm². Even for the highest fluences, which had a dramatic effect on the spectroscopic performance, the detector was recovered after an appropriate annealing procedure. The radiation damage was studied as a function of depth inside the detector material. A numerical model that emulates the physical processes of the charge transport in the CdZnTe detector was used to derive the electron transport property as a function of fluence.