At DSRI, in collaboration with the cyclotron facility at Copenhagen University Hospital, we have performed a study of radiation effects exposing a 2.7 mm thick CZT drift strip detector to 30 MeV protons. The detector characteristics were evaluated after exposure to a number of fluences in the range from 2 x 10(8) to 60 x 10(8) p(+)/cm(2). Even for the highest fluences, which had a dramatic effect on the spectroscopic performance, we were able to recover the detectors 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 CZT detector was used to derive the charge trapping parameter, mutau(e), (the product of charge mobility and trapping time) as a function of fluence. The analysis showed that the electron trapping increased proportionately with the proton dose. The radiation contribution to the electron trapping was found to obey the following relation: (mutau(e)(-1))(rad) = (2.5+/-0.2) x 10(-7) x Phi (V/cm)(2) with the proton fluence, Phi in p(+)/cm(2). The trapping depth dependence, however, did not agree well with the damage profile calculated using the standard Monte Carlo simulations, TRIM , for the proton-induced radiation effects. The present results suggest that proton-induced nuclear reactions contribute significantly to the radiation damage. Further work will elaborate on these effects.
Nuclear Instruments and Methods in Physics Research, 2003, Vol 512, Issue 1-2, p. 98-105
electron trapping; proton irradiation; radiation damage; CdZnTe drift strip detectors