Radiation damage effects by 25MeV protons and thermal annealing effects on thallium bromide nuclear radiation detectors

In this study, TlBr detectors were irradiated with 25MeV protons accelerated by an AVF cyclotron. Isothermal annealing was performed to restore the performance of the detectors. In order to characterize the radiation damage and thermal annealing effects on the TlBr detectors, we measured current-voltage (I-V) characteristics, mobility-lifetime (mu tau) products and spectrometric responses. The I-V and mu tau measurements suggest that electron traps have been induced by 25MeV protons in the TlBr crystals. X- and gamma-ray energy spectra were measured for two different electronic conditions: the electric signals induced mainly by electron carriers traversing the crystal were used for one case and the signal induced by hole carriers were used in the other case. After irradiation of 25MeV protons, the Am-241 X- and gamma-ray spectra obtained in the former showed significantly degraded energy resolution. No degradation of energy resolution, however, was observed in the latter case. Noticeable improvements of the degraded detector performance have been observed after the thermal annealing.