Characterization of radiation damage and thermal annealing effects on thallium bromide nuclear radiation detectors

In this study, TlBr detectors were irradiated with 25 MeV 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 (μτ) products and spectrometric responses. The I-V and μτ measurements suggest that electron traps have been induced by 25 MeV protons in the TlBr crystals. X- and γ-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 25 MeV protons, the ²⁴¹Am X- and γ-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.