부산대학교 도서관

In this paper we investigate the spectrometric deterioration of semi-insulating GaAs detectors degraded by high doses of 5 MeV electrons, beyond the previously set limit of their operation ability of 1 MGy. The spectrometric characterization is made by measuring the 59.5 keV $\gamma$-rays from 241 Am, evaluating their charge collection efficiency (CCE). The accumulative dose has deteriorated the CCE of detectors, at 200 V reverse biasing, from initial 74% down to 15% at 2 MGy, independently of the dose rate in the range from 20 to 80 MGy/h. The 75% of tested detectors were able to operate with 24% CCE after 1 kGy degradation. On the other hand, only 33% of them sustain operable after next dose step of 1.25 MGy. The highest applied degradation-dose withstand operable only one detector of all twelve samples, demanding the noise subtraction to achieve the observable signal from registered photons.