The Behaviour of HgI2 Nuclear Detectors Irradiated with High X-Ray Fluences

Nuclear detectors of HgI2 exposed to high fluences of up to 40 keV x-rays of counting rates up to 1012 photons sec-1 cm-2 which correspond to about 400 R/min show linear dependence of the dc current of the detector with the x-ray dose. Polarization can cause the deterioration of the dc current within the detector with a decay time which varies from several seconds to several hours at the highest fluence after which the dc current reaches a steady value. Better crystals, however, show practically no time deterioration of the dc current. The dc response of HgI2 nuclear detectors to high fluences of x-ray pulses of several milliseconds duration was also measured. Both the rise times and decay times varied between 0.4 to 0.8 millisecond for uncollimated and 0.06 to 0.3 millisecond for collimated x-rays.