Radiological X-ray response of polycrystalline mercuric iodide detectors

A first image of some tiny screws were obtained for the first time with polycrystalline HgI2 acting as the photoconductor material deposited on a-Si direct conversion X-ray image sensors, produced by Xerox- Pale Alto Research Center. The initial results are very promising and show a high X-ray sensitivity and low leakage current. The response of these detectors to a radiological X-ray generator of 65 kVp has been studied using the current integration mode. Already its sensitivity expressed in mu C/R*cm(2), is very high, values of 20 mu C/R*cm(2) have been measured for films of 100-250 microns thickness and bias of 50-200 volts respectively, which is superior to the published data for competing materials such as polycrystalline PbI2 and a-Se detectors. The fabrication and characterization measurements of the Polycrystalline HgI2 thick film detectors will be given. The characterization data which will be reported here consists of: a) sensitivity, b) dark currents, c) stability of sensitivity dependence on the number of exposure, d) X-ray response dependence on dose energy and e) signal decay dependence on the number of exposures.