| Popis: |
The x-ray response of polycrystalline HgI2 for direct detection x-ray imagers, is studied using test arrays with 512 X 512 pixels of size 100 micron. We quantify the contributions to the x-ray sensitivity from electron and hole charge collection, x-ray absorption, effective fill factor and image lag, for x-ray energies from 25-100 kVp. The data analysis compares the measured sensitivity to the theoretical limit and identifies the contributions from various loss mechanisms. The sensitivity is explained by the ionization energy of approximately 5 eV, coupled with small corrections arising from incomplete x-ray absorption, incomplete charge collection, and image lag. Hence, imagers with HgI2 approach the theoretical maximum response for semiconductor detectors, with external array sensitivity demonstrated to within 50 percent of the limit. |
