The x-ray capture, conversion into charge carriers, ion transport mechanisms and image formation mechanisms within a high-gas pressure digital radiographic system, operating up to 60 atm., are presented and analyzed. In detail, the physics of the high-pressure KCD imaging detectors is exposed, analyzed and related to the detector and image quality parameters. Specifically, this study indicates that ion diffusion cannot account for all the experimental observations. It advances the hypothesis that, at sufficiently high pressures, formation of molecular clusters with narrowed mobility distribution take place, through energy exchange mechanism, with local potential forces such that they compensate the space charge distortion of the applied field strength.
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