Measurement of x-ray photogeneration in amorphous selenium

The use of low-mobility photoconductors in x-ray imaging, especially amorphous selenium (a-Se), is currently of great interest. Detailed measurements of the photoconversion gain factor W± and gain fluctuations σ have been obtained to facilitate applications using a-Se and to provide a better understanding of the charge formation process. The measurements were made with an x-ray spectrometer constructed using a-Se as the x-ray absorber. Pulse height spectra of known monoenergetic x-ray sources were measured to determine the response of the a-Se. Both the gain and fluctuations calculated from the data were found to depend on the x-ray energy ε, and the applied field E, indicating the recombination of a larger amount of charge that was created initially.