Optical features of a LiF crystal soft x-ray imaging detector irradiated by free electron laser pulses

Optical features of point defects photoluminescence in LiF crystals, irradiated by soft X-ray pulses of the Free Electron Laser with wavelengths of 17.2 - 61.5 nm, were measured. We found that peak of photoluminescence spectra lies near of 530 nm and are associated with emission of F3+ centers. Our results suggest that redistribution of photoluminescence peak intensity from the red to the green part of the spectra is associated with a shortening of the applied laser pulses down to pico - or femtosecond durations. Dependence of peak intensity of photoluminescence spectra from the soft X-ray irradiation fluence was measured and the absence of quenching phenomena, even at relatively high fluencies was found, which is very important for wide applications of LiF crystal X-ray imaging detectors.