Effect of 254-nm UV illumination on color centers and photoluminescence in LiF crystals and its application to Fluorescent Nuclear Track Detectors

The effect of UV light with a wavelength of about 250 nm on color centers in LiF after alpha and beta irradiation has been studied. It has been demonstrated that using a simple UV sterilizing lamp it is possible to effectively bleach F, F 2 and F 3 + centers. Measurements of the absorption and emission spectra revealed complex patterns of color center concentration changes depending on the radiation dose and type. While concentrations of F and F 2 centers consistently decrease with increasing bleaching time, concentration of F 3 + centers initially increases before declining after extended bleaching times. From a practical standpoint, the most significant finding is that the fluorescent tracks in a LiF crystal are completely erased after a relatively brief period of UV illumination. This paves the way for a simple, purely optical method of resetting LiF fluorescent nuclear track detectors (FNTD), enabling their reuse.