Luminescent properties of LiF crystals for fluorescent imaging of nuclear particles tracks

Abstract Fluorescent nuclear track detectors (FNTD) based on LiF crystals were used for imaging ionizing particle tracks (including high-energy iron ions), by exploiting photoluminescence of radiation induced F2 and F3+ color centers. The relation between photoluminescence emission spectrum of LiF and quality of FNTD images was investigated. It was found that in the applied experimental conditions, the emission within the green band (530 nm, F3+) is very weak compared to the red band (670 nm, F2). The optimum signal to noise ratio was achieved with setting the measuring window at wavelengths longer than 570 nm. Good quality track images in the green spectral range were obtained only for the highest ionization density: for stopping iron ions. Investigations of the bleaching phenomenon revealed a strong decrease of the PL intensity after long excitation times, in the range of several minutes. The amount of this decrease depends on the used excitation power. In the conditions which were typically applied during FNTD measurements the intensity loss was negligible.