RADIATION EFFECTS IN KMgF 3 CRYSTALS

Effects of x, beta and UV irradiation on Tb3+ and Eu2+ doped KMgF3 crystals were studied. Thermoluminescence (TL) excited by VUV radiation was compared to that induced by x and beta rays. TL excitation spectra showed maxima at 125, 140, 155 and 180 nm. The main TL peaks appeared after VUV irradiation at about the same temperatures and with the same thermal activation energies as after x or beta irradiation, indicating that these peaks are due to the same trapping levels. In samples, which had previously been exposed to ionizing radiation, TL could also be excited with longer wavelengths that could not excite any TL in un-irradiated crystals; this is attributed to a process of phototransfer (PTTL). The x and UV excited luminescence was measured at LNT and RT and showed essentially the same main emission bands that appeared in the TL and PTTL peaks of these crystals. The dose dependence of the 730 K TL peak in of KMgF3 :Eu2+ was linear up to about 2000 Gy. The TL sensitivity of KMgF3 :Eu2+ was by an order of magnitude higher than that of KMgF3 :Tb3+ , which was by a factor of two greater than that of the known TLD-l00 phosphor.