Optical and dosimetric properties of variously doped SrF2 crystals

Abstract

Optical properties and irradiation effects of Nd3+-, Pr3+-, Tb3+- and Tm3+-doped SrF2 crystals and their possible application to solid-state dosimetry were studied and compared to those induced in pure SrF2 crystals. Optical absorption, thermoluminescence (TL), X- and light-induced luminescence (XL and PL) as well as optically stimulated luminescence and phototransferred TL (OSL and PTTL) were measured in the various samples. Special attention was given to effects of monochromatic vacuum ultraviolet (VUV) radiation. TL was excited in the pure and doped samples by X and β rays as well as by VUV radiation. TL peaks appeared after VUV irradiation at the same temperatures and with the same thermal activation energies as after X or β irradiation, indicating that they are due to the same processes. The VUV excitation spectra showed two maxima at about 145 and 130nm. Comparison of the TL sensitivities of the various TL materials, showed that the sensitivity of SrF2:Pr3+ was by more than an order of magnitude higher than that of the known LiF:Mg,Ti (TLD-100) phosphor. The sensitivity of pure and of the Nd, and Tb-doped SrF2 were by a factor of 2–4 higher than that of the TLD-100 and that of SrF2:Tm was slightly lower. The main emission bands of SrF2:Pr3+ are located in a convenient spectral region between 460 and 640nm, where most of the standard photomultipliers are sensitive. The dose dependence of the 460K TL peak in SrF2:Pr3+ is nearly linear in a wide range up to above 27000Gy.