Thermoluminescence of some Pr^{3 +} doped fluoride crystals

Irradiation effects and dosimetric properties have been studied for CaF₂, KYF₄ and CsY₂ F₇ crystals doped with Pr^{3 +}. In particular, thermoluminescence (TL) excitation spectra have been measured in the 120-200 nm region and the CaF₂ : Pr^{3 +} and KYF₄ : Pr^{3 +} crystals show excitation maxima at 135 and 140 nm, respectively. Some of the main TL peaks appear after vacuum ultraviolet (VUV) irradiation at the same temperatures as after β irradiation, indicating that they are due to the same radiation-induced trapping levels. Optically stimulated luminescence (OSL) and phototransferred TL (PTTL) have also been recorded in pre-irradiated samples and stimulation spectra have been measured. The OSL emission spectra show some of the same bands as in the case of the XL and TL, indicating that they are due to the same luminescence centers. The TL sensitivity of CaF₂ : Pr^{3 +} is ∼5 times higher than that of TLD-100, and the TL sensitivity of KYF₄ : Pr^{3 +} is slightly higher than that of TLD-100, whereas the sensitivity of CsY₂ F₇ : Pr^{3 +} is much lower. The main TL peaks of KYF₄ : Pr^{3 +} and CaF₂ : Pr^{3 +} appear above 480 K and, accordingly, only low TL fading is expected during storage at RT. The dose dependence of the main TL peaks is nearly linear in a dose range up to about 2000 Gy.