Effects of type of radiation on glow curve and thermoluminescence emission spectrum of CaF 2:Tm

Abstract

Thermoluminescence emission spectra of CaF 2:Tm (TLD-300) samples irradiated with 48 keV X-rays 60Co gamma rays, 4.5 MeV alpha particles and 15 MeV neutrons were measured in the 300–650 K temperature region. Seven emission bands were observed of which the one in the infrared (at 803 nm) is very intense. The emission bands can be assigned to 1D, 1G, 3F and 3H levels characteristic for Tm 3+ de-excitation in a cubic field. All observed lines in the spectrum are due to 4f-4f transitions. The spectra undergo remarkable changes in intensity when the temperature is raised from room temperature up to 350°C, while the number of the emission bands remains constant. The glow curve structure is both dependent on emission wavelength and the type of radiation. Evidence has been found that the trapping structures responsible for glow peaks 2 and 3 alter under the influence of high LET (α) radiation. For glow peaks 4–6 the filling of the traps alters with the type of radiation. The observations can be explained assuming a TL process involving several hole trapping centres but with only one luminescent centre (Tm 3+) active at all temperatures.