Thermoluminescence of LiF TLD-100: Emission-spectra measurements

Abstract

The thermoluminescence of LiF TLD-100 dosimeter crystals has been studied using recently developed equipment for determining simultaneously the emission intensity and the emission spectrum as a function of sample temperature. Measurements were made on numerous samples exposed to 60Co irradiations at room temperature and at exposures varying from 500 to 3×107 R. Spectra were obtained at 1.38 and 5.5 °C intervals over the temperature range 20–350 °C. Below 105 R the thermoluminescent emission can be described by a single Gaussian-shaped band whose peak energy and full width vary irregularly with temperature and not in accord with the well-known expressions, given in the text, relating the emission-spectra peak energy and full width at half-maximum to the sample temperature. However, the emission is accurately described by three Gaussian-shaped bands whose approximate peak energies and full widths are 3.01, 0.90; 2.90, 0.72; and 2.71, 0.96 eV. The peak energies and full widths of these three bands vary with temperature in the expected manner. In addition to these bands, comparatively low-intensity bands are observed at exposures above 105 R at approximately 4.0, 2.98, 2.50, and 2.3 eV, with the possibility of another band at roughly 1.5 eV. The recorded data for each emission band was subjected to all corrections required to obtain glow curves which are strictly proportional to the number of processes occurring per unit time. In other words, the corrected glow curves are as free as possible of the systematic errors which might render them unsuitable for determining the kinetics. The glow curves extend from room temperature to 350 °C and contain nine prominent glow peaks. Below approximately 80 °C, the emission is confined to the 2.71-eV band. Above approximately 200 °C, the emission is confined to the 3.01-eV band. All three prominent emission bands contribute to the intermediate-temperature glow peaks. With increasing dose, the low-temperature peaks progressively diminish in intensity and the emission shifts to the higher-temperature peaks.