Testing emergency radiation doses by metastable TL peaks in quartz: Preliminary investigations

In the case of nuclear or radiological emergencies, rapid examination of individuals from affected areas is necessary. The limited capacity of existing laboratories and dosimetric methods requires narrowing down, using short−term emergency dosimetry, the areas in which people should be examined first. Quartz, the abundant mineral widely used in dating and luminescence retrospective dosimetry, is an obvious candidate for a dosimeter in such cases. Until now, most dose reconstruction studies using quartz from buildings, structures and ceramics have used high−temperature thermoluminescence (TL) or optically stimulated luminescence (OSL) from relatively stable trapping systems. The separation of residual signals from long−term exposure to natural radioactivity and time−consuming measurement sequences is an issue with the high−temperature methods. While less explored for dose reconstruction, the TL emission below 200 °C from metastable traps holds the potential for emergency dosimetry due to reduced interference with background radiation effects. The presence of this TL signal in quartz shortly after radiological events would clearly indicate recent high dose−rate exposure. In this research, the dose−response of the nominal 150 °C and 210 °C TL signals and short−lived OSL signals from two reference quartz samples have been tested. It was found that, in the case of bright grains, both TL peaks can be used for dosimetry in the 0.05−3.0 Gy range. Contrary to earlier studies showing that the electron lifetime in traps responsible for the peak at 150 °C is sufficient for short−term emergency dosimetry, we demonstrate that the 150 °C peak consists of two components of different lifetimes. As well as having different lifetimes, one component quickly decreases under light exposure, while the other, originating from deeper traps, is light−resistant. Both components can be used for dose estimation. Nevertheless, the second component, which demonstrates better thermal stability, is more suitable for emergency dosimetry.