The thermoluminescence peaks of quartz at intermediate temperatures and their use in dating and dose reconstruction

Thermoluminescence properties of the quartz peaks occurring at intermediate temperature range were studied. Two main peaks (named peak I and peak II), placed at approximately 150°C and 200°C using a heating rate of 2°C/s were observed. They proved to have a linear dose response up to approximately 1 Gy; for higher doses non-linear behaviours were observed. Moreover, sensitisation phenomena occurred as consequences of successive cycles of irradiations and heating treatments. Lifetimes of 720±70 days and 580±70 years (at a temperature of 15°C) for peak I and II respectively were derived. Thermal activation energy and frequency factor of these two glow peaks were equal to (1.22±0.02) eV and to (3.39±1.46)·1013 s-1 for peak I, and to (1.36±0.02) eV (2.23±0.75)·1013 s-1 for peak II. The quartz glow peaks at intermediate temperatures were then used in TL dating of three building materials samples (one brick and two tiles) of age in the range 55-75 years. The total dose absorbed by the samples was assessed by using different procedures such as regeneration dose method, additive dose and single aliquot regeneration dose. The various components of annual dose rate were estimated using different and complementary techniques, such as beta dosimetry, alpha counting, gamma spectrometry and flame photometry. The results obtained demonstrate that the quartz glow peaks at intermediate temperatures can be successfully used in TL dating of young samples (i.e. samples having an age of few decades). Moreover, the precision of the method makes the use of these peaks promising in dose reconstruction applications, for the assessment of accidental dose values of some tens of milliGrays.