Temperature distribution in thermoluminescence experiments. I. Experimental results

Abstract

In a typical thermoluminescence experiment, a sample rests on a metallic strip which is heated in a controlled fashion so that the strip temperature rises linearly with time. Thermal contact is improved by the use of an inert exchange gas, usually argon. With this procedure, samples of interest emit light spectra of low intensity as electrons escape from traps. The technique is applied, for example, to dating of artefacts or geological materials, to radioactive dosimetry, and to the characterization of optical materials. In this paper the authors present data which show that it is unsafe to make the common assumption that, during ramping, the light-emitting parts of the sample have the same temperature as the heating strip. They have performed experiments designed to demonstrate sizeable temperature differences. This is important where data from different laboratories are compared and they conclude that practitioners should routinely take note of the following points. Firstly, ramping rates should be as low as possible consistent with the optical sensitivity available (there is a trade-off between the two, but temperature differences are likely to be important where ramping rates exceed 5 K s-1). Secondly, it is advisable to use helium as exchange gas rather than the more usual argon, because it is a much better conductor of heat. Thirdly, users should do a few basic thermal experiments with their apparatus so that, with the aid of formulae given in the paper which follows this one, they can make corrections where these are important. This is the first of a linked pair of papers on this subject; it is primarily about experimental results, while the second paper offers some theory which can be applied.

Ion size effects on thermoluminescence of terbium and europium doped magnesium orthosilicate

“…This is frequently overlooked but the problem has been discussed in a number of publications. 16,[29][30][31][32] The fast heating rate data are unsuitable for kinetic analysis. A second problem is that emission bands normally broaden with increasing temperature and may vary in terms of their luminescence efficiency.…”

Influence of Li dopants on thermoluminescence spectra of CaSO4 doped with Dy or Tm

“…Of greater importance is that the low heating rates ensure that there are only small temperature gradients from the thermocouple, at the heater, to the surface of the samples. Tighter thermal coupling avoids the problem encountered in the commercial systems where the apparent signal temperature (measured at the heater stage) differs from the actual temperature of the emitting surface of the TL sample [15][16][17][18][19]. The glow peak data could be replicated within about one degree.…”

Common mistakes in luminescence analysis

“…Nevertheless many journal articles continue to appear with modelling based on the heater temperature, despite a number of publications which have given detailed indications of the errors involved, or empirical suggestions as to how to minimise them [2][3][4][5]. …”