An experimental study of techniques in thermoluminescence dating
The phenomenon of thermoluminescence (TL) cannot yet be said to be
completely understood, and cases of anomalous results from TL dating
programmes are not infrequent, although explanations are rarely given.
It is therefore useful to put TL dating into a firmer physical
framework in which all relevant phenomena can be adequately described,
whence the best action can be taken to avoid spurious results.
However, TL dating embraces many varied aspects of physics, and a
solution to all the problems is not a simple task. This thesis is
intended to be an experimental study of some of the main physical
techniques in thermoluminescence dating. Following a brief review of
the whole field, selected areas presented here have been investigated
in more detail.
A new TL reader has been implemented with novel design features,
including microprocessor controlled heating cycles, a switch-mode power
supply direct current heating, all based on a modular concept to
facilitate future improvements in the hardware. The use of a
microprocessor as the heating controller should enable further
development (eg. data collection and processing) to be a
straightforward task. Non-linear heating profiles can be generated for
glow curve analysis and for providing pre-heat zones.
The radioisotope content of ceramics and soils is important in TL
dating, and a comparison of commonly used radio assay techniques has
been made with the aim of assigning a minimum detectable activity toeach technique for a given required accuracy. The analytical methods
have been applied to various ceramic samples, and the derived dose
rates within the shards are calculated and presented for comparison.
Some theoretical aspects of TL described in this thesis include a
computer model to simulate common TL phenomena, which is used to
investigate the effects of varying the model parameters. A complete
solution of the equations determining glow curve shapes produced by
hyperbolic heating profiles is presented, with techniques for
extracting the mathematical constants describing the model, from them.
A brief intercomparison of five quartz samples of differing origins
is presented with a trace element analysis of the samples to determine
whether there exists a correlation between trace element concentration
and the magnitude of the TL properties.