Thermoluminescence Response of Lithium Fluoride to Energetic Light Ions

Thermoluminescence measurements were made on thin lithium fluoride (LiF) specimens exposed singly or in a stack to various ion and gamma/x-ray sources, and the results were analyzed in an attempt to correlate individual thermoluminescence peaks with basic underlying processes. A low temperature composite peak at 440-460 K, commonly observed in gamma irradiated specimens, has been found for all our exposures, and we attribute it specifically to interactions that result in low ionization densities. A high temperature peak has been found to be prominently stimulated in specimens subjected to ion bombardment. Based in part on our calculations of elastic collision processes, this peak is interpreted as relating at least in part to displacement-damage-type traps produced directly by energetic ions in the LiF lattices. Two additional groups of thermolumin-escence response exist in the intermediate temperature range (490 - 550 K) and appear to be associated with higher ionization densities. Overall, our results to date appear to confirm that the local ionization density (irrespective of how it is produced) is a principal factor in shaping the glow curve. It is also very likely that the enhanced defect concentration resulting from ion-produced atomic displacements provides added deep traps and therefore contributes to the observed (high-temperature) response. We feel that a better understanding of how the high temperature traps are formed and filled is essential for establishing the correlations needed in using thermoluminescence techniques for high energy neutron dosimetry.