Microdosimetric Track Interaction Model Applied to Alpha Particle Induced Supralinearity and Linearity in LiF:Mg,Ti

Abstract

Abstract A microdosimetric, track interaction model for heavy charged particles has been developed which is capable of quantitatively predicting the experimentally observed supralinearity of the alpha particle TL dose response of peak 8 in LiF:Mg,Ti as well as the linear behaviour of the lower temperature glow peaks. The linear behaviour at low dose is due to lack of track interaction arising from the highly localised nature of the alpha particle dose deposition profile. Track dose overlap in the radiation absorption stage is shown to be incapable of increasing the TL efficiency at virtually all values of the nearest neighbour track axis separation distance. The alpha induced supralinearity of peak 8 can therefore be explained only via greatly increased charge carrier migration lengths in the glow curve heating stage which brings about significant nearest neighbour track interactions above approximately 108 alpha particles per cm2 (approximately 10 Gy in LiF). The linear behaviour of the lower temperature peaks (up to a fluence of approximately 1010 particles per cm2) yields a charge carrier mean free path of approximately 250 Å (cf. 5000 Å for peak 8) which implies that at low glow peak temperatures there is little inter-track migration of charge carriers in the luminescence recombination stage.