Mathematical modelling of TL supralinearity for heavy charged particles

Microdosimetric phenomena, not addressed by conventional kinetic calculations in the framework of 'conduction band/valence band' atomic models, play an important role in the thermoluminescence (TL) dose response. In this paper we discuss how the track interaction model (TIM), incorporating first, second and third nearest neighbour interactions, describes the alpha particle induced linear/supralinear behaviour of peaks 5,7,8 and 8 in LiF:Mg,Ti. The increasing supralinearity with glow peak temperature is shown to arise from increasing charge carrier migration distances in the luminescent recombination stage, 150 Å, 300 Å, 3000 Å and 5000 Å for peaks 5,7,8 and 9 respectively. The track interaction model should be viewed as the model providing the microdosimetric framework which, when coupled with other appropriate physical mechanisms (spatial localisation of traps and recombination centres, competing centres in the recombination stage, variation in the capture cross section with temperature, etc) can be used to describe all the dominant features of the linear/supralinear behaviour of LiF:Mg,Ti.