THE TRACK INTERACTION-MODEL FOR ALPHA-PARTICLE INDUCED THERMOLUMINESCENCE SUPRALINEARITY - DEPENDENCE OF THE SUPRALINEARITY ON THE VECTOR PROPERTIES OF THE ALPHA-PARTICLE RADIATION-FIELD

Thermoluminescence (TL)-fluence response characteristics for peaks 5, 7, 8 and 9 in LiF:MS,Ti (TLD-100; Harshaw/Bicron) were measured for 5 MeV alpha particles, in both 'non-parallel' and 'near-parallel' geomet ries,and for 1 MeV alpha particles in 'near-parallel' geometry. The on set of supralinearity in the non-parallel configuration is always at a significantly lower fluence (by approximately a factor of five) than in the nearly parallel configuration. This dependence of the onset of supralinearity on the vector properties of the alpha particle radiatio n field is interpreted as 'proof positive' of the dominant importance of track interaction effects in the linear/supralinear behaviour of th e glow peaks of TLD-100. A mathematical expression for the linear/supr alinear behaviour for heavy charged particles in near-parallel geometr y has been developed and fitted to the TL-fluence response curves. The model incorporates both possibilities of electron and hole diffusion in the glow curve heating stage as well as the contribution to the sup ralinearity of all the participating nearest-neighbour track interacti ons. The model is capable of yielding excellent fits to the experiment al data; the inclusion of hole diffusion and retrapping is preferred t o predict the very abrupt transition from linear to supralinear behavi our for the high-temperature peaks.