Calculation of the Relative Effectiveness of Alanine Detectors to X Rays and Heavy Charged Particles using Microdosimetric One-Hit Detector Model

Abstract

Systems described by one-hit Poissonian statistics which show a sub-linear response after high doses of rays and a decreased efficiency for densely ionising radiation are called 'one hit detectors'. The microdosimetric one-hit detector model has been applied to predict the ESR signal of alanine after X rays, rays and heavy charged particle (HCP) irradiations. The two fitted parameters of the model are d, the target diameter, scaled by the density of the target p, and α, the saturation coefficient, which describes the probability of the effect occurring after an energy deposition event within the target. For alanine the best fitted model parameters are d = 6 nm, α = 0.2 x 10 -4 Gy -1 . The model-derived target size exceeds the typical molecular dimension of alanine molecules. For alanine the target size may be related to the effective range of the free radical recombination in alanine. The model calculation can be applied in the dosimetry of soft X rays and in proton beam dosimetry.