Evaluation of the relative radiation sensitivity of alanine to alpha radiation by electron paramagnetic resonance spectroscopy

Using ESR spectroscopy the relative radiation sensitivity of alanine to alpha radiation with respect to the standard gamma-ray 60Co source was assessed. The results of the evaluations have shown that radiation-chemical yield of free radicals in alanine by gamma radiation is 1.5±0.2 times higher than that by alpha radiation source 239Pu with an energy of 5.14 MeV. The study of absorbed dose formation of alpha radiation in a standard alanine dosimeter having the shape of a cylindrical tablet with a diameter of 4.8 mm and a height of 2.9 mm when irradiated at the surface of a flat source was made using Monte Carlo calculations. It was shown that the majority of registered dose of alpha radiation by EPR spectroscopy is caused by paramagnetic centers formed in a thin layer bordering the source with a thickness not exceeding the maximum range of the alpha particles (a few tens of micrometers). However, about 40% of the total dose in the dosimeter tablet of the given size during irradiation was due to the alpha particles emitted by the adjacent to detector areas of the source that hit the lateral surface of the detector. The calculated data were confirmed experimentally by estimating the reduction of the signal after the mechanical removal of the contact layer and the layer from the side surface of the alanine dosimeter.