Dependence of α-particle backscattering on energy and source backing

Measurement of α-particle sources using 2π counting detectors requires corrections for backscattering, and these depend on the material used as source backing and on the α-particle energy. This dependence has been analyzed theoretically by some authors, although assuming some simplifying approximations. In this work, we analyze the dependence of the backscattering coefficient B on energy and source backing, but by means of the Monte Carlo simulation code SRIM, thus avoiding the simplifying approximations assumed in the theoretical models. To study the dependence on the backing, we simulated 210Po point sources deposited on various backing materials with atomic numbers ranging from 4 to 79. The dependence on energy was studied by simulating α-particle point sources deposited on a platinum backing, with energies between 3 and 8 MeV. We found that the dependence of the backscattering coefficient B on α-particle energy and also on the mass number A of the backing approximately follows power function laws, in concordance with the theoretical models, although with exponents somewhat different from those established theoretically. In addition, although it was found that the scattering angle distribution is not Gaussian, our results confirm that there is a linear relationship between the backscattering coefficient B and the mean scattering angle Φ, as suggested by the Crawford theory.