Determination and analysis of ionization/excitation distributions for alpha particles in silicon detectors

Abstract

As known, the detector response function in the detection of alpha particles is characterized by the following distributions: electronic excitation and ionization, electron–hole pair statistics, and electronic noise contribution. The distribution due to the ionization–excitation process is of particular relevance, because it is not Gaussian and contributes essentially to the asymmetry of the alpha lines. For this work, we adapted the well-known code SRIM, to obtain and analyze the ionization/excitation distributions for alpha-particles in silicon, in a wide range of energies from 0.5 to 10 MeV. These curves were later well-fitted to a function corresponding to the convolution of a Gaussian with exponentials truncated in the low-energy zone of the distribution. A detailed study about the dependence of all the fitting parameters on energy was performed. The parametrization carried out in this work can also be an useful tool to generate the corresponding ionization–excitation curves required in the task of reproducing real alpha-particle spectra.