Ionization Cluster Size Distributions Created by Low Energy Electrons and Alpha Particles in Nanometric Track Segment in Gases

Abstract

The interaction of ionizing radiation with nanometric targets is a field of interest for many branches of science such as: radiology, oncology, radiation protection and nanoelectronics. A new experimental technique known as nanodosimetry has been developed for the qualitative as well as quantitative description of these types of interactions. The work presented here is a contribution to this development, namely by further improvement of the new experimental technique called the Jet Counter, originally developed at the Andrzej So{\l}tan Institute for Nuclear Studies. The Jet Counter is a unique device in the world for studying the interaction of low energy electrons with nanometer targets in the range 2-10 nm (in unit density). The basic experimental result is the frequency distribution of ionization cluster size produced by ionizing particles in a gaseous (nitrogen or propane) nanometric track segment. The first experimental data on the frequency distribution of ionization cluster size produced by low energy "single" electrons (100 eV - 2000 eV) in target cylinders of nitrogen (N2) 0.34 {\mu}g/cm2. in diameter are presented. New experimental data on the frequency distribution of ionization cluster size produced by 3.8 MeV {\alpha}-particles in a target cylinder of nitrogen (N2) and propane gas (C3H8), ranging from 0.1 to 0.5 {\mu}g/cm2 in diameter are presented. Experimental results are compared with Monte Carlo simulations. A Bayesian analysis is applied for convoluting the measured spectra to the true cluster size distributions. New quantities characterizing the interaction of ionizing radiation with the nanometre level are proposed, namely - P1, M1 and F2. It has been shown that these quantities may substitute for the traditional (macro) dosimetric quantities.