Fast Carbon-Ion and Proton Induced Electron Emission from Condensed-Phase Biological Targets

Abstract

Fast charged particles interact with matter through various ionization and excitation pathways that aren't fully understood. Predicting the effects of these interactions is vital in many fields such as radiation therapy, space exploration, and materials processing. Monte Carlo models of the spatial distribution of dose deposited in tissue require cross section data of the incident charged particles and the secondary electrons they produce in biological media. Because the interaction cross sections cannot be directly measured in condensed-phase materials, precise measurements of electron emission from solids can test and improve track-structure simulations of charged-particle transport in solids. In this thesis, doubly differential electron emission yields [gamma]([epsilon], [theta]), as a function of electron energy [epsilon] and emission angle [theta], were measured for proton and carbon-ion beams in the energy range of 0.2-4.0 MeV/u with gold and amorphous solid water targets. Energy analysis was conducted using the electron time of flight, thus focusing on low-energy electrons that dominate the emission spectrum. The experimental data are presented for various projectile and target combinations, and are compared to results from the track-structure simulations.