Chapter six – Inelastic Collisions of Energetic Protons in Biological Media

Abstract

We study the energy deposited by swift proton beams on materials of biological interest, such as liquid water, DNA, and PMMA. An appropriate description of the target energy-loss function, which provides its electronic excitation spectrum, is obtained from available experimental optical data properly extended to non-vanishing momentum transfers. The main magnitudes characterizing the energy-loss distribution of the beam particles in the target are calculated analytically (in the dielectric framework) and compared with available experimental data. The depth–dose distribution of the energy delivered by the proton beam on the biological targets is simulated by the SEICS (Simulation of Energetic Ions and Clusters through Solids) code, which includes the main interaction phenomena between the projectile and the target constituents by means of Molecular Dynamics and Monte Carlo techniques. Also, the proton-beam energy distribution at several depths in the target for liquid water and PMMA are simulated, and finally, the properties of PMMA as a water-equivalent material are discussed.