Interactions of Particulate Radiation with Matter

Abstract

Particle radiation includes electrons, protons, neutrons, heavy nuclei (including alpha particles), and mesons but does NOT include photons for the purpose of describing particle radiotherapy. Particles can be described as charged or uncharged and heavy or light. Charged particles are usually directly ionizing by acting through coulombic forces while uncharged particles are indirectly ionizing, often causing ionization as a secondary consequence of other reactions. Unlike photons, particles have specific distances to travel (ranges and path lengths). The release of excessive energy produces a Bragg Peak when a heavy charged particle comes to the end of its path length. There are specific interactions for particles that define the radiation dose and distribution.