Interaction of Ionizing Radiation with Matter

Charged particles (electrons, positrons, protons, helium nuclei, …) will ionize matter in a direct way, in contrast to neutral particles (neutrons, neutrinos, …) or short-wavelength electromagnetic radiation (X rays and γ rays), which will ionize only indirectly. Strictly speaking, radiation is never directly measured, rather it can only be detected via its interaction with matter. A large number of specific interaction processes exists. These interactions are characteristic for each of charged particles, neutrons, neutrinos, X rays, and γ radiation.