5 - Radiation and Materials

Abstract

Bombarding particles may have low or high energy. They may be charged, uncharged, or photons; they may be heavy or light in the scale of masses. The targets may be similarly distinguished, but they may also exhibit degrees of binding that range from none, to weak, to strong. In most interactions, the higher the projectile energy in comparison with the energy of binding of the structure, the greater is the effect. Radiation of especial interest includes electrons, heavy charged particles, photons, and neutrons. Each of the particles tends to lose energy by interaction with the electrons and nuclei of matter, and each creates ionization in different degrees. The ranges of beta particles and alpha particles are short, but gamma rays penetrate in accord with an exponential law. Gamma rays can also produce electron–positron pairs. Neutrons of both high and low energy can create radiation damage in molecular materials. This chapter discusses radiation and materials. It also describes neutron reactions, that is, the interaction of neutrons with matter. Neutrons may be scattered by nuclei elastically or inelastically. It may be captured with resulting gamma ray emission, or may cause fission. If their energy is high enough, neutrons may induce (n, p) and (n, α) reactions as well. Neutrons of both high and low energy can create radiation damage in molecular materials.