ABSTRACT
This chapter discusses the mechanisms by which ionizing radiation interacts and loses energy as it moves through matter. The study of this subject is extremely important for radiation measurements because the detection of radiation is based on its interactions and the energy deposited in the material of which the detector is made. Charged particles traveling through matter lose energy in the following ways: in Coulomb interactions with electrons and nuclei, by emission of electromagnetic radiation, in nuclear interactions and by emission of Cerenkov radiation. Every free charged particle that accelerates or decelerates loses part of its kinetic energy by emitting electromagnetic radiation. The calculation of energy loss due to emission of bremsstrahlung is more involved than the calculation of energy loss due to ionization and excitation. Electrons and positrons behave in essentially the same way with regard to energy loss, slowing down, and penetration through matter.
