primary electron

The bombarding electrons are called primary, and the emitted electrons are designated secondary. The amount of secondary emission depends on the properties of the material and the energy and angle of incidence of the primary electrons. Material properties are characterized by the secondary-emission ratio, defined as the number of secondary…

…is called, by convention, the primary. Thus, maximum energy loss (ignoring atomic binding) is half the incident energy. Incorporating this effect, the stopping number of an electron is given by a complicated expression that involves a different arrangement of the parameters found in the stopping number of heavy charged particles;…