PENELOPE 2003 - OECD Nuclear Energy Agency

Chapter 3
Electron and positron interactions
In this chapter we consider the interactions of fast electrons and positrons of kinetic
energy E with matter. For the sake of simplicity, we start by assuming that the particles
move in a single-element medium of atomic number Z and density ρ, with N atoms per
unit volume. The extension to compounds, and mixtures, is normally done on the
basis of the additivity approximation, i.e. the molecular DCS is approximated as the
incoherent sum of the atomic DCSs of all the atoms in a molecule.
E
θ
E
E
E−W
θ
θ s
E s
= W−U i
Elastic scattering
I nelastic scattering
W
E +
E
θ
E−W
E
E −
θ −
θ +
Bremsstrahlung emission
P o sitro n annih ilatio n
Figure 3.1: Basic interactions of electrons and positrons with matter.