Movement of charge carriers in electric and magnetic fields

Abstract

For the detection of charged particles many detector principles exploit the ionisation in sensing layers and the collection of the generated charges by electrical fields on electrodes, from where the signals can be deduced. In gases and liquids the charge carriers are electrons and ions, in semiconductors they are electrons and holes. To describe the ordered and unordered movement of the charge carriers in electric and magnetic fields the Boltzmann transport equation is introduced and approximate solutions are derived. On the basis of the transport equation drift and diffusion are discussed, first in general and then for applications to gases and semiconductors. It turns out that, at least for the simple approximations, the treatment for both media is very similar, for example also for the description of the movement in magnetic fields (Lorentz angle and Hall effect) or of the critical energy (Nernst-Townsend-Einstein relation).