Particle transport

Particle transport in Geant4 [SA03] is the result of the combined actions of the Geant4 kernel’s Stepping Manager class and the actions of processes which it invokes–physics processes and the Transportation ‘process’ which identifies the next volume boundary and also the geometrical volume that lies behind it, when the track has reached it.

The expected length at which an interaction is expected to occur is determined by polling all processes applicable at each step.

Then it is determined whether the particle will remain within the current volume long enough, otherwise it will cross into a different volume before this potential interaction occurs.

The most important processes for determining the trajectory of a charged particle, including boundary crossing and the effects of external fields are the multiple scattering process and the Transportation process, which is discussed in the second following section.