The user can define artificial limits affecting to the Geant4 tracking.
G4UserLimits(G4double uStepMax = DBL_MAX, G4double uTrakMax = DBL_MAX, G4double uTimeMax = DBL_MAX, G4double uEkinMin = 0., G4double uRangMin = 0. );
Maximum step length
Maximum total track length
Maximum global time for a track
Minimum remaining kinetic energy for a track
Minimum remaining range for a track
uStepMax is affecting to each step, while all other limits
are affecting to a track.
The user can assign
G4UserLimits to logical volume and/or to a
region. User limits assigned to logical volume do not propagate to
daughter volumes, while User limits assigned to region propagate to
daughter volumes unless daughters belong to another region. If both
logical volume and associated region have user limits, those of logical
A G4UserLimits object must be instantiated for the duration of whatever logical volume or region to which it is assigned. It is the responsibility of the user’s code to delete the object after the assigned volume(s)/region(s) have been deleted.
Processes co-working with G4UserLimits¶
In addition to instantiating
G4UserLimits and setting it to logical
volume or region, the user has to assign the following process(es) to
particle types he/she wants to affect. If none of these processes is
assigned, that kind of particle is not affected by
- Limitation to step (
G4StepLimiterprocess must be defined to affected particle types. This process limits a step, but it does not kill a track.
- Limitations to track (
uTrakMax, uTimeMax, uEkinMin, uRangMin)
G4UserSpecialCutsprocess must be defined to affected particle types. This process limits a step and kills the track when the track comes to one of these limits. Step limitation occurs only for the final step.
G4UserLimits can be found in examples/basic/B2 : see
G4StepLimiter process is added in the Geant4 physics list via the
G4StepLimiterPhysics class in the
main() function in