Created attachment 861 [details] this is my code Recently I have been using geant4 to calculate the movement of low-energy electrons and positrons (eV -level) in materials. I found that electrons and positrons has interact when their energies are above 100eV, but when the energies are below 100eV, they do not interact, but directly become zero (that is, their energies do not have tens of eV states). I used SetUserLimits to set the minimum energy to 0.1eV and selected the electromagnetic process to G4EmStandardPhysics_option4. I don't know if I chose the wrong physical process, or if the set energy truncation is not effective, or if geant4 can't calculate the interaction process of electrons and positrons with energies less than 100eV.
*** Problem 2604 has been marked as a duplicate of this problem. ***
Hello, it is not a problem of any Geant4 model but a problem of understanding of Geant4 tracking logic. Likely documentation for this subject should be reviewed and extended. G4UserLimits is a mechanism of tracking cut of particle applied for a logical volume, which is not connected with any physics model. We have alternative independent tracking cut common to all ionisation processes for all particles, which does not connected with geometry. These two mecanisms are working independently. A user may add or not add G4UserLimit to the concrete geometry (but default NOT). Ionisation tracking cut is working in all cases for all charged particles. Its values are defined in EM physics constructors and are printed in EM log file at initialisation of Geant4. To change its value one should use UI command: /process/em/lowestElectronEnergy 50 eV /process/em/lowestMuHadEnergy 300 keV potentially lowest energy may be zero but this may be not a good variant: tracking of particles may require too many steps and huge CPU. VI
Thank you. I've got it.
I have one more question. I modified G4UserLimits . If it doesn't cut the energy, what does it do?
