I wonder what is the range of momentum (minimum momentum) because I tried 1eV muon but it didn’t work, then I tried 1 keV electron it still didn’t work.
And if the momentum should larger than a certain value, say 100 keV, then how does garfield++ simulate the secondary ionization? Most of the first ionized electrons should definitely less than 1 keV level.
So I believe that garfield++ is using different method to simulate first ionization (Heed+ calculate cross section?) and secondary ionization (Track::SetW() with some model?)?
Indeed, Heed uses a different algorithm for simulation delta electrons than for simulating the ionisation by the primary charged particle. You can use TransportDeltaElectron if you want to simulate delta electrons.
The PAI model (which is used in Heed for calculating the differential energy loss cross-section of the primary charged particle) is applicable if the particle velocity is large compared to the velocity of the atomic electrons.