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Forum: Fast Simulation, Transportation & Others
Re: Question low-energy tracks incorrectly stopped (Tom Roberts)
Date: 30 Nov, 2015
From: Tom Roberts <Tom Roberts>

I went back and tried this using Geant4 9.5.p01, with the same results (mu+ with KE ~ 1eV has its status set to fStopButAlive at the end of the first step, regardless of which process limited the step). I mistakenly thought I had used such slow muons with previous versions; they actually had KE ~ 100 eV or more and did not do this.

In the Geant4 code I found a test that does set track Status to fStopButAlive for KE < 10*eV, but it is in a hadronic process (G4hImpactIonization). I'm still stumped where this is happening for mu+. Does anybody know?

Note that Geant4 has no hope of simulating the generation of these very slow muons [#], so in the Geant4 simulation I have to inject them as initial "beam" particles. I now have a work-around: inject them inside a volume with material=Vacuum, and set the maxStep in that volume to be larger than its size. When the muon leaves that volume, it will be stopped right at the boundary, rather than penetrating a few nanometers into the other material -- I can live with this. The only limit is that I must not have any Vacuum/Vacuum boundaries.

[#] it is really muonium, and the beam is generated via its chemical potential in superfluid He.

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1 Idea: Re: low-energy tracks incorrectly stopped   (Vladimir Ivanchenko - 04 Jan, 2016)
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