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Forum: DNA/Very Low Energy
Date: 19 Apr, 2016
From: Tom Roberts <Tom Roberts>

I am trying to track very low energy particles in vacuum (G4_Galactic). For instance, an e- with KE=1 eV (p=0.001 MeV/c, beta=0.002).

This used to work, for at least a decade up to and including geant4-09-06-patch-02.

In geant4-10-02 the track is stopped immediately (process=Stopped:Transportation). Indeed there seems to now be a threshold of 1 keV below which tracks are stopped as soon as they are created, even in vacuum.

Where is this documented? How can I change that threshold?

Tracking very low-energy e- is not very useful; my real interest is muonium for which I have written code, including processes MuoniumDecay and MuoniumSurface which adsorbs them onto any surface they hit. MuoniumDecay gives two neutrinos, a 5-53 MeV e+, and a 13.6 eV e- (boost to the lab doesn't change these very much). We have an E field that immediately accelerates the very slow e- into a detector. I want to track very slow Mu atoms in vacuum, let them adsorb onto surfaces, and see where they decay, including their e- when they decay in vacuum.

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