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On Fri, 04 Mar 2011 15:55:25 GMT, Georgia de Nolfo wrote:
> I'm having trouble understanding the output of TestEm15. If I run the > example in its default mode, I force MSC to occur at every step. > However, if I "activate" ionization and Bremms in the electron.mac > example, every step is associated with either an eIoni or Bremm and > there are no MSC processes registered. Presumably, this means that the > pathlength for eIoni and Bremm are much shorter than MSC --when I > increase the density of water, MSC events do occur even with ionization > & bremm turned on.
Yes, this is correct. However /tracking/verbose print only the process responsible of the step lenght. But several processes may be applied at that step; it is the meaning of 'alongStep' action. In perticular MSC is always applied, at each step.
In TestEm15, event is killed at the first step. Therefore Ionis or Brem act only as a step limiter. > > I guess I don't understand the relevance of "forcing" MSC at each step. > I also don't understand the importance of the "ratings" in the processes > (see below). > > pmanager->AddProcess(new G4eIonisation, -1, 1, 1); > pmanager->AddProcess(new G4eBremsstrahlung, -1, 2, 2); > > Doesn't GEANT4 determine the next process by determining the smallest > physical step size? What is the numbering scheme meant to do in > AddProcess?
I attach a tutorial. See slides 6-9 > > I'm actually interested in determining the interactions of electrons in > a thin target, say a gas at 1 atm. Is there a specific model in GEANT4 > that I should invoke for this application? > Normally, no. But it may depend of the thickness of target, and energy of incident particle.