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Keywords: low-energy particles ions
Forum: Particles
Re: Question gun/ion syntax and equilibrium charge (Robert Weller)
Re: None Re: gun/ion syntax and equilibrium charge (Vladimir Ivanchenko)
Date: 27 Jun, 2003
From: Robert Weller <Robert Weller>

I'm using the low energy electromagnetic processes including G4hLowEnergyIonisation
exclusive. For 1 MeV alphas and 5 MeV carbon I don't see much to worry about. For
alphas, using either "alpha" or "gun/ion 2 4 2" gives a more or less equivalent result, and
an average range value that I believe. Similarly, for 5 MeV carbon ions the result seems

I'm not as comfortable with the iron example, however. I see noticable, unexpected,
although admittedly not tremendous, differences between "gun/ion 26 56 1" and 
"gun/ion 26 56 26" for 10 MeV iron nuclei.

Perhaps more troubling, I also saw what were clearly two _backscatters_ of iron
projectiles in a silicon slab. I was using a box 5 microns deep for these tests. In addition,
the command line "gun/ion 26 56 56" was accepted and ran, producing a noticably
shorter track than the other variations. What should one interpret "gun/ion 26 56 56"
to be? I can't think of an interpretation that makes any sense, if I understand what these
parameters are supposed to be.

Regarding cutoffs, I think I should be ok. I'm pushing things pretty hard for these tests,
with 5 angstrom cuts, and all even-potentially-sensible processes turned on. Here
is the ion code from my physics list. It is quite nice, actually, to see the ionization and
occasional photon emission enduced by the ions.
    else if(particleName == "GenericIon") {
      G4MultipleScattering * aMultipleScattering = new G4MultipleScattering();
      G4hLowEnergyIonisation * ahadronLowEIon = new G4hLowEnergyIonisation();
      ahadronLowEIon->SetElectronicStoppingPowerModel(particle, "ICRU_R49p");
      ahadronLowEIon->SetFluorescence(true); // fluorescence switch
      ahadronLowEIon->SetCutForSecondaryPhotons(lowESecPhotonCut); // fluor. threshold
      ahadronLowEIon->ActivateAugerElectronProduction(true); // Auger switch
      ahadronLowEIon->SetCutForAugerElectrons(cutForAugerElectrons); // Auger threshold
      pmanager->AddProcess(aMultipleScattering, -1, 1, 1);
	  pmanager->AddProcess(ahadronLowEIon, -1, 2, 2); 

As a new user, I'm strongly inclined to blame myself for these oddities. Nevertheless,
I have quite a bit of experience in low energy ion beam applications, and what I'm seeing
here with this iron nucleus is worrysome. 


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1 None: Re: gun/ion syntax and equilibrium charge   (Vladimir IVANTCHENKO - 01 Jul, 2003)
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