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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
sensible.

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->SetBarkasOn();
      ahadronLowEIon->SetNuclearStoppingOn();
      ahadronLowEIon->SetNuclearStoppingPowerModel("ICRU_R49");
      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. 

Bob

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