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Forum: Particles
Re: Question gun/ion syntax and equilibrium charge (Robert Weller)
Re: None Re: gun/ion syntax and equilibrium charge (Vladimir Ivanchenko)
Re: More Re: gun/ion syntax and equilibrium charge (Robert Weller)
Date: 01 Jul, 2003
From: Vladimir Ivanchenko <Vladimir Ivanchenko>

On Fri, 27 Jun 2003, Bob Weller wrote:

> *** Discussion title: Particles
> Email replies to PublicHyperNews@slac.stanford.edu must include:
>   In-Reply-To: <"/particles/28/1/1"@geant4-hn.slac.stanford.edu>
>   Subject: ...change this to be about your reply.
> 
> 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
> 

Hello Bob,

There were a difficult point for ion simulation until the newest release 
5.2 - multiple scattering for GenericIons were not well simulated. I would 
even recommend to comment it out - results will be stable and close to 
expectations - msc is small for heavy ions. 

If a precise simulation required the specific ion can be described as a
static one - see example/extended/electromagnetic/TestEm7 - there is an
example of IonC12. You can describe IonFe56 with the initial charge you
need.

VI

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