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Keywords: low energy ions, full cascade, LXe, nuclear recoils, Coulomb elastic scattering, screened potencial, Thomas-Fermi
Forum: Hadronic Processes
Re: None low energy Xe-Xe full cascade: what's the best physics list? (Ricardo Pinho)
Re: None Re: low energy Xe-Xe full cascade: what's the best physics list? (Vladimir IVANTCHENKO )
Date: 23 May, 2007
From: Ricardo Pinho <ricardo@lipc.fis.uc.pt>

Hi. First of all I want to thank you for your reply.

> If your interest is concentrated to energy of Xe ion below 150 keV, than
> there is no Xe nuclear cascade at all because of Coulomb barier. The only
> processes are scattering and ionisation.

I'm not quite sure of what cascades are you talking about: the ones of nuclear reactions with fragments and all? 
Yes, that seems to be the only cascades already implemented on Geant4. But No, I was talking about successive 
nuclear recoils (by Coulomb elastic scattering).

> In both standrad and low-energy implementation ion scattering is taken
> into account in average as a nucleat=r stopping power. This may provide
> simulation of ranges but not recoil.

If that is so, can't I just use the energy lost at each step by nuclear stopping as the energy of the recoil atom, 
i.e., the kinetic energy of the secondary particle I would then create at each step? I'm interested on average 
values, or better stated, the continuous slowing down approximation, but I could even turn NuclearStoppingFluctuations 
On. By the way, in G4hNuclearStoppingModel.cc, you have the following:

00106   // Default is nuclear stopping fluctuations On
00107   //  nStopingPowerTable->SetNuclearStoppingFluctuationsOn();
00108   nStopingPowerTable->SetNuclearStoppingFluctuationsOff();

A issue I talked about earlier was the incomplete and sometimes confusing nature of the Physics manual. In chapter 
12.10.9 Nuclear stopping powers (of 12.10 Hadron and Ion Ionisation) you state that you use the Molière approximation 
to the screened Coulomb interaction potencial, in the framework of Thomas-Fermi of witch you present some reduced 
variables, but without presenting the formulae of the cross section/stopping power itself! You forward us to Molière's work:

G. Molière. Theory of Scattering of Fast Charged Particles. I.
Single Scattering in a Screened Coulomb Field. Z. Naturforschung, A2:133, 1947.

witch I found it very hard to find, at least here in Portugal.
By the way, is there any example of the creation of secondary particles in the user's code? Is the best way for 
doing this the creation of a Physical process? I would probably need inheritance of G4hLowEnergyIonisation.cc.
I've also asked before for more control of Nuclear Stopping through G4hLowEnergyIonisation.cc, with the example 
of something similar to SetNuclearStoppingOff but for the Electronic Stopping and direct control of NuclearStoppingFluctuations
for example...

> Unfortunatelly, we have no adequate scattering process so far.
> There is a new process G4CoulombScattering, which simulates single
> scattering of charged particle with recoil. It was tested only for
> relatively high energy and only for electrons, muons, and protons. never
> for ions. Just now I cannot tell you is it applicable for low energy ions
> or not (currently I am very busy with other things).

If that is so, can you please forward this and my other requests/questions entried at the forums and condensed 
on the .txt file attached to my original mail to the rest of the Geant4 Low Energy Electromagnetic Physics group ?
Or at least give me their direct contact please.

Thank you, ricardo pinho at lip.

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