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## Re: Partially charged ions

Forum: Particles
Re: Partially charged ions (Jean Claude Thiry)
Re: Re: Partially charged ions (Vladimir IVANTCHENKO )
Re: Re: Partially charged ions (Jean Claude Thiry)
Re: Re: Partially charged ions (Vladimir IVANTCHENKO )
Re: Re: Partially charged ions (Jean Claude Thiry)
Date: 29 Jan, 2008
 ```On Tue, 22 Jan 2008, Jean Claude Thiry wrote: > *** Discussion title: Particles > Email replies to PublicHyperNews@slac.stanford.edu must include: > In-Reply-To: <"/particles/327/1/1/1/3"@geant4-hn.slac.stanford.edu> > Subject: ...change this to be about your reply. > > Hi, > > I was rereading this thread and I noticed I might have misunderstood > your answer. You said you force the charge of an ion to be equal to its > mean value depending on its velocity, etc. > > Does this mean that YOU fix that value, or does it mean that GEANT is > fixing it? > > Example: I'm shooting Zirconium ions, at a mean energy of about > 100.*MeV. According to the Nikolaev formulae I obtain a mean charge of > about +20 for that ion. Now the question is whether I have to shoot ions > with a Z of 20 and an A value of 90 (corresponding to Zr) or do I shoot > "real" Zr ions (Z=40, A=90) and Geant will deal with the mean charge > value to obtain correct results? > > Best Regards > > Jean Claude Thiry > Hello, If you are using standard EM physics, then after each step of an ion in media its mean change will be recalculated and updated for G4DynamicParticle object. This is nothing to do with initial change of an ion. Since 9.1 we have introduced a new process G4ionGasIonisation which is not following this rule but uses fixed ion charge defined at the beginning of tracking so far. This process is development and need more validation. We plan to introduce a more realistic model. By the way, your question should be posted in EM physics forum VI ```