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Forum: Physics List
Re: Question Is it possible to change physics process type just for a given volume/region? (Kamil Sedlak)
Date: 15 May, 2007
From: Vladimir IVANTCHENKO <vnivanch@mail.cern.ch>

On Tue, 15 May 2007, Kamil Sedlak wrote:

> *** Discussion title: Physics List
> Email replies to PublicHyperNews@slac.stanford.edu must include:
>   In-Reply-To: <"/phys-list/376"@geant4-hn.slac.stanford.edu>
>   Subject: ...change this to be about your reply.
> 
> Dear All,
>   I am using the G4MultipleScattering process in my detector setup.
> There is an alternative process G4CoulombScattering, which is believed
> to be better suited for the thin materials.  However, switching from
> G4MultipleScattering to G4CoulombScattering everywhere increses 
> the execution time of my jobs by factor of ~10.
>   Therefore I would like to use G4CoulombScattering only in a few very thin 
> volumes, while employ G4MultipleScattering elsewhere.  Is this possible?
> I did not find such an example, even though the "User's Guide: 
> For Application Developers" (geant 4.8.3, chapter 5.2.1.1) indicates
> this might be possible:
> 
>    * The processes described above use physics model classes, 
>    which may be combined according to particle energy. 
>    It is possible to change the energy range over which 
>    different models are valid, and to apply other models 
>    specific to particle type, energy range, and G4Region.
> 
> (I found a similar posting at
> http://geant4-hn.slac.stanford.edu:5090/HyperNews/public/get/emprocess/504.html
> , where an unofficial way of solving a similar problem is provided).
> 

Hello,

Unfortunatelly, for today we do not provide yet an easy way to define 
scattering models per region. A good example is PAI model definition in 

$G4INSTALL/examples/electromagnetic/TestEm8

but this is for ionisation process when one defines a special model per 
detector region.

For you case first you need to understand for what particles you wish to 
have single scattering? If only for muons, hadrons - it is easy in physics 
list. If you need single scattering for electrons, than there is a 
question: what electron energy is interesting for you? It may be useful 
simply kill low energy electrons.

If you need all electrons, then situation is more complicate. May be the 
best is private contact to me, if you will be at CERN soon make a visit.

regards,

-- 
    Vladimir Ivanchenko  
    ### CERN PH SFT Tel: +41-22-76-78-871  Vladimir.Ivantchenko@cern.ch ###

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