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Forum: Physics List
Re: None Proton Physics (Sean Kirkwood)
Date: 27 May, 2008
From: Vladimir IVANTCHENKO <vnivanch@mail.cern.ch>

On Tue, 27 May 2008, Sean Kirkwood wrote:

> *** Discussion title: Physics List
> Email replies to PublicHyperNews@slac.stanford.edu must include:
>   In-Reply-To: <"/phys-list/484"@geant4-hn.slac.stanford.edu>
>   Subject: ...change this to be about your reply.
> 
> Hi,
> 
> We are simulating proton absorption in silicon detectors and noticed that
> as the proton energies reach about 50 - 100 MeV that the deposition curve
> looks "broken up".  Rather than a smooth curve as expected from a Bethe
> equation, it appears as though the deposition is taken from a look-up
> table.  The curve would go straight for a few MeV and then drop to the 
> next level, as though it found a new table entry.
> 
> My questions are:
> 1. Is GEANT4 using a look-up table for proton absorption?
> 2. Are there other physics models I should incorporate?
> 3. Where can I get a good sandwich?
> 
> Thanks for your time,
> Sean
>

Hello Sean,

Few comments: 
 - better to send this post to emproces Forum.
 - it is important to specify version of G4

 - we have observed this effect: it happens when small cuts and small 
steps are used. 

In G4 tables are used to speedup computations. However, recently we 
faced situations, when default parameters provide biased result. The
simplest way to fix is to increase number of bins:

/process/eLoss/binsDEDX 480

Please, use this command after

/run/initialize

Let us know if the problem disappear.

VI

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