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Forum: Event and Track Management
Re: None changing step length in spite of cut value (Alfredo Tomás)
Date: 19 Dec, 2006
From: Vladimir IVANTCHENKO <vnivanch@mail.cern.ch>

On Tue, 12 Dec 2006, Alfredo Tomás wrote:

> *** Discussion title: Event and Track Management
> Email replies to PublicHyperNews@slac.stanford.edu must include:
>   In-Reply-To: <"/eventtrackmanage/579"@geant4-hn.slac.stanford.edu>
>   Subject: ...change this to be about your reply.
> 
> Hello,
> 
> I'm simulating electrons, ions and gammas in low energy range 
> (about 10-100 keV) with special interest in the track features. The
> simulations seem to be OK but I can't control the length of the step 
> which I would want to be short (less than a micron). 
> I have tried to do it by several ways:
>    with the command setCut in an initial macro,
>    setting the cuts in the PhysicsLists,
>    and defining an activeVolume in DetectorConstruction,
> but no success.
> In spite of this what I observe is changing step lengths depending on
> the kind of particle and its energy. Heavier the particle, shorter the
> length and more energetic the particle, larger the length. The last seems 
> reasonable to me so I wonder if it could be happening that the low energy 
> electromagnetic processes I'm using are deciding the step length by 
> theirself because they may contain tables of cuts.
> 
> Thanks in advance.
> 

Hello,

When you are trying to simulate gaseuos detectors it is difficult to
control the step size by cuts, because you will need practically zero cut
value. The optimal solution is to use step limitation. The standard way of
applying of user step limits is suggested by Makoto, another you can find
out in examples/extended/electromagnetic. Note also that artifitially 
small step size can be a problem for physics processes: 1 um inside gas is 
too much from my point of view.

VI

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