Re: Energy deposit in thin regions

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Sun Jun 13 2004 - 23:41:51 CEST

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    What you say applies to regions WITH a field, not without. If there is
    no field, FLUKA knows very well how to optimize the step size without any help
    from the user. STEPSIZE should not be used unless there is a field: but many
    users, out of habits taken with other programs, tend to use it when it is not
    needed. It is a pity, because it spoils the performance without providing
    any advantage.

      Alberto

    On Sun, 13 Jun 2004, John Clem wrote:

    >
    >
    > It has been my understanding the maximum step size in a non-vacuum
    > region without a field should not be greater than ~ 1/3 of its minimum
    > dimension to allow the multiple-scattering routines to work properly.
    >
    > This is briefly discussed in the documentation under STEPSIZE
    >
    > John
    >
    >
    > On Sat, 12 Jun 2004, Paolo MAESTRO wrote:
    >
    > >
    > > Hi Fluka users,
    > > I simulated a sampling calorimeter
    > > made of tungsten layers (0.35 cm thick)
    > > alternated with planes made of 0.05 cm thick scintillator.
    > > I noticed that protons (150 GeV kin. energy),
    > > passing through the detector as minimum ionizing particles,
    > > deposit energy in each scintillator plane only at the end of
    > > the considered region at the boundary with the next region.
    > > To explain better, if a scintillator plane extends
    > > from z= -0.35cm to z=-0.4 cm
    > > , dumping the energy deposit in MGDRAW & ENDRAW
    > > subroutine of mgdraw.f, it turns out that
    > > the deposit is recorded at z=-0.4 cm, i.e.
    > > at the boundary with the next tungsten layer.
    > > This has no physical meaning, and I guess it depends from
    > > the fact that the step size is bigger than the considered region
    > > thickness. I tried to set by hand a step size for the scintillators planes
    > > using the STEPSIZE options and it seems working well.
    > > But I wonder:
    > > - which is the empirical rule to set the min and max stepsize ?
    > > (I tried min = 1/50 scintillator thickness and max = 1/10)
    > > - in my case, do I need to set STEPSIZE also for tungsten layers?
    > > - is this procedure to avoid the energy deposit at boundaries correct ?
    > >
    > >
    > > Many thanks for your help.
    > > Best regards
    > >
    > > Paolo Maestro
    > >
    > >
    > >
    > >
    >
    > 

    -- 
Alberto Fassò
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
fasso@slac.stanford.edu
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