Re: Maximum value of a surface parameter

From: Anna Ferrari <>
Date: Fri, 19 Aug 2011 20:23:57 +0200 (CEST)

Hi Andrew,

  it is maybe useful to add that if you use geometries very big (or very
small), you should adjust the WHAT(2) parameter in GEOBEGIN in order to
optimize the tracking and the boundary identification in the geometry
where you are tracking.
  I just copy from the manual:

>WHAT(2) > 0.0 : absolute accuracy parameter (Aa) in units of 1.E-6 cm.
> It is used for tracking and boundary identification.
> Aa should be larger than Ar*L , where L is the largest
> coordinate value in the geometry description (excluding
> the outer blackhole shell containing it) and Ar is the
> relative accuracy achievable in double precision (of the
> order of 1.E-14 - 1.E-15).
> Default = 0.0001

An example: suppose you need to describe a geometry with a system earth +
atmosphere and suppose to take the first 60 Km of atmosphere, putting some
Km of vacuum around. You will have then the external, not black hole
sphere of around 6.5E8. Then a value what(2)=6.5 (in unit 1.E-6) is good
for your purposes.



> Dear Flexperts
> Are you aware of any limitation in FLUKA that means there is a limit in
> the size of a given volume.
> Let me clarify, let us say we have a region in space that we want to
> define using 6 planes. Say (+PLA1 -PLA2 +PLA3 -PLA4 +PLA5 -PLA6) for
> example.
> Is there any fundamental limit, other than that of the compiled program
> which cannot accept a double number larger than the machine limit.
> e.g. is PLA1 XYP 1.0E12 be acceptable?
> Thanks
> Andrew

Anna Ferrari
Institute of Safety Research
Institute of Radiation Physics
HZDR Dresden-Rossendorf
D - 01314 Dresden (Germany)
Tel. +49 (0) 351 260 2407
Received on Sat Aug 20 2011 - 15:08:55 CEST

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