Re: Difficult geometry problem

From: <>
Date: Fri, 11 Jun 2010 16:18:17 +0200

Hello Joseph,

First of all, I sympathize. I know what it's like to struggle with some
complex geometry issues.
Maybe juse a hint there: when I modelize some complex geometry such as
accelerator facilities, I use the high accuracy fixed format to define
It is very useful especially when you introduce some cosines like the
ones which corresponds to your "awkward angles".
It is set in the geometry title card just under the geobegin card, by 0 -10.
It allows you to define your bodies coordinated and parameters in double
precision format.
It is a rather long work, I did it for several hundreds of bodies once,
but it was useful.

I tried your file and indeed the informations in the *.err, *.log, *.out
files indicate some normalization problem during the particle tracking.

I never used the ARB, BOX bodies, the problem could not come from those?

Hope it helps,


Le 10/06/2010 06:04, Joseph Comfort wrote :
> I have been struggling off an on for the past few months to produce the
> attached .inp file, from CAD drawings and specific information, for a
> beamline configuration. Something is wrong with the geometry, and I am
> at a loss to find it.
> We have a neutral beam along X=Y=0, passing in and out of vacuum regions
> through a charged-particle beamline. There are awkward angles (8 deg.
> and a later 13-deg. bend). Some cylinder bodies are longer than they
> really are, and then cut by infinite planes to fit as a way of trying to
> avoid precision errors.
> The file passes all of the Fluka geometry tests I have thrown against
> it, including some with tiny steps, giving no errors. It can be run
> through Flair without errors to generate a plot (a potion of the
> configuration is attached). I can run 100 and even 1000 RAY particles
> with no errors. However, Fluka crashes after just a few events when
> neutrons are used, with extensive pages of MA ARRAYs and FPD ARRAYs.
> I tried to see what I could get from the RAY particles. But the file is
> not readable by the code given in the manual. With some extra output I
> added, I get:
> File name?
> ni30_n001_fort.10
> nrayrn,mreg,mlattc,mmat,ekin= 2 0 26 1054835810 2.80259693E-44
> Incomplete data on file about ray starting point
> For the neutron case, the .err and .log files have nothing beyond the
> usual standard information. The .out file is far too big to be useful
> and can be easily generated, and so is not attached.
> One wish: It would be really, really helpful if there was some
> intermediate structure in the geometry, i.e., a complex region that
> could be built and then added as a unit into the geometry stream with a
> position and rotation (with all precision issues taken care of).
> Perhaps some user subroutine link. For the 'AirReg2' region, I wrote a
> separate program to handle all of the displacements and rotations, and
> then entered the relevant data into the .inp file manually. Very
> tedious, and surely prone to many errors! In the end, I was thrilled to
> find that the X=0 line was exactly where it should be. Yet, there must
> be a better way; e.g., something that one might be able to apply XML
> coding to.
> I'm not looking for someone to spend a lot of time in the ,inp file, but
> I need some good suggestions. Maybe the solution will be very simple,
> but I have not found it.
> Thank you,
> Joe Comfort
Received on Fri Jun 11 2010 - 17:12:50 CEST

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