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Question Indexing Node Number outside number of slices 

Forum: Geometry
Date: 08 Dec, 2011
From: Michael Douglass <Michael Douglass>

Hello,

I am experiencing a strange problem in my geant4 code. I have a small cube world volume made of a water material with dimensions 0.72 x 0.72 x 0.72 mm. Inside of this world volume I have 8000 parametrized cubes. Each of these cubes has different dimensions, rotations and randomized positions. The size of these cubes vary in size from 7 - 15 microns. I am confident that none of these geometries are overlapping.

I am experiencing a "fatal error" when running this simulation under windows xp and ubuntu v10. I have run the code through a debugger and have localized the problem to G4ParametrisedNavigation at line 422 of geant4.9.4_p01 in the function ComputeSafety(). The current voxel node number at the point it crashed was 85, but I only have 75 slices in the world volume according to the code.

Some other interesting values that I observed in this code were: pMaxlength = 1.797 e ^(+308)

The pGlobalPoint was (-0.037,-0.115,0.458). The z-coordinate is outside by world volume which has maximum limits of -0.33 mm to 0.33 mm.

The distEndPointSq = (pGlobalPoint-fstependpoint)^2 = 0

Just to be clear, I have not voxellised any of my regions. The voxellisation appears to be an inbuilt geant4 process. I am not using sensitive volumes.

I am using 5 keV gamma particles using the livermore physics list. The track that caused the error appeared to be a secondary electron track which moved beyond the boundries of the world volume.

The problem appears at exactly the same time if I use a fixed starting random seed and at different times when using a random seed. Each simulation ends with the words "Segmentation Fault". I assume this is to the fact that it is trying to access element 85 of the voxel slice matrix which only has 75 slices. (fVoxelHeader).

I read in a geant4 presentation on the Internet that it is possible to delete voxel optimisation and this may fix the problem. However, I am not familiar with this concept.

I am currently attempting to increase the size of the world volume to see if that fixes the problem. I believe this may just cover up the problem if it does fix the problem. I have also tried adjusting the energy cut values which did not fix the problem, although the error occurred at a different track.

I would appreciate any advice that people have to offer.

Thank you

Kind Regards

Michael Douglass

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1 Idea: Re: Indexing Node Number outside number of slices   (Michael Douglass - 08 Dec, 2011)
2 Feedback: Re: Indexing Node Number outside number of slices   (Gabriele Cosmo - 08 Dec, 2011)
1 More: Re: Indexing Node Number outside number of slices   (Michael Douglass - 08 Dec, 2011)
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