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None Re: Peculiar problem: Overlapping Voxels in Parallel World affects particle tracks 

Forum: Biasing and Scoring
Re: Question Peculiar problem: Overlapping Voxels in Parallel World affects particle tracks (Joseph DeCunha)
Re: None Re: Peculiar problem: Overlapping Voxels in Parallel World affects particle tracks (Makoto Asai)
Date: 28 Jun, 2016
From: Joseph DeCunha <Joseph DeCunha>

Thank you for your reply! Very interesting.

Yes, the code for the spherical mesh was taken from a colleague, the class was derived from G4PVParameterised.

That thought had crossed my mind -- that perhaps the tracks themselves might be modified but as high numbers of particles were generated perhaps the results would be statistically indistinguishable.

I'm curious about what you've said about the mesh volumes affecting the generation of random numbers. Would the Geant4 Physics Reference manual be a good resource to learn more about that?

Thanks again,

Joseph

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None Re: Peculiar problem: Overlapping Voxels in Parallel World affects particle tracks  by Makoto Asai <Makoto Asai>,   28 Jun, 2016
Re: None Re: Peculiar problem: Overlapping Voxels in Parallel World affects particle tracks (Joseph DeCunha)
You may want to try defining your spherical mesh made of G4Orb and place a smaller G4Orb object as a daughter of the mother G4Orb object rather than using parameterized volume and placing G4Sphere touching to each other. Touching surface of the inner surface of the larger spherical shell and the outer surface of the smaller sphere is always a difficult situation for the navigator due to the numerical rounding errors.

Fate of a track in terms of which physics process actually happens is determined at the beginning of that track so that number of steps does not affect to it. But for every "along-step" physics processes such as ionization, we use random numbers to fluctuate energy deposition, etc., thus we consume random numbers. Thus, the random numbers used to determine the fate of the next track are affected by the number of steps of the previous track. This part is described in the application developers guide. Physics reference manual describes details of each physics models we use.

Makoto

Question Re: Peculiar problem: Overlapping Voxels in Parallel World affects particle tracks  by Juliana Cristina Martins <Juliana Cristina Martins>,   05 Feb, 2018
Re: None Re: Peculiar problem: Overlapping Voxels in Parallel World affects particle tracks (Makoto Asai)
Hi there, I have a question concerning overlapping voxels in parallel world.

I created three command-based scoring meshes that overlap at a certain point with each other. I am scoring Dose Deposit. When I analyze the dose scored by those meshes, I see a strange peak that coincides with the voxel where the meshes overlap!

Is it possible that the dose is somehow accumulating in the intersection?

Any ideas on that would be helpful...

thanks a lot, Juliana

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