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Keywords: Suggested remedy
Forum: Run Management
Re: Question What does the "Relocation Within Safety Error" Mean (Michael Famiano)
Date: 05 Jul, 2002
From: John Apostolakis <John Apostolakis>

Dear Mike,

The message that you have encountered exists to warn users of a problem that the Geant4 transportation process and geometry navigator have found. "ERROR: A relocation within safety has caused a volume change!" means that although the step was very small, the navigator found that a different volume was entered due to this step.

 There are two possible causes:
- the geometry description of your setup is not well defined
- another physics process is causing small steps at a boundary, 
   and, due to this, the Transportation/Navigator have become confused.

So it is possible that the Transportation has indeed 'stumbled' upon a problem in your geometry description. In case this is so, please check in which volume you believe the location (-26.49996,-2.486792,31.7641) in global coordinates is in. If it is not on a boundary between volumes called 'crystal_phys' and 'al_cov_phys' then the Navigator is indeed confused. In this case, you can also use '/tracking/verbose 1' for this event to check how the track arrived at this location.

Or else, it could be our problem. We have received a problem report documenting such a case in which this message was generated in a correct geometry, due to the interaction of photons at very short distances in a strongly absorbing medium. It could be that this is similar to your case.

This code is primarily for providing a (small) check of the geometry setup. As it can be triggered by other conditions even when your geometry is correct, we have decided that it is counterproductive. So we have now suppressed it in the latest release of Geant4, release 4.1 made on June 28th.

I suggest to you to try this release to see whether our fix for the above problem also resolves your problem.

Best regards, John Apostolakis

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