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Question Magnetic field with parallel world 

Forum: Geometry
Date: 17 Sep, 2014
From: Ken Sutherland <Ken Sutherland>

I am simulating a scanned proton beam nozzle. The target is a parametrized patient CT volume. I want to embed spherical gold markers in the patient volume to estimate the effect of dose shadowing. However, it seems that parametrized volumes cannot be mother volumes. So I have been trying to place the gold markers in a parallel world. It seems to work as long as I don't activate the scanning magnets. I've traced it down in my code to a call to G4FieldManager::SetDetectorField(). If I leave this line of code in, the program crashes (Access violation) in G4PathFinder::ComputeStep()

  // Prepare the information to return

  pNewSafety  = fCurrentPreStepSafety[ navigatorNo ]; 
> limitedStep = fLimitedStep[ navigatorNo ];
  fRelocatedPoint= false;

I can see that "navigatorNo" is 1, so I'm assuming that the arrays are not being allocated for the parallel world for some reason. If I comment out the call to SetDetectorField(), then it runs OK, but I have no steering magnets.

I've been reading "Parallel Geometries in Geant4: foundation and recent enhancements" and there seems to be something about magnetic fields and parallel worlds. Should I try using "G4SafetyHelper"?

In the attached image, the gold marker is the red sphere. It is in the parallel world. The gold marker is the only thing in the parallel world.

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/09/17/22.30-45345-Parallel.png

Thanks for any advice!

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1 None: Re: Magnetic field with parallel world   (Tom Roberts - 18 Sep, 2014)
2 None: Re: Magnetic field with parallel world   (John Allison - 18 Sep, 2014)
1 None: Re: Magnetic field with parallel world   (Makoto Asai - 18 Sep, 2014)
(_ Question: Re: Magnetic field with parallel world   (Ken Sutherland - 20 Sep, 2014)
(_ None: Re: Magnetic field with parallel world   (Makoto Asai - 20 Sep, 2014)
(_ Question: Re: Magnetic field with parallel world   (Ken Sutherland - 29 Sep, 2014)
1 None: Re: Magnetic field with parallel world   (Joseph Perl - 29 Sep, 2014)
2 None: Re: Magnetic field with parallel world   (Makoto Asai - 29 Sep, 2014)
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