Message: Re: Neverending simulation loop (G4SubtractionSolid, G4Paraboloid, G4OpticalPhoton) Not Logged In (login)
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More Re: Neverending simulation loop (G4SubtractionSolid, G4Paraboloid, G4OpticalPhoton) 

Forum: Geometry
Re: None Neverending simulation loop (G4SubtractionSolid, G4Paraboloid, G4OpticalPhoton) (Jonathan Toebbe)
Date: 29 Jun, 2008
From: Gabriele Cosmo <Gabriele Cosmo>

On Wed, 18 Jun 2008 23:08:35 GMT, Jonathan Toebbe wrote:
> I'm trying to implement an off-axis parabolic mirror by using a  
> G4SubtractionSolid. I construct a cylinder and a paraboloid, and then  
> subtract the paraboloid (offset appropriately by a G4Transform3D)  
> from the cylinder. To test my mirror, I have constructed a  
> rudimentary simulation that centers my mirror (made of perfectly  
> reflective silver) in a world volume filled with air and fire a  
> collimated beam of optical photons at the mirror.
> 
> Photons are launched in the +x-direction, and I control the  
> orientation of the mirror. When the mirror is aligned parallel to the  
> incoming beam, Geant initializes the photon... and then sits there  
> forever... Here is an example of the output:
> 
> > Idle> /run/beamOn 1
> > /run/beamOn 1
> >
> > [CUT OUT EXCESS VERBOSITY]
> >
> > Start closing geometry.
> > G4GeometryManager::ReportVoxelStats -- Voxel Statistics
> >
> >     Total memory consumed for geometry optimisation:   0 kByte
> >     Total CPU time elapsed for geometry optimisation: 0 seconds
> > Start Run processing.
> >
> > ********************************************************************** 
> > ***********************************
> > * G4Track Information:   Particle = opticalphoton,   Track ID =  
> > 1,   Parent ID = 0
> > ********************************************************************** 
> > ***********************************
> >
> > Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng  
> > TrackLeng  NextVolume ProcName
> >     0     -200    -12.8    -8.02  2.48e-06        0         
> > 0         0       World initStep
> 
> When I tilt the mirror to *any other angle* (including being off by  
> only 1.0*deg from parallel), Geant tracks the photons successfully.  
> Here's a sample output when the mirror was only 1.0*deg away from  
> being aligned the way I need it to be:
> 
> > Idle> /run/beamOn 1
> > /run/beamOn 1
> >
> > [IDENTICAL EXCESS VERBOSITY SNIPPED]
> >
> > Start Run processing.
> >
> > ********************************************************************** 
> > ***********************************
> > * G4Track Information:   Particle = opticalphoton,   Track ID =  
> > 1,   Parent ID = 0
> > ********************************************************************** 
> > ***********************************
> >
> > Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng  
> > TrackLeng  NextVolume ProcName
> >     0     -200    -4.22    -3.69  2.48e-06        0         
> > 0         0       World initStep
> >  Photon at Boundary!
> >  Old Momentum Direction: (1,0,0)
> >  Old Polarization:       (1,0,0)
> >  New Momentum Direction:  
> > (-0.05293133382954407,0.02184222449822722,-0.9983592495329496)
> >  New Polarization:        
> > (0.05293133382954407,-0.02184222449822722,0.9983592495329496)
> >  *** SpikeReflection ***
> >     1     3.48    -4.22    -3.69  2.48e-06        0      203        
> > 203      Mirror Transportation
> >     2     3.48    -4.22    -3.69  2.48e-06        0        0        
> > 203       World Transportation
> >     3    -22.8     6.64     -500  2.48e-06        0      497        
> > 701  OutOfWorld Transportation
> >
> > Run terminated.
> > Run Summary
> >   Number of events processed : 1
> >   User=0s Real=0s Sys=0s
> > 1 event has been kept for refreshing and/or reviewing.
> 
> The only difference I observe in the failed run is some mention of  
> the geometry optimization. I'm very new to Geant, and thus reached  
> the limits of my ability to debug things very rapidly. Please help!

Hi Jon,

I suggest you to open a problem report in Bugzilla and provide (or tell where
to find) all the details, geometry setup, input macros, etc... such that we can
reproduce the faulty behavior.
The information about the optimization has nothing to do with the problem,
it is printed out according to the verbosity level you use for the run.

Cheers, Gabriele

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