[Gate-users] track stuck

[Jon Moody]

I've seen this warning frequently in parallel hole SPECT simulations,
where the track gets stuck in the collimator volume.  Apparently it's a
known issue in Geant4 mentioned here:

https://savannah.cern.ch/bugs/?36284
http://hypernews.slac.stanford.edu/HyperNews/geant4/get/geometry/552.html?inline=1

In my simulations, the navigator seems to be able eventually to unstick
the track, because no further errors were reported.  If the navigator
does not fail, e.g., with the message:

/ERROR - G4Navigator::ComputeStep()
        Track stuck, not moving for 25 steps
        in volume <VOLUME> at point (-996.4833727,-70.8652797,1218.517277)
        direction: (0.1410743748,0.02025641235,0.989791745).

*** G4Exception : StuckTrack
      issued by : G4Navigator::ComputeStep()
Stuck Track: potential geometry or navigation problem.
*** Event Must Be Aborted/

then it is probably just a harmless warning.

--
Jon


On 10/21/2010 6:43 AM, Niccolo.Fuin at uclh.nhs.uk wrote:
> Hi Gate Users,
>
>  
>
> I've got this WARNING message from during the simulation of a single
> SPECT camera, with a single point source and a LEHR paralellel hole
> collimator (so a pretty simple simulation):
>
>  
>
> Track Stuck, not moving for 10 steps
>
> ....
>
> .....
>
> Potential geometry or navigation problem!!
>
>  
>
> Have you got any idea about how I provoked this kind of problem??
>
> Many many thanks
>
>  
>
> Awaiting for your kind reply
>
> Niccolo'  
>
>
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