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Question Problem with GetGlobalTime() / GetLocalTime() for optical photons 

Forum: Event and Track Management
Date: 16 Apr, 2009
From: Paul Papacz <Paul Papacz>

Hello Experts,

I have been working with the GEANT-framework for a few months now and I found many solutions and ideas in this forum. Thanks for this.

But now I have a problem I cannot solve.

I am simulating a piece of scintillating material with an embedded WLS fiber.

Here I find a problem when accessing the GlobalTime/LocalTime of the optical photons.

In some cases (about 1 of 100) the GetGlobalTime()/GetLocalTime() method delivers a "nan" value. The photon still exists, propagates and can be visualised and detected in a sensitive detector, but no time information is available.

Here's a little excerpt of the tracking of such a photon:

*********************************************************************************************************
* G4Track Information:   Particle = opticalphoton,   Track ID = 6286,   Parent ID = 3164
*********************************************************************************************************

Step#      X         Y         Z        KineE    dEStep   StepLeng  TrakLeng    Volume     Process
    0   -219 um   1.09 mm  -2.36 cm   2.64 eV      0 eV      0 fm      0 fm   WLSFiberCore    initStep
    1   -145 um   1.03 mm  -2.38 cm   2.64 eV      0 eV    220 um    220 um   WLSFiberCore  Transportation

UserSteppingAction: theStep->GetPreStepPoint()->GetGlobalTime(): 4.6064893
UserSteppingAction: theStep->GetPreStepPoint()->GetLocalTime(): 0
UserSteppingAction: theStep->GetPostStepPoint()->GetGlobalTime(): nan
UserSteppingAction: theStep->GetPostStepPoint()->GetLocalTime(): nan
UserSteppingAction: theStep->GetDeltaTime(): nan

UserSteppingAction: theTrack->GetGlobalTime(): nan
UserSteppingAction: theTrack->GetLocalTime(): nan
UserSteppingAction: theTrack->GetTrackID(): 6286
UserSteppingAction: theTrack->GetKineticEnergy(): 2.6379985e-06

    2   -145 um   1.03 mm  -2.38 cm   2.64 eV      0 eV      0 fm    220 um   av_1_impr_1_InnerCladPart_log_pv_3  Transportation

UserSteppingAction: theStep->GetPreStepPoint()->GetGlobalTime(): nan
UserSteppingAction: theStep->GetPreStepPoint()->GetLocalTime(): nan
UserSteppingAction: theStep->GetPostStepPoint()->GetGlobalTime(): nan
UserSteppingAction: theStep->GetPostStepPoint()->GetLocalTime(): nan
UserSteppingAction: theStep->GetDeltaTime(): nan

UserSteppingAction: theTrack->GetGlobalTime(): nan
UserSteppingAction: theTrack->GetLocalTime(): nan
UserSteppingAction: theTrack->GetTrackID(): 6286
UserSteppingAction: theTrack->GetKineticEnergy(): 2.6379985e-06

    3    470 um   1.55 mm  -2.55 cm   2.64 eV      0 eV   1.83 mm   2.05 mm   WLSFiberCore  Transportation

UserSteppingAction: theStep->GetPreStepPoint()->GetGlobalTime(): nan
UserSteppingAction: theStep->GetPreStepPoint()->GetLocalTime(): nan
UserSteppingAction: theStep->GetPostStepPoint()->GetGlobalTime(): nan
UserSteppingAction: theStep->GetPostStepPoint()->GetLocalTime(): nan
UserSteppingAction: theStep->GetDeltaTime(): nan

UserSteppingAction: theTrack->GetGlobalTime(): nan
UserSteppingAction: theTrack->GetLocalTime(): nan
UserSteppingAction: theTrack->GetTrackID(): 6286
UserSteppingAction: theTrack->GetKineticEnergy(): 2.6379985e-06

    4    470 um   1.55 mm  -2.55 cm   2.64 eV      0 eV      0 fm   2.05 mm   av_1_impr_1_InnerCladPart_log_pv_2  Transportation

UserSteppingAction: theStep->GetPreStepPoint()->GetGlobalTime(): nan
UserSteppingAction: theStep->GetPreStepPoint()->GetLocalTime(): nan
UserSteppingAction: theStep->GetPostStepPoint()->GetGlobalTime(): nan
UserSteppingAction: theStep->GetPostStepPoint()->GetLocalTime(): nan
UserSteppingAction: theStep->GetDeltaTime(): nan

UserSteppingAction: theTrack->GetGlobalTime(): nan
UserSteppingAction: theTrack->GetLocalTime(): nan
UserSteppingAction: theTrack->GetTrackID(): 6286
UserSteppingAction: theTrack->GetKineticEnergy(): 2.6379985e-06

...

As you can see time information is only available at the very first PreStepPoint!

I would be glad about every help/idea.

Thanks Paul P.

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1 Feedback: Re: Problem with GetGlobalTime() / GetLocalTime() for optical photons   (Gumplinger Peter - 06 May, 2009)
2 None: Re: Problem with GetGlobalTime() / GetLocalTime() for optical photons   (Paul Papacz - 23 Jul, 2009)
1 Feedback: Re: Problem with GetGlobalTime() / GetLocalTime() for optical photons   (Gumplinger Peter - 23 Jul, 2009)
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