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Forum: Processes Involving Optical Photons
Re: None Confused by scintillation yield
Date: 18 Oct, 2013
From: Gumplinger Peter <Gumplinger Peter>

On Fri, 18 Oct 2013 15:52:27 GMT, matt_b wrote:
> I have an alpha scintillation yield defined at 1000 photons/MeV.
> 
> I have an alpha particle that I create in the middle of my liquid
> scintillator. I see the following from steppingVerbose:
> 
> *********************************************************************************************************
> * G4Track Information:   Particle = alpha,   Track ID = 1,   Parent ID = 0
> *********************************************************************************************************
> 
> Step#   Time           X           Y           Z        KineE    dEStep     Volume     Process
>     0      0 ps      -10 um      -10 um      -10 um      1 MeV     0 eV   scintillator    initStep
> G4VRestDiscreteProcess::PostStepGetPhysicalInteractionLength [ Scintillation]
> 
> Particle = alpha Energy Dep. = 1 Yield = 1000
> 
> Exiting from G4Scintillation::DoIt -- NumberOfSecondaries = 1005
>     1 0.5914 ps   -5.894 um      -10 um      -10 um      0 eV      1 MeV  scintillator     ionIoni
> 
> Particle = alpha Energy Dep. = 0 Yield = 1000
> 
>  Exiting from G4Scintillation::DoIt -- NumberOfSecondaries = 994
>     2 0.5914 ps   -5.894 um      -10 um      -10 um      0 eV      0 eV   scintillator  Scintillation
> 
> I am confused why step 1 deposits no energy, but 994 photons are
> created? Am I missing something here in my understanding? Or have I made
> a mistake in my code somewhere?
> 

The initStep is printed before the first step is taken. Next, comes your output and the one from G4Scintillation, and finally the information about the step is printed. So, 1005, corresponds to dEStep == 1 MeV coming from ionIoni.

It is step 2 that deposits no energy via the energy loss process, the alpha is already at rest, but still there is a process that apparently generates sub-cut-off charged particles whose kin. energy is attributed to energy 'going to the medium'. I don't know what that process could be. You have to write out all processes invoked during that step. For that you have to call:

G4SteppingVerbose::AtRestDoItInvoked()

with verbosity >=3

I am curious.....

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1 None: Re: Confused by scintillation yield   (matt_b - 21 Oct, 2013)
(_ Feedback: Re: Confused by scintillation yield   (Gumplinger Peter - 21 Oct, 2013)
(_ None: Re: Confused by scintillation yield   (matt_b - 22 Oct, 2013)
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