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Question Optical Photons Spectrum 

Forum: Processes Involving Optical Photons
Date: 21 Jan, 2011
From: Dragos Constantin <Dragos Constantin>

Dear Colleagues,

I have a hard time understanding what is going on with the optical photons spectrum. My setup consists of a monoenergetic gamma source (662keV) and a scintillating crystal with a detector at the bottom. There are at least two other messages under "Processes Involving Optical Photons" related to the same subject. Please see:

http://hypernews.slac.stanford.edu/HyperNews/geant4/get/particles/170.html

and

http://hypernews.slac.stanford.edu/HyperNews/geant4/get/opticalphotons/303.html

In short the spectrum is not linearly interpolated between the specified points in the material table. I have attached a "ps" file with the plot of the optical photon spectrum (normalized) alongside the (energy,scint) points defined in the material table.

I am extracting the information in a file like this:

//=========================================

// implemented in StepingAction

//=========================================

if (thePrePVname  == "physicalCrystal_name" && thePostPVname == "physicalArray_name")
{
  if(particleType == G4OpticalPhoton::OpticalPhotonDefinition())
  {
    if(theTrack->GetParentID()>0) //<<----- is this necessary ?
    {
      outputFile << thePostPoint->GetKineticEnergy()<< G4endl;
    }
  }
}

//=========================================

e.g. I am writing in a file the energy of any optical secondary photons which reaches the detector. On a side note I believe in my case all the optical photons are secondary particles becuase my gun is emitting 662keV gammas. Hence I should not test them for being secondary particles. Please correct me if I am wrong.

Then I do in matlab:

%=========================================

energy=load('spectrum.dat');

hist(energy,1000);

%=========================================

What is wrong here? I have looked at the Geant4 code as pointed by Peter Gumplinger in one of the previous postings about this issue and Geant4 should interpolate the "FASTCOMPONENT" property. Any ideas about this reoccurring issue?

Thank you,

Dragos

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2011/01/21/10.35-29808-photon_spectum.ps

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1 Feedback: Re: Optical Photons Spectrum   (Gumplinger Peter - 21 Jan, 2011)
(_ More: Re: Optical Photons Spectrum   (Gumplinger Peter - 21 Jan, 2011)
(_ More: Re: Optical Photons Spectrum   (Gumplinger Peter - 21 Jan, 2011)
1 Idea: Re: Optical Photons Spectrum   (Benton Pahlka - 21 Jan, 2011)
1 Feedback: Re: Optical Photons Spectrum   (Dragos Constantin - 26 Jan, 2011)
2 Feedback: Re: Optical Photons Spectrum   (Dragos Constantin - 26 Jan, 2011)
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