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Disagree Re: number of optical photons remains constant 

Forum: Processes Involving Optical Photons
Re: Question number of optical photons remains constant (Cejo George)
Re: Feedback Re: number of optical photons remains constant (Gumplinger Peter)
Re: Question Re: number of optical photons remains constant (Ashwath Rao)
Date: 02 Apr, 2012
From: Gumplinger Peter <Gumplinger Peter>

Hello Ashwath,

Please, see the 'Application Developers Manual':

http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/ForApplicationDeveloper/html/ch05s02.html#sect.PhysProc.Photo

where it reads:

"Optical photons are generated in GEANT4 without energy conservation and their energy must therefore not be tallied as part of the energy balance of an event."

> 1) We feel that each gamma after the interaction can be identified by

> the sum of the optical photon energies rather than plotting the

> individual op. photon energies !! (ARE WE RIGHT SIR..?)

In any case, it is incorrect to assume that the total energy deposited by a gamma ray in a scintillating medium will go into a number of optical photons, whose energy sum equals the deposited energy. Only a tiny fraction of the energy deposited in a scintillating medium will actually go into optical photons.

The caution in the manual is for people who think that they can add the energy of the photons to the energy deposited and conserve the original available energy of the event. This is not the case, as the energy of the optical photons is extra/additional and hence the balance is not conserved.

Please, see example /novice/N06/src/ExN06StackingAction.cc how simple it can be to count the number of optical photons (albeit the variable is unfortunately called 'gammaCounter')

> 2) What is the range of op. photon energy values? below 1300 eV.?

You, the user, decides what is the scintillation photon spectrum.

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1 Question: Re: number of optical photons remains constant   (Cejo George - 03 Apr, 2012)
(_ Feedback: Re: number of optical photons remains constant   (Gumplinger Peter - 03 Apr, 2012)
(_ Agree: Re: number of optical photons remains constant   (Ashwath Rao - 05 Apr, 2012)
(_ Feedback: Re: number of optical photons remains constant   (Ashwath Rao - 06 Apr, 2012)
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