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Forum: Processes Involving Optical Photons
Re: Question Optical Photon Interaction in Silicon (Ibrahim)
Date: 14 Jun, 2010
From: Gumplinger Peter <Gumplinger Peter>

Hi Ibrahym,

> But the energy deposition which I got is ZERO in all pixels of Silicon

> detector! Does anybody know where is the problem?

You need to absorb the optical photons on your silicon's surface. For this you need to define the silicon as a "metal" with a given absorption (reflectivity) probability and detection efficiency; e.g. as if it was the photo cathode of a PMT. If an optical photon now hits the silicon, it will be absorbed (or reflected) and if absorped, an energy deposition equal to the optical photon's energy will be registered at this location. How this then triggers scoring in your parallel geometry, I am not sure, but my guess is it should work just as it worked for the original energy deposition in your detector by the x-ray.

Please, see /examples/extended/optical/LXe how an optical photon sensitive surface (photo cathode) needs to be defined. Without this, optical photons will simply cross your silicon (if you defined an index of refraction) or be stopped because they reached a volume that is neither a 'metal' nor a dielectric (e.g. has an index defined). If they are simply stopped, no energy is (presently) deposited and hence no scoring can be triggered.

It just occurs to me that as an alternative, if you hope to trigger the scoring but do not want to define the silicon as a 'metal', you could try and change the code in G4OpBoundaryProcess.cc by adding the following line:

aParticleChange.ProposeLocalEnergyDeposit(thePhotonMomentum);

before every line in the file that reads:

aParticleChange.ProposeTrackStatus(fStopAndKill);

Hope this helps, Peter

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