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Forum: Processes Involving Optical Photons
Re: Question Questions about optical processes (IW)
Date: 18 Jun, 2012
From: Gumplinger Peter <Gumplinger Peter>

> 1) In the
> scintillation process, how does Geant4 decide the energy of each photon
> produced?

It uses the information that you provide as either FASTCOMPONENT or SLOWCOMPONENT.

> Does it use information about the scintillation material
> (molecules) at all?

No, G4 does not simulate solid state physics and scintillation 'from first principles'.

> I ask this because the examples N06 and LXe do not
> seem to define a range for the photon energies, just the photon number
> yield.

The range of photons produced by scintillation is the range of the 'PhotonEnergy' array that you provide in the call to AddProperty:

See:

http://www-geant4.kek.jp/lxr/source/examples/novice/N06/src/ExN06DetectorConstruction.cc#L138

> (and what about photon polarization?)

Please, read the documentation:

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

5.2.5.2. Generation of Photons in processes/electromagnetic/xrays - Scintillation

It reads:

Each photon's frequency is sampled from the empirical spectrum. The photons originate evenly along the track segment and are emitted uniformly into 4&#960; with a random linear polarization and at times characteristic for the scintillation component.

> 2) If I want to simulate
> total internal reflection between two dielectrics, is it imperial that I
> declare the border surface polished?

No.

> Does a ground border surface
> accounts for total internal reflection?

Yes, Snell's law is calculated with respect to the sampled micro facet normal.

> 3) I have a world volume filled
> with vacuum and two other volumes standing side by side, with surfaces
> intersecting at z=z0. A logical border surface is declared between
> physical volumes for all possible 3x2=6 possibilites.

Ok.

> When a photon is
> incident from one of the volumes into the next, does Geant4

Geant4 will find the logical and physical surface that you've defined for the transition between vol1 and vol2 in question and in that order.

> runs 2
> optical boundary processes between each of the volumes and vacuum (i.e.
> is there an "intrinsic" gap between the volumes?)

No, of course not. No 'gaps' as there is no gap in reality.

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