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Forum: Processes Involving Optical Photons
Re: Sad Polish and ground - where it refers finally ? (Yuri Soloviev)
Re: Feedback Re: Polish and ground - where it refers finally ? (Gumplinger Peter)
Re: Feedback Re: Polish and ground - where it refers finally ? (Yuri Soloviev)
Date: 03 May, 2010
From: Gumplinger Peter <Gumplinger Peter>

> 1. If this concept is valid both to the unified and glisur model

The 'glisur' model does NOT have a backpainted option. This is something strictly for the 'unified' model.

> 2. I guess for the glisur model the "old" concept is still valid, is it correct?

No, as I said, the glisur model has no backpainted option.

> 3. Does parameter sigmaalpha (or setpolish) refer ro the wrapper in "new" concept?

No, the reflectivity parameters of the unified model, refer only to initial interface for a backpainted surface; the interface between the dielectric and the thin dielectric gap. For LobeReflections the parameter sigmaalpha is used to sample the facet normal. The wrapper is polished if you specify 'polishedbackpainted' and a Lambertian reflector if you specify 'groundbackpainted'. The wrapper cannot be of a more complicated combined type like the initial interface with the reflectivity parameters. It's either Lambertian or mirror.

The glisur model has no option for a wrapper.

> 4. How the "ground" and "polish" should be interpreted without wrapper?

Well, if there is no wrapper the initial interface is the only interface between the original dielectric and the one across the surface.

> Or the "new" concept is valid only with wrapper ?

If you have 'groundbackpainted', the 'ground' refers to the wrapper but also to the initial interface. If you also specify the unified reflectivity parameters, they'll be used to decide on the type of reflectifity from the initial interface (with the thin gap). This decision however ONLY applies if the photon is reflected.

> Under "new" concept:

The "new" concept is different only by the fact that the 'ground' and 'polish' now also refers to the wrapper.

> Sorry for so many questions, I just want to know what I am doing with Geant4 > in my simulations.

No worries! I should probably device a flow chart of the decisions made in the code and how all these options interplay.

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