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Forum: Geometry
Re: None How to introduce a Hole in a LogicalBorderSurface
Re: Feedback Re: How to introduce a Hole in a LogicalBorderSurface (Gumplinger Peter)
Re: Question Re: How to introduce a Hole in a LogicalBorderSurface (Susanne Jungmann)
Date: 15 Dec, 2010
From: Gumplinger Peter <Gumplinger Peter>

Hi Susanne,

> I do have a similar problem. I'd like to build a rectangular solid that
> has a coarse surface but one side polished! Is it right that I simply
> build a third volume, attache it to my rectangle and don't define a
> G4LogicalBorderSurface for the interface volume 1-3?!

Yes, you define a 3rd volume (it can be rather thin but thinckness > kCarTolerance) and place it such that it butts up with volume 1. If you don't define a G4OpticalSurface for this vol1/vol3 combination, the default is used which is a perfectly polished dielectric-dielectric interface.

> 
> Since I'm studying optical photons, can I be sure, that they are not
> already reflected or refracted by the coarse surface of volume 1 but
> only by the very thin volume 3 with the polished surface?

The navigator at the boundary 'knows' of the volume it is arriving from (is still in) and the volume across the boundary. If there is no G4LogicalBorderSurface found with the combination vol1/vol3, the G4OpBoundaryProcess will use the default.

> Concerning BoundaryAbsorption and so on?

The default surface (polished, dielectric-dielectric) has NO absorption at the boundary. If you need absorption at the boundary between vol1/vol3 you'll need to define a G4LogicalBorderSurface for the volume combination vol1/vol3 (which will just the same, replace the one for vol1/vol2 when the photon arrives at your exit window).

Hope this clarifies the situation further, Peter

P.S. We should be having this discussion in the 'Optical Photon Physics Forum' next time (maybe with a link to these postings).

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