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Feedback Re: Surface Properties:how to model a diffusive (98%) and absorbing (2%) surface  

Keywords: surface absorbing diffuse
Forum: Processes Involving Optical Photons
Date: 28 Jul, 2005
From: Gumplinger Peter <Gumplinger Peter>

> The value of G4double polish should be set to 0.0 (default), isn't it?

No, with the 'glisur' model, the opposite, polish=1.0, is default:

        G4OpticalSurface(const G4String& name,
                         G4OpticalSurfaceModel model = glisur,
                         G4OpticalSurfaceFinish finish = polished,
                         G4SurfaceType type = dielectric_dielectric,
                         G4double value = 1.0);

> I use the G4AssemblyVolume class to construct the scintillator,

I have never used G4AssemblyVolume. In fact, I don't really know what it does but I question whether you actually need to resort to it for your application.

> Could I use the same "code logic" in case of the glisur-model but
> dielectric_dielectric?

No, in the glisur-model, the 'REFLECTIVITY' is only associated with a reflector; a 'dielectric_metal' G4SurfaceType. However, this reflector doesn't actually have to be a 'metal', in the chemical sense, it can also be a 'paint' (epoxy).

You could use the unified-model. In that case, you can specify: finish = groundfrontpainted and you will have a 'REFLECTIFITY' associated with the 'dielectric_dielectric' type.

I suggest you stick your array of NaI modules into a mother volume which is as large as the array's outside dimensions (your EpoxyElement_log). Then, your code snippet is correct, except for either:

new G4OpticalSurface("EpoxySurface",glisur,ground,dielectric_metal,0.0);

or

new G4OpticalSurface("EpoxySurface",unified,groundfrontpainted,
                                                dielectric_dielectric);

Now, this encloses your scintillator array completely and optical photons reflect everywhere. Where is your photon sensor?

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