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Question Re: Convergence to diffuse reflection 

Forum: Processes Involving Optical Photons
Re: Question Convergence to diffuse reflection (Charles Sosa)
Date: 16 Oct, 2017
From: Charles Sosa <Charles Sosa>

Hi, I'd just like to follow up with this! I'll rephrase my question:

What is the simplest way to model a perfectly diffuse reflector? It seems there are a few pathways to achieve this. For example, assuming we're using the UNIFIED model, we can set:

Case 1:

SetType: Dielectric_Metal, SetFinish: Ground, SigAlpha: 0 radians

Case 2:

SetType: Dielectric_Dielectric, SetFinish: GroundFrontPainted

Should these two cases produce the same optical photon reflection profile? I imagine they would differ slightly if the surface roughness of case 1 were increased.

Thank you!

CharlesOn Mon, 25 Sep 2017 17:26:27 GMT, Charles Sosa wrote:

> Hi, I'm simulating a cylindrical scintillator wrapped by a perfectly
> diffuse reflector with no air gap. One face of the scintillator is set
> as a detection surface. My questions involve the reflector.
> 
> 1. As I understand it, a perfectly diffuse reflector with no air gap
> between the scintillator and the reflector can be modeled by selecting
> the SetModel to be UNIFIED, the SetType to be dielectric_dielectric, and
> the SetFinish to be groundfrontpainted. Is this understanding correct?
> I'm referencing the attachment.
> 
> 2. If the first statement is correct, would it therefore be redundant to
> add the following three reflector properties:
> specularspikeconstant(SS)=0, specularlobeconstant(SL)=0, and
> backscatterconstant(BS)=0, where lambertian (L) reflection is implicit
> (SS+SL+BS+L=1) to such a reflector configuration (namely: UNIFIED,
> dielectric_dielectric, groundfrontpainted)?
> 
> 3. Out of curiosity, if I selected polishedfrontpainted instead of
> groundfrontpainted (with UNIFIED and dielectric_dielectric), in addition
> to setting SS=SL=BS=0 (L=1), would the reflector converge to Lambertian?
> I'm wondering if the reflector constants would override the
> specularspike reflection mode designated by polishedfrontpainted.
> 
> Thanks!
> 
> Charles
> 
> Attachment:
> http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2017/09/25/09.11-13073-unifiedModel.png
> 

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