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Question Re: Optical Surfaces and Sigma_Alpha 

Forum: Processes Involving Optical Photons
Re: Question Optical Surfaces and Sigma_Alpha (Wolfgang Lukas)
Re: Feedback Re: Optical Surfaces and Sigma_Alpha (Gumplinger Peter)
Date: 01 Jul, 2009
From: Wolfgang Lukas <Wolfgang Lukas>

Dear Peter,

thank you very much for your prompt and detailed answer!

> Careful, the prob_ss etc. parameters correspond to the interface between
> the scincillator and the (implied) gap of the 'backpainted' option, not
> to the reflector behind the gap. This reflector is in the present
> implementation always assumed to be a Lambertian reflector. If this is
> not what you want, then I am afraid, you'll need to explicitly implement
> the gap in geometry and the dielectric_metal surface with the reflector
> as "polished" (in addition to the dielectric_dielectic interace between
> scint and gap also "polished").

Thank you! - I really want to understand the implementation of the whole optical boundary process correctly, so may I ask some further questions:

a) is there a practical difference between "polishedbackpainted" and "groundbackpainted" with "prob_ss = 1.0"?

b) ... and "groundbackpainted" with "prob_sl = 1.0" + "sigma_alpha = 0.0"? (I just found out: this should be treated exactly as the case above)

c) is there a practical difference between "dielectric_metal" + "polished" and "polishedfrontpainted"?

d) I am biasing my scintillation yield down from 9200 to 92 photons/MeV and weight my results to save CPU time. Is that too much? It looks good to me, though.

> Use 100% 'specular lobe' and sigma_alpha of the order of 10deg for
> diffuse and order 1-2deg for Teflon (but those are not very educated
> suggestions!).

Thank you very much, these suggestions shall be educated enough for my purpose! :-)

However, that will only make sense if I define a physical air gap and set the "specular lobe" & "sigma_alpha" for the back surface, right? Because with a "painted" surface it would affect the front interface (scintillator-gap) ...

I also realised that last December similar questions were raised in this forum by Estela Suarez. I will do some tests and hope to solve some of them. Especially the comparisons between models with/without the air gap (CPU time and detection efficiency) shall be interesting.

Many thanks, Wolfgang

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1 Feedback: Re: Optical Surfaces and Sigma_Alpha   (Benton Pahlka - 01 Jul, 2009)
1 Feedback: Re: Optical Surfaces and Sigma_Alpha   (Gumplinger Peter - 02 Jul, 2009)
(_ Feedback: Re: Optical Surfaces and Sigma_Alpha   (Benton Pahlka - 03 Jul, 2009)
2 Feedback: Re: Optical Surfaces and Sigma_Alpha   (Gumplinger Peter - 02 Jul, 2009)
1 Idea: Re: Optical Surfaces and Sigma_Alpha   (Wolfgang Lukas - 22 Sep, 2009)
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