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Forum: Processes Involving Optical Photons
Re: Question Specular lobe and specular spike constant (Jenny Nilsson)
Date: 12 Nov, 2013
From: Gumplinger Peter <Gumplinger Peter>

Hello Jenny,

> I have obtained some results that seems somewhat odd.

Please, take a look at the code:

http://www-geant4.kek.jp/lxr/source/processes/optical/include/G4OpBoundaryProcess.hh#L274

There are only three of the four reflection probabilities that you can set:

SS, SL and BS

and the program assumes that the forth (L = Lambertian) adds up to 1.

> If SL = 0.7 and SS, BS = 0 then L = 0.3 and the results seems ok

OK, here you've set the three probabilities and L comes out to be 0.3 as you want.

> If SL = 0.7 and SS = 0.3, then the results look very much like SL = 1.
> If SL = 0.9 and SS = 0.1, then the results look very much like SL = 1.

Have you set BS = 0.?

Well, that shouldn't matter because the default is:

http://www-geant4.kek.jp/lxr/source/processes/optical/src/G4OpBoundaryProcess.cc#L113

e.g. L = 1 and all others are 0.

Are you restarting your program for every case?

Do you have access to your G4 source? If so, simple debug the ChooseReflection method and see why things aren't coming out as they should.

Peter

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