Re: Optica Photon Transport in Scintillators

Hi Francesco, for what it's worth, a number of years ago we used usrmed
for this type of application (IceTop EAS detector response). I recall an
intermediate boundary was placed very near the reflecting surface and
the outbound (after the reflection) photons crossing the intermediate
boundary were scattered within usrmed using a 2d-Gaussian (external code
to FLUKA) centered about the original outbound directional cosines. The
Gaussian width was used to control the roughness level.. In any event,
this allowed the option to explore different reflectivity functions
including spectral dependence and absorption.. Not sure the
intermediate boundary is still necessary with the latest version.. John

-- 
 >>John Clem
 >>Research Associate Professor
 >>Bartol Research Institute
 >>Department of Physics and Astronomy
 >>University of Delaware
 >>Newark, DE 19716
 >>off 302-831-4354
 >>cell 302-388-1218
Francesco Cerutti wrote:
> Dear Ali,
> 
>> The linking and then making the modified version occurs successfully, but
>> there is no option to "call" this routine in the input file.
> 
> provided that optical photons are generated thorugh OPT-PROD in the 
> input file and they cross a boundary, frghns is called
> 
>> However the net effect of perturbation in the "normal vector of the surface"
>> and perturbation in the "outgoing ray" from the reflection would be the
>> same.
>> What I want is to introduce a Lambertian reflection law.
> 
> as I wrote, frghns is just expected to give back a roughness coefficient 
> in the FRGHNS variable, any other action on its input variables (like 
> direction cosines) is lost. In order to do what you aim at, you can go 
> through usrmed (recently discussed for other purposes): there you can 
> reset the optical photon direction cosines on your boundary surface as you 
> wish, and reflect it back (without forgetting in this case to put 
> NEWREG=MREG).
> 
> Hope this helps
> 
> Francesco
> 
>