|Message: Re: Optical photons and Shashlik calorimeter||Not Logged In (login)|
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> thank you very much for your help. I didn't think about the possibility > to create SkinSurfaces on the volumes around the scintillator tiles > because I feared that the surface has an order with respect to the > crossed volumes.
Yes, that's true for G4LogicalBorderSurface. Here, the surface used is the one that corresponsed to the ordered pair of G4VPhysicalVolumes.
> Instead you are telling me that a "ground" SkinSurface > (for example) assigned to the fiber hole logical volume is seen in the > same way by an optical photon crossing from the scintillator tile to the > hole and vice-versa?
Yes, correct! But that very same surface is also seen when a photon leaves the cladding of the fiber (and, thinking about it, this is probably not what you want). A skin surface is always "seen" - either direction - unless some other surface has higher presidence.
> Regarding the piece of code you have posted me, I understood the logic > behind it, but I am not sure where to put it: as far as I understood is > a check performed every step, so I have to put it in my SteppingAction > class?
NO! You (the user) don't have to 'put it' anywhere. This code is in G4OpBoundaryProcess::PostStepDoIt where to program decides which surface to use.
> I have another (hopefully) last question: at the moment I am using the > following values for the ground surface: sigma_alpha=0.2, > specular_lobe=0.3, backscatter=0.3, specular_spike=0.1 (lambertian > should be calculated by difference and thus be equal to 0.3). I am > wondering if I have to add also a "reflectivity" parameter to the ground > surface. In principle I would say no (the surface is not painted) but I > want to be sure.
No, you don't.