Hi, I’m new on Geant4 and I’m looking at the optical examples, specifically invoice2. I’m not understanding the physical constants in the macro file and I can’t find any explanation on the internet.
Can someone please explain me what’s the meaning of this values and why is there so many for every constant?
/opnovice2/boxProperty RINDEX 0.000002 1.3 0.000008 1.4
/opnovice2/boxProperty ABSLENGTH 0.000002 1000000 0.000005 2000000 0.000008 3000000
/opnovice2/surfaceProperty SPECULARLOBECONSTANT 0.000002 .1 0.000008 .1
/opnovice2/surfaceProperty SPECULARSPIKECONSTANT 0.000002 .01 0.000008 .01
/opnovice2/surfaceProperty BACKSCATTERCONSTANT 0.000002 .05 0.000008 .05
/opnovice2/surfaceProperty REFLECTIVITY 0.000002 .99 0.000008 .99
Hi @Miguel_Ralha. Those values are the optical properties of the box and surface in that example; they describe how optical photons interact with the material. For example, RINDEX is the refractive index of that material. There is some description of these in the Application Developers Guide.
There are so many because these are the values for different energies - the energy is set first, then the value of that property for that energy. For instance, at 0.000002 MeV, the refractive index is 1.3; at 0.000008 MeV, it is 1.4. This is described in the README file for the OpNovice2 example.
This is different to other examples, where the optical properties are set in DetectorConstruction.cc. In that case, the photon energies are defined separately, and each optical property is defined at those energies.