|Message: questions about the parameter sigma alpha and ground-, polishedbackpainted||Not Logged In (login)|
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I have still problems in understanding some definitions, which describe the reflection and tranmission of photons on the interface. If I have understood it right then the value sigmaalpha is a parameter of the surface roughness. 1 indicates maximal roughness and 0 stands for a polished surface. First I thought, if the model is unified, the type is dielectric-dielectric and the finish ground, that if sigmaalpha is 0 than there should be only spike reflection, like on a polished interface. But this is not the case, because sigmaalpha omly defines the facet normal which replaces the global normal, if the finish is ground. It does not have any influence on the kind of reflection: lobe, spike, backscatter or lambertian. This is strange because s.o. expects that the relation between these different reflections should vary with the degree of roughness. If the model is unified, the type is dielectric-dielectric and the finish is ground only lambertian reflection should occure. What is the difference between the reflection with sigmaalpha=0 and sgmaalpha=1? What is the physical explanation? Is the explanation the following? - sigmaalpha=0 means that there are no macro facets but there exsists surface roughness, which generates lambertian reflection? - change of sigmaalpha from 0 to 1 means that macro facets are formed with an increasing steepness from 0 to 1. Am I right?
I have also other questions: Is the reflection of the wrapping at the finish groundbackpainted always lambartian or can it be changed to spike reflection? Is this the same with polishedbackpainted? If not, is there another possibility to have ground surface of the scintillator and a polished surface for the wrapping?
Thanks for your help.
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