Hi, A colleague how works with DETECT2000 gave me this answer: """""""""""""""""""""""""""" METAL simulates a dielectric/metal interface : when a scintillation photon arrives on this interface, it is whether reflected following Snell Descartes laws with a probability of Rc or absorbed. Thus it simulates a perfect (if Rc =1) reflector PAINT simulates a lambertian reflexion = a perfect diffusor Using METAL or PAINT, the optical index of the second medium is ignored. This is not the case with POLISH or GROUND optical coatings where Fresnel factor is taken into account. Rc is then the probability for the optical photon to return in medium one in a lambertian way knowing it has already been transmitted in medium two. """""""""""""""""""""""""""" Cheers, Simon <div class="gmail_quote">On Fri, Apr 10, 2009 at 10:28 AM, Рмос <<a href="mailto:xchengbio2006@gmail.com">xchengbio2006@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Dear Gaters:       I guess someone here  is also very familiar with DETECT2000.There is a question:       When the surface of scintillation crystal is polished/matte,and teflon covered, people choose"POLISH 0.98RC"/"GROUND 0.98RC" for simulation .Then what about "METAL" and "PAINT".It seems they were seldom mentioned.       If someone can introduce something about that or recommend some literature, I'll appreciate for that very much. _______________________________________________ Gate-users mailing list <a href="mailto:Gate-users@lists.healthgrid.org">Gate-users@lists.healthgrid.org</a> <a href="http://lists.healthgrid.org/mailman/listinfo/gate-users" target="_blank">http://lists.healthgrid.org/mailman/listinfo/gate-users</a> </blockquote></div>