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Question Semi-reflective surfaces 

Forum: Processes Involving Optical Photons
Date: 27 Mar, 2018
From: Andrea Rappoldi <Andrea Rappoldi>

        Hi,

        I want to simulate the scintillation light produced inside a
  large LAr TPC, which is substantially composed of two identical volumes
  (filled with liquid argon) separated by a thin perforated metallic
  wall (the "cathode"), so that (part of) the scintillation light
  produced in one of the volume can also propagate in the other one
  (see the attached picture) and detected by an array of PMTs.

        From an optical point of view, the metallic wall can therefore
  be considered a semi-reflecting surface, with a "transparency" (the
  ratio between the total area of all the "holes" and the area of the
  wall) of about 50%.

        Regarding the scintillation light detection, it is not
  necessary to simulate the behaviour of "each" hole (with its
  position and size), but only a "statistical" response: a given
  fraction of the photons can propagate from a volume to the other
  one, and the remaining ones are reflected.

        So, my question is: how to define such a "semi-reflecting"
  optical surface (provided it is possible, of course) ?

        I found on Geant4 User documents that in the case of a
  dielectric_metal surface, a photon can be reflected or absorbed
  (in the sense that if it is not reflected, it is absorbed).

        The problem is further complicated by the fact that it is not
  possible to access or modify the source code of the simulation program,
  that has to be used as a "black box".
        The only way to define the parameters of the simulation is to
  provide a full gdml file with all the needed definitions (materials,
  geometry, etc.), that the program uses as input file.

        Thanks in advance,

                                        Andrea

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2018/03/27/13.28-31041-catodo2.jpg

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1 None: Re: Semi-reflective surfaces   (Daren Sawkey - 05 Apr, 2018)
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