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Question surface with 98% reflection and 2% transmission of optical photons 

Keywords: optical photons reflectivity transmission surfaces
Forum: Geometry
Date: 25 Mar, 2008
From: Matthew <mablackston@gmail.com>

Hello,

I'd like to model a surface that reflects optical photons 98%
of the time and transmits them 2% of the time.  I've tried defining
LogicalBorderSurfaces and LogicalSkinSurfaces and adjusting the 
the reflectivity parameter, but this parameter seems to have no effect
how much is reflected or transmitted.  It seems that the only
thing geant cares about is the indexes of the two surfaces.  The 
only time the reflectivity setting has an effect, it absorbs rather 
than transmits the photons.  Is it possible to set the reflectivity 
of the surface as I'm attempting?

Here's an example of some of the code I've tried:

  OptSurfReflector = new G4OpticalSurface("ReflectorSurface");

  new G4LogicalBorderSurface("slitBorder", lg_physV, slit_physV, OptSurfReflector);
  
  OptSurfReflector->SetType(dielectric_dielectric);
  OptSurfReflector->SetFinish(ground);
  OptSurfReflector->SetModel(unified);
  OptSurfReflector->SetSigmaAlpha(0.001);

  const G4int NUM=2;

  G4double en[NUM] = {2.038*eV,4.144*eV};
  G4double specularlobe[NUM] = {1.0,1.0};
  G4double specularspike[NUM] = {0.0,0.0};
  G4double backscatter[NUM] = {0.0,0.0};
  G4double rindex[NUM] = {1.35,1.4};
  G4double efficiency[NUM] = {1.0,1.0};
  G4double reflectivity[NUM] = {0.9,0.9};

  G4MaterialPropertiesTable *MPTReflect = new G4MaterialPropertiesTable();
  MPTReflect->AddProperty("RINDEX",en,rindex,NUM);
  MPTReflect->AddProperty("SPECULARLOBECONSTANT",en,specularlobe,NUM);
  MPTReflect->AddProperty("SPECULARSPIKECONSTANT",en,specularspike,NUM);        
  MPTReflect->AddProperty("BACKSCATTERCONSTANT",en,backscatter,NUM);
  MPTReflect->AddProperty("REFLECTIVITY",en,reflectivity,NUM);
  MPTReflect->AddProperty("EFFICIENCY",en,efficiency,NUM);

  OptSurfReflector->SetMaterialPropertiesTable(MPTReflect);

Thanks for your help,
Matthew

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1 Feedback: Re: surface with 98% reflection and 2% transmission of optical photons   (Peter Gumplinger - 27 Mar, 2008)
(_ None: Re: surface with 98% reflection and 2% transmission of optical photons   (Matthew - 08 Apr, 2008)
(_ Idea: Re: surface with 98% reflection and 2% transmission of optical photons   (Peter Gumplinger - 10 Apr, 2008)
(_ Feedback: Re: surface with 98% reflection and 2% transmission of optical photons   (Matthew - 14 Apr, 2008)
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