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None Cannot get reflections from Teflon 

Forum: Processes Involving Optical Photons
Date: 24 Oct, 2014
From: Alan James Bell <Alan James Bell>

I am new to G4. I am trying to make a model involving a scintillator crystal surrounded by a small air gap followed by a wrap of Teflon. I am having a problem with the optical photons generated in the crystal not reflecting back off the teflon. They refract as they enter the air gap. If I set the teflon absorption length large enough, I can see they refract when they enter the teflon. But I am seeing only a very few reflected photons. Most are being absorbed in the teflon. Here is my code. I would appreciate if someone could have a look and see what I am missing. Thank you in advance.

... 
G4double PhotonEnergy[32] =                                                   
   {    
     1.7559*eV, 1.7982*eV, ..... 3.6132*eV
   };  

    //************************AIR GAP*****************************
    G4double rIndexAir[32] =
    {
        1.0, 1.0,... 1.0
    };
   G4double AbsAir[32] =
   {
    1.0*km, 1.0*km, ... 1.0*km
   };
   // ***** Set Refractive index and absorption length to the air gap. ****
    G4MaterialPropertiesTable* Gap_mpt = new G4MaterialPropertiesTable();
    Gap_mpt->AddProperty("RINDEX", PhotonEnergy, rIndexAir, nEntries);
    Gap_mpt->AddProperty("ABSLENGTH", PhotonEnergy, AbsAir, nEntries);
    Gap_mat->SetMaterialPropertiesTable(Gap_mpt);

    //************************AIR GAP*****************************
  G4double rIndexWrap[32] =
  {
    1.35, 1.35, ... 1.35
  };

G4double wrapAbsorption[32] =
  {
    2*mm, 2*mm, ... 2*mm
  };

   // ***** Set Refractive index and absorption length to the wrap ****
  G4MaterialPropertiesTable* wrap_mpt = new G4MaterialPropertiesTable();
  wrap_mpt->AddProperty("RINDEX", PhotonEnergy, rIndexWrap, nEntries);
  wrap_mpt->AddProperty("ABSLENGTH", PhotonEnergy2, wrapAbsorption, nEntries);
  wrap_mat->SetMaterialPropertiesTable(wrap_mpt);

// ************* Create a Material PropertiesTable for the wrap surface ********

  G4MaterialPropertiesTable* wrapSurface_mpt = new G4MaterialPropertiesTable();

// create wrap optical property arrays with high reflectivity

  G4double wrapReflectivity[nEntries] = {
    0.99, ...0.99
   };  // 1.0 = fully reflective surface.

  G4double wrapEfficiency[nEntries] = {
     0.1,  0.1,  ... 0.1
  };

 G4double specularlobe[nEntries] = {
     0.0, ... 0.0,
  };

  G4double specularspike[nEntries] = {
     1.0, 1.0, ... 1.0     
  };

 G4double backscatter[nEntries] =
    {
    0.0, 0.0, ... 0.0
    };  

   G4double SigmaAlpha[nEntries] = {
      0.1, 0.1,  ...  0.1
    };

// ******* CREATE A WRAP OPTICAL SURFACE *********
  G4OpticalSurface* WrapSurface = new G4OpticalSurface("WrapSurface");
  WrapSurface-> SetType(dielectric_dielectric);
  WrapSurface->SetModel(unified);
  WrapSurface->SetFinish(polished);

 // ********Add and Set these optical properties the wrap surface *********
  wrapSurface_mpt->AddProperty("REFLECTIVITY", PhotonEnergy, wrapReflectivity, nEntries);
  wrapSurface_mpt->AddProperty("EFFICIENCY",PhotonEnergy, wrapEfficiency, nEntries);
  wrapSurface_mpt->AddProperty("SPECULARLOBECONSTANT",PhotonEnergy,specularlobe, nEntries);
  wrapSurface_mpt->AddProperty("SPECULARSPIKECONSTANT",PhotonEnergy, specularspike,nEntries);
  wrapSurface_mpt->AddProperty("BACKSCATTERCONSTANT",PhotonEnergy,backscatter,nEntries);
  wrapSurface_mpt->AddProperty("SIGMA_ALPHA",PhotonEnergy,SigmaAlpha,nEntries);

  WrapSurface->SetMaterialPropertiesTable(wrapSurface_mpt);

  //***** SET THE BORDER SURFACES *************************
 // Surface border of teflon and air gap

 new G4LogicalBorderSurface("WrapSurface",
                             GapPV,                         // Physics Volume of the air gap
                             wrapPV,                       // Physics Volume of the Wrap
                             WrapSurface );             // The surface 

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/10/24/07.44-56168-Result.png

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1 Feedback: Re: Cannot get reflections from Teflon   (Gumplinger Peter - 24 Oct, 2014)
(_ None: Re: Cannot get reflections from Teflon   (Alan James Bell - 25 Oct, 2014)
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