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Question Question on reflectivity definition  

Forum: Processes Involving Optical Photons
Date: 11 Oct, 2011
From: Wenliang Li <Wenliang Li>

Dear Experts

I am relatively new to geant.

In our Geant4 simulation we have a piece of quartz window in front of the PMT, and we are trying to compute the reflection for the quartz window. Here is what we do.

****************** // Create the PMT window surface here G4OpticalSurface *CerToWindow = new G4OpticalSurface("CerToWindow");

CerToWindow->SetType( dielectric_dielectric ); CerToWindow->SetModel( glisur ); CerToWindow->SetFinish( polished );

G4double pp[NUM] = { 1.2407*eV,  7.755*eV,   7.519*eV,   7.2982*eV, 6.893*eV, 
                     6.20355*eV, 5.51422*eV, 4.9628*eV,  4.1357*eV, 3.5449*eV, 
                     3.102*eV,   2.757*eV,   2.48142*eV, 2.2558*eV, 2.06785*eV, 
                     1.90878*eV, 1.7724*eV,  1.6542*eV,  1.5509*eV, 1.45966*eV };

G4double ref[NUM] = { 0.0,  0.0,   0.42,   0.58,   0.75, 
                      0.88, 0.89,  0.8957, 0.898,  0.8993,
                      0.9, 0.8997, 0.8996, 0.8995, 0.8995,
                    0.8995, 0.8992, 0.8992, 0.8990, 0.8990 };

G4double rindex[NUM] = { 1.4584, 1.4585, 1.4585, 1.4585, 1.4585, 
                         1.4585, 1.4585, 1.4585, 1.4585, 1.4585, 
                         1.4585, 1.4585, 1.4585, 1.4585, 1.4585, 
                         1.4585, 1.4585, 1.4585, 1.4585, 1.4585};

G4MaterialPropertiesTable *CerToWindowTb = new G4MaterialPropertiesTable(); CerToWindowTb->AddProperty("RINDEX" , pp , rindex , NUM ); CerToWindowTb->AddProperty("REFLECTIVITY" , pp , eff , NUM );

*********

Simulation results:

   If I set ref as 

    G4double ref[NUM] = { 1, 1, 1, 1, 1, 
                          1, 1, 1, 1, 1,
		          1, 1, 1, 1, 1,
		          1, 1, 1, 1, 1 };
   I see all photon passing through the quartz window.

   If I set ref as:
    G4double ref[NUM] = { 0, 0, 0, 0, 0, 
                          0, 0, 0, 0, 0,
		          0, 0, 0, 0, 0,
		          0, 0, 0, 0, 0 };    

   I see all photon reflected off the quartz window.

Question is :

If I set ref[NUM] = {0.3,..}, should it mean 30% of the photon is reflected on the surface?

Therefore ref[0,..] should give me 0% reflection? But why do I have 100% reflection?

I wonder one can help me to clarify the definition of the REFLECTIVITY.

Many thanks in advance&#12290;

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1 Feedback: Re: Question on reflectivity definition   (Gumplinger Peter - 11 Oct, 2011)
(_ Agree: Re: Question on reflectivity definition   (Wenliang Li - 17 Oct, 2011)
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