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Question Problems with optical surface properties 

Forum: Geometry
Date: 22 Dec, 2008
From: YUE Ke <YUE Ke>

Hello,

I am simulating a CsI(Tl) scintilltor coupled to a photomultiplier (PMT) through a 0.3 mm thick silicone optical grease. I have three questions about my detector construction:

1. What is the unit of the parameter sigma_alpha, degree of radian?

2. I define the optical grease as a surface between crystal and PMT (glass) like:

//-------------- the surface between CsI and pmt

 G4double SiliconeGrease_RIND[Num] ={1.46, 1.46, 1.46};
 G4double Reflectivity[Num] = {0., 0., 0.};
 G4MaterialPropertiesTable* pmtSuface_mt = new G4MaterialPropertiesTable();
 pmtSuface_mt->AddProperty("RINDEX", Sur2_PP, SiliconeGrease_RIND, Num);
 pmtSuface_mt->AddProperty("REFLECTIVITY", Sur2_PP, Reflectivity, Num);

 G4OpticalSurface* OppmtSurface = new G4OpticalSurface("pmtSurface");
 OppmtSurface->SetMaterialPropertiesTable(pmtSuface_mt);
 OppmtSurface->SetType(dielectric_dielectric);
 OppmtSurface->SetFinish(polished);
 OppmtSurface->SetModel(unified);
 G4LogicalBorderSurface* pmt_surf;
 pmt_surf = new G4LogicalBorderSurface ("pmtSurface",CsI_phys,pmt_phys,OppmtSurface);

I’m not very sure if the “Reflectivity” set to 0 (G4double Reflectivity[Num] = {0., 0., 0.}) is correct. I think that means the optical photons are absorbed at the far side of the thin layer of grease. But I want optical photons pass through this surface without absorption.

3. I define photocathode (Al) like:

//---------photocathode

phcath_log  = new G4LogicalVolume(phcath_sol, phcath_Al, "phcath_log");
phcath_phys = new G4PVPlacement(0, G4ThreeVector(0., 0., phcathVPosition),
                        phcath_log, "phcath_phys", pmt_log, false, 0);

G4double photocath_EFF[Num]={1.0, 1.0, 1.0}; 
G4double photocath_REFL[Num]={0., 0., 0.};
G4MaterialPropertiesTable* phcath_mt = new G4MaterialPropertiesTable();
        phcath_mt->AddProperty("EFFICIENCY",CsI_PP,photocath_EFF,Num);
        phcath_mt->AddProperty("REFLECTIVITY",CsI_PP,photocath_REFL,Num);

G4OpticalSurface*  phcathSurface = new G4OpticalSurface("phcathSurface",
           unified, polished, dielectric_dielectric);
phcathSurface->SetMaterialPropertiesTable(phcath_mt);
G4LogicalBorderSurface* phcath_surf;
phcath_surf = new G4LogicalBorderSurface ("phcath_surf",pmt_phys,phcath_phys,phcathSurface);

but when I changed the value of photocath_EFF, the number of detected photons was not changed, why? And when I changed the Surface type to dielectric_metal, the number of detected photons is always returning 0. Can somebody tell me why the optical photons can not be detected by this type.

Thank you very much.

YUE Ke

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1 None: Re: Problems with optical surface properties   (YUE Ke - 04 Jan, 2009)
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