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Question Questions on how use the optical photon 

Forum: Processes Involving Optical Photons
Date: 23 Jan, 2014
From: Filippo Ambroglini <Filippo Ambroglini>

Dear all, I would like to start use the optical photon simulation on my calorimeter simulation then I have some question to address.

First of all I have start to look at the documentation on the Application guide on the example and also in the forum.

The first question regard the material definition.

Looking at the code on the optical example I have found these lines:
  const G4int polynum = 4;
  G4double polyEnergy[] = {2.00*eV,2.87*eV,2.90*eV,3.47*eV}; 
  G4double rIndexPolystyrene[wlsnum]={ 1.5, 1.5, 1.5, 1.5};
  G4double absorption[wlsnum]={2.*cm, 2.*cm, 2.*cm, 2.*cm};
  G4double scintilFast[wlsnum]={0.00, 0.00, 1.00, 1.00};
  fMPTPStyrene = new G4MaterialPropertiesTable();
  fMPTPStyrene->AddProperty("RINDEX",ployEnergy,rIndexPolystyrene,polynum);
  fMPTPStyrene->AddProperty("ABSLENGTH",polyEnergy,absorption,polynum);
  fMPTPStyrene->AddProperty("FASTCOMPONENT",polyEnergy, scintilFast,polynum);
  fMPTPStyrene->AddConstProperty("SCINTILLATIONYIELD",10./keV);
  fMPTPStyrene->AddConstProperty("RESOLUTIONSCALE",1.0);
  fMPTPStyrene->AddConstProperty("FASTTIMECONSTANT", 10.*ns);

I this forum tread http://hypernews.slac.stanford.edu/HyperNews/geant4/get/opticalphotons/517.html I have found a list of all possible parameter that can be used but in any part of the Application guide (the pdf version) I have found an explanation of FASTCOMPONENT and SLOWCOMPONENT.

Looking at the example in the application guide I have made the hypothesis that with this parameter we are going to set the Q.E. of the material as a function of the various energy is that correct?

Anyhow in the next documentation version it will be possible to have a table with all the possible parameter and a brief description this will make the life of a new user easier ;-)

Then I would like to have if is possible some hint on the geometry definition.

My calorimeter is made by several layer of scintillator in the between of the layer there will be carbon finer support structure and each layer will be packed with "white teflon" except a couple of small area in which we will put the APD.

1) I have to define something for the carbon finer support structure in order to avoid the waste of time on propagating optical gamma on these structure or I have to take care at the stepping action level like it has been done on the LXeSteppingAction.cc?

2) My calo layer will be 10 cm x 4 cm X 1 cm (X,Y,Z) the APD with active 
    area of 1 cm x 1 cm will be placed at the center of the two 4 cm x 1 cm 
    sides. There is way to set for the optical surface of the scintillator this configuration 
    OpSurface -> SetType(dielectric_dielectric);  
    OpSurface -> SetModel(unified);
    OpSurface -> SetFinish(polishedbackpainted);
    except for the area where I put the APD detector in which I would like to have 
    a simple polished surface that will be contiguous with the APD? 

Thanks in advances for the help.

Best regards, Filippo

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