Wavelength Shifting Materials

Geometry, Fields and Transportation
1

Hello G4 users,

I am a 1st year PhD student working on the SWGO detector prototypes with WLS.

I am trying to replicate HAWC’s tank with PMT’s to better my understanding. And i’m starting off by trying to create 1 PMT with WLS material around it, all submerged in water.

I am very new to Geant4…
ive started off by trying to create a sphere-like shape to represent the PMT, using the G4Sphere() class reference, with a cylinder underneath. the cylinder is ‘inside’ the WLS ‘slab’.

However i am not sure how to get the WLS aspect to occur. i’ve tried following the example but it is too complicated for me.

This is how im implementing the materials…

G4NistManager *nist = G4NistManager::Instance();  //the geant4 nist material database

	Polyethylene = new G4Material("Polyethylene", 1.200*g/cm3, 2); //defining material object
	Polyethylene->AddElement(nist->FindOrBuildElement("H"), 4); //adding the hydrogen element to object
	Polyethylene->AddElement(nist->FindOrBuildElement("C"), 2); //adding the Carbon element to object

	G4double energy[2] = {1.239841939*eV/0.9, 1.239841939*eV/0.2}; //momentum of photons usng conversion factor *eV / wavlength of red light and blue light

	G4double rindexPolyethylene[2] = {1.49, 1.49}; //refractive index
	G4double rindexWorld[2] = {1.333, 1.333}; //refractive index of the world volume (air)
	G4double rindexAir[2] = {1.0, 1.0};

    G4double WLS_energy[4] = {2.00*eV,2.87*eV,2.90*eV,3.47*eV};
    G4double WLS_rindex[4]={ 1.60, 1.60, 1.60, 1.60};
    G4double WLS_abslength[4]={9.00*m, 9.00*m, 0.1*mm, 0.1*mm};
    G4double WLS_emission[4]={1.0, 1.0, 0.0, 0.0};

	G4MaterialPropertiesTable *mptWLS = new G4MaterialPropertiesTable();
	mptWLS->AddProperty("RINDEX", WLS_energy, WLS_rindex, 4); //adding property to this object
	mptWLS->AddProperty("WLSABSLENGTH", WLS_energy, WLS_abslength, 4);
    mptWLS->AddProperty("WLSCOMPONENT", WLS_energy, WLS_emission, 4);
    mptWLS->AddConstProperty("WLSTIMECONSTANT", 0.5*ns);

	Polyethylene->SetMaterialPropertiesTable(mptWLS);

What else do i need to do to make the WLS work?

2

You have to include optical physics in your physics list. Go through the WLS example and see how optical physics is specifically added in the physics list.

I believe if you do that and include your materials properties correctly, it should work

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