Wavelength Shifting Materials

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);


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

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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