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Keywords: Cerenkov Scintillation OpticalPhoton
Forum: Processes Involving Optical Photons
Date: 26 Jul, 2002
From: Gumplinger Peter <Gumplinger Peter>

AddProperty (in G4MaterialPropertiesTable.cc#129) instantiates a G4MaterialPropertyVector(PhotonMomenta,PropertyValues,NumEntries). The 'vector' has to have at least 2 entries. The implementation is more general than the case whereby a scintillator has zero line width emission lines. You can specify a whole continuous spectrum over a range of photon momenta. For practical purpuses this should not be a problem for you as you can make the emission line as narrow as you like.

NumEntries is not the number of emission lines, but rather the number of spectral points you specify. No line width is ever infinitesimal narrow anyway. So, for example, if you have narrow emission lines (with equal intensity, one at 10eV and another at 11eV, you could specify the following array pair:

( 9.999eV,0.0) (10 eV,1.0) (10.001eV,0.0) (10.999eV,0.0) (11 eV,1.0) (11.001eV,0.0)

i.e. you approximate your emission spectrum with narrow saw tooth lines. G4 does a numerical integration over this array and then samples the photon momentum in the usual way [see G4Scintillation::BuildThePhysicsTable() and the "Determine photon momentum" part of G4Scintillation:PostStepDoIt]

SetResolutionScale method has nothing to do with the optical photon momentum spectrum. It rather specifies the intensity smearing for a given energy loss in the scintillator; i.e. the number of photons generated.

G4int NumPhotons = (G4int) MeanNumPhotons +
      int( ResolutionScale * G4RandGauss::shoot(0.0,sqrt(MeanNumPhotons)));

It is the 'extra' smearing which multiplies the statistical one in NumPhotons.

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1 None: How to disnable Cerenkov Effect in a specified material/volume   (Dvorak - 21 Jun, 2003)
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