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Question Bug in Wavelength Shifting (G4OpWLS) process ? 

Keywords: Wavelength Shifting WLSTIMECONSTANT
Forum: Processes Involving Optical Photons
Date: 02 May, 2006
From: Apostolos Tsirigotis <Apostolos Tsirigotis>

I am developing a detector description for a scintillator detector with optical fibers to collect the optical photons produced. The Fibers are Wavelength Shifters, so I include the G4OpWLS optical process in the simulation. As described in the Application Developers Manual, the Constant Material Property "WLSTIMECONSTANT accounts for any time delay which may occur between absorption and re-emission of the photon". I suppose that this time constant is the time constant for the de-excitation of a fiber molecule after the absorption of the photon. If so, the time delay between absorption and re-emission of the photon should be exponentially distributed. But in fact, as implemented in the code (G4OpWLS::PostStepDoIt), this delay is a delta function :

---------------------------------------------

G4VParticleChange* G4OpWLS::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep)

{

......

WLSTime = aMaterialPropertiesTable->GetConstProperty("WLSTIMECONSTANT");

.......

G4double aSecondaryTime = (pPostStepPoint->GetGlobalTime()) + WLSTime;

.......

G4Track* aSecondaryTrack = new G4Track(aWLSPhoton,aSecondaryTime,aSecondaryPosition);

.......

}

-----------------------------------------------

Is there a physics reason that this time delay is a delta function or is it a bug?

Thank you.

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1 Feedback: Re: Bug in Wavelength Shifting (G4OpWLS) process ?   (Peter Gumplinger - 02 May, 2006)
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