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Keywords: Cerenkov Scintillation OpticalPhoton
Forum: Processes Involving Optical Photons
Date: 25 Jul, 2002
From: Gumplinger Peter <Gumplinger Peter>

Hi Jacek,

You are talking about a material in which you want to simulate both Cerenkov radiation and scintillation. I assume that you know the index of refraction of this material at all relevant wavelength; i.e. from 2eV to 10eV, and that the material is dispersive.

You have to specify n for all optical wavelengths you want to propagate. The Cerenkov process will now generate photons between p_min and p_max were the lower limitation for the momentum follows from:

n(p_min) = 1/beta

and p_max is 10eV.

If you know that your optical detection device is not sensitive to wavelength >4eV, then I suggest adding a UserSteppingAction (or a UserStackingAction) which immediately discards an optical photon above 4eV but below 10eV.

The arrays you give in the calls:

myMat->AddProperty("RINDEX", PPCKOV, RINDEX, NUM1);

and

myMat->AddProperty("SCINTILLATION", PP, SCINTILLATION, NUM2);

, i.e. PPCKOV and PP, can be different in value and size, but NUM has to be at least 2! You can make your scintillation line as narrow as you like, but the width cannot be zero.

G4double SCINTILLATION = 1.0; // does this mean 100 percent ???

'1.0' is a relative strength. The absolute value can be anything. Important is that the values at different momenta are relative to each other. So, for example, the same value (a choice is 1.0) over the whole spectrum simply means that the emission probability of a photon in that range is flat.

How can the Geant4 know what is the RINDEX and ABSORPTION at 10eV ?

Well, it doesn't unless you provide it.

If you are not interested in certain wavelengths of Cherenkov photons, for your own reasons, then you can discard them in the aforementioned UserActions at little performance penalty.

Regards, Peter

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1 None: Re: Cerenkov + Scintillation (+ OpticalPhoton)   (Jacek M. Holeczek - 26 Jul, 2002)
(_ Feedback: Re: Cerenkov + Scintillation (+ OpticalPhoton)   (Peter Gumplinger - 26 Jul, 2002)
(_ None: How to disnable Cerenkov Effect in a specified material/volume   (Dvorak - 21 Jun, 2003)
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