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Question Re: optical photon self-absorption in scintillator 

Forum: Processes Involving Optical Photons
Re: Question optical photon self-absorption in scintillator (Benton Pahlka)
Date: 16 May, 2011
From: Eric <Eric>

Hello-

I am trying to simulate a situation where the a scintillator can have a WLS, but only for a portion of the scintillator's emission spectrum, and when it is re-emitted it will likely be out of the absorption range, and therefore only absorbed once.

What I'm experiencing is that since my initial emission, WLS absorption, and WLS emission spectra don't all match up, Geant will take a photon that is created out of the WLS absorption range, and just use the lowest value for that spectrum, absorbing it again.

For example:

Intial Emission Spectrum: 2.5 - 4.5 WLS Absorption Spectrum: 3.5 - 4.5 WLS Emission Spectrum: 2.5 - 3.5

In this situation, I would like any photon initially created with an energy of 3.5 - 4.5 to be absorbed and re-emitted with a new energy of 2.5 - 3.5, never to be reabsorbed again, but Geant seems to over ride this and treat it as a 3.5 eV photon anyway, despite being out of range.

Is there a mechanism is Geant to do this?

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Feedback Re: optical photon self-absorption in scintillator  by Benton Pahlka <Benton Pahlka>,   16 May, 2011
Re: Question Re: optical photon self-absorption in scintillator (Eric)
Hi,

You should be able to do this if you define your WLS absorption spectrum in the 2.5 - 3.5 eV range to be very high, say 100 meters or more.

In general, I try to have all my spectra span the same wavelength set, even if some values are zero or very large.

Benton

On Mon, 16 May 2011 20:10:21 GMT, Eric wrote:

> Hello-
> 
> I am trying to simulate a situation where the a scintillator can have a
> WLS, but only for a portion of the scintillator's emission spectrum, and
> when it is re-emitted it will likely be out of the absorption range, and
> therefore only absorbed once.
> 
> What I'm experiencing is that since my initial emission, WLS absorption,
> and WLS emission spectra don't all match up, Geant will take a photon
> that is created out of the WLS absorption range, and just use the lowest
> value for that spectrum, absorbing it again.
> 
> For example:
> 
> Intial Emission Spectrum: 2.5 - 4.5 WLS Absorption Spectrum: 3.5 - 4.5
> WLS Emission Spectrum: 2.5 - 3.5
> 
> In this situation, I would like any photon initially created with an
> energy of 3.5 - 4.5 to be absorbed and re-emitted with a new energy of
> 2.5 - 3.5, never to be reabsorbed again, but Geant seems to over ride
> this and treat it as a 3.5 eV photon anyway, despite being out of range.
> 
> Is there a mechanism is Geant to do this?
> 

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