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Forum: Processes Involving Optical Photons
Re: Question queries regarding border surfaces (Athreya Shankar)
Re: None Re: queries regarding border surfaces (Davinder Siwal)
Re: Question Re: queries regarding border surfaces (Athreya Shankar)
Re: Feedback Re: queries regarding border surfaces (Gumplinger Peter)
Re: None Re: queries regarding border surfaces (Athreya Shankar)
Date: 06 Dec, 2011
From: Gumplinger Peter <Gumplinger Peter>

Hi Athreya,

> But I would like to clarify one further point- generally WLS fibers are
> characterised by several parameters like trapping efficiency, reemission
> probability, etc. I would like to know how to set these values- or are
> they directly reflected in the refractive indices and absorption length
> data?

The parameter 'trapping efficiency' is not available as such. You have the following choices, assuming you specify your fiber and its cladding as distinct physical volumes:

(1) "RINDEX" - index of refraction for the fiber and each concentric cladding shell as well as the scintillating bar.

(2) in principle, you can define each border with its own G4OpticalSurface, that between fiber and clad_1 (clad_1 and clad_2, in case) and clad_1(2) and the scintillating bar.

(3) you can define an absorption length "ABSLENGTH" for the fiber; this is an absorption without the emission of a subsequent wavelength shifted photon.

(4) you can specify a WLS absorption length "WLSABSLENGTH" for the fiber; this absorption leads to a reemission of a photon in the WLS photon spectrum.

(5) you specify the WLS emission spectrum "WLSCOMPONENT"

(6) and you may specify the emission time constant "WLSTIMECONSTANT"

Please, see the example in examples/extended/optical/wls for details. In fact, this example deals with the very problem of WLS fibers in scintillation bars.

If you don't know some of these data for your fiber, you'll have to experiment until you get the desired 'trapping efficiency' and 'reemission probability'.

Hope this helps, Peter

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