[Gate-users] Wavelength-shifting (WLS) fibres coupled to scintillators

[Vesna Cuplov]

Hello Filipe,

 I want to simulate scintillation photons produced by 511 keV gammas and
> their optical path through a LYSO scintillator with mirror polished ends
> and reflective side surfaces. One end of the crystal is coupled to a
> wavelength-shifting fibre (double-cladded BCF-91A fibre), such that crystal
> and fibre make a 90 degree angle.
>
> As I am not experienced with Gate (using vGate 2.1), I have many doubts
> regarding the proper physics and geometry necessary for the simulation,
> namely of the optical photons path, optical boundaries and fibre geometry.
> Is there anyone who has simulated similar experiments with this kind of
> fibres, for example in the AxPET project, who can help me out?
>
> I've already recompiled Gate with optical ON.
>
>
>
> In order to define the reflective surfaces of the crystal, do I need to
> first define the volumes with the reflective material or is it possible to
> define the surfaces only with the crystal volume?
>

If your crystal is the LYSO material, you just need to define your crystal
volume with the LYSO material properties in Materials.xml. For the polished
ends and reflective surfaces, you define the surfaces with the finish,
reflectivity, .... parameters in Surface.xml.

  Is it necessary to define separate volumes with the different materials
> of the fibre (core, first clad and 2nd clad)? In this case, it is a
> square fibre, so what would be the best way to do it?
>

For the WLS fiber, you can describe it as one volume or more detailed
volumes. I think one volume would be enough as long as you have its
properties which are the absorption/emission wls spectra, mixture (in case
you use one volume that is a mix of sub components) refractive index, ...

Are these physics processes enough: Scintillation, PhotoElectric, Compton,
> GammaConversion, OpticalAbsorption, OpticalWLS, OpticalBoundary ?
>

You might also need OpticalRayleigh and OpticalMie which are the physics
processes related to the optical photon scattering. In that case you would
need the Mie and/or Rayleigh scattering lenghts, material anisotropy for
Mie scattering. This depends on your crystal and fiber materials.

I hope this helps,
vesna
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