Optical Surfaces and Sigma

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Hello everyone,

I am simulating a scintillation detector setup with a 662 keV gamma source, a plastic scintillator, a photomultiplier tube and a coupling piece. My aim is to find suitable modifications for the setup (geometry, materials) in order to increase the number of optical photons hitting the PMT cathode.

To make sure I am doing things correctly, I'd like to ask you a few questions:

1) EM model for optical photons:

If I only have energies up to 662 keV (gamma) and mostly optical photon physics, which EM model should I use? LowEnergy, Penelope, Livermore, or StandardEM?

2) optical surfaces:

I wrap my plastic scintillator in various materials (e.g. Teflon, Aluminum foil) and/or apply diffuse paint. The scintillator surface itself is polished. Previously I used to define a physical air gap between scintillator and wrapping materials. Now I eliminated the gap and switched to the "...backpainted" and "...frontpainted" options for optical surfaces. Do I apply these correctly?

... Teflon wrap = polishedbackpainted

... Diffuse paint = groundfrontpainted

... Alu wrap = polishedbackpainted (with prob_ss = 1.0 for spike reflections at the aluminum surface - this should hopefully work just like a polished dielectric-metal surface with an air gap?)

3) sigma_alpha values:

Can you recommend any "typical values" of sigma_alpha for diffuse paint and Teflon?

Many, many thanks in advance!

Best regards, Wolfgang

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Optical Surfaces and Sigma_Alpha