Reflection type for NEG-coating

General discussion
1

Hello,

I'm using Synrad+ in combination with Molflow+ to create a pressure profile of a storage ring section.

I intend to use NEG-coated vacuum-chambers.

Do you know or have experience what reflection type I have to use for NEG-coated chamber walls or which refelection type matches best to simulate NEG-coating?

Further I'm intrested to understand the mechanism behind  the energy vs. incident angle table. What does the percentage means. Is it the probability of the Photon to be absorbed?

Maybe you can help with a short explanation or a link where this issue is explained.

Thank you very much in advance.

Best regards,

Adriano

2

Hello,

After discussion with Roberto (the author of the code), I can't give a good advice on NEG reflectivity - we plan to do measurements at CERN since it's a common issue, but for the moment you have to approximate the solution by choosing some metal, for example copper as reflecting material.

The material reflectivity tables are indeed showing the reflection (not absorption!) probability on the Y axis, the photon energy on the X axis, and the different curves correspond to certain grazing angles.

Although not that simple, in general higher grazing angles tend to get asorbed more, and lower energies tend to get reflected more.

These curves are generated from the Fresnel formulas, which in turn use the (complex) refractive index of the metal (that depends on the photon energy) and the incident angle.

If you'd like to read more about it, there is a short summary of the reflection model of Synrad in section 2.5.1 of my thesis.

In general, doing coupled simulations with Synrad and Molflow is a difficult process with may caveats, so don't hesitate to get back to me when you stumble into problems.