30/01/19 - The following powerpoint shows the results discussed with LMA people.

What came out from the discussion is:

- Their cleaning method uses demineralized water drop on a spinner. It is probably the explanation of the circular traces on the mirror's surfaces but we still don't know what is this deposit (XPS is running out on 2 of this mirrors at this time).

-  According to their point of view, the spots could come from the coating deposition technique and are "normal". No real explaination, should not come from the substrat which is ultra-polished but can come from some clustering in the coating.

We gave them 2 of the mirrors so they can check if it is possible to clean them. They'll also do a measurement of the mirror's topology.