[Daniel, Mai ,Torrey]
The leading theory on the ~520 Hz resonance seen in the spectrum of the cavity error signal is some part of the flexture mount mirrors resonating. To test this theory we pushed on the mirror with viton to see if the resonance is damped/moved at all. Our initial test has a viton O ring pushing on M2 of the cavity only. We did this with and without pushing on the mirror, results seen here image.png. We are skeptical of these results and tomorrow will:
a) repeat this test several times. It is time consuming as the force on the cavity mirrors misaligns the cavity.
b) instead of relying on the ambient noise of the room to ring up, use phones to drive at say 520 +/- 20 Hz at constant locations between tests.
Can you rig up something to do a swept sine of a speaker placed on the table? This will probably be enought to drive the resonance.
When you "push with an o-ring" I think that will absorb energy from vibrational modes. Is that correct?
Is it possible to have the entire cavity sit on viton? A quick way to do this is to have a sheet of viton between the cavity and the table.
We shipped out some of the "platforms" that were inside the Holometer vacuum systems. These have recesses for viton balls so the platform is stable. I do not recall the cutoff frequencies of that system, but it eliminated our acoustic problems.