J. Kissel, S. Pai

I've processed the results of using the B&K hammer accelerometer system to characterize the resonances of the support structure for the TCS Steering Mirrors in BSC2 (SM 2, D1101851). These have been of concern after Robert identified them as potential scattered light sources in LHO aLOG 39290. Since, they've had standard SUS vibration absorbers (D1002424) installed to help reduce the Q of their resonant features (see preliminary testing at T1700535).

We have no before-vibration-absorber data other than Robert's spectrograms, but I attach the new results with vibration absorbers installed.

I also attach a crude screenshot comparing these results against Robert's spectrograms, and the resonant features roughly line up. #sanitycheck

The results show that, while the majority of the resonant features *above* 30 Hz have a nice low Q, there remains a feature at 25.62 Hz (for TCSY's mirror) and 20.88 Hz (for TCSX's mirror) that is still particularly high Q. 

Edit -- I attach a zoom of these ~25 Hz resonances, as well as the raw data and a script written to analyze it.