I took un-damped spectra (amplitude spectra density) of all the suspensions today to check for rubbing or mechanical/electrical issues. The latest results (orange trace) have been compared with the ones taken in 2020 (blue trace, LHO alog 56019 which were judged healthy) and the dotted line is the bosem sensor noise. Given below are the results for some of them (while I am still processing others):-
For now I have just glanced through the plots and will look into the details later.
Quads - ETMX, ETMY, ITMX, ITMY : They look healthy to me, although I need to cross check the tall peaks of ETMX (for F1, F2, F3 sensors).
HSTS - MC1, MC2, MC3, PR2, PRM, SR2, SRM :
MC1 RT BOSEM (also L and Y dof) looks to be a bit worse than previous measurements- see page 5 on MC1. Later, I requested Oli to take a transfer function measurements on MC1 and they looks healthy. He will post the plots later. Perhaps RT bosem on MC1 is degrading with time.
On MC2, sensor T3 (MC2 page 3) shows a broad peak at 15Hz approximately (this also needs to be cross checked)
HLTS - PR3, SR3 : the results look better than the ones taken in 2020, however I still need to cross check the resonant peaks.
The results for the other remaining suspensions will posted after processing them.
Having looked through all the un-damped SUS spectra of most concern is the MC1 M1 stage RT channel BOSEM. I would suspect a fault in the read-back electronics chain (e.g. the ADC, AA-chassis or Satellite Box) rather than a fault in-chamber with the BOSEM. If this elevated noise has not been observed in subsequent measurements, then it could be intermittent and therefore tricky to track down. So I would recommend monitoring the MC1 M1 stage RT channel for elevated noise.