I have been looking at the in-vacum violin modes at LHO for the first 8 harmonics and thought it could be useful to upload the frequencies here for current works on setting up the active dampers. 

The data used to identify these frequencies is the recent 15 hours long stretch of low noise detector state on the 3rd January at 04:00:00

Each harmonic has the 32 violin modes identified (with a couple of missing ones at the higher order harmonics). 8 split modes per suspension and 4 QUAD suspensions.

These frequencies will be added to the LHO violin mode table which also include the 'Historical data' of the violin mode harmonics before the May 2018 swap of the ETMX, ETMY and ITMX. Comparing new and old values shows that the non replaced ITMY has also changed its violin mode frequencies.

The next step will be to measure the new Q's of these violin modes and grouping violin modes of all harmonics per test mass without exciting the suspension, as done during O2. 

NOTE: On the LHO violin mode table above there is a comment on the MODE 6 filter for ETMY: ' this doesn't seem to damp well, is it really an ETMY mode?'

The reason for the apparent inefficiency of this filter is that there are at least 2 modes in that region, potentially 3 modes as shown next on a high resolution spectrum during the time when the filter was active (I think):