edmond.merilh@LIGO.ORG - posted 11:00, Friday 27 January 2017 - last comment - 11:21, Friday 27 January 2017(33677)
H1 out of Observing for 4.735K Damping
At Keita's request I've taken H1 out of Observing and set the mode to corrective maintenance. THe notch filter for the 4735 has been on but DARM still shows a spike in that frequency range. Keita will make some further adjustments to try and mitigate this. Update: while i'm making this log he has damped it. We will watch it for a short while to make sure it holds.
4.7k violin has been better than before since a bandstop was turned on in DARM chain (alog 33585) but it's not completely gone.
Typical behavior is that it dies down quickly after relocking, looks OK for two hours or so, then starts to ring up very slowly (first attachment).
We took H1 out of ofservation while L1 was down, changed the phase of violin damping setting (second attachment), confirmed that this damps down the violin (you can see this at the very end of the first attachment), accepted the change in SDF and went back to observation. We used 7 minutes.
I assume that the damping loop was tuned without the bandstop in DARM, and when the bandstop was inserted the damping needed retuning.