The stopband filter we put in the ETMX OL servo yesterday seems to have done the job of preventing the ringups:
In the attached trend of the OLPIT 3-10 Hz BLRMS, you can see the ringup start around 6AM local time this Sunday, the 25th.
Around noon on Monday (1800 UTC), Evan and Alexa start damping the mode using the bandpass filter in the OL PIT servo. They stop around 2100 UTC when the mode is small. It then rings up for the next 7 hours until we turn the stopband filter on.
Then it rings down with a 1/e time of ~4 hours (which implies a bounce mode Q of ~440,000 if nothing else is driving it).
We should make sure to install these on all of the test mass OL servos.
Added the Bounce + Roll bandstop filter to all the ETM/ITM OLDAMP filter banks. In some cases, I have overwritten existing 'notch' filters there for this purpose. Its not a good idea to use 'notch' for these mechanical modes which drift in frequency.
I made the Roll bandstop wider since there's no phase hit from this higher frequency filter. The vertical lines in the plot show the expected bounce frequency (9.775 Hz) and the roll frequency (13.81 Hz) which has some small natural spread between the optics, but I figure this should catch them all, even when the VEA temperatures drift.
