thomas.shaffer@LIGO.ORG - posted 08:40, Thursday 07 September 2023 - last comment - 10:06, Thursday 07 September 2023(72732)
Found some violin modes without gain (not nominal) again
I found 3 violin modes that had their damping gains at a non-nominal setting of 0 for this lock. Rahul noticed this with EMTX mode 3 yesterday as well, so it seems to be something we need to keep an eye on. It's not anything we have to fret about since the ringups are incredibly slow if at all, but we might need to tune the violin guardian. Today's findings:
ETMX mode 3 gain off just like yesterday, but trending the monitor for 13 hour lock, it seems to be stable if not decreasing, so I'll leave it.
ETMY mode 7 and 15 were also found off and these have been very slowly coming up, so I've brought their gains back to nominal.
This happened during the evening lock (Wed) for few modes at 1kHz. I will look into what causing them to switch off the gain at the start of the lock. The modes were really low on monitor (less than 1) and they remained like that for a long time, hence I didn't switch them ON at that time.