The following report has been submitted to the On-call interface.
On-call events -> Interferometer Sensing & Control
Title: DIFFp TY oscillations
Author(s): casanueva
| Called at: 01:11, 29-06-2025, by: Berni |
| Remote intervention: Started: 01:13, 29-06-2025; Ended: 01:35, 29-06-2025 |
| On-site intervention: Started: ; Ended: |
| Status: Resolved |
| Operator when issue resolved: Berni |
Details:
The operator contacted me because there were few failed lock acquisitions in CARM NULL 3F, and told me he saw an oscillation on the DIFFp loops. I checked and indeed the DIFFp TY was oscillation at VERY low frequency. On Friday, I had to decrease the gain of the same loop because it was oscillation during the automated increase of gain before engaging the Full Bandwidth loop. So I had commented it. However, this was not the case anymore on Saturday night, and without the increase of gain the loop oscillated with low stability margin. So I commented back the increase of gain and it worked.
I also noticed that the servo of the DIFFp TY then increased its gain further from 8 to 40. I remember having this problem last year so I looked at old logbook entries and I found out that tuning the CH we managed to reduce this effect (#63623). To keep this in mind if it causes more problems.
* Note that any files attached to this report are available in the On-call interface.
