elenna.capote@LIGO.ORG - posted 10:05, Friday 24 October 2025 - last comment - 10:47, Friday 24 October 2025(87716)
1 Hz instability investigations
I'm going to use this post to keep running notes of the 1 Hz investigations:
- After being at high power for more than 30 minutes, we went to low noise and left DHARD P in its high bandwidth configuration.
- After some minutes, the 1 Hz oscillation appeared in the ASC
- Indication that DHARD P is NOT the only culprit here
- I averted the lockloss by running the High Gain ASC script
- after the script completed I reengaed the LSC FF since that is not the issue here
- we had been at high power long enough that the CSOFT P gain was dropped to 20, and I can't change it because the thermalization guardian won't let me
- I measured DHARD P around 1 Hz with all ASC in high bandwidth
- DHARD P looks very stable at 1Hz, the phase is fine and there is no UGF at this frequency
- at 9:54 local I transitioned all the YAW arm loops to their low bandwidth state
- LOCKLOSS at 10:03- no oscillations, no saturation warnings, just a "fast" lockloss
DHARD P at 1 Hz attached.
Images attached to this report
Comments related to this report
We edited the thermalization guardian so that it should set the csoft p gain to 20 only once, after 30 minutes (as before), then after that a user can change it as they wish.