oli.patane@LIGO.ORG - posted 14:15, Tuesday 12 August 2025 - last comment - 15:54, Tuesday 12 August 2025(86324)
Lockloss
Lockloss at 2025-08-12 21:12UTC after 25 minutes locked
Lockloss at 2025-08-12 21:12UTC after 25 minutes locked
Oli, Elenna, Keita, Sheila, Jennie, Camilla
Oli noticed that ICS_LCOK had a check that the fast shutter didn't fire. Elenna and Oli then confirmed this.
We found that the fast shutter did not fire because the threshold of light at the AS port was not high enough to fire it. There was no danger here and it should not have fired. This is a rare occurrence where the light goes towards the input rather than output and is caught by baffles.
See plots of today's lockloss with no spike of light and no fast shutter closing via HAM6 GS13 vs a normal (earthquake) LL where the light spikes (especially as seen on Keita's 81080 VP power monitor) and the fast shutter closes.
It is unusual that we have had this rare type of lockloss twice in a couple of months (27th June: 85383). So this can be monitored, I added this plot to the "lockloss select" command by putting it into /sys/h1/templates/locklossplots
Keita requested we checked the power on ASC-AS_C is at it's normal level with a 2W DRMI lock. It is within the normal range of the last three locks, see attached.
I checked the vacuum channels and there was no excursion around the lockloss time so we didn't burn anything
Back to Observing 22:46 UTC