jim.warner@LIGO.ORG - posted 00:11, Friday 07 April 2017 - last comment - 09:54, Friday 07 April 2017(35378)
Shift Summary
TITLE: 04/07 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 69Mpc
INCOMING OPERATOR: TJ
SHIFT SUMMARY: Commissioning changes made staying locked difficult, but sorted now. TJ attempting to do his shift remotely (otherwise he's "out sick")
LOG:
3:30 UTC Noticed range was falling off & ASC was ringing up
4:00 UTC Lockloss, started trying to detangle commissioning changes from earlier, got locked again, but range deteriorated again and ASC range up again. Sheila helped me figure out that her CSOFT changes hadn't been added to the ISC_LOCK guardian, so CSOFT currently still has to be turned up by hand. We should sort this out tomorrow.
Just to clarify what happened:
ITMY oplev has been going bad, it got bad enough to start causing locklosses during the commissioning window yesterday, so we spent some of our commissioning time doing corrective maintence to get rid of oplev damping. Since my change to the CSOFT gain got overwritten in the guardian (not sure why) it didn't come on with the same gain next lock. This meant that we had the radiation pressure instability that the oplev damping was originally intended to suppress, which is different from the 0.44 Hz oscillations we've been having for the past few weeks which are actually caused by the oplev.
So the original cause of the trouble was not commissioning, but the oplev going bad.