alexan.staley@LIGO.ORG - posted 02:42, Wednesday 11 February 2015 - last comment - 15:13, Wednesday 11 February 2015(16628)
Just shy of 2 hour lock
Sheila, Dan, Daniel, Evan Jeff, Lisa, Alexa
Starting at 08:43:06 UTC Feb 11, 2015 we had a DC lock for ~1:54min. We lost lock again because of the 9 Hz bounce mode in ETMY. We had tried damping with the L2 stage, which helped a bit but still ultimately caused the lock loss. Tomorrow we should try damping with M0, as done at LLO (LLO#16686).
Sheila has pointed out that we might as well notch out the bounce mode resonances in the DHARD WFS loops. So now there is a 9.8 Hz stopband filter installed in FM9 of DHARD_P and (in an abundance of caution) in DHARD_Y.
Some important times from the lock:
Lock sequence started at ~8:17 UTC when arms locked on green
Handoff to POPAIR at 8:27 UTC (this is the last step in the ISC Guardian before the handoff to DC readout - see LSC matrix element 3_10 in the attached plot)
DARM offset applied and OMC locked at 8:40
DARM handoff to DC readout at 8:44
Lock lost at 10:36 UTC