Title: Owl Mid-Shift Update, 10:48UTC, 3:49PT
H1 State: relocking and making it to Low Noise but engaging the ISS Second loop is gltiching all of the ISS and the IFO
Help this shift: Kiwamu on the phone, Kiwamu's alog about engaging the ISS Second Loop manually, Jim's alog about DRMI Split Mode
Details:
07:00UTC - I arrive and IFO is down due to an earthquake.
07:00-08:00 - PRMI locked 3 times, but can't hold due to the earthquake
08:00-09:00 - PRMI locks and I align, then I transition to DRMI and thus the "Split Mode" announcements start, and after multiple "Split Mode" locks I call Kiwamu, he says do a MICH Dark and SRC align
09:20 - MICH Dark and SRC Align alignments are successful, and I take the IFO to Down and Init, and take IFO to full-lock
10:07:41 - Guardian tries to engage the ISS Second loop, I wait, then start the procedure in Kiwamu's alog, and then he called back and we tried unsuccessfully to engage the ISS second loop
10:40:38 - the IFO lost lock due to our work trying to engage the ISS Second Loop - Kiwamu is drining in
11:03 - IFO has not relocked, but I don't know why since I've been writing the alog...
More to come...
It seems that the ISS issue was related to a too-low diffraction power in the first loop.
Please check the ISS diffracted power and adjust it to 8 +/- 1% if having an issue with the engagement of the ISS 2nd loop.
When the ISS was unsuccessful engaging the ISS, diffracted power was at about 5% which should be 8%. Ideally, the diffracted power should not affect the 2nd loop so much, but in reality, for some reason the stability of the 2nd loop seems to be quite sensitive to the diffracted power only when engaging it. After a few failures in engaging the ISS, Cheryl and I tried to engage it a couple of times by hand with no success. Eventually I accidentally unlocked the whole interferometer because we had a wrong gain in ISS_SECONDLOOP_SIGNAL. Oops.
In the next lock trial, we let the IMC_LOCK guardian do it with the right diffracted power of about 8%. This went very smooth without a failure. Probably we should consider making another PID loop to automatically adjust the diffracted power so as to maintain it at around 8% when engaging the 2nd loop.