jenne.driggers@LIGO.ORG - posted 11:32, Wednesday 05 December 2018 (45706)
Wed AM locking
- Initial alignment: Tried first to just lock, but arm powers were low in both green and red (both X and Y), and I was having to move all 3 suspensions to get something reasonable, so it seemed worth it to just do a quick alignment.
- SRCL mode hop offset - put back into guardian yesterday afternoon (forgot to alog)
- Locked to Increase_power, then fast lockloss
- Barely got to 20W, the lost lock. OMC SUS was saturating, as were test masses.
- See first figure (with "Lockloss1" in the title). Looks like something happens in MCL (CARM), then other LSC loops get a kick quickly after that.
- Locked, increased only to 10W. OMC SUS started saturating from ASC after about 2 min. Held ASC loops by turning master input gain to 0 for all 4 loops, and also reduced gain of the PosY and AngY loops to 0.2 from 0.4 and 0.35 to reduce signal sent to OMC.
- Walked up to 20W (sat at 10W for a few min, then 13W, then 16W, then 18W, then 20W). MCL looks similar to last lockloss, but other LSC loops don't have same kick. MCL "buzzed" a few times in the last seconds before lockloss at 164.9Hz, not a nice sine wave, looks like something is saturated or slew rate limited or something.
- MCL seems also to have a ring up near the very end at 183Hz.
- See 2nd and 3rd figures (with "Lockloss2" in the title) for the buzzing and the MCL ring up.
- Shutter failed the auto-check, but looking at AS_C sum vs. AS_A sum, it's clear that the fast shutter closed appropriately after the lockloss.
- The lockloss this happened for the AS power fluctuated up and then back down, before lockloss and the full power going to AS (and the shutter closing). So, I wonder if our auto-checker gets confused when the power fluctuates just before lockloss.
- ISS AC coupling wasn't working, as a result of Stefan's guardian work yesterday (now fixed), but this seems to have been our problem. Now able to get to nom low noise!
- Running A2L, then on to a day of noise hunting / calibration time-dependent correction work.
Images attached to this report
