jenne.driggers@LIGO.ORG - posted 19:08, Saturday 23 February 2019 (47100)
Locking Notes
- Let guardian take things through Lownoise_ESD_ETMX as they were (with Georgia and Craig's gain of 30 in EX L2 LOCK_L), got through the transition, but had a 6 Hz ring-up. Lockloss.
- This happened again much later in the day, after some ITMY spot position moves, but this time it was a 6.2Hz ring up. Again, lost lock just as we were transitioning back to ETMX.
- Skipped blending part of CHARD_BLEND (did do the ADS dither line amplitude reduction)
- Seems not so good. IFO pretty wavy alignment-wise once at COIL_DRIVERS.
- Re-blending.
- Split out ETMX_ESD to 2 states. The first one (TRANSITION_FROM_ETMX) does most of the stuff that the old LOWNOISE_ESD_ETMX did, but does *not* switch back to ETMX. The new version of LOWNOISE_ESD_ETMX now just does the transition back to ETMX, and then engages the DARM lowpass that was at the end of the old version of the state. So, in total, I believe that nothing procedurally has changed, but we can now switch away from EX with one state, and not have to copy-and-paste everything into a guardian shell every time. Probably someday we'll want to revert this, but it seems useful for now.
- Maybe because I had waited so long becuase of looking at CHARD BLEND, but the transition worked this time, go to LOWNOISE_LENGTH_CONTROL just fine.
- Manual-ed to do RF9 modulation depth reduction (it's been out of the path for several weeks).
- Putting it back in the path.
- Moving spot on ITMY seems to be able to change the 9 MHz RIN coupling.
- Next lock, trying to 'jump' over the point absorber, ended up right on top of it according to the HWS (+3.9mm up in pitch according to A2L), and lost lock due to 4.7 Hz ringup. Looked like an ASC problem, although that frequency sounds a lot like our recent DARM length problems.
- Twice today I've had to toggle the ALS Y laser's noise eater. In the attached figure, you can see that even when nicely locked, the Yarm green transmission is very noisy. Around -25 sec I toggled the noise eater, and the transmission quieted down.
- With my furthest ITMY spot position, the POPX PZT is just barely starting to rail in pitch. The beam is still well centered (0.03 normalized units off), but if we want to move the ITMY even further we will likely have to move the PRC axis to get this back (or go move the beam out on the table, but we should be able to handle it by moving the PRC axis).
- The ITMY L2 drivealign P2L gain started today at -1.33. DanB will put it back there before he leaves, unless it's clear that the newer position is much better.
Images attached to this report
