jenne.driggers@LIGO.ORG - posted 10:57, Friday 15 March 2019 (47560)
Locking notes - ALS X glitches; 74.75 Hz frequency line makes it impossible to lock.
- ALS X had glitches this morning. Sometimes they looked more like our classic 'rainy day' glitches, and other times it looked like the noise eater was oscillating (the difference being how often the glitches / noise happens - if it's constant, it's the noise eater).
- Toggling the ALS X end laser's noise eater twice, the second time waiting more than 20 seconds before turning it back on, seems to have helped. The first time I toggled it off, the noise immediately went away, but then started coming back a few minutes later. Since the second time, it hasn't really been noisy.
- There is also some kind of big oscillation at 74.75 Hz. It's very obvious when we get to TR_CARM if you look at the arm buildups or the CARM error signal. A few times we've lost lock while doing TR_CARM and / or CARM_150_pm, but this last lock we made it through those, and lost lock on RF_DARM.
- This last lock, I measured the COMM loop and the TR_CARM version of the loop once we'd made that transition, and both seemed totally fine loop-stability-wise.
- Sheila reminded me that Craig and Dan had some lines on (alog 47542) - I disabled the common mode board's excitation input, and the line is gone. All better now.
- Lost lock at lowering the 9MHz modulation depth - Sheila has now turned off that excitation point.