Hang, Matt, Evan, Stefan, Rana
WE mostly were chasing weird locklosses and instabilities, but also managed to implement a few noise improvements:
- SRCL FF better shaping via fitting and better measurements.
- A2L decoupling gave us 10-30 Hz improvement.
- MICH FF tuned up a bit. New measurments taken; fitting and filter generation yet to be done.
- ASC tune up: hard/soft modes for CARM.
- ETMY Butterfly mode identified and notched.
Of the locklosses, some were just due to marginal points in the transitions and loop margins. The main issue over the past few days turned out to be that the TIDAL servo was turned OFF somehow on Friday evening. After switching that back on for ETMY, we have returned to having long locks. The highpassing of SRCLFF has removed the high power pitch instabilities that we were seeing.
We were able to get > 40 Mpc with 10W input. The butterfly mode of ETMY @ 6053.81 Hz is preventing us from turning on the OMC DC whitening right now, so we don't know how good our range really is, but our low frequency
We also got a change to reimplement a small amount of the ASC changes from before last maintenance day:
- We reverted back to the true hard/soft basis for common pitch only (these settings are not controlled by the guardian right now). The attachment shows the OLTF of the cSoft loop with true soft actuation. Note the absence of the hard mode.
- We turned up the gain on cHard pitch by 20 dB (not in the guardian).
Next:
- Revert back to true hard/soft basis for common yaw.
- Try out hard/soft basis for differential pitch and differential yaw.
Note, Rana reports that the tidal was OFF at the far right switch on the IMC_F Filter Module (picture attached shows this switch now on as it should be).
