Headline summary: We are very nearly back to NLN, only prevented in returning by the violin modes which are too high to engage OMC whitening. We have not yet been able to calibrate because of a very fast lockloss of unknown source.

The alog was down for most of the afternoon and evening, so I will do my best here to copy mesages from the mattermost chat, which served as the temporary alog.

Minor struggles in returning to full lock:

• The first lock, we did have to by-hand reduce the CARM offset to go to CARM_TO_REFL successfully.
• We reset the green references after ASC converged.
• The next lock (after setting green references and doing an initial alignment) this worked automatically, so no changes were made to guardian.
• MICH P rang up one lockloss, so I reverted the MICH ASC control to an older high bandwidth design. We will need to check the impact on the noise later

Once we achieved full power, we proceeded to try to solve some of the final instabilities leftover from last week. Changes made to avoid locking stability problems:

• New order of states. We now run: Max Power > Low Noise Coil Drivers > Transition from ETMX > Low noise ESD ETMX > Low Noise ASC > Low noise Length Control
  • we got a lot of saturation warnings because of the amplitude of the ADS lines in coil drivers, so the guardian now turns OFF the lines completely, and then turns them back on in lownoise ESD
  • I didn't change state numbers, but I changed the order, and some of the weights to ensure this is the path taken
  • this was tested successfully
• We no longer engage the DHARD P boost in FM8. This may have some effect on the noise which must be checked later
• We tested laser noise suppression; there are no problems
• While in OMC whitening, I ran a quick DARM OLG with Fransisco. There is slightly less phase, but overall it looks fine, at least compared to the reference. However, we don't have a lot of phase margin in general, should we fix that?

The plan was to try testing simulines again, however! We have had multiple very fast locklosses with no known origin. Two have happened shortly after arriving at OMC whitening. These are not coming from ASC and I don't see any ringup in DARM or LSC loops.