- Had to rerequest HAM2 HPI ROBUST ISOLATED state to get HAM2 ISI to ISOLATED. Then was able to lock ALS. - Got back up to NOMINAL LOW NOISE at 23 watts. - Fast lockloss - Struggled to relock ALS, something to do with X arm fiber polarization being bad. I enabled the polarization controller, which seems to spin wildly until it's shut off. Eventually it found a better polarization for the X arm. - Lockloss as soon as I entered LOW NOISE COIL DRIVERS (directly after LOWNOISE ASC). - Again, lockloss as soon as I entered LOW NOISE COIL DRIVERS (directly after LOWNOISE ASC). - Stepped through the LOWNOISE ASC state by hand and made it with no problems. Added some wait times to the state, otherwise did not change. - For a third time, lockloss at the end of LOWNOISE ASC. This time the state didn't move onto LOW NOISE COIL DRIVERS because of the waits I added at the end of the state. The problem seems to be with H1:ASC-CHARD_Y FM3 (a 40 Hz cutoff filter) being turned on, but that could just be because that's the last thing that happens in LOWNOISE ASC. Could also be because LOWNOISE ASC is happening when the IFO is thermalizing, so optical gains could be changing under our feet. Adding more, longer waits... - Fourth time lockloss at the end of LOWNOISE ASC. Could see a clear pitch oscillation on the AS camera, turns out it was a DHARD P oscillation at 6 Hz (see plot 1). Probably a loop stability issue. - In LOWNOISE ASC at 23 watts, DHARD P FM7 (some LF boost/angular suspension resonance shaper thing) gets turned on, gain goes from -50 to -40, and FM1 (a 20 Hz cutoff filter) gets turned on. - Fifth time lockloss during LOWNOISE ASC, this time while I was going through slowly by hand. The last thing I did was step 4, engaging the arm ASC cutoff filters. (I did all four at once like an idiot.) I had left DHARD P at -50 gain. No 6 Hz oscillation this time, just a quick death. - Made it through LOWNOISE ASC by turning on the cutoff filters slowly and one by one. Made guardian so that it will do it that way too. - Leaving the IFO trying to lock DRMI with NOMINAL LOW NOISE requested. Range was 60 Mpc at NLN, absolutely CRUSHED by Livingston, they are literally off the charts here at Hanford.
About the polarization controller:
Immediately after turning on the polarization controller, click the restore button. 43559 Maybe we can edit the medm screen to make this more obvious. The problem is that the controller restores the paddles to the last position that they were manually set to (by turning knobs). Patrick created the restore button so that we can use it to reset the paddles to the last position that they were set to using the remote interface.