Laura Nutall, Georgia, Craig, Sheila, Stefan, Thomas, Danny

Laura pointed out this alog from Valera 42651, based on this we decided to try switching the upper stages of DARM control from ETMY to ETMX.  The attached script should do the switch, some of these things need to be added to the guardian before we try to use the use_ETMX flag to go to ETMX.  The attached screenshot (and template) show the measurement from L2 excitation to DARM for both test masses once we set up the actuation path.  We haven't seen fringe wrapping since making the switch at 6:30 UTC.  Craig has been updating the calibration, which is why our range has been changing. 

Locking notes from earlier today:

• We had difficulty with engaging ALS DIFF when the sensor correction gain was wrong.  The clue that something was wrong was that although our ground BLRMS indicate that the ground motion was under 1um/sec rms, by counting fringes we could see that the differential motion of the Y arm was about 3 um/sec rms peak.  With the correct sensor correction Georgia counted  about 1.5 um/sec peak velocity by letting the green arms swing. Once Hugh and Jeff fixed the sensor correction, 46315, we were able to lock ALS DIFF without any problems, so it seems like this 2 Hz oscillation during the engagement is dependent on the input motion. 
• We had some problems with the ASC engagement again. When the dither loops came on, the other loops were unable to follow and we lost lock once.  (We don't have soft limiters for the dithers, and we reduced the CHARD gain so that the dithers aren't covered by the CHARD noise in DARM).  We increased the CHARD P gain by 16 dB during the engagement to match the gain of CHARD Y, and changed the +46dB filter to +30dB so that the final gain is the same (we also adjusted the gain in LOWNOISE_ASC to have the same overall gain for CHARD P).  We also increased the gain of SRC1Y during the dither loop engagement by 20dB, but weren't able to do the same for SRC1P.  If we continue to have difficulties with the dither engagement we can try increasing the gain of SRC1P (by less than 20dB) and both SRC2 loops, or we could add soft limiters to the dither loops. 
• We lost lock due to an ~3Hz instability of the soft P loops a couple of times at the end of the ENGAGE_SOFT_LOOPS state.  We decreased the gain of CSOFT P by a factor of 2 and decreased the gain of DSOFT P by 25%, by commenting out the final gain increases for these in the guardian. 
• Once we were at 30W Georgia moved the A2L gains back to what they were last week, and we didn't see any dPd theta instability, so it seems that these gains are fine. 
• We reduced some of the wait times that we had for waiting for POP18 to decay during the power up.  We also removed some of the logic that was stepping the PRCL gain as we increased power, because we noticed that the PRCL gain was too high and we had gain peaking.  We could further simplify this process.