S. Dwyer, D. Hoak, J. Driggers, J. Bartlett, J. Kissel, C. Cahillane
We had trouble with the transition to ETMY, which turned out to be the same problem that we had with ETMX ESD driver this morning (20652) -- the Binary IO configuration was toggled such that high-voltage driver was disconnected, but we were still driving through the high voltage driver. This was the source of several lock losses during this evening's maintenance recovery. We'd found it by comparing a conlog between now and during yesterday's DARM OLGTF measurements by the calibration group. Once we fixed it, we made sure to accept the configuration in the SDF (where we looked first, but it turns out that the wrong configuration had been stored there).
For the record, the attached screenshot shows the correct configuration for ETMY BIO. The good configuration is with have HI/LO Voltage OFF to run with the low voltage driver and the HI Voltage Disconnected (i..e the switch is OFF). In the same screenshot, we show what the DARM loop gain looks like with (yellow) locked on EX alone, (blue) a half-transition to EY when EY is in the bad configuration, (red) a half transition to EY with EY in the good configurtation.
The noise tonight: excess stuff between 30 and 200Hz (first plot). The lower frequency end is very nonstationary and coherent with LSC (second plot) and ASC (third plot) signals. Between 100 and 200Hz it's quite stable. The ISS second loop is not on.
MICH Feedforward appears to be off or mistuned.
The ISS should not be running far from the hard-coded 8% diffracted power. 13% (reported in 20663) is probably too close to the upper limit... I would not change the second loop target value, but rather set the inner loop offset so that the diffrected power runs near 8%.
The amount of excess noise was anomalously bad from this lock stretch. It's not so surprising that the MICH FF was not working.
The current 17+ hour lock has a more typical DARM noise, at least during the high-range stretches. Here the MICH FF seems to be mostly working, although we could get rid of some more coherence by retuning it.
Also note the coherence with PRCL in the region where we have the PSL PZT peaks...
