We are trying a 0.1W differential ring heater change on each segment. Going up in ETMX RH and down in ETMY first. The aim is to see if noise couplings get better and if we can improve our build up again. This should bring our arm modes closer from the 2nd order mode resonances. The Y-arm modes are quite close to the 10.4kHz acoustic mode forest, hopefully one doesn't ring up as we move through. AWG lines are on for this.
When I was dropping ETMY 1.4->0.4W there was a brief period where the builds up looked better, locks were short though so we only saw snapshots. Arm power was trending up towards 390kW. But after a day or so it settled to something lower. So changing the ETMY ring heater lower could win us some arm power back again.
During the ETMX RH increases we did a month or so ago the build ups just kept getting worse with more, which is what we are seeing again after last nights changes.
One more time, I have made this incredibly suspicious looking plot to trend the WFS 45 and circulating power.
A correction to the frequency noise coupling. I did not have the LSC feedforward off, so the low frequency looked better than it is. Unfortunately we are not winning much down there after the TCS changes.
I've reverted this 0.1W differential step, there has not been any clear benefit to it and maybe causing some other PI modes at 20kHz to ring up.
We are seeing the REFL WFS 45 yaw signals trend with the changing circulating arm power as the ring heaters change. No other WFS signal changes with arm power like this.