After deciding to stop with the RH changes we've started moving the CO2s to try and optimise around the new arm modes.
We only had time for dropping CO2X so far, stepping it down from 4W to 1.6W (almost the same as CO2Y = 1.7W). The arm powers have improved slightly. Frequency noise coupling has increased at high frequency, low frequency not much change, maybe a small improvement around 50-100Hz.
Interestingly, jitter coupling seems to be decreasing with the CO2X drop which has increased a lot since the ITM change (68036). I put three lines at 111 (down to 40%), 167 (down 50%), and 387 (down 47%) Hz, and coherence is down across the range.
Gave way to the calibration team, but will try more CO2 X and Y changes later.
When the IFO relocked last night the old 4W on CO2X settings were reapplied. I've changed lscparams and reloaded CO2_PWR to request 1.15W on CO2X if we loose lock again.
I'm currently stepping CO2X back down to 1.15W requested (1.7W in) in 0.2W/15min steps. It should be done ~10:30am. From there we can try some common CO2 changes up and down in power. AWG_LINES is injecting.
From Dan's comment about H1:ASC-CAM_YAW_OUTPUT drifting off, I look at the Hartmann data from the recent CO2 tuning step to identify relative difference in position of CO2 center to that of IFO beam. The differnce confirms misalignemnt is mainly in yaw for both input test masses
| Test mass | Δx | Δy |
| ITMX | -7.4 mm | -2.5 mm |
| ITMY | -9.5 mm | +6.4 mm |
The wavefront maps correspond to CO2 and IFO heating are obtained from recent locks with CO2 tuning. In these plots, the contour lines are for CO2 and contour filled-maps are for IFO beam self-heating
Estimated coordinates of WF center in sensor pixel number:
| Test mass | Actuator | Coordinates |
| ITMX | Self-heating | [534.3±3.9, 446.5±2.7] |
| ITMX | CO2 | [496.7±16, 439.1±22] |
| ITMY | Self-heating | [513.5±0.6, 565.7±0.5] |
| ITMY | CO2 | [474.9±5.9, 600.1±6.0] |