Sheila, Jenne, Gabriele, Hang, and Danny
- Today we started off with the new RH and CO2 settings suggested in alog 44576. I initially didn't consider the double pass through the compensation plate so the change in CO2 needed to be reduced by a factor of 2. Even with this new CO2/RH setting the sideband imbalance at 20 W was still off and we were losing lock on time scales that could not accommodate CO2 adjustments.
- TCS tuning at 10 W
- With CO2X at 0.1W and CO2Y at 0 W is when we saw the best upper and lower sideband balance
- Increased CO2X and CO2Y by .3 W to restore the ITMY HWS spherical power when IFO is at 2 W
- Powering up to 20 W
- Found that the following IFO hot and cold settings were the best settings of the evening:
- These settings are already implemented in guardian.
- The interferometer is still not stable at 20 W
- Side note: We only used ITMY HWS for this tuning because of the large amount of noise on the ITMX HWS. Work is being done to make this sensor more usable.
As Danny says, the interferometer isn't stable with 20W of input power and these TCS settings, but we think that these settings have reduced the sideband imbalance.
In our first attempt to power up to 20W with these settings, (SRC still uncontrolled) we saw an oscillation in DSOFT pitch at around half a Hz. With the SRC uncontrolled we could have a worse coupling of differential arm power to the test mass pitch. This is why Hang implemented a version of DSOFT P which is similar to our higher bandwidth DSOFT P. 44602
The next time we powered up there was a large oscillation in our vertex LSC loops at around 20 Hz. Since we have seen that the sideband imbalance is better and that the ration of 9 to 45 is lower with these TCS settings, we probably need to retune the LSC phases and input matrix.