This morning I moved ITMX pit by -3.8 urad to get more recycling gain. The recycling gain increased from 26 to 30. Assuming that the ASC loops (DHARD and CHARD) suppressed the angle of the misalignment but not the translation, I must have introduced a translation of 7.4 mm upward. In addition, when I increased the PSL power from 3 to 10 W in the full lock, I saw that both ITMs tilted only in pitch by roughly +0.5 urad according to the oplev signals. This means that the beam on ITMs were lower than the center of the optic by roughly 5 mm (see Evan's calculation in alog 16344), though, to be accurate, one has to take the ASC loops into account which I did not. Anyways, I believe that my move on ITMX also improved the centering on ITMX as well. We should check the optical torque when the interferometer is fully locked.

I updated the green camera reference position of ITMs from 241.6 to 248.5 and from 216.5 to 218.0 for ITMX and ITMY respectively. After a lockloss by accident, we confirmed that we could lock back to this new high recycling gain point without re-tuning the ITMX angle. I could not finish optimizing the angle of ITMX or check the yaw alignment yet due to the lock loss. We know that we can get a recycling gain of 33 (alog 17158), so this work continues.