To understand the origin of the offsets I had to add ot almost all IMC ASC loops, I recentered the two IMC WFS, using the picomotors.

The offsets changed, but they didn't go to zero. So we can now conclude that the offsets are dependent on the WFS centering, as expected.

Then, I started moving around the beam on MC2_TRANS QPD, again using the picomotors. This alos had an effect on the intensity noise coupling. I removed all offsets from the loops, moved the beam on MC2_TRANS, trying to minimize intensity noise. This task was particularly difficult, for two main reasons. First, every time I moved the beam on MC2_TRANS, I had to recenter the beam on WFS_A and WFS_B. Second, HAM3 ISI tripped few times, messing up with my tests.

However, I believe I found a good position of the beams on the QPDs/WFSs. At present, there are no offsets in the loops, and the beam spot position on MC2_TRANS should be good enough to give us low intensity noise.

I checked the optimal offsets using the usual scatter plots, and it appears that things could still be improved with an offset in DOF_1_YAW, so the present position is not yet optimal. More tweaking tomorrow, but only in the case the present offsets remain stationary over night.

I also recenter IM4_TRANS_QPD.