We set all quadrant gains of IMC WFSA to [1 1 1 1] from [1, 0.25, 1, 4]. (WFSB was already all 1.)
We also disabled IMCWFS error offsets in servo filters.
After this, we steered IM2 to bring the beam position on IM4 trans back (at first we tried IM3, but it would make the OSEM output to become larger, and they're already close to saturation).
IFO locked after this without any problem.
We haven't done any jitter coupling optimization and I don't know if Robert had time to do it.
The first and the second attachment show the current and the old settings, respectively.
In the first one, yellow boxes show what we changed. Red box show what we changed but are somehow reverted (automatically?).
This is just an observation related to entry 22482 where I was investigating the relation between ISS and IMC.
After Keita and Cheryl set the IMC WFS gains back to 1, it seems to have shifted the pointing to the ISS array a little bit. See the attached trend.
The QPD signals at the ISS array have moved by 0.1 or so both in PIT and YAW when the WFS gain was changed to 1. Both PIT and YAW moved towards the center of the QPD although SUM seems to have decreased at the same time. I am not sure what exactly was going on. We may need to optimize the pico-motors to minimize the jitter-coupling to the ISS array.