Reports until 23:39, Thursday 08 October 2015
H1 IOO
keita.kawabe@LIGO.ORG - posted 23:39, Thursday 08 October 2015 - last comment - 14:31, Tuesday 13 October 2015(22362)
IMC WFSA quadrant gains all set to 1 (Cheryl, Keita)

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.

Comments related to this report
keita.kawabe@LIGO.ORG - 12:01, Friday 09 October 2015 (22370)
Link

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?).

  • IMC WFSA I2, Q, I4, Q4 gains were set to 1 based on the measurement done in July (alog 20065).
  • IMC WFSA and WFSB head input matrix (not the WFS servo input matrix) were changed. This is apparently used to account for 90deg-ish geometric rotation of the beam due to non-ideal use of periscope inside HAM2.
    • Quickly measured by injecting a 20Hz-ish line into IOOPZT PIT or YAW, one at a time, and minimizing YAW or PIT error.
    • WFSA matrix didn't change much. Rotation doesn't seem to make sense, but I haven't done the PIT/YAW sensing calculation for a rotated beam myself. I'll do it and see if it really doesn't make sense.
    • WFSB matrix now looks more like a 90 degree rotation.
  • We disabled the offsets but somehow they were enabled again, it seems.
Images attached to this comment
kiwamu.izumi@LIGO.ORG - 14:31, Tuesday 13 October 2015 (22484)PSL
Link

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.

Images attached to this comment