aLIGO LHO Logbook

H1 ISC

sheila.dwyer@LIGO.ORG - posted 20:43, Monday 16 July 2018 - last comment - 08:57, Tuesday 17 July 2018(42925)

arms locked with green

Hang, Craig, Jenne, Sheila, Keita

Both arms are locked with green. PR3 and BS have been roughly aligned so that the beams come out onto ISCT1.

Because of the suspension problem described in 42922, we cannot use the slow feedback to the arms. (the environment is very quiet today so this is OK). We also cannot use the new WFSs loops that Hang designed since we cannot actuate on the PUM.

The Y arm gave us a few problems:

We phased the PDH signal, changing its phase by 8 degrees to maximize the ratio of I/Q in response to an excitation of the laser frequency. (Craig and Daniel also shifted this phase on June 13th 42506)
We were confused for a while by clipping of the beam between the beam splitter and ISCT1. The aperture for yaw seems especially small. Once Keita and I unclipped this it seems like we can roughly align the cavity while the WFS signals are roughly zero, although closing the loops doesn't work.
~~I noticed/remembered that we have a very strange matrix for the green WFS, and it seems strange that this matrix was the same for both end stations (was this an error or intentional?)~~ Keita reminded me that these WFS are oriented so that one quadrant is on top, so the matrix is set for that orinetation.
The Y arm green DOF2 was unstable because the low pass in the WFS B signal was turned off. This is a strange low pass which we plan to remove in Hang's new loops, but it is necessary for stability of our old loops.
I turned off the ISI-> M0 FF, I actually don't think this was a problem though.

For the X arm:

The PLL wouldn't lock, so we went to the end station and Jenne raised the crystal temperature from 27.08C to 27.18C.
The ETMX ISI was not isolated, isolating it allowed us to lock the X arm stably (for several minutes at a time)
The Green WFS for the X arm worked with the camera servo off (the image in the camera has some extra beams).

Next steps:

X arm: fix suspension problem so we can use slow feedback (and possibly send WFS to PUM), move CP or camera mask to deal with extra light on camera
Y arm: check for clipping on ISCT1, inject a frequency line to check phasing and matrix for green WFS
Also we could move forward with HWSX work and alignment on ISCT1

Comments related to this report

jeffrey.kissel@LIGO.ORG - 08:57, Tuesday 17 July 2018 (42928)CDS, ISC, SUS

Link

In prep for the fix to the QUAD's actuator fix, I've reconciled their SDF system. The only interesting settings differences were that the *mis*alignment* offsets had changed on ETMX (likely because they were accepted when the calibration gains were OFF, or rather, unity having been left that way after taking a set of transfer functions). ETMX also had some diffs with its ESD commands, but they're differences likely left over from charge exploration, so I reverted them.

Also, for ease of restoration, I went into the FULL TABLE and accepted all of the alignment offsets. ALSX was LOCKED with these alignment settings, ALSY was flashing / fringing, so they'll be at least close.

Attached are screenshots.

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