Keita, Elenna, Jenne

The ALS Y WFS were not working when engaged. I checked the WFS autocentering and we saw that the power on WFS B was very low, indicating clipping. The auto centering servo could not run because the threshhold was too low to engage, but even with sweeping the PZT steering mirror, we could not increase the WFS B sum great than 150 ct. Trending showed that both WFS A and B were close to 3000 ct in March when we last locked ALS on both arms.

We could make large moves in TMSY and ETMY to bring the power up on both WFS, but the autocentering would rail. Keita stated this indicated something was very wrong, and we could be clipped somewhere on the way to WFS B.

Keita and I drove down to EY, and opened the table. We confirmed that WFS A is labeled correctly by covering it with a card. We could see a strange clipping pattern in front of WFS B. We looked along the path and saw that a bundle of cables related to the HWS and the old analog camera placed there were hanging partly in the beam. Once we moved the cables out of the way, the power on WFS B return to 2800 ct, which is nominal. Now the autocentering of WFS B works.

We removed the analog camera from the table, and coiled the remaining cables on top of the cable rack above the table. We also unplugged the power cable for the camera.

Ok, we were confused about why WFS A was not working, but it turns out I accidentally turned off the integrators when we were troubleshooting the WFS earlier today (sorry).

If we request WFS on in the guardian, the WFS engagement causes a lockloss. However if we go to a No WFS slow controls state, and then engage the WFS by hand it does not cause a lockloss. However, the WFS loops are not yet converging.

Image 1 shows the beam clipping on the cables on the table.

Image 2 shows the beams unclipped.

Image 3 shows our cable solution.

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Edit the following morning to add: given my gaffe regarding the integrators in the auto centering loops, I took a moment to look at the guardian code. When we run 'LOCKED_SLOW_WFS_ETM_TMS' the integrators are engaged by the guardian, but when I was turning on the WFS by hand, I had forgotten to turn on the top mass integrators on ETMY and TMSY. This explains why we engaged the WFS but the loops didn't converge. However, that still doesn't solve the problem, because the reason why I turned the loops on by hand was because running the 'LOCKED_SLOW_WFS_ETM_TMS' was causing a lockloss.