[Keita, Elenna]

Sheila and I struggled to lock SRY last Friday, 91360. Keita and I revisited today.

To start, I ran the usual SR2 alignment, which centers the beam on AS_C, and the AS centering which centers OM1,2 on AS A and B.

Then, we could see a large beam at the center of the AS AIR camera, and a strange fringing beam at the top edge of the camera. We swept SRM in both pitch and yaw to both edges and saw the beam disappear. This convinced us that we were seeing the two beams we needed to overlap in SRY, however, there was not an SRM alignment that could overlap the two beams.

Keita first moved ITMY 10 urad in pitch, and was able to overlap the two beams. He then undid that alignment and moved the beamsplitter instead. We were able to achieve the SRY fringing and then lock SRY with the guardian. The resulting beam ended up on the top edge of th AS AIR camera view.

Using that beamsplitter alignment, we then relocked MICH dark, which required a large movement of ITMX, since we had decided to maintain the beamsplitter and ITMY alignment. ITMX is now at P: -135 and Y: 113.1 on the sliders. This means it has been moved relative to where it should be according to a previous arm alignment we achieved.

We can still see the MICH fringes on the ISCT1 refl camera with this alignment.

We can also lock PRX, with a movement of PRM. We still see no beam on POP A or B, so Keita is scanning the input alignment.

The attached screenshot shows the alignment sliders after we locked SRY, MICH, and PRX.

I'm not sure if we are happy with this alignment overall, since we're not sure if this is where we want the ITMs.