Sheila and I took a bit of time at the end of maintenance to touch up the COMM and DIFF paths on ISCT1.

We first removed one of the shims that was under the DCPD circled in light blue. This was shimmed up a few weeks ago (alog82783) to get more light on the pd without realigning the entire path since we had more PR suspension moves to do. Two shims were added at the time, and we were only able to remove the larger of the two, but it placed the beam close to center in height. The second attachment shows before the shim was removed.

The COMM path looked clearly not well coaligned viewed from before the last lens in the path. Sheila walked the two optics circled in pink to bring them closer together and ended up with a positive beatnote. At first we could increase the beatnote but visually the two beams seemed to get worse, but she ended up getting to a spot that worked for both.

The DIFF beatnote was already pretty good, but we touched it up a bit more using the optics circled in red. While here, we also added a beam dump behind the lower of the two circled optics. We ended up with a DIFF beatnote around -8.