[Jenne, Vaishali, Karl]
We have replaced the razor beam dump on ISCT1 that was causing scattered light problems (see alog 35538) with an Arai-style black glass dump, provided by the 40m (see 40m log 8089, first style). You can see the new dump just to the left of the PD in the attached photo. I was thinking about sending the reflection from this dump (after several black glass bounces) to the razor dump, but I can't see any reflection with just a card, so skipped this step for now. We can come back to it with an IR viewer if we have more time in the future.
We're on our way to NLN, so maybe we'll see if this helps any, if we happen to get high ground motion sometime.
[Jenne, Vaishali, Karl, Betsy]
Koji pointed out to me that even though the new black glass beam dump had been sitting on a HEPA table at the 40m, since it has been so long since it was cleaned, it could accumulate a bit of dust or film.
So, we temporarily put the razor dump back, disassembled the black glass dump, and with Betsy's guidance cleaned the surfaces of the black glass with first contact. We then reassembled the dump and put it back on the table.
Taking advantage of a few minutes while those working on the cleanroom took a short break, we transitioned to laser hazard so that we could do a fine alignment of the beam dump with the DRMI flashing. The LVEA was transitioned back to laser safe after this brief work was completed, so that the cleanroom team could work more easily.