This is a memo for work candidates to be done immediately after O4a.

• The attached photo was taken on Sept. 13 2022, and the same one as Fig. 1 of 22084.The same information can be extracted from Fig. 2 of 20233 (this was on Mar. 25 2022) as well. Looking at these photos, though as a hindsight, the way to fix the STM2 pillar seems weak especially in the pitch direction: the foot flange is partly out of the top surface of the optical table, and two clamps are in line; moreover or first of all rather, the usage of the two clamps themselves are worng; they should have not been used like this. With this, the contacting is not by surface but lines, unfortunately. Hope sufficient accessibility.
• Interestingly, we had checked the rigidity of the STM2 (and 1) structure in the IFI chamber the other day (on Mar. 28 2022) by hands (see 20259). So they would be enough rigid for hands.

Maybe, after O4a, one candidate of works would be to open the K400 flange in the minus Y direction of the IFI chamber to access the foot flange of the STM2 pillar, and at least add another clamp there. If possible I'd like to also open the minus X side to replace the currently-installed wrongly-used two clamps, but that would mean the vacuum pipe connecting the IFI chamber and the large GV should be detached, which would pay much...

Anyway, going back to my original proposal, if we will detach the REFL window, the same procedure to deal with the final beam dump for ghost beams from the REFL window should be also taken into account. See 22244.