Ushiba, Hirata, Akutsu; following 21817.

Summary

• Added clamps to fix some dummy or balast masses on the TMSY-VIS table along with keeping the balance of this table as much as possible.
• Tentatively installed a Cat.B viewport window through which the TMSY transmission beam came out of the EXT chamber.
• Tweaked the subsequent optics on the in-air optical table to compensate the displaced optical paths due to the above two.

Details

In the last time (21817), we found some dummy or balast masses had not been fixed with clamps since June 2019 (9153); see Fig.1. We started with clamping them. Before touching the components on the TMSY-VIS table, we put an iris diagphram in front of the Gr periscope on the in-air optical table for a work reference. Choosing "nice" combination of directions of the clamps (Fig. 2), we somehow succeeded to mostly recover the initial balance of the TMSY-VIS table; the resultant Gr beam spot on the iris was about only 1 beam size shifted (Fig. 3), so I judged it would be sufficient. Maybe the reason why I left those masses free would be that I could not have sufficient lnegth screws to fix these slightly tall masses at that time. Today we mixedly re-used some clamping parts used for NAB and mid baffles in the past.

Then, we installed the high quality viewport window (Cat.B) prepared the other day (22264). The thicker side is now set to minus X direction (Fig. 4), or it is in the right when looking at the viewport from the in-air table. As is the usual case, 0.75 deg wedge on this window tilted the Gr/IR beam paths. Then the beam spot on the iris shifted in the opposite direction (Fig. 5 to compare with Fig. 3; interesting! and still tolerable, maybe) So, we tweaked some optics on the in-air table to bring the beam not-so-edge, and maximize the PD output or centered the images on the gige cameras. Further alignment considering ASC or pitch/yaw coupling have to be done later by some commissioners if necessary.

Remaining tasks

• We forgot to bring dedicated M8 bolts and small washers to fix the high quality viewport window, so we will bring them to complete the installation of this window.
• An oplev window installation will be done tomorrow.
• Final check inside the vacuum chamber.
• Power budget...
• Where are sensor cards for Y end????