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tomotada.akutsu - 21:39 Wednesday 24 November 2021 (18985) Print this report
WAB@IXC finalization for O4

Yano, Hirata, Akutsu (help: Ushiba, Tomaru, Tamaki); refer to the same/similar activities like 7590, 8223, 8412... and JGW-G1808538; check some relevant pages in the KAGRA wiki as well.

Abstract

Brought the WAB suspension structure back to its nominal position in the IXC chamber; not yet finished today.

Details

This is the first WAB finalization in these two years. It is better to have a look to each of the klog posts referred above in order to remind what is that. The WAB suspension at IXC has been in the saving mode for a year (15367, 15383, where you can find the status at that time). 

Today, using the original (crane type) WAB traverser, we once tried to bring the WAB suspension back to the nominal position. But immediately we found the WAB base plate would interfere against the security frame of the cryopayload. So those cryo people took care of the adjustment of the security frame. Then again we brought the WAB suspension to the "nominal" position and fixed the base plate with some clamps. After detaching the WAB traverser, we immediately found that the base plate was slightly displaced from the nominal position (~ 1cm) in the "transverse" direction (or +/- Y direction of the interferometer, or the perpendicular direction w. r. t. the X arm direction). Actually, the test mass and the WAB's center to center was seemingly not matched. After some discussion, we found that we did not lock the transverse-DoF fixing in the traverser, and so this would make the displacing.

So we again mounted the WAB traverser, and carefully checked if the WAB can enter the duct (otherwise the center line of the duct and the WAB would not match), and confirmed our reason-estimating would be right. So we carefully adjusted the transverse DoF (or positioning), and locked the trans-DoF fixing this time, and finally brought the WAB suspension to its nominal position. By the way, although this document would say that the gap between the WAB and the recoil mass would be 10 mm, we set this 20 mm for safety risk mitigation.

We also replaced the old version of the adapter block to the cooler head with the newer one. As written like in 8412, 5->10->15 Nm torque was applied to the four M8-40 screws to fix the block.

Next step

As described, today we consumed too much time. We will do additional works such as connecting 6N-Al heat links, thermometers, and so on tomorrow.

Comments to this report:
tomotada.akutsu - 9:51 Friday 26 November 2021 (19009) Print this report

Some photos.

  • Fig. 1: view from -Y flange
  • Figs. 2 and 3: the gap between the WAB base plate and the security frame of the cryopayload is about 20 mm in the longitudinal direction (along with the X arm).
  • Fig. 4: just for a reference: the gap in the transverse direction.
  • Fig. 5: close-up view of the gap between the WAB and the test (recoil) mass.
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