With Enzo and Hirata-san.

Today:

• We helped Mirapro with sealing the BS tank for pumpdown.
• They started by removing the top section of the tank.
• To allow them to check the O-ring at the bottom flange of the service port ring, we locked the IP, checked the internal cables and variously removed cables from cable clamps or disconnected them entirely from the inside of the flange until we were confident that there was at least 200 mm of slack. We did likewise on the outside.
• Mirapro then put back the tank top, connected it to the ring and raised both about 100 mm. They were able to inspect the O-ring and found it to be OK.
• They put the tank top and ring back down, bolted the service ring to the tank and removed the tank top again.
• We put back all the cables that had been disturbed and tested as much as possible in the time available, including all sensors and the IM and BF picos and the #2 IF FR, which had been unplugged.
• We tested the BF FR and took the opportunity to adjust the BF LVDT from -254 µm to +7 µm.
• We tested the SF FR, and also tried to zero the SF LVDT, which had been at 3420 µm. We noticed that the -1090 count offset in the LVDTINF filter had been off (so the 3420 µm was spurious) and turned it back on. Even with the offset on, the lowest we could get the keystone with the FR was 1140 µm, so we backed off a bit and left it at 1600 µm.
• We took the opportunity to manually operate the F0 vertical FR to lower the F0 keystone, which had been sitting very high (≈7700 µm) and was touching the upper limit screws, defeating the vertical isolation. We used up most of the range of the FR to get the keystone down to 1140 µm, and then temporarily pressed the keystone further to check that it was indeed in the middle of the range. The lower limit turned out to be around -8700 µm.
• We unlocked the IP and rechecked the GAS LVDT positions: F0 445 µm, SF 1610 µm and BF 5 µm.
• Mirapro then added the tank top.