Scraps of text for incorporation in the VIS Meeting Minutes

KAGRA/Subgroups/VIS/MeetingNAOJ

Type B (Mark)

Past week report

At Kamioka (Mark, Fabian, Enzo, Hirata-san):

• Inspected LLB in tank - in a good position, but not very clean - apparent water spots and dirt.
• Found the geophone adapter plates.
• Retested SF FR stepper - still good.
• Finally got SF LVDT working:
  • Found a short in the primary coil due to Al foil used for mechanical reinforcement at vacuum feedthrough connection.
  • Did a full calibration and found that linear range was too small (0.75 mm!) and did not cover nominal keystone height.
  • Decreased gain to increase linear range.
  • Adjusted the height of the yoke and secondary coil unit to center the linear region around the nominal keystone height.
  • Implemented velocity damping.
• Found all parts for the LBB and damper rings.
  • Cu segments and some other parts were very dirty - wiped carefully for now, but should be properly cleaned before final install.
  • Outrigger parts for LBB have M16 thread cut directly into Al but should have had M16 helicoils. This is a galling risk with Ag-coated rod receptacles. Hirata-san organized rework.
  • Some special lock nuts are in short supply and are being borrowed from supply at ATC for next batch of BFs.
• Made remaining two geophone in-air descrambler cables (total three).
• Installed a thermometer supplied by Kokeyama-san on the tower around the BS tank.
• Prepared the SF damper.
  • Designed a pattern of magnets for the two-segment arrangement of SF damper and laid it out on the magnet ring with the template.
  • Moved the Cu segments on SF cap by 30° (the cap had not been in the right position earlier).
• Reinstalled PI:
  • Raised the PI with the crane and hooked the SF damper ring. Some of the rods did not fit the receptacles due to tolerance issue, but by going through a large number of rods and receptacles, we found three working sets.
  • Craned the PI onto the frame and suspended the SF/... section, this time with the hex cable clamp on the F0-SF rod.
  • Tensioned the PI yaw return spring, installed (but did not cable) the yaw stepper and adjusted the yaw of the SF/... section. We worry the return spring is not stiff enough.
  • Installed (but did not cable) the geophones.
  • Recentered the IP. The extra weight from the geophones (≈42 kg) and SF damper ring (≈17 kg) had brought the IP to near the point of instability, so we removed one arc weight (≈17 kg) and rearranged the other two in the top row to be symmetrical.
  • Added ballast to set the height of the F0 keystone. We now have about 6 kg in hand (due to removing one of the Cu segments for the SF damper). This should be enough margin for cables, temperature fluctuations etc.

Plan for coming weeks

For more detail, see KAGRA/Subgroups/VIS/TypeB/ToDo.

Week of 5/29, 6/6:

• Cabling:
  • Route BF/... cabling up past SF to PI.
  • Route SF cabling up to PI.
  • Add Type 3 extensions to SF/... cables.
  • Move vacuum flanges to positions on assembly frame more convenient for next stage (accessible from second floor, one on each corner of frame).
  • Move in-air cabling to match flange positions.
  • Cable and test PI vertical LVDT.
  • Calibrate PI vertical LVDT.
  • Set yoke on PI vertical LVDT (if necessary).
  • Cable and test PI yaw stepper.
  • Cable and test PI vertical stepper.
  • Cable and test PI horizontal steppers.
  • Cable and test PI horizontal LVDTs.
  • Calibrate PI horizontal LVDTs.
• Crane into tank.