[Rahul Betsy Keita Ali Koji]

The extraction of the old OMC (Unit #3) and installation of the new OMC (Unit #1) went exceptionally well.

= OMC Extraction =

Tuesday morning, we resumed HAM6 work from the OMC extraction.
Rahul and Koji went into the chamber. Rahul positioned close to HAM5, and Koji was on the other side.
They followed the extraction procedure (E1600164) after some rehearsals.

• Unhooked the wire clamps on Rahul's side.
• Unhooked the wire clamps on Koji's side.
• Lifted the OMC from both sides and extracted it to Koji's side.

During the OMC extraction, assistance from two others was very effective in supporting wires from both HAM6 openings, preventing the wires from touching the OMC. (The procedure to be updated)
The extracted OMC was placed in the fixture on the ISI and moved back to the work table for further action.

= Balance Mass Migration =

Balancing masses were transferred from the previous OMC to the new one (Attachment 1). At the same time, a Viton ring and a 10g mass were added to each corner for the body mode damping (See T1700471).
The mass distribution differed from what Koji had figured out from the past unclear photos. But the masses could be fixed to the OMC using various 1/4-20 screws that were prepared for this.
Only light torque was applied to the fixing screws to avoid delamination/fracture of the mounting brackets below the mass mount.

= Final OMC cleaning =

All the optical surfaces were cleaned by FirstContact except for a couple of surfaces where the access was quite limited. (Attachment 2)

We let the FC paint dry during lunch and then resumed peeling them off, combined with discharging with Top Gun.
The surfaces were checked with a flashlight to find any residual.
A FC residual was located not on the optical surface but on the corner of a tombstone prism. It was cleaned with additional FC paint.

In parallel with the cleaning work, Ali and Keita worked on the review of DCPD-related cable shielding in HAM6.

= OMC Installation =

The reverse process of the extraction has been performed.

• Brought the OMC in the OMCS frame
• Hooked the wire clamps on Rahul's side.
• Hooked the wire clamps on Koji's side.

When inserting the clamps into the clamp hooks, sometimes incomplete mating happens due to friction between the copper cone and the frosted glass cup.
This can be fixed by pushing the clamp into the slit by a small flat-head driver, while the tension on the wire was released by lifting that side of the OMC.

= EQ stop release =

Reverse process of the OMCS mass clamping.

• OMC EQ stops were released:
  We noticed a corner of the OMC on the HAM5 side was bottoming on an EQ stop.
  We decided to lower the EQ stop by releasing the fixing screws for the EQ stop holder. The holder was tilted, and the OMC became free.
• IM blade stops (Qty 4) released
• IM EQ stops 1/4-20 hex nuts (Qty 2) released
• IM EQ stops (Qty 12) released
• Top blade stops (Qty 2) released

This made the OMC free. Rahul quickly checked the transfer functions of the OMCS as well as the damping control.

We decided to stop here. (Attachment 3)

Next Steps:

• Beam alignment
• Possible suspension alignment
• Check electrical connections
• Reinstall the OMC shroud panels