[Stephen, Aidan, Wednesday 09 June]

Summary and Plan:

• Poor sealing at the output valve (The Gap) needs to be resolved.
• Planning to install #4-40 helicoils today (chamber will remain sealed, will need to remove output valve and cover output orifice, then transport the chamber to the WB EE shop for redrilling of holes.)
• Meeting with Nina and Aidan this afternoon to iterate one more time.

Troubleshooting steps taken:

1. Aidan took us through the full sequence of pump down and disassembly to bring me up to speed.
2. We opened the lid and inspected the old o-ring.
   1. Signs of plastic deformation and of small flecks of particulate near sealing surface - good idea to change.
3. We found new o-rings in a box from the Cryo lab, and one of these was swapped in after a good wipedown with IPA.
4. Upon pumpdown, Aidan compared behavior and found no meaningful change to rate of pumpdown or stable pressure in e-4 torr range after 10+ minutes.
   1. By valving off [chamber + gauge] from pump line, it was clear that there was a leak in that volume, as within seconds the pressure rose from e-4 torr to e-2 torr, and stabilized at _(need to confirm - e0?)_ torr over ~10 minutes.
5. Attempted to squirt IPA along o-ring seals, but there was not good access to the sealing surfaces, so this was a null test
6. Looked closer at all of the chamber features, and noticed The Gap between chamber wall and chamber output valve, pictured in [Attachment 1]. Not good! But promising as a leak source.
   1. Three of the four screws were found to be loose due to apparent thread damage.
7. IPA was squirted into The Gap at stable pressure of e-4 torr, but no change in pressure was noticed.
8. Longer #4-40 screw reinstallation was attempted, and I could feel a small amount of pull at the very tip of the screw, but tightening the screws led to that small pull to fail as well - need to rework.
9. The Clamp was installed and The Gap was closed [Attachment 2].
   1. When isolated from the vacuum pump, the chamber pressure progressed more slowly. Within seconds, we were at e-3 torr, and over 10 minutes the pressure stabled at e-2 torr, about 30x lower pressure per Aidan's records.