Started a new run this afternoon, with the following goals:
1) confirm that the first run (QIL/2695) went smoothly, by performing a visual inspection in the chamber while setting up for the first run.
- kapton tape affixing inner shield RTD lead junctions to inner shield had fallen. These junctions were simply hanging - not ideal, but apparently not too harmful. Not likely to impact temperatures, in my opinion, but could have led to shorts or glitches in data.
- all RTDs appeared to be fixed and well-contacted to surfaces
- Everything seemed to be in good shape with the copper bar, no apparent issues
2) obtain a second run with similar configuration, now that the rigid copper bar linkage has been implemented.
3) vary a single important parameter relative to the first run, namely the inner surface emissivity of the inner shield, so that the impact of that parameter may be observed.
- Added Aluminum foil (matte side visible) to the inner shield inner surfaces (lid and cylinder, both). Anywhere there was previously black Aquadag, there is now matte aluminum foil.
- Kept the same apertures for viewport access and for electrical and thermal connection passthrough, basically attempted to achieve identical shield coverage.
- There is one small sliver of black aquadag visible at the location of the electrical leads, but I didn't worry about patching that small area.
- Pumps on at ~3:40 pm
- Cooling started at 4:13 pm (pressure ~6 mTorr, rapidly falling with turbo pump spinning up from ~70% to ~85% over a 1 minute interval). Coldhead RTD is responsive.
- All photos will be posted to the QIL Cryo Vacuum Chamber photo album.
- Note from check in on Monday afternoon, ~ 69 hours after start: everything looks good, and the workpiece temperature (~127 K) seems to reflect the emissivity change.