Tuesday, November 6, 2012

Day 13, November 6, 2012 -- Leaks and fixes

Remember how excited I was a couple days ago that our cryostat was closed and pumping? Well, it turns out that it had a leak, and a big one at that. After some time trying to debug where the leak was coming from and only being able to vaguely determine it came from somewhere near the window, we vented the cryostat and put the whole window assembly on its small test setup (to avoid having to repump the entire cryostat just to leak check the window). We were able to determine that the glue joint that held our plastic window to an aluminum sealing ring (that then mated to a regular rubber o-ring) had nearly completely de-bonded at some point between our testing in Texas and here, and it turns out that broken epoxy is a terrible vacuum seal (no surprise there).

After mulling over various options, we decided to eliminate the aluminum ring completely and sand the window smooth enough to mate with the o-ring directly. This approach has worked successfully on various other experiments, and we were able to make it work for us as well. We also did a thermal test by leaving the window test setup outside for an hour or so until it got to about -10C and found that it still held vacuum.

Elsewhere in the high bay, the gondola team got the star cameras mounted to the inner frame and some of the other electronics boxes mounted, Franky and Jeff continued work on the BROs, and Kyle worked on checking out one of our so-called "general housekeeping" (GHK) boards that reads various sensors from around the gondola and controls other bits of hardware.

Kyle, Shaul, and I ended up staying late at the high bay to finish the leak testing and re-close the cryostat. We got back to McMurdo a little before 10PM, and I went straight to bed.
 
No pictures today, since we were pretty busy. Now go vote!

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