Monday, April 13, 2009

Day 19, 4/13/05 -- The road to 250 mK

After a restful (hah!) weekend, work continues in the high bay. The cryogen boiloff situation has settled down substantially, and when I came in this morning I calculated roughly a liter per hour boiloff rate -- and things are still cooling. Based on the last run, though, we won't be ready to cool detectors until the 15th.

I spent a good part of the morning talking to Mark from CSBF regarding rigging and ballast hoppers. We checked with the CSBF electronics crew and it looks like we'll be able to put the ballast hoppers along the sides of the battery table, perhaps saving as much as 2 feet in height compared to mounting them at the bottom -- height that can be then used to lower our payload and provide much-needed clearance to our GPS antenna structure.

We noticed that the pressure in the cryostat has been slowly creeping upward starting yesterday, from a few microTorr to about 10-15 microTorr. Worried that there was a leak, we decided to leak check once more now that the pressure is low enough to check in the leak checker's more sensitive range. Luckily, we didn't find a leak, but we're still puzzled as to the origin of this strange increase. Also, I drove one of the NASA forklifts -- that was fun.

Jerry and Daniel stayed late last night after the clouds cleared and were able to take some images with the star camera that will be useful for debugging. Milligan found this morning that our spare flight computer board has been acting flaky and will need replacement. The gondola team also is finding that they're having issues with the serial ports on the flight computer crate and are actively investigating that (even as of now, roughly 11 PM). And the detector gang has been looking at SQUID noise in various hardware configurations of the instrument.

Luckily, while we've been waiting for the focal plane to cool, the weather has been nice: High 60's, fairly sunny, and not too much wind. Makes for good basketball weather. Sadly, it doesn't make for good basketball players -- watching a bunch of physicists play basketball is fairly comical.

Today's pictures:

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