Day 15, 6/11/2012 -- Of Helium and Half-wave Plates

Unlike yesterday (which was so slow that I spent the afternoon at the apartment and didn't bother taking any pictures or posting), today was a virtual whirlwind of activity.

First, we were joined by Shaul, back from his sabbatical in Israel, and ready to PI the heck out of the project. Second was Ilan, who is stopping by Palestine (also from Israel) for a few days on his way to a conference in Hawaii. But most importantly, we were joined by our most adored visitor: liquid helium. Inside the EBEX cryostat.


This morning started by pumping the small bit (~5" out of 28" filled on Saturday) of remaining liquid nitrogen in the helium tank into the nitrogen tank. Then, we started the helium transfer, which went smoothly. Now starts the arduous task of refilling the cryostat every ~6 hours until the boiloff starts do decrease -- and at 250L for the first fill and 150L per subsequent fill, now you understand why we had 2000L of liquid helium sitting around the high bay the past few days! We refilled once this afternoon around 4PM, Kyle and Ilan are filling again at ~9:30PM, and Jeff and I get the early morning shift at 3AM. After the first day, then the helium starts lasting longer -- 8 hours, then 12 hours, then a whole day, and soon thereafter reaches its steady-state hold time of ~14 days. Of course, that's when we start cycling fridges and doing detector work.

The other big success of the day was that the half-wave plate was successfully ungripped and rotated, which is sometimes a bit harrowing. But not this time!

Pictures:
https://picasaweb.google.com/104253244018605213307/EBEXInPalestine20120611