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Refilling the Liquid Helium of Bicep2

A week or two ago, Physicist Jon Kaufman gave me a brief tour of the Bicep2 Microwave Telescope, operating here at the South Pole. Aa I reported earlier, the telescope operates at a very very low temperature – only a few millikelvin above absolute zero. In this particular telescope, to get down to that temperature, liquid helium is used in a series of nested cryostats – each reducing the temperature further. In order to maintain the cold temperature needed, liquid helium must periodically be added from an outside source. A few photos of Jon performing a recent refill of liquid helium:

Here’s what the master control console looks like.

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Jon taking a few notes before beginning the fill

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That grey puff coming out of the tip of the filling hose is actually liquid helium. Strangely, as we were working around the telescope as it was off-gassing lots and lots of helium, we could breathe in deeply near the vent hose (warmer, gaseous helium) and our voices would get high – just like sucking on a party balloon.

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The exhaust hose gets so cold that it actually condenses gas from the air into liquid. That’s liquid nitrogen and oxygen (and a blend of others) dripping off the hose.

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A quick trip up to the roof just to check things out on a nice day. This is a look inside the groundshield, at the moveable top of the telescope.

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