The South Pole Cryogenics Laboratory, usually known as Cryo Barn, was originally established to service various telescopes and science experiments with cryogenic cooling liquids such as Liquid Helium and Liquid Nitrogen. However, in recent years, most new experiments which operate at cold temperatures have been of the “closed loop” variety – that is, they don’t vent or leak any of their coolant. Therefore, most of the new experiments don’t need the regular coolant refils that Cryo Barn was built to provide. Last week, I got to watch as the last Liquid Helium dewar was filled from the main tank, and then shipped off to the Bicep2 CMB Telescope. A few pics:
Cryogenics Technician Flint Hamblin prepares the main Liquid Helium holding tank for transfer to the smaller transport dewar.
Fill volume of the dewar is measured by weight, and here Flint is seen checking the dewar weight as it’s suspended from the ceiling.
Liquid Helium is at about 4 Kelvin, or -452.2 degrees Fahrenheit. During the fill, the valves and piping that handle the liquid helium get extremely cold. In fact, they get cold enough to condense out the gasses from the air, turning the air into liquid. In this picture, the wet drips seen coming off the exhaust nozzle are drips of liquid nitrogen and oxygen condensed out of the surrounding air. Basically liquid air. The small grey plume coming out of the tip of the nozzle is actually a small amount of liquid helium, instantly vaporizing. The small white crust seen at the tip of the nozzle is solid air.
The dewar is transported from Cryo to MAPO on a sled pulled by a snowmobile. Here’s Flint and Physicist Jon Kaufman on the snowmobile, as I ride on the sled with the dewar.
The final step of the process, hoisting the dewar up into MAPO, where it’s used to fill the Bicep2 CMB telescope.