I was lucky enough to have my camera on me yesterday at work while our low temperature group was beginning cool down on their fridge. These pictures were taken while they were adding fresh liquid He to the fridge. Thought it'd be interesting since I've never seen liquid He before. Best of all - these pictures will be used by my department on promotional material (yay, I get published!).
1. The Fridge. http://einstein.drexel.edu/~vkasli/_gallery/_MG_2448.JPG
The guys working in this lab are studying how to make qubits that'll be used for quantum computing talk to each other. The fridge is used to cool Josephson junctions down to very low temperatures (T < 10 mK) to create the quantum qubits. This is down by letting liquid He boil off (think of sweat evaporating off your skin cooling you down).
3. The magic stuff - liquid He! http://einstein.drexel.edu/~vkasli/_gallery/_MG_2460.JPG
Initially when the tank outlet is opened up, all you gets is a stream of cold He gas. As the tubing cools, the liquid He in the tank stops boiling off and you can see a stream of actual liquid escaping the nozzle before it vaporizes. At this point, it can be introduced into the fridge without heating the already cool fridge up.
4. Details of the top of the fridge. http://einstein.drexel.edu/~vkasli/_gallery/_MG_2461.JPG
Condensation forms on the outside of the fridge as the liquid He transfers. After a few minutes, the condensation will start freezing forming lots of ice around the parts you see here. After another 15-20 minutes of transfer, air will start liquefying around the exposed metal parts at the mouth of the fridge inlet.
Nopes, not a typo. Compared to what these guys cool down to, intergalactic space at 2.73 K is really hot!
The LHC magnets don't need as much cooling because they use superconductors with as high a superconducting temperature as is economically optimal (initial purchase cost vs lifetime operating cost).
Here they need really low temperatures because in addition to to the Josephson effect requiring superconductivity, you want really low energy stable states that you can study easily.
It's not my group but no - no condenser. They don't stay cool long enough for a condenser to be economic (atleast when the prof got his startup fund before the 2008 price hike it wasn't economically sound to get a condenser). So far they've just used a bath of He and let it evaporate. Typically they go through about 200 liters (~$2000) of He in the cool down phase and then another 35 liters per day (~$350) to stay cold (typically they stay cold for a week). Right now the problem is getting good samples to test. They also have some weird noise issue that seems to be linked to the local metro/rush-hour traffic! ;D
