Slashdot videos: Now with more Slashdot!
We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).
The magnets they use to shape and steer the beam require about 12,000 amps, so they use superconductors. Between 2K and 4.5K, the superconductor undergoes a phase change and becomes non-superconducting, and the resistance goes from zero to not zero all of a sudden. The 12,000 amps suddenly produces an incredible amount of heat (P=I^2R) which drastically increases the pressure from the liquid He. That much pressure means the He needs to escape (violently), causing all sorts of trouble. It's called a 'quench.'