Superconductivity for mirror fusion

Mirror experiments have led the way in applying superconductivity to fusion research because of unique requirements for high and steady magnetic fields. The first significant applications were Baseball II at LLL and IMP at ORNL, which used multifilamentary niobium-titanium and niobium-tin tape, respectively. Now the USSR at Kurchatov is building a smaller baseball coil with a 6.5 mm square multifilamentary niobium-titanium superconductor similar to the Baseball II conductor. However, the largest advance in fusion magnets will be used in the Mirror Fusion Test Facility (MFTF) now under construction at LLL. Improvements in the technology of the previous LLL experiment, Baseball II, have been made using new conductor joining techniques, a ventilated wrap-around copper stabilizer, and stronger structural welding methods. The MFTF coil winding is proceeding on a separate former to allow parallel construction of the main structure. Not only does this shorten the project schedule to equal that of other conventional constructions, but a second vacuum barrier is created between the magnet helium and the plasma environment for reliable operation. In the future, LLL envisions a superconducting version of the Tandem Mirror Experiment and a possible hybrid reactor leading to economical fusion power.