Design, fabrication and test of the react and wind, Nb3Sn, LDX floating coil conductor

The Levitated Dipole Experiment (LDX) is a novel approach for studying magn etic confinement of a fusion plasma, In this approach, a superconducting ri ng coil is magnetically levitated for up to 8 hours a day in the center of a 5 meter diameter vacuum vessel. The levitated coil, with onboard helium s upply, is called the Floating Coil (f-Coil). Although the maximum field at the coil is only 5.3 tesla, a react-and-wind Nb3Sn conductor was selected b ecause the relatively high critical temperature will enable the coil to rem ain levitated while it warms from 5 K to 10 K. Since pre-reacted Nb3Sn tape is no longer commercially available, a composite conductor was designed th at contains an 18 strand Nb3Sn Rutherford cable. The cable was reacted and then soldered into a structural copper channel that completes the conductor and also provides quench protection. The strain state of the cable was con tinuously controlled during fabrication steps such as: soldering into the c opper channel, spooling, and coil winding, to prevent degradation of the cr itical current, Measurements of strand and cable critical currents are repo rted, as well as estimates of the effect of fabrication, winding and operat ing strains on critical current.