An innovating insulation for Nb3Sn wind & react coils:: Electrical tests

If Nb3Sn is the best superconductor candidate for the realization of high field magnets (for 10-11 Tesla), its implementation remains delicate because of the great brittleness of material after the heat treatment necessary for the formation of Nb3Sn compounds. The conventional insulation for Nb3Sn Wind & React coils requires performing, after the heat treatment, a vacuum resin impregnation, which adds to the cost and raises failure risk. We have proposed a one-step innovating ceramic insulation deposited directly on the un-reacted cable. After the heat treatment, we obtain a coil having a mechanical cohesion, while maintaining a proper conductor positioning and a suitable electric insulation. We have shown that using this insulation in a coil manufacturing process does not affect the electrical properties of the Nb3Sn wires. A solenoid of small dimensions (9 * 20 turns on an internal diameter of 22 mm) has produced a magnetic field of 3.8 T at 740 A. It was tested with success in high external magnetic fields: the quench limits have been imposed by the strand and the insulation was not damaged.