Multi-composite wire for high performance pulsed magnets

The multi-composite (MC) wire is a new concept in the pursuit of obtaining the ideal conductor for high performance pulsed magnets. The MC wire consists of a braided, insulating sleeve enclosing a bundle of thin wires: conductor (Cu, CuNb) and reinforcement (e.g., high strength steel), with all free spaces filled by a tight packing of high strength fibers that do not need to be insulating (e.g., carbon fibers). The MC concept is based on the fact that thin wires are inherently stronger. This concept allows winding around a small bore and much flexibility: the composition and geometry of the MC core can be varied even along the length of a continuous wire - to obtain the desired properties of strength and electrical conductivity. Prototype MC wires were made with soft Cu and carbon as core materials, with ultimate tensile strength of 1.2 GPa and 1.7 GPa and conductivity of 38% IACS at 300 K. Several coils were designed and manufactured with similar bore (18 mm) and pulse duration as our standard user coils with internal reinforcement. Although the coil structure was not yet optimized, fields in excess of 50 T were obtained, leaving much room for improvement.