HIGH-STRENGTH CONDUCTOR FOR PULSED MAGNETS

Magnetic inductions in excess of 30 T are produced in pulsed magnet systems. The coils for such systems call for a conductor with a combination of high conductivity, about 50% that of pure copper, and high strength, in excess of 1 GPa. High conductivity is required to limit the temperature rise during the pulse. High strength is required to resist the enormous Lorentz forces exerted on the conductor. These properties must be developed at 77 K, the temperature to which coils are precooled. In addition, the conductor must be ductile at room temperature to allow fabrication and coil winding. The desired combination of properties can only be achieved in a composite conductor in which the major component is copper. Macrocomposite conductors consist of copper and reinforcement arranged in such a way that the resultant properties are described by the rule of mixtures. Examples are copper with a stainless steel jacket or copper with a titanium core. In microcomposites the reinforcement is distributed on such a fine scale that strengths exceed the rule of mixtures. Examples are copper-niobium in situ composites and silver-copper two-phase alloys. The development of both types of composite is outlined in this paper.