Materials for 100 T monocoil magnets

The development of improved conductors and reinforcement materials is instrumental for the achievement of ultra-high fields with monolithic magnets. They have the advantage that there is no coupling between the coils of the traditional two-coil systems, and that the magnet can be built much smaller, and it has longer pulse times. The fields that can be achieved are determined by the strain limitation of the conductor, and the strength and stiffness of the reinforcement. We have investigated the material requirements for this type of magnet to define the objectives for material development. It follows that future material development activities for reliable 100 T magnets should focus on conductors with the following specifications (all values are at 77 K): a) Ultimate conductor strength of 1.2GPa, b) Conductivity of 500 percent IACS, c) 10 percent strain to failure, d) Fatigue strength of 1 GPa at about 5000 full load cycles from tensile stress at peak pulse to compressive stress after the pulse of about 0.6 GPa. It is equally important to improve the reinforcement materials. At the NHMFL, we use with great success a combination of Zylon fiber and MP35N superalloy. We have increased the isotropic strength of MP35N at 77 K to 2.6 GPa (modulus 240 GPa), and are working on further improvements.