Design principles for optimized pulsed magnets

Simulation calculations have been carried out to explore the distribution of stresses and temperature in typical pulsed user magnets with internal reinforcement. The coils are considered as consisting of units each comprising one layer of conductor supported by one or more layers of reinforcement. In the inner layers of the coil these units have the tendency to separate due to the increase of relative deformation with increasing radius, while part of the force in the outer layers is transmitted to an outer reinforcing shell. The maximum equivalent stress in the inner units can be equalized by adjusting the thickness of the reinforcement layers. The anisotropy of fiber composites increases the stress steeply from the outer surface to the inner surface within each reinforcement layer; this imposes a limit on the thickness of the reinforcement. In the inner layers of the coil, Joule heating is enhanced by magneto-resistance and the skin effect. The temperature distribution can be equalized by subdividing the coil into sections made with wire of different cross section, in order to avoid overheating of the inner layers.