Stability and Vibrations of Internal Windings of High-Current Superconducting Solenoid Magnets

Abstract

High field solenoid magnets may experience internal damage or eventually collapse due to the powerful magnetic fields they produce. Elastic deformations of the conductor and insulation in these magnets deserve attention because they can cause local damage that can lead to electrical breakdown. In conventional stress analysis of cylindrically wound magnets, the magnetic field gradient, or magnetic stiffness, is usually neglected. However, in this thesis the magnetic stiffness is shown to have a significant effect on the elastic stability and vibration of these magnets. One-turn and multi-turn superconducting rings were used to study the effects of deformations on stability and vibration. Both static and dynamic methods were used to determine the critical buckling currents. The dispersion of natural frequencies with increase in current and subsequent in-plane and out-of-plane buckling of the rings near the critical buckling current were observed. A model based on ring theory and magnetic stiffness was developed to explain experimental observations and showed a fair to good agreement between experimental and theorietical values of the buckling current. This model was used to evaluate the buckling current of 7-and 10-turn magnets. The analysis showed buckling concentrated in the outer turns.