Buckling of a Superconducting Ring in a Toroidal Magnetic Field

Experimental evidence and a theoretical model are presented for the magnetoelastic buckling of a rigid superconducting ring in a steady circumferential (toroidal)magnetic field. The theoretical model predicts a coupled translation and pitch displacement of the coil in the buckled mode. A discussion is given of both the linear and nonlinear magnetic perturbation forces. The experiments were conducted in liquid helium (4.2°K). The lowest natural frequency of the rigid coil on elastic springs was observed to decrease near the buckling current. Agreement between theory and experiment is fair. These results may have design implications for poloidal field coils in magnetic fusion Tokamak reactors.