A toroidal bitter plate magnet for an ignition test reactor

A toroidal field magnet based on the Bitter plate principle has been designed for an Ignition Test Reactor. The magnet plate has greater than usual radial extent in order to accommodate plasma compression in the direction of the major radius. The toroidal field at the center of the compressed plasma is 9.5 T with low ripple. The radial extension of the plates gives rise to unusually high vertical forces and consequently high stresses. The structural design is based on fatigue analysis, with a life of 10,000 full power pulses, each of 6.5 second duration, and a safety factor of 10 on life. The torsional moment generated by the superimposed vertical field is resisted by frictional shear between the plates which requires high circumferential pressure throughout the plate. In order to supplement the circumferential pressure generated by the centripetal Lorentz forces, the vertical field coils are used mechanically to provide a high radial pressure on the outer edge of each plate. Further details are discussed, concerning irradiation, cooling, and remote maintenance. Results are included from computer codes developed for the computation of toroidal field stress, thermal stress, torsional shear and magnetic field ripple. (author)