A superconducting magnet for Stanford University

Abstract

The Department of Energy is currenty developing three MHD magnet concepts for application to baseload coal power generation technology. One concept is a rectangular saddle magnet having nonmetallic substructure for conductor support. This magnet is to be installed at DoE'S Component Development & Integration Facility at Fhtte, Montana, Another is a circular saddle magnet in which the radial Lorentz forces are contained by interlayer bands which take the place of a superstructure. This technique was used for the U-25 magnet currently in operation in Moscow. A larger version is being developed for the Coal-Fired Flow Facility (CFFF) at the University of Tennessee Space Institute. The third concept is the Stanford Superconducting Magnet (SSM), a circular saddle magnet having a metallic substructure to support the conductors. It will be a part of the MHD research facility at Stanford University. The specific metallic substructure described in this paper was designed in 1979. This design is being modified during 1980 to incorporate features of the CASK concept into the substructure design. The producibility features of CASK are prototypical of baseload-size magnets, The revised design will be reported in a forthcoming paper. Two major advantages of using a substructure to support the conductors are (1) conductor movement within the winding is controlled which, in turn, limits frictional heating of the conductor, and (2) the substructure reacts a substantid portion of the magnetically induced loads. Energy dissipation and voltage protection in metallic subplates is discussed. An analysis of the eddy current in the,substructure during a rapid quench has shown that the dissipation is only 2.5% of the total 93 MJ stored in the winding. Quench voltages have required the use of coil-to-subplate shorting resistors within the winding to reduce subplate stray capacitance effects and to limit ground fault currents. One unexpected benefit of eddy current has been discovered. During seismic event or MHD channel-induced vibration of the winding, eddy currents induced in the vacuum vessel provide substantial damping for the control of resonant amplitude, The damping magnitude is360 J/cycle for a Stanford-sized magnet.