Advanced superconducting MHD magnet design for a retrofit power plant

A magnet has been designed for an MHD (magnetohydrodynamic) topping cycle retrofit of a conventional power plant. The channel power output will be ~35 MWe. The magnet which will have 4.5-T peak on-axis field, will be constructed of an unusual NbTi superconductor wound into four subunits per dipole half. These will consist of three 45° saddle coils with circular or ellipsoidal end turns and a single planar coil with a modified racetrack shape that will serve principally as a field-shaping coil. This planar coil also allows a substantial reduction in the ratio of peak to central field strength. Among the unique features of this design will be the use of flexible bands in tension as the primary element of the transverse force containment structure. The conductor will be of the cable-in-conduit type with a cable having a low copper-to-superconductor ratio and a thick-walled aluminum conduit sheath. The sheath will support the axial loads on the saddles and will also provide thermal mass for protection against overheating in the event of an energy dump. The analysis and design of this magnet system and its projected advantages in both performance and economics are discussed