ETF magnet design alternatives for the national MHD program

The national MHD program of the U.S. Department of Energy will require an Engineering Test Facility as the next significant step following operation of the Montana Component Development and Integration Facility. Toward that end the MHD Magnet Technology group at FBNML is evaluating five superconducting magnet design concepts. The facility rated at 200 MWe, will require a magnet with an on-axis field of 6T, an inlet bore area of ∼2m²and an outlet bore area of ∼4m². The magnet will store\sim6\times 10^{9}. The designs under evaluation include a straightforward rectangular saddle coil set which is a scale-up of the CDIF magnet, a circular saddle design which is a scale-up of the Coal Fired Flow Facility magnet, a "Cask" design using staves and corper blocks as the principal support structure, an advanced design using internally-cooled, cabled superconductor to minimize substructure and eliminate the need for a helium vessel and, finally, a modular design that involves six coils with individual helium vessels and an integrated structure. Each of these designs is being considered in terms of operating characteristics, fabricability, transportability and cost. The characteristics of each design will be described and relative advantages summarized.