Bitter-type toroidal field magnet for ZEPHYR

Under contract to the IPP an Garching, MBB conducted a feasibility study concerning stress computations, design and material technology of a Bitter-type magnet for the ZEPHYR project. The big overall dimensions of the magnet (6,50 m diameter, 2,80 m high), access for diagnostics and neutral injection (16 ports), the possibility of remote handling of activated parts and very high forces form the main requirements for design and material technology. A design with 16 identical modules (coils) was chosen, each coil consisting of 16 Bitter-plates, plate housings and one diagnostic/neutral injection wedge. The structural parts are connected by bolts and form the bending stiff structure of the magnet. The most critical area of the magnet is the inner wedge-shaped part of the coils ("throat area") with extremely high tension, compression and shear stress values, to which temperature effects contribute heavily. Steel-copper compounds are found to be the best Bitter-plate materials. Copper-plating austenitic steel can be done galvanically or by explosive techniques. Cold-worked austenitic steels (e.g. type 1.3974, 1.4406) fulfil the requirements in the throat, in the flat-plate region milder steels (e.g. ATVSMO, 1.3974) can be used. Different plate concepts are being considered. Plasma-sprayed Al2O3/TiO2and reinforced epoxy layers are provided as insulating materials in different magnet areas. The study has been finished in Sept. 1980 with the conclusion, that a Bitter-type magnet would be feasible, but that as the next step further activities would be absolutely necessary in the fields -stress optimization in the throat area and -material development and testing with large scale samples.