Design and Analysis of a 25T Resistive NMR Magnet

A 25 Tesla resistive magnet with homogeneity of 1 ppm over 10 nun diameter spherical volume is being designed at the National High Magnetic Field Laboratory in Tallahassee, FL. The magnet consists of three concentric axially cooled Bitter stacks connected electrically in series. It will produce a peak field of 24.1 T in a 50 mm warm bore while consuming 15 megawatts of power and 25 T at 16.3 MW. Each of the stacks is designed to have a high uniformity by itself so the tolerance in axial positioning is not critical. Details of the magnet design, sensitivity to manufacturing tolerances and current distribution between cooling rings is presented.