TEMPERATURE COMPENSATION IN HYBRID MAGNETS WITH APPLICATION TO THE FERMILAB STACKER AND RECYCLER RING DIPOLE DESIGN

Design theory of hybrid (permanent magnet plus iron) accelerator magne ts with application to the proposed permanent magnet recycler and stac ker rings at the Fermi National Laboratory is presented. Field stabili ty in such devices requires that changes in the strength of the perman ent magnet material with temperature be compensated. Field tuning tech niques, including those employing variable capacitance between energiz ed pole and magnet yoke and those employing variable energization of m agnet pole pieces, are described. Mechanical configurations capable of achieving temperature, compensation passively, including use of expan ding liquids/gases and bimetallic springs are outlined. Active configu rations, relying on a actuator, in addition to temperature compensatio n, have the additonal benefit of enabling magnet tuning about a nomina l operating field level.