Activation of Trapped Field Magnets by Flux Pumping

High temperature superconducting trapped field magnets (TFM) offer great potential as an alternative to second generation YBCO wire, both in cost and performance. The difficulty of activating this material is the primary problem hindering their incorporation into electromechanical devices. An alternate method called flux pumping is discussed in which the magnetic field trapped within a precooled TFM is increased, i.e., pumped up incrementally. A boundary element formulation is employed to illustrate what happens to the current density within the TFM during this pumping procedure. This is followed by a rigorous analytical formulation to simulate flux pumping within a 2-cm diameter TFM; the simulation is compared to an experiment using a NdFeB magnet as the pumping source.