Rotational Hysteresis Loss in High-Field Superconductors

The rotational hysteresis loss in hard type II superconductors is calculated using the critical state model. For materials that can be characterized by a magnetic field‐independent critical current density J_c the surface rotational loss is $$\mathrm{W(}\mathrm{rot}{)}_s{\text{=[5/4π(6)]}}^{\text{1/2}}{\mathrm{(H}}_0^3{\mathrm{/J}}_c)\mathrm{erg}/{\mathrm{cm}}^2-\mathrm{cycle}.$$ In this expression H₀ is the amplitude in gauss of a rotating field applied parallel to the surface of a semi‐infinite slab while J_c is measured in amperes per square centimeter. This loss is 3.84 times the equivalent loss for alternating fields. In addition, it is shown that by measurement of the hysteresis loss or hysteresis torque as a function of field, one may calculate the field dependence of the critical current.