超伝導体の交流損失の基礎

Abstract

The basic topics for AC losses in superconductors are reviewed briefly. The AC losses are affected by various factors such as the variation in critical current density, strong nonlinearity of transport property and the complicated electromagnetic environment in superconducting apparatus. Several general expressions to evaluate AC losses are presented from the physical viewpoint of local power dissipation, Poynting's vector and the area surrounded by a magnetization curve. The fundamental properties of AC losses are discussed for each step, from the initial stage of superconducting materials to the final stage of a superconducting apparatus system. The measurement techniques for AC losses based on both electromagnetic and thermal principles are explained for some practical cases. Finally, the guidelines to suppress AC losses in typical superconducting power devices are proposed.