Introduction

Abstract

Chapter 1 covers various fundamental superconducting properties that determine the flux pinning and electromagnetic phenomena in type II superconductors. The content is mostly based on the Ginzburg-Landau theory, which describes well the magnetic properties of type II superconductors. In particular, it is shown that the center of a quantized flux line must be in the normal state so that the Josephson current does not diverge due to the singularity in the gradient of the phase of the superconducting order parameter there. This causes a loss due to the motion of normal electrons in the core that is driven by the electric field, which is induced when flux lines are forced to move by the Lorentz force. At the same time such a structure of the core contributes to the flux pinning event. The role of the kinetic energy in determination of the upper critical field is also shown. This will help the readers to understand the kinetic energy pinning mechanism for the artificial Nb pinning centers introduced into Nb-Ti, which is discussed in Chap. 6.