Electromotive force and magnetization process of a superconducting traveling-wave flux pump

TL;DR

This paper introduces a novel method using a traveling-wave flux pump to control vortices in high-temperature superconductors, enabling precise DC current output by manipulating vortex motion and magnetic fields.

Contribution

It presents a new flux pump technique for macroscopic vortex control and demonstrates high-precision DC current regulation in superconducting magnets.

Findings

DC current originates from motional electromotive force, not induced emf

Magnetic fields modulate the magnitude and polarity of the output current

Numerical simulations confirm flux control by applied fields

Abstract

Understanding and controlling the motion of superconducting vortices has been a key issue in condensed matter physics and applied superconductivity. Here we present a method for macroscopically manipulating the vortices based on travelling wave flux pump to accurately output industrial-scale DC current into high-temperature superconducting (HTS) magnets. DC magnetic fields are used to adjust the polarity of the vortices and thus modulate the direction of the output current, which demonstrates that the DC current of the flux pump originates from the motional electromotive force ( e.m.f. ) other than the induced e.m.f.. In addition, applying different strengths of DC fields can modulate the magnitude of the output current. Further numerical simulation suggests how the flux inside the superconducting tape is controlled by different applied fields. We build a controlled flux flow model to correctly explain the behavior of vortices controlled by the flux pump, and how the motional e.m.f. is created by manipulating the vortices. Based on the method, we achieve high precision regulation of output current using adaptive control of the DC magnetic field, allowing the flux pump to output DC current just as accurate as a typical commercial power supply. This work advances the technic for macroscopic manipulation of vortices.