Pinning mechanism and engineering critical current density considerations in the design of MgB2superconducting coils

Abstract

Superconducting coils are designed for the generation of specified magnetic fields (low, intermediate, or high). To function in different field regimes, it is important to analyze the pinning mechanics and the types of pinning centers in the superconductor in a precisely defined magnetic field. Correct identification of pinning centers would allow for the formulation of approaches to increase the critical current density and critical magnetic field, ultimately making it possible to reduce the cost of producing superconducting coils (with smaller amounts of wire needed). This paper will present a method to analyze pinning centers in MgB2 superconductor wires in low, intermediate, and high magnetic fields at 4.2 K, 20 K, 25 K, and 30 K. This method allows us to elucidate the influences of doping, isostatic pressure, and reduction of the wire diameter on individual pinning centers in a specific magnetic field. In this article, we also show a method to analyze the types of pinning centers and their impact on the engineering critical current density (Jec). This method not only allows for the identification of the types of pinning centers, but also identifies which type allows for a shift in the Jec criterion of 100 A/mm2 to enable higher magnetic fields.