An electrical engineering approach to the stability of MgB2 superconductor

Abstract

The high critical temperature, 39 K, and usable critical current characteristics of MgB2 make it a highly interesting superconductor for practical applications. Unlike conventional low temperature superconductors, it can be used around 20 K where cooling is relatively easy with a cryocooler. In addition, long-length MgB2 conductors can be manufactured of inexpensive materials with standard techniques. Though the MgB2 was found superconductive only in 2001, industrially manufactured conductors are already now available and several promising demonstration projects are underway. To develop a new application using the MgB2, detailed design methods are required. Many modelling tools, but not all, can be adopted from devices constructed of conventional superconductors.

This thesis begins by introducing readers to the mathematical formulation of phenomenon models required for the research presented in the attached publications. After this background, I first study conductor characterisation in a conduction-cooled measurement station, because short-sample characterisation forms the basis of magnet design. From there I move to propose a model for computing the critical current of coils consisting of a ferromagnetic matrix. Based on the coil design, a stability margin must be determined for the coil. Here, I present a numerical model for computing the minimum propagation zone, a model that can be further used to determine the minimum quench energy and the normal zone propagation velocities. At the end of the thesis, I consider a scientific industrial-scale induction heater project ALUHEAT. First, I introduce the basics of quench analysis and, then simulate a quench in the main coil of the induction heater with the developed quench program. In the quench analysis, I also design protection for the coil.