Electromagnetic modelling of a tokamak fusion reactor magnet system using 2G High-temperature superconductors

Huber, Felix

Thesis

Electromagnetic modelling of a tokamak fusion reactor magnet system using 2G High-temperature superconductors

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Creator

Huber, Felix

Rights statement

Strathclyde Thesis Copyright

Awarding institution

University of Strathclyde

Date of award

2024

Thesis identifier

T17078

Person Identifier (Local)

201850704

Qualification Level

Doctoral (Postgraduate)

Qualification Name

Doctor of Philosophy (PhD)

Department, School or Faculty

Department of Electronic and Electrical Engineering

Abstract

The current challenges in reducing carbon emissions and the increasing demand for electric energy necessitate novel solutions for large-scale energy production. Nuclear fusion, a focus of research for nearly a century, has made significant breakthroughs in the past decade. Among these, the commercialization of high-temperature superconductors (HTS) stands out as a promising technology for future commercial fusion reactors. HTS materials, with their high critical current limits, enable high magnetic field operation, surpassing the capabilities of current low-temperature superconductors (LTS). Since the size and power of a fusion reactor scale with the fourth power of the magnetic field, achieving high magnetic fields is crucial for making fusion reactors economically viable. The Tokamak fusion reactor uses magnetic field coils arranged in a toroidal configuration to confine plasma, where fusion reactions occur. Effective confinement and control of the plasma are essential for generating fusion power, making the magnet system a critical component in Tokamak design. The complex electromagnetic behaviour of HTS necessitates numerical investigations, which are conducted using finite element modelling (FEM). Numerical methods like the T-A formulation enable the simulation of complex geometries with numerous turns, essential for producing the required magnetic field strengths in a fusion reactor. This thesis develops a novel design process for a large-scale fusion reactor magnet system using HTS, evaluated through the T-A formulation to assess the feasibility of exploiting HTS materials for large-scale fusion reactors. This evaluation considers achievable magnetic fields, required surface area, and the length of superconducting material. The initial study investigates loss behaviour in HTS, providing advanced insights into reducing hysteresis losses at magnetic fields higher than the full penetration field. Subsequently, an original method is devised to design a fully insulated HTS coil, from a single tape to a complete coil. This approach allows for the design of a coil comprising multiple pancakes and winding packs and optimizing the number of tapes needed to achieve a target magnetic field. This method is then applied to design the poloidal field coils (PFC) and toroidal field coils (TFC) systems for an ITER-like fusion reactor using HTS tapes. Each magnet system is investigated independently concerning current and magnetic field distribution and losses, viii particularly focusing on the identified reduction in losses at high magnetic fields. While the PFC system, consisting of three PFCs, is analysed in 2D, the TFCs require a 3D analysis due to the D-shape of the coil. A novel modelling strategy is developed, utilizing the T-A homogenisation advantages in a 3D model. This advanced numerical modelling strategy allows for the investigation of complex 3D geometries, such as a D-shaped coil. The work presented in this thesis enables the design and electromagnetic analysis of HTS magnet systems for Tokamak fusion reactors. This is achieved through advanced insights into the loss behaviour of HTS materials in high magnetic fields. Additionally, the research introduces an original design process for high-field HTS magnets. Finally, it incorporates a comprehensive 2D and 3D modelling strategy for the electromagnetic investigation of these magnets.

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