PhD Defence Anvar Valiyaparambil Abdulsalam | Optimization of Cable Performance of Nb3Sn and MgB2 Cable-in-Conduit and ReBCO-CORC® Conductors for Magnets in Fusion Devices

Optimization of Cable Performance of Nb3Sn and MgB2 Cable-in-Conduit and ReBCO-CORC® Conductors for Magnets in Fusion Devices

Anvar Valiyaparambil Abdulsalam is a PhD student in the Department of Energy, Materials & Systems (EMS). (Co)promotors are prof.dr.ir. H.H.J. ten Kate, prof.dr.ir. J.M. van Oort and dr. A. Nijhuis.

Nuclear fusion promises a safe, carbon-free source of energy. However, confining the extremely hot plasma, whose temperature is several orders of magnitude higher than that at the surface of the Sun, requires powerful magnets built from superconducting cables. The superconducting cables used in magnet systems must carry a huge amount of current to produce such high magnetic fields. Hence, these cables need to withstand very high magnetic fields and the resulting electromagnetic forces. Careful design of superconducting cables is vital for the success of fusion reactors such as ITER and DEMO.

The electromechanical performance of three types of superconducting cable used in fusion magnets is investigated in this thesis: Nb3Sn and MgB2 Cable-In-Conduit Conductors (CICCs), and REBCO CORC cables. The thesis combines experimental and numerical modeling techniques, including the JackPot-ACDC code developed at the University of Twente. The costly experimental work required collaboration from different universities and industries worldwide. The thesis examines AC loss, inter-strand contact resistance, and mechanical degradation under different operating conditions. For the Nb3Sn cables, several demonstrator cables were manufactured and tested to identify a design that minimizes coupling loss and strand damage while offering sufficient mechanical support. A cabling pattern developed at the University of Twente was found to perform best. The Twente design was subsequently used to manufacture and validate sub-size MgB2 cables from two different strand manufacturers.

For the REBCO CORC cables, detailed finite-element models of the three-dimensional stress-strain state were developed. The FE models analyzed bending, tensile, and transverse mechanical loads. The FE models were then validated against dedicated experiments, revealing how different design factors govern cable flexibility and current-sharing between the superconducting tapes.

Together, these findings provide practical design guidelines and validated modeling tools to support the development of more reliable superconducting cables for the magnet systems of future fusion power plants.