Prospects of an alternative superconductor technology for fusion reactors

Abstract

New concepts for Tokamak fusion reactors are enabled by ReBCO high temperature superconductors, either to achieve toroidal magnetic fields in the range of 20 T, and/or by operating temperatures above 4.2 K, e.g., 20 K. The application of ReBCO tapes is challenging because common techniques for the manufacturing and quench protection of magnets, developed for classical multifilamentary superconductors, such as NbTi and Nb3Sn, cannot be applied directly. Less risky would be the use of a ternary molybdenum chalcogenide (TMC) superconductor, which was under development before the discovery of high temperature superconductors. Although a low temperature superconductor, the upper critical field is extremely high resulting in a comparable field dependence of the critical current to ReBCO. Because of the improved superconductor fraction of a multifilamentary TMC conductor, the expected engineering current density can be one order of magnitude higher. In addition, a TMC conductor has the potential for cost efficiency and a performance index around 1 $/kAm at 20 T seems be possible.