High-temperature superconducting magnet

An electromagnet wound from high-temperature superconductor, a material that loses all electrical resistance at relatively high temperatures. It reaches stronger fields than earlier superconducting magnets.

Superconductivity is the loss of all electrical resistance below a certain temperature. With no resistance, a large current flows without generating heat, so a strong magnetic field can be held with very little power. In 1986 Georg Bednorz and Alex Müller found a copper oxide that becomes superconducting at a temperature far higher than anyone had expected^[1]. High here still means well below minus 100 °C, but this family of materials stays superconducting even in very strong magnetic fields.

The performance of a fusion machine depends strongly on field strength. In 2021 CFS and MIT in the United States reached 20 tesla with a large magnet wound from high-temperature superconducting tape^[2]. That put the same performance within reach of a much smaller machine and helped set off the wave of private fusion ventures. The industry still has little experience of mass-producing such magnets in the numbers a reactor needs.