Applied superconductivity, which emerged in the 1960s, often remains a hidden niche technology, yet one with significant societal impacts: in healthcare with MRI scanners and NMR spectrometers—the two major commercial applications—in our understanding of the universe through particle accelerators, and in the promise of abundant carbon-free energy through magnetic fusion reactors... These devices rely on the ability of superconductors to carry very high current densities without the Joule effect at very low temperatures—and are therefore entirely dependent on cryogenics, which for a long time relied primarily on helium (a few Kelvin).
The late 1980s saw the discovery of high-critical temperature superconductors (HTS) that could be used in liquid nitrogen. By breaking the barrier of helium cryogenics for many applications, there were high hopes for significant growth in the superconductivity market. The extreme complexity of these materials initially dashed those hopes, but researchers’ ingenuity proved up to the challenge, leading to the design of high-performance HTS. These superconductors, particularly REBCO tapes, reached a pre-industrial stage in the early 2020s. A review of the current state of the art will be presented.
One unique property of these materials has attracted a great deal of interest: their ability to carry high current densities at low temperatures—below 20 K—under very strong magnetic fields, far exceeding the limits of conventional superconductors (approximately 20 T). REBCO tapes bring a new paradigm. The first spectrometers equipped with HTS tapes are now available on the market, increasing resolution and sensitivity to facilitate a better understanding of neurodegenerative diseases for example, thanks to extreme magnetic fields (30 T). These are the first commercial devices to use HTS, aside from current leads.
This technological breakthrough is generating enormous interest in magnetic fusion, since a reactor’s power density varies as the fourth power of the magnetic induction strength. Doubling the magnetic induction—made possible by HTS—results in a reactor that is 16 times smaller. This is a significant advancement and paves the way for compact fusion, hence the intense activity and frantic global race in this field. Investments in this field exceed several billion dollars. This activity has enabled REBCO tapes to progress and become a commercial product. Nevertheless, numerous challenges remain, such as the need to withstand enormous magnetic forces or manage colossal heat fluxes. An overview of international activities in HTS magnetic fusion will be provided.
Operation at higher temperatures, in liquid nitrogen—an inexpensive green fluid—is of interest for other applications that do not require high magnetic induction, such as power cables or fault current limiters. These are innovative, one-of-a-kind devices that offer very promising prospects for electrical grids. Based on the virtually instantaneous transition from a zero-resistance element—invisible to the grid—to a highly resistive element as soon as the current exceeds a certain value, it offers unique possibilities for power grids by solving the issues associated with fault currents.

The final example is the electric aircraft powered by fuel cells using liquid hydrogen. Since cryogenics is practically “free,” an SHTC electrical system is a natural choice, especially since it offers compactness and low weight—two key advantages in aeronautics—in addition to a new function with superconducting fault current limiter.