A special new tape could make small, efficient nuclear fusion reactors possible

A revolutionary new high-temperature superconducting tape could lead to the development of small, efficient tokamak nuclear fusion reactors.
Christopher McFadden
Image of some of the spools of tape to be used in the Sparc reactor.


A groundbreaking high-temperature superconducting tape has been devised that could prove revolutionary in our quest to develop sustainable nuclear fusion, reports IEEE Spectrum. Currently used in constructing a new tokamak reactor at a US Army Reserve base near Boston, the tape could be the secret to smaller, highly-efficient fusion reactor design.

A revolutionary material

The tape, developed by Commonwealth Fusion Systems (CFS), is the product of decades of research at the Massachusetts Institute of Technology (MIT). CFS's technology stands out due to its use of high-temperature superconducting tape. This tape is layered and stacked to form powerful electromagnets that can contain the plasma and prevent most charged particles from colliding with the tokamak's walls.

The innovative approach is expected to create a smaller and more cost-effective high-performance tokamak compared to previous methods.

Currently, two primary approaches are being studied to develop fusion energy. Magnetic confinement involves using electromagnets to contain plasma within a tokamak. The other, inertial confinement, utilizes laser technology to heat and compress a fuel-filled target to initiate a reaction. Advancements in materials science and high-speed computing, modeling, and simulation are also being used to drive progress in both approaches.

CFS, IEEE Spectrum reports, is the top fundraiser in the magnetic-confinement field, with over $2 billion secured for constructing its Sparc pilot plant.

When cooled below a specific temperature, superconducting materials can conduct direct-current electricity without resistance or energy loss. High-temperature superconducting (HTS) magnets can operate at much higher temperatures than the superconducting magnets that are typically used in tokamaks. The latter often require more complex and costly cooling systems involving liquid helium.

A special new tape could make small, efficient nuclear fusion reactors possible
CFS is using HTS and has built its first-of-its-kind high-field large-bore superconducting magnet.

While the term "high temperature" may sound dangerous, HTS materials function within a range of 20 to 77 kelvins, which is between -328 degrees Fahrenheit (-200 degrees Celsius) to -418 -328 degrees Fahrenheit (-250 degrees Celsius). Although still very cold, this temperature range is significantly warmer than the temperatures required for typical superconductors, which can only operate at temperatures close to absolute zero.

The team’s superconductor of choice was yttrium barium copper oxide, or YBCO. To make YBCO tape, some manufacturers first use a laser to vaporize bulk YBCO into a plume. That plume then deposits as a thin film of YBCO onto a steel substrate, followed by an oxygenation process to change the YBCO’s structure into a state that enables superconductivity.

“These new materials are allowing a new path to fusion energy because, in addition to their superconducting abilities at higher cryogenic temperatures, they are also able to go to very high magnetic fields,” Scott Hsu, a senior advisor at the U.S. Department of Energy (DOE) and the agency’s lead fusion coordinator told IEEE Spectrum. “These properties provide the possibility to design smaller, less complex, and lower-cost fusion systems that are quicker to build and easier to take apart for maintenance," he added.

It's tremendously exciting

Small tokamaks like those being developed by CFS could disrupt the trend of the past 40 years in fusion energy research, which has focused on constructing increasingly larger machines. The largest of these is Iter, an international collaborative effort to build a massive tokamak in Cadarache, France. Construction of the Iter fusion experiment (formerly known as the International Thermonuclear Experimental Reactor) began in 2013 and has consumed the majority of global public funding dedicated to fusion energy research. The Iter Organization now estimates the project will cost $22 billion, far exceeding the original 2006 estimate of $5.6 billion.

“Iter is a tremendously exciting and useful experiment, but it has a size problem,” says CFS’s Sorbom. “If you could somehow shrink that tokamak, you could build it much faster and cheaper," he added.

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