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- Nuclear fusion comes in all shapes and sizes, and while donut-shaped tokamaks are the most common, many companies and universities are investigating other ways to bring star power in cheaper and more efficient ways.
- One of the ways is magnetic mirror confinement, a concept popular in the 1980s that was recently resurrected, thanks in large part due to recent breakthroughs in high-temperature superconductors, by the University of Wisconsin-Madison and its spinoff company, Realta Fusion.
- On July 15, the resulting Wisconsin HTS Axisymmetric Mirror (WHAM) achieved first plasma, a major milestone for the device, and now the team will work on improving efficiencies and hopefully bringing fusion-powered industrial heating and grid energy to the masses faster than other proposed methods.
The race toward nuclear fusion, the near-limitless energy source that powers our Sun, is quickly becoming a packed field. Many laboratories leverage tokamaks to confine plasma and induce nuclear fusion while others opt for stellarators, z-pinch devices, and even inertial confinement technologies that blast fuel capsules with an array of lasers. Now, the University of Wisconsin-Madison and the private company Realta Fusion are backing a different horse—magnetic mirror confinement.
On July 15, the university’s Wisconsin HTS (high-temperature superconducting) Axisymmetric Mirror (WHAM) achieved “first plasma,” officially setting in motion a new idea for bottling the power of stars on Earth. Well, sort of new.
Magnetic mirror, which uses superconducting magnets to create a “magnetic bottle” that traps energetic plasma, was a popular fusion concept in the 1980s. In fact, Lawrence Livermore National Laboratory worked magnetic mirror confinement in tandem with its now-famous inertial confinement facility. Due to technological limitations and lack of funding at the time, the fusion industry went down the toroidal tokamak path.
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However, in 2020, UW-Madison brought back the concept and spun off the company Realta Fusion to chase this energy dream. This new milestone provides a huge boost to an idea that the industry had largely written off almost half-a-century ago, but is now resurrected in large part due to breakthroughs in HTS magnet technology.
“The outlook for decarbonizing our energy sector is just much higher with fusion than anything else,” UW-Madison’s Cary Forest, who led the development of WHAM, said in a press statement. “First plasma is a crucial first step for us in that direction.”
Boiled down to its most basic design, WHAM is a cylindrical chamber with two electromagnets at either end. Charged particles of hydrogen isotopes (deuterium and tritium) make a helical (spiral) path along this cylinder, and when they encounter a strong enough magnetic field, these particles reverse motion, which is the whole “mirror” part of this technique.
This increases the chance of these two isotopes fusing, resulting in a neutron (which deposits its heat into a surrounding blanket) and an alpha particle (helium nucleus), which overcomes the magnetic barrier and is captured by “dish-shaped direct energy converters,” according to Realta Fusion. Initially, the idea could be used for industrial heating processes, which is a significant contributor to greenhouse gas emissions.
“We believe fusion is the solution,” Kieran Furlong, co-founder of Realta Fusion, said back in 2022. “However, current fusion projects are taking too long, they’re too capital intensive, and they’re too complex. Realta is developing a reactor…that will be a much better fit in terms of time, capital, and risk for the early adoption of fusion energy by applying advances in superconducting materials, plasma physics, and computing power to simpler, linear fusion configuration.”
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Since then, Realta Fusion was one of eight fusion companies to receive Department of Energy milestone funding in 2023, and now that the team has achieved first plasma, they are ready to move into “discovery phase” in the hopes of improving efficiency and answering lingering technological questions—and there are lots of questions to answer.
"Can we build the magnets?” Forest asked in a press statement. “Can we increase the stability of the plasma, which is inherently unstable? How well can we confine the plasma?These questions will take several years to address well, and if we can understand and predict everything about this device, then it will provide the foundations for the next device, the break-even device.”
Contributing Editor
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.
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