A team of scientists has made a major breakthrough in fusion energy technology. They’ve built the first-of-its-kind fusion experiment using permanent magnets, a surprisingly simple technique that could potentially slash the cost of future fusion power plants.
The team, based at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), pioneered a new design for a type of fusion machine called a stellarator.
But what’s a Stellarator in the first place?
Stellarators use intricate magnetic fields to confine plasma, the superheated state of matter needed to fuel the fusion reactions that power the sun and stars. If harnessed on Earth, fusion could offer an abundant source of clean energy.
Stellarators and tokamaks are both devices designed to contain the incredibly hot plasma needed for nuclear fusion.
The key difference lies in how they create the magnetic field that keeps the plasma in place. Tokamaks use a strong current flowing through the plasma itself, along with external coils, while stellarators rely solely on complex, twisted coils to shape the field. This makes stellarators inherently more stable than tokamaks, and suitable for continuous operation. However, tokamaks are currently better at keeping the plasma hot. Scientists hope to use stellarators as power plants in the future, potentially replicating the fusion process that occurs within stars like our Sun.
Why magnets matter
Traditionally, stellarators create their complex magnetic fields with precisely constructed and expensive electromagnets. But the PPPL team’s innovative device, called MUSE, breaks the mold. Instead of electromagnets, they rely on permanent magnets – the same kind that adorn your refrigerator. This drastically simplifies construction.
“Using permanent magnets is a completely new way to design stellarators,” explains graduate student Tony Qian, whose research was key to MUSE’s development. “This technique allows us to test new plasma confinement ideas quickly and build new devices easily,”
MUSE’s clever design isn’t just about affordability. Scientists theorized that permanent magnets could be used in this way, but it took decades for someone to pull it off. Senior research physicist at PPPL Michael Zarnstorff first realized the potential in 2014: “I realized…permanent magnets could generate and maintain the magnetic fields necessary to confine the plasma so fusion reactions can occur,” he reveals.
The stellarator advantage (and its past problems)
Stellarators hold an advantage over a popular alternative fusion machine design known as a tokamak. Tokamaks also use magnetic fields, but they rely on electric currents flowing within the plasma itself. Those currents can be unstable, making fusion reactions harder to sustain. Stellarators don’t have this issue, allowing them to run continuously.
The catch? Stellarators’ traditional magnets have been notoriously difficult to design and manufacture. This engineering challenge has relegated the design to an underdog position despite its potential edge. MUSE, however, could change the game entirely with its readily available, easily shaped magnets.
More than just clever engineering
MUSE’s design embodies a crucial theoretical property called quasisymmetry. This means that while the stellarator’s shape might look irregular, the strength of its magnetic field is remarkably consistent throughout. This uniformity helps keep the plasma neatly contained, making fusion more likely. MUSE is designed to be superbly quasisymmetrical – far surpassing previous stellarators.
The PPPL team is now preparing for experiments to analyze MUSE’s quasisymmetry, providing crucial insight into how well it will actually perform. Ultimately, MUSE’s success offers a glimpse into a future where fusion power plants are more affordable and accessible – and permanent magnets play a starring role in this clean energy revolution.
