The quest to control the ultimate goal of clean energy is potentially taking a step in the right direction thanks to the same principles behind refrigerator magnets. Earlier this week, researchers at the Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) introduced their new stellarator–a unique fusion reactor that uses off-the-shelf and 3D-printed materials to contain its superheated plasma.
First envisioned over 70 years ago by PPPL’s founder, Lyman Spitzer, a traditional stellarator works by using electromagnets precisely arranged in complex shapes to create magnetic fields using electricity. Unlike tokamak reactors, stellarators do not need to run electric current specifically through their plasma to create magnetic forces—a process that can interfere with fusion reactions. However, tokamaks effectively confine their plasma so well that they have been the preferred reactor choice for researchers, especially when considering a stellarator’s comparative costs and difficulties. Because of all this, Spitzer’s design has largely gone unused for decades.
[Related: The world’s largest experimental tokamak nuclear fusion reactor is live.]
The engineers behind the new stellarator known as MUSE, however, say their solution could overcome these obstacles. Instead of electromagnets, the device uses permanent magnets—although much more powerful and finely tuned than ones found in everyday novelty and souvenir collectibles. MUSE requires permanent magnets made using rare-earth metals that can surpass 1.2 teslas, the unit of measurement for magnetic flux density. In comparison, standard ferrite or ceramic permanent magnets usually show between 0.5 and 1 teslas.
“I realized that even if they were situated alongside other magnets, rare-earth permanent magnets could generate and maintain the magnetic fields necessary to contain the plasma so fusion reactions can occur, and that’s the property that makes this technique work,” Michael Zarnstorff, a PPPL senior research physicist and MUSE principle investigator, said in a statement.
Building a stellarator with permanent magnets is a “wholly new” approach, PPPL graduate student Tony Qian added. Qian also explained that the stellarator alteration will allow engineers to both test plasma confinement ideas and build new devices far more easily than before.
In addition to the promising design changes, MUSE reportedly performs what’s known as “quasisymmetry” better than any previous stellarator—specifically, a subtype called “quasiaxisymmetry.”
In very simple terms, quasisymmetry means that a magnetic field’s shape inside a stellarator differs from the field around the stellarator’s physical shape. Nonetheless, the overall magnetic field strength remains consistent, effectively containing plasma and increasing the chances for fusion reactions. According to Zarnstorff, MUSE achieves its quasisymmetry “at least 100 times better than any existing stellarator.”
The researchers plan to further study MUSE’s quasisymmetry and accurately map its magnetic fields, which affect the chances of achieving stable, net positive fusion reactions.
Whether scientists will or will not discover the breakthroughs necessary to make green fusion energy a reality in the near future remains to be seen. But thanks to some creative problem-solving using what are essentially very heavy duty fridge magnets, the long-overlooked stellarator could prove a valuable tool.
