A team of researchers from The University of Texas at Austin, Los Alamos National Laboratory, and Type One Energy Group has made significant progress in addressing a long-standing challenge in sustaining fusion energy, bringing the goal of reliable fusion power, and the promise of affordable clean energy, closer to reality. The study was published in the journal Physical Review Letters.
Predicted motions of hundreds of particles in a fusion reactor. The motions predicted with the new method (orange, red) agree very closely with those predicted by Newton’s laws (blue, green), but can be calculated 10 times faster. Image credit: University of Texas at Austin.
A major obstacle hindering fusion energy development has been the ability to contain high-energy particles within fusion reactors. The leakage of high-energy alpha particles prevents the plasma from reaching the necessary temperature and density to sustain the fusion reaction. Engineers design intricate magnetic confinement systems to prevent this leakage; however, these systems often have imperfections in the magnetic field, and predicting and eliminating these imperfections requires significant computational resources.
The research team details the discovery of a shortcut that can enable engineers to design leak-proof magnetic confinement systems ten times faster than the current standard method, without compromising accuracy. While several other significant challenges remain for all magnetic fusion designs, this advancement addresses the primary obstacle specific to stellarators, a type of fusion reactor initially proposed in the 1950s.
What’s most exciting is that we’re solving something that’s been an open problem for almost 70 years. It’s a paradigm shift in how we design these reactors. A stellarator uses external coils carrying electric currents that generate magnetic fields to confine a plasma and high-energy particles. This confinement system is often described as a “magnetic bottle".
Josh Burby, Assistant Professor and Study First Author, Physics, The University of Texas at Austin
While Newton's laws of motion offer a very precise method for identifying the locations of leaks in this "magnetic bottle," it demands an immense amount of computational time. Furthermore, designing a stellarator often requires scientists to simulate hundreds or thousands of slightly different designs, adjusting the arrangement of the magnetic coils and iterating to eliminate these leaks—a process that would necessitate an impractical amount of computation on top of the already significant demand.
Consequently, to conserve time and resources, scientists and engineers commonly use a simpler, but less accurate, method called perturbation theory to approximate the locations of these leaks. This lack of accuracy has hindered the development of stellarators. The new method, however, relies on symmetry theory, offering a different and more effective way to understand the system.
There is currently no practical way to find a theoretical answer to the alpha-particle confinement question without our results. Direct application of Newton’s laws is too expensive. Perturbation methods commit gross errors. Ours is the first theory that circumvents these pitfalls.
Josh Burby, Assistant Professor and Study First Author, Physics, The University of Texas at Austin
The method also offers potential benefits for tokamaks, another widely researched magnetic fusion reactor design, by addressing a related challenge: runaway electrons. These high-energy electrons can strike and damage the reactor's inner walls. The new approach can help pinpoint weaknesses in the magnetic field where these runaway electrons might escape.
Burby's co-authors from UT include postdoctoral researcher Max Ruth and graduate student Ivan Maldonado. Additional authors are Dan Messenger, a postdoctoral fellow at Los Alamos National Laboratory, and Leopoldo Carbajal, a computational scientist and data scientist at Type One Energy Group, a company focused on developing stellarators for electricity generation.
The study received funding from the US Department of Energy.
Journal Reference:
Burby, J. W., et al. (2025) Nonperturbative Guiding Center Model for Magnetized Plasmas. Physical Review Letters. doi.org/10.1103/PhysRevLett.134.175101