UT Austin researchers advance magnetic fusion design with new confinement method

Fusion reactors aim to confine high-energy alpha particles to sustain the extreme plasma conditions required for fusion. However, particle leakage has long undermined this goal. Engineers have traditionally relied on complex magnetic confinement systems, but pinpointing and eliminating weak spots in the magnetic fields demanded significant computational resources.

In a new study published in Physical Review Letters, the team introduced a computational shortcut that allows engineers to design robust confinement systems for stellarators up to ten times faster than conventional methods, without compromising accuracy. This advance tackles the core challenge unique to stellarators, a class of fusion reactors proposed in the 1950s.

"What's most exciting is that we're solving something that's been an open problem for almost 70 years," said Josh Burby, UT physics assistant professor and lead author. "It's a paradigm shift in how we design these reactors."

Stellarators use external coils to generate magnetic fields that trap plasma, creating a so-called "magnetic bottle." While Newtonian mechanics can predict holes in this bottle with precision, the method is computationally intensive. Iterating over multiple design variations to fix field holes becomes practically unfeasible.

Engineers have instead turned to perturbation theory to estimate problem areas, trading speed for accuracy. The new approach uses symmetry theory to avoid both high computational costs and the inaccuracies of perturbation methods.

"There is currently no practical way to find a theoretical answer to the alpha-particle confinement question without our results," Burby said. "Direct application of Newton's laws is too expensive. Perturbation methods commit gross errors. Ours is the first theory that circumvents these pitfalls."

Beyond stellarators, this method also has implications for tokamaks, another leading magnetic fusion design. It may help predict where runaway electrons might breach reactor walls, thus supporting safer and more efficient fusion development.

Research Report:Nonperturbative Guiding Center Model for Magnetized Plasmas