Physicists Gave Up on This Fusion Technique in the 1980s. Now It’s Working

Fusion energy feels like a perpetually elusive goal, but with new ideas and better equipment, scientists have been inching closer to harnessing the power of the stars. But some physicists are testing a different combination: better equipment for an old idea. Physicists recently reported the successful experimental demonstration of helicon current drive at the DIII-D National Fusion Facility. First proposed in the 1980s, helicon current drive uses a specific type of high-frequency radio wave to drive the hot plasma of a fusion reactor, producing an internal electric current to stabilize the reaction. However, the equipment at the time simply wasn’t able to deliver on the theory, which was why the idea was shelved until now. But thanks to major strides in reactor equipment, scientists tested and successfully demonstrated helicon current drive for the first time. Physicists Bob Pinsker, Jeff Lestz, and Bart Van Compernolle of General Atomics were co-lead authors of the paper describing the results, published recently in Physical Review Letters. The key to nonstop fusion Most leading fusion setups employ a tokamak, a donut-shaped machine that uses magnetic fields to confine plasma. One set of magnetic coils generates a toroidal field the long way around the donut, whereas a current-carrying magnet called a solenoid creates a second magnetic field the short way around the donut, according to an explainer by the U.S. Department of Energy. However, as Pinsker explained to Gizmodo, the operational length of the tokamak is “intrinsically limited” in its duration—pulse length—as the plasma current is driven by a transformer-like arrangement. At a certain point, the solenoid needs to be reset, and the plasma must be shut down. This inherently creates disruptions in how long a tokamak can operate. For instance, Pinsker said, the pulse length of the tokamak at DIII-D is limited to only about 10 seconds. Larger reactors can sustain these pulses for around 500 seconds (8 minutes) or even 1,000 seconds (17 minutes), he added. Ultimately, however, tokamak reactors operating this way can’t be run in a “steady state,” which is what most design studies indicate is needed for them to be commercially viable, Lestz said. As a result, scientists have explored what’s called “non-inductive” methods to drive the tokamak current using different electromagnetic waves. “So helicon current drive does not constitute a different approach to fusion energy,” Pinsker explained. “[R]ather, it is another technology that can be applied to the tokamak to enhance that approach.” A theory ahead of its time The idea behind these methods, according to Pinsker, is to introduce radiofrequency energy into the torus so that it excites certain types of waves in the plasma. These then resonate with electrons in the plasma, which pushes the electrons along, generating a current. This has been demonstrated on several tokomaks. However, the approach used in that experiment may fall short in penetrating deeper into the plasma, Lestz added. Scientists theorized that a different type of radio wave in the same frequency range—a helicon—could address these concerns. According to Pinsker—whose doctoral thesis centered on this proposal—there were three main reasons that things didn’t work out in the 80s. First, the plasmas in the tokamaks at the time were “insufficiently reactor-like” to properly absorb helicon waves. Second, the wave-launching technology wasn’t efficient enough. Finally, diagnostic techniques weren’t advanced enough for scientists to check for non-inductive currents in the plasma. “Everybody who tried it in the 80s was kind of hoping for a miracle,” Pinsker said in an interview with the American Nuclear Society (ANS). “We were hoping that that part of the model was wrong. […] The problem always was that we didn’t have a reactor around to test it in.” Predictions come to life But in the next few decades, the field saw dramatic changes. As early as 2014, Pinsker and colleagues prepared to revive the old theory, and a new round of experiments began in the summer of 2024. DIII-D had a specialized antenna called a “comb-line,” which could launch helicon waves toward plasmas hot enough to absorb them. What’s more, improvements in measurement techniques meant the team could take an even closer look at how their experiments unfolded. The specialized antenna used to launch helicon waves at DIII-D. © Lestz et al., 2026 In short, this time, it worked. Pinsker reported to ANS that the team could clearly identify heating in the plasma resulting from the absorption of the helicon wave. But before getting too excited, the researchers took extra care in validating statistical evaluations. Pinsker added to the ANS, recalling how they “really went to extremes to make sure that we couldn’t be accused of cherry-picking and showing one fluke shot that had a big effect.” In ‘some’ years The results seem impressive, but there’s still a long road ahead, Pinsker said. DIII-D is also an experimental facility and can’t replicate “reactor-like conditions,” for which helicon current drive holds the most promise, Lestz told Gizmodo. “Like any good experiment, I would say that our results suggest many avenues for further work and raise a number of follow-up questions,” Pinsker added. “I think that the most straightforward way to significantly improve on our results would be [to] substantially increase the amount of power we could couple to helicon waves in the plasma.” In short—as with most fusion research—only time will tell. But the new findings are proof that with time, science does find a way. And that’s a promising idea, I think.