Physicists Bob Pinsker<\/a>, Jeff Lestz<\/a>, and Bart Van Compernolle<\/a> of General Atomics<\/a> were co-lead authors of the paper describing the results<\/a>, published recently in Physical Review Letters.<\/p>\n The key to nonstop fusion <\/p>\n Most leading fusion setups employ a tokamak<\/a>, a donut-shaped machine that uses magnetic fields to confine plasma. One set of magnetic coils generates a toroidal<\/a> 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<\/a> by the U.S. Department of Energy.<\/p>\n However, as Pinsker explained to Gizmodo, the operational length of the tokamak is \u201cintrinsically limited\u201d in its duration\u2014pulse length\u2014as 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.<\/p>\n Ultimately, however, tokamak reactors operating this way can\u2019t be run in a \u201csteady state,\u201d which is what most design studies indicate is needed for them to be commercially viable, Lestz said. As a result, scientists have explored what\u2019s called \u201cnon-inductive\u201d methods to drive the tokamak current using different electromagnetic waves.<\/p>\n \u201cSo helicon current drive does not constitute a different approach to fusion energy,\u201d Pinsker explained. \u201c[R]ather, it is another technology that can be applied to the tokamak to enhance that approach.\u201d<\/p>\n A theory ahead of its time <\/p>\n 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.\u00a0However, the approach used in that experiment may fall short in penetrating deeper into the plasma, Lestz added.<\/p>\n Scientists theorized that a different type of radio wave in the same frequency range\u2014a helicon\u2014could address these concerns. According to Pinsker\u2014whose doctoral thesis centered on this proposal\u2014there were three main reasons that things didn\u2019t work out in the 80s. First, the plasmas in the tokamaks at the time were \u201cinsufficiently reactor-like\u201d to properly absorb helicon waves. Second, the wave-launching technology wasn\u2019t efficient enough. Finally, diagnostic techniques weren\u2019t advanced enough for scientists to check for non-inductive currents in the plasma.<\/p>\n \u201cEverybody who tried it in the 80s was kind of hoping for a miracle,\u201d Pinsker said in an interview<\/a> with the American Nuclear Society (ANS). \u201cWe were hoping that that part of the model was wrong. [\u2026] The problem always was that we didn\u2019t have a reactor around to test it in.\u201d<\/p>\n Predictions come to life <\/p>\n
![\"Diii](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/11\/diii-d-helicon-traveling-wave-antenna.jpg\")
The specialized antenna used to launch helicon waves at DIII-D. \u00a9 Lestz et al., 2026 <\/p>\n