A nuclear fusion startup has claimed a significant advance after testing an unconventional reactor design in New Zealand, reporting that it sustained plasma at roughly 300,000 degrees Celsius for 20 seconds. The result, if independently verified, would represent one of the more notable achievements among the growing roster of private fusion ventures pursuing alternatives to the massive government-backed tokamak projects that have dominated the field for decades. But the claim also arrives without published data on net energy gain, leaving a central question unanswered: can this “inside-out” approach actually scale to produce usable power?
Inside the Junior Levitated Dipole Experiment
The technical foundation for the startup’s claim rests on a device called the Junior Levitated Dipole Experiment, detailed in an arXiv preprint authored by OpenStar staff and collaborators. The experiment uses a high-temperature superconducting magnet made from REBCO material, generating a field strength of roughly 5.6 T. In the preprint, the team describes a multi-metre vacuum chamber and electron cyclotron resonance heating (ECRH) on the order of tens of kilowatts. The preprint reports that the device achieved first plasmas in late 2024, establishing a baseline for the more ambitious temperature and duration claims that followed.
What makes this setup unusual is the magnet geometry. Rather than wrapping plasma inside a doughnut-shaped tokamak, the levitated dipole suspends a single magnet coil inside the chamber and confines plasma around it. The design inverts the standard relationship between the magnetic field and the hot gas it contains. Proponents argue this configuration could dramatically reduce the size and cost of a fusion reactor, because it eliminates many of the structural components that make tokamaks so expensive. The tradeoff is that levitated dipole research remains far less mature, with fewer experimental benchmarks to validate long-term plasma stability or energy output at scale.
The 300,000 Degree Claim and Its Limits
The headline number, plasma sustained at approximately 300,000 degrees Celsius for 20 seconds, places the startup’s achievement in a middle tier of fusion milestones. For context, the core of the sun operates at roughly 15 million degrees Celsius, and most tokamak experiments aim for temperatures well above 100 million degrees to achieve the conditions needed for deuterium-tritium fusion. At 300,000 degrees, the Junior experiment is orders of magnitude cooler than what a commercial reactor would require. The 20-second duration, however, is notable for a device of this type and scale, suggesting that the magnetic confinement held steady long enough to gather meaningful diagnostic data.
The critical gap in the public record is any measurement of energy balance. No published data from the startup or its collaborators addresses how much energy the plasma produced relative to the energy pumped in. Without that metric, the claim functions more as a proof of concept for the levitated dipole approach than as evidence of a path to net energy. Fusion research is littered with milestones that sounded impressive in isolation but failed to translate into practical power generation. The National Ignition Facility’s 2022 ignition result, for instance, produced a net energy gain in the fusion reaction itself but still consumed far more energy to operate the lasers that triggered it. Any serious evaluation of the Junior experiment will require similar accounting.
Seventeen Years of Research Behind the Result
The intellectual roots of this project trace back nearly two decades. Mataira, a physicist central to the effort, was completing his PhD at Victoria University of Wellington’s Robinson Research Institute after more than a decade of work connected to the underlying concept. That long arc of academic work fed directly into the engineering choices visible in the Junior device, particularly the use of REBCO high-temperature superconducting tape, which has only become commercially viable in recent years. The Robinson Research Institute has been a center for applied superconductor research in New Zealand, giving the team access to specialized fabrication and testing capabilities that most fusion startups lack.
Choosing New Zealand as the testing ground may also carry practical advantages, though the company has not published detailed comparisons of permitting or workforce factors. More concretely, the work described in the preprint and the reporting around the trial places the prototype and its testing in New Zealand, away from the traditional fusion research hubs of Massachusetts, Oxford, and southern France.
How This Compares to the Tokamak Mainstream
The dominant approach to fusion energy remains the tokamak, a reactor design that uses powerful external magnets to confine plasma in a toroidal, or doughnut-shaped, chamber. ITER, the international tokamak project under construction in France, has consumed tens of billions of dollars and decades of planning. Its first full-power deuterium-tritium experiments are not expected until the 2030s. Against that backdrop, the appeal of a compact levitated dipole is obvious: if the physics works, the hardware is simpler, the magnets are smaller, and the path from prototype to commercial unit could be shorter and cheaper.
But “if the physics works” is doing significant heavy lifting in that sentence. Levitated dipoles have been studied in academic settings since MIT’s Levitated Dipole Experiment operated in the 2000s, yet no device of this type has come close to demonstrating fusion-relevant temperatures or confinement times. The Junior experiment’s 300,000-degree result is a step forward for the concept, not a step toward commercial viability. The startup would need to increase plasma temperatures by at least two orders of magnitude while maintaining or improving confinement duration, and then demonstrate that the energy produced exceeds the energy consumed. Each of those steps represents a distinct engineering challenge that has not been solved in any fusion configuration outside of brief, non-repeatable laboratory shots.
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*This article was researched with the help of AI, with human editors creating the final content.
