Here\u2019s what you\u2019ll learn when you read this story:<\/p>\n
A nuclear fusion reactor in Germany has reached world record numbers for runtime.<\/p>\n<\/li>\n
The tokamak dominates fusion research in 2025, but stellarators are making a comeback.<\/p>\n<\/li>\n
A stellarator is still a donut shape, but extended and twisted, with different pros and cons.<\/p>\n<\/li>\n<\/ul>\n
In an announcement this year, the Max Planck Institute for Plasma Physics shared a breakthrough<\/a> from its world class stellarator, Wendelstein 7-X. The stellarator is a nuclear fusion reactor<\/a> with the same goals and principles as a tokamak reactor, but with a different footprint that comes with unique challenges. W7-X, based at the Planck Institute\u2019s campus in Greifswald in northern Germany, is now purportedly on par with the much larger Joint European Torus (JET) tokamak reactor in southern England.<\/p>\n As of now, neither achievement has been published in a peer-reviewed journal, and we\u2019re also still a long, long ways away from net positive nuclear fusion energy\u2014let alone the \u201cinfinite energy<\/a>\u201d promised by industry investors. Still, it\u2019s exciting to set a new benchmark.<\/p>\n For several decades now, the popular paradigm for nuclear fusion research has been the tokamak<\/a>. This is a donut shape, or torus, filled with an open space where plasma is circulated. But it\u2019s more like a New York bagel, with a smaller hole and denser bulk. The stellarator, with an elongated and twisted chamber, is a Krakow bagel<\/a>.<\/p>\n The stellarator predates the tokamak, but in the early years of nuclear fusion experimentation, the tokamak passed the stellarator in popularity. Now, however, both are neck and neck again\u2014if these results hold up, that is.<\/p>\n W7-X, which came online in 2015, reached the end of its most recent campaign in May. The Planck Institute said in a statement:<\/p>\n In the OP 2.3 campaign, which ended on May 22, the international W7-X team achieved a new world record for the triple product [which is a way that researchers can get an idea of how close they are to the fusion reaction sustaining itself] in long plasma discharges: on this last day, they sustained a new peak value of this key fusion parameter for 43 seconds.<\/p>\n<\/blockquote>\n The team credits emerging technologies in their field, like ion cyclotron resonance heating (ICRH), for their new benchmark. ICRH is comparable to an existing paradigm in the field called electron cyclotron resonance heating (ECRH), which usually uses microwaves to make plasma<\/a>. ICRH\u2014which uses radio waves but is otherwise a similar idea\u2014can work better for certain particle types or configurations.<\/p>\n The triple product these researchers describe is a mathematical benchmark in nuclear fusion energy research. Once the entire industry can reach a certain value, proponents say, we can begin to use nuclear fusion as an energy source. W7-X did not reach net positive energy, but it seems to have broken the existing record for energy output versus input. After publicizing their results, the W7-X team heard from the JET team (whose work on their final runs in 2023 has not been published yet), and the two projects have reportedly achieved comparable numbers<\/a>. The W7-X team claims that this means their experiment had the same results as the JET team\u2019s experiment using just \u2153 the plasma.<\/p>\n These reactors must reach enormously high temperatures, sustain them, and sustain them long enough that more energy is produced than used. To be clear, no nuclear fusion reactor has reached net positive energy, so benchmarks in this calculation are just chipping away at a goal we have not yet achieved. The W7-X website<\/a> said of the triple product: \u201cThis marks the point where the energy balance becomes positive, and the fusion reaction can sustain itself without continued external heating,\u201d but that\u2019s not the whole story. There\u2019s a lot to be accounted for in terms of the equipment itself, the facilities, the cooling required, and so forth. No one has reached the conservative benchmark for net energy using the triple product, so even less than zero, so to speak, have reached the true benchmark accounting for energy costs.<\/p>\n\n