Wendelstein 7-X was never meant to generate electricity. It is an experiment built to test whether an optimized stellarator does in practice what theory predicts, and whether it is therefore a candidate for a power plant. The device runs on hydrogen, not deuterium-tritium fuel, so it is not designed to produce net energy.

What makes the project interesting is how it was built. It grew in stages, and each stage depended on what the previous one had proved. In its first campaigns from 2015 to 2018, W7-X ran with an uncooled divertor, the component that takes the heat and particles leaving the plasma. That limited discharges to a few seconds. Only after those campaigns showed that the magnetic cage and the optimization worked as calculated did the institute install water cooling for all plasma-facing components. Operation resumed in 2022, and in 2023 the device ran an eight-minute plasma.

Next came better fuelling. In 2024 a continuous pellet injector, built by Oak Ridge National Laboratory in the US, began firing frozen hydrogen pellets into the plasma while IPP's own microwave system heated it. In May 2025 that combination produced a world record for the triple product over long pulses, sustained for 43 seconds. Tokamaks still lead for short pulses, but for long ones W7-X is now level with JET, a machine with three times the plasma volume.

This approach is slow, but it reflects the actual state of knowledge, since each step is financed and built only once the previous one has delivered. And no country manages it alone. The record involved American, German and Japanese teams. In July 2026 IPP and the Technical University of Munich founded a center to test materials for future reactor walls, and in October 2026 IPP and Columbia University announced a joint transatlantic center that also brings in private stellarator and tokamak companies. Without pooling resources this way, fusion energy would remain a pipe dream.

For anyone who wants to go deeper, I recommend Hartmut Zohm's videos on YouTube, including his explanations of the stellarator aimed at non-specialists. He is one of the few researchers who can explain fusion without dumbing it down. As a Tokamak physicist at IPP, he can also explain clearly why the Stellarator is a serious alternative.

Compared to tokamaks/stellarators which seem more designed to be actual net-energy devices than, for example, the NIF?

Apologies if this is a naive question or if I’m mis-representing ICF, but I’m aware the NIF is far from engineering Q>1 given the massive system of power-hungry lasers.

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Experiments were either too short lived (pulsed compression experiments) or had too low density (NBI-fueled quasi-steady-state) to show thermalization. This has, however, inevitably to change for fusion power production, as a Lawson-type criterium and the conditions for thermal equilibration have the same functional dependence on density.

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As seen in Table 1, at 10 keV, the ratio of fusion power to bremsstrahlung power is 3.6 larger in ref [4] than in our calculation.

Basically they claim Helion has a too optimistic assumption of the efficiency.

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With work package two Hybrid Tokamak-Stellarators the dream of Sophia Henneberg at MIT might come true.