Proxima Fusionʼs simulation-driven engineering approach to designing stellarator power plants builds on the groundbreaking results of the Wendelstein 7-X (W7-X) experiment, the world's most advanced stellarator at the Max Planck Institute for Plasma Physics (IPP) in Germany.
W7-X first came into operation in 2015 and accomplished its full design targets in 2022, following years of engineering and assembly spearheaded by Proxima technical advisors Felix Schauer and Lutz Wegener and an investment of over €1.44 billion by the German government and the European Union. Since then, its experimental results have repeatedly broken key performance records to demonstrate continuous steady-state operation.
Some of the most notable achievements of W7-X include:
But W7-X didn’t only achieve record-breaking plasma performance: it laid the foundation for a new generation of optimized modular-coil stellarators, a concept first developed at IPP in the 1970s. The conceptual difference in coil topology between classical stellarators and modular coil stellarators can be seen in the below figure:
Employing a modular coil design, no helical windings need to fit within the toroidal field coils, simplifying machine assembly. Such a design also provides greater geometrical flexibility, allowing optimization for low neoclassical transport as well as low Pfirsch-Schlüter currents, and, in turn, low Shafranov shift.
But arguably the most impactful result of the W7-X experiment was proving the feasibility of optimized quasi-isodynamic (QI) stellarators, like the ones Proxima Fusion is building now. Thanks to W7-X, QI stellarators have been proven to be inherently stable, with a negligible toroidal current. In tokamaks, the required toroidal current is approximately proportional to the toroidal magnetic field, so increasing the latter requires one to go to large currents. By eliminating this relationship and controlling the full confinement magnetic field by external coils as much as possible, via the modular coils, one can obtain steady-state operation without the risk of sudden losses of confinement (“disruptions”). This reduces the need for active plasma stabilization and results in lower recirculating power requirements.
QI stellarators also offer the possibility of protecting internal material surfaces via small confinement regions surrounding the main confined plasma—the so-called magnetic islands. The concept of an “island divertor” (see figure) is unique to QI stellarators, whose lack of a net toroidal current makes the islands resilient against changes in magnetic field during different operational scenarios. Over its first campaigns, W7-X has already shown exciting results from its island divertor, spearheaded as a concept already in W7-AS in the 1990s. In the present W7-X campaign, which started on September 10, 2024, after a one-year upgrade, W7-X promises to bring more exciting results on divertor performance. Proxima Fusion is building on these developments by employing the island divertor concept of QI stellarators to its designs.
As the IPP’s first-ever spin-out company, Proxima is uniquely equipped to build on the success of W7-X and accelerate the timeline to putting fusion on the grid, enabled by recent advances in simulation and high-temperature superconducting (HTS) magnet technology.
By bringing together fusion scientists from the Max Planck Society with experts in engineering and computer science, Proxima is iterating QI stellarator designs at lower costs and a higher speed than ever before, proudly carrying forward the legacy of W7-X as we work to make commercial fusion a reality.
Proxima Fusion GmbH, Mühldorfstraße 8, 81671 München, Deutschland
Eingetragen beim Amtsgericht München unter HRB 283423, Geschäftsführer Dr. Francesco Sciortino, Lucio Milanese
Registered at the District Court of Munich under HRB 283423, Managing Directors Dr. Francesco Sciortino, Lucio Milanese
