German stellarator fusion design concept unveiled

Thursday, 27 February 2025

Stellaris builds on the record-breaking results of the Wendelstein 7-X research experiment in Germany, the most advanced QI stellarator prototype in the world, directed by the Max Planck Institute for Plasma Physics (IPP) and the product of over EUR1.3 billion (USD1.4 billion) in funding from the German Federal Government and the European Union. In February 2023, Wendelstein 7-X succeeded for the first time in generating a high-energy plasma that lasted for eight minutes. The facility is designed to generate plasma discharges of up to 30 minutes in the coming years.

Published in Fusion Engineering and Design, Proxima Fusion - which was spun out of IPP in 2023 and was founded by a team which includes six former IPP scientists - says the Stellaris concept is "a major milestone for the fusion industry - advancing the case for quasi-isodynamic (QI) stellarators as the most promising pathway to a commercial fusion power plant".

A stellarator fusion reactor is different to a tokamak fusion reactor such as the Joint European Torus in the UK or the ITER device under construction in France. A tokamak is based on a uniform toroid shape, whereas a stellarator twists that shape in a figure-8. This gets round the problems tokamaks face when magnetic coils confining the plasma are necessarily less dense on the outside of the toroidal ring.

_{(Image: Proxima Fusion)}

According to Proxima Fusion, Stellaris is designed to produce much more power per unit volume than any stellarator power plant designed before. The much stronger magnetic fields that are enabled by high-temperature superconducting (HTS) magnet technology allow for a significant reduction in size compared with previous stellarator concepts. It says smaller reactors can therefore be built more quickly, provide more efficient energy generation, and promise to be more cost-effective in both construction and operation. The Stellaris concept also makes use of only currently available materials, meaning it will be buildable by expanding on today's supply chains.

The company says its simulation-driven engineering approach has enabled rapid design iterations, leveraging advanced computing. Stellaris, it says, is the first QI stellarator-based power plant design that "simultaneously meets all major physics and engineering constraints, as demonstrated through electromagnetic, structural, thermal, and neutronic simulations".

Proxima Fusion says the Stellaris design incorporates groundbreaking technical features, including: a magnetic field design that obeys all key physics optimisation goals for energy production; support structures that can bear the forces present when operating at full power; a showcase that HTS technology can be effectively integrated in high field stellarators, while ensuring effective heat management on internal surfaces; and a neutron blanket concept that is adapted to the complex geometry of stellarators.

The company plans to demonstrate that stellarators are capable of net energy production with its demo stellarator Alpha in 2031, and aims to deliver fusion energy to the grid in the 2030s.‍

"The path to commercial fusion power plants is now open," said Francesco Sciortino, co-founder and CEO of Proxima Fusion. "Stellaris is the first peer-reviewed concept for a fusion power plant that is designed to operate reliably and continuously, without the instabilities and disruptions seen in tokamaks and other approaches."

"For the first time, we are showing that fusion power plants based on QI-HTS stellarators are possible," added Jorrit Lion, co-founder and chief scientist of Proxima Fusion. "The Stellaris design covers an unparalleled breadth of physics and engineering analyses in one coherent design. To make fusion energy a reality, we now need to proceed to a full engineering design and continue developing enabling technologies."