The Evolution of Stellarators – From Experimental to Commercial Fusion Energy
Type One Energy is commercializing fusion energy technology in the southeast United States, but the company’s roots go back to experimental stellarator devices like CSX at Columbia University, HSX at the University of Wisconsin-Madison and W7-X at the Max Planck Institute for Plasma Physics in Germany.
“We are really standing on the shoulders of giants in fusion in general, but in stellarators in particular,” said Thomas Sunn Pedersen, Ph.D., Chief Technology Officer at Type One Energy.
Type One Energy is building the world’s first high-temperature superconducting (HTS) stellarator, the Infinity One stellarator testbed and fusion workforce training platform at TVA’s Bull Run Energy Complex near Knoxville, Tenn. It is the latest evolution in advanced stellarator technology and may soon lead to widespread commercialization of fusion energy, starting with the Infinity Two commercial fusion power plant project.
Today’s fusion momentum didn’t appear overnight. Decades of theory, experimentation, and incremental engineering—from HSX to W7-X and beyond—built the foundation for Infinity One and Infinity Two. Each device along the way answered hard questions, validated critical physics, and unlocked new design possibilities.
This is the story of several experimental stellarators and the scientists and engineers who built and operated them.
What is a Stellarator?
The stellarator is the most advanced magnetic confinement fusion technology, using a twisted plasma shape to create a steady-state fusion system which can supply continuous power output. Type One Energy’s peer-reviewed physics basis is now considered the “gold standard” in commercial fusion power, according to the prestigious Journal of Plasma Physics. The underlying stellarator technology leverages breakthrough advances in HTS magnets and exascale supercomputing.
Unlike tokamaks, which require large internal plasma currents that introduce instability risks, stellarators generate all their confining magnetic fields using external coils. This is a big advantage, which means simpler operation, intrinsic stability, and steady state potential.
Helically Symmetric eXperiment (HSX)
The Helically Symmetric eXperiment (HSX) at the University of Wisconsin-Madison was the world’s first optimized stellarator—demonstrating that mathematic optimization of magnetic fields can dramatically improve stellarator performance for hotter plasma, better control, and more predictable operation.
HSX was built and/or operated by Type One Energy co-founders David Anderson, Ph.D., Chris Hegna, Ph.D. and John Canik, Ph.D. Over the years, thousands of engineering and physics students have used the machine in pursuit of fusion energy.
Wendelstein 7-X (W7-X)
Operated by the Max Planck Institute for Plasma Physics (IPP) in Greifswald, Germany, Wendelstein 7X (W7-X) is currently the world’s most advanced stellarator experiment. According to Thomas Sunn Pedersen, Ph.D., Chief Technology Officer at Type One Energy, W7-X is “the most interesting stellarator experiment in the world,” delivering performance that rivals the best tokamak confinement results but with the advantage of inherent steady state capability.
Before joining Type One Energy as CTO, Dr. Pedersen served as Director of Stellarator Edge & Divertor Physics at W7-X in Germany from 2011 to 2023.
The key breakthrough at W7-X was computational optimization. W7-X demonstrated that stellarators designed with advanced computer modeling could confine plasma as well as or better than competing fusion approaches. This experimental validation gave both scientists and investors enormous confidence that the path toward a commercial stellarator power plant is real.
Remarkably, W7-X achieved these milestones using low temperature superconductors, which limit magnetic field strength. Today, with HTS materials capable of much higher fields, an even more powerful and compact generation of stellarators is within reach.
At Type One Energy, Dr. Pedersen and his team are pursuing what they believe is the fastest route to commercial fusion: a new class of highly optimized, high-field stellarators. Plans for Project Infinity™ include at least two stellarators: a prototype and a commercial power plant.
Infinity One will be the first stellarator to fully harness high temperature superconductors to achieve stronger magnetic fields—showing that HTS based stellarators are viable and setting the stage for a new performance frontier. The machine will not generate electricity but will verify all conditions necessary for steady state fusion energy.
Infinity Two is envisioned as the world’s first stellarator-based, commercial fusion power plant, a machine capable of putting net electricity on the grid by 2034. Infinity One’s results will serve as a validation engine—optimizing design and confirming performance expectations.
Pedersen says Type One Energy’s goal is bold but achievable: net electricity within a decade and rapid scaling afterward to meaningfully impact global energy systems.