The U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) is among the winners of a 2024 Edison Patent Award from the Research & Development Council of New Jersey for the invention of the planar coil stellarator, a device that eliminates the twisty coils of previous stellarator designs.

The invention replaces those twisty coils with flat magnets to create fusion energy, the same energy that powers the sun. PPPL’s central mission is to develop fusion as a safe, clean and virtually limitless energy source. The first stellarator was invented by PPPL founder Lyman Spitzer in 1953. 

The planar coil stellarator was developed by David Gates, a principal research physicist at PPPL. Gates is currently the chief technical officer at Thea Energy, a commercial fusion energy company based in Kearny, New Jersey.

The invention is among 14 patents and 66 inventors from 13 organizations to be honored at the 45th Annual Edison Patent Awards ceremony on Nov. 21. Thea Energy has licensed the technology and two other inventions from Princeton University.  

“This recognition echoes the significance of the commercial impact that the planar coil stellarator will have as a more practical approach to fusion, solving for the Achilles’ heel of the system: large modular coils,” Gates said. “Thomas Edison was a revolutionary thinker and inventor, and it’s a great honor to receive this award.”
 

PPPL’s fifth Edison Patent Award

The award will be PPPL’s fifth Edison Patent Award. PPPL won in 2022 for a liquid centrifuge device, in 2020 for a fusion-powered rocket engine, in 2017 for an extreme ultraviolet (EUV) microscopy and EUV lithography and X-ray imaging technique that could be used to etch computer chips, and in 2016 for a method of producing radionuclide molybdenum that could be used in medical imaging. 

Gates said he is grateful for PPPL’s support and encouragement. He especially appreciates the help of Kenneth Hammond, a PPPL research physicist, and Caoxiang Zhu, a former PPPL physicist and current professor in the Department of Plasma Physics and Fusion Engineering at the University of Science and Technology of China, who were named on the original portfolio patent application. 

“I’m very pleased PPPL has received this recognition,” said Steve Cowley, Laboratory director. “It demonstrates PPPL’s role in encouraging and supporting the development of commercial fusion energy and the spirit of inventiveness of our talented staff.”
 

A different approach to creating fusion energy 

Stellarators offer some advantages over traditional fusion devices called tokamaks, which are doughnut-shaped. Unlike tokamaks, stellarators have no risk of damaging disruptions and can operate in a steady state without driving additional current into the plasma. 

But the complex three-dimensional design of stellarators can make them more costly to build and leads to difficulty controlling the three-dimensional magnetic field, Gates said. The planar coil stellarator uses flat, high-temperature superconducting magnets to confine and shape the plasma. The magnets are wound on a device that’s similar to a bobbin on a sewing machine. Each of the magnets in the array is controlled by software that can make the plasma behave like it would in a stellarator with complex coils, making it easy to adjust coil currents while operating under real-world conditions, Gates explained.

Gates led a team of researchers who received a $3 million grant from the DOE Advanced Research Project Agency-Energy (ARPA-E) in 2020 to develop a simplified stellarator with permanent magnets.

Funding from DOE program for public-private partnerships

Thea Energy (then called Princeton Stellarators) was one of eight companies to receive funding from the DOE’s $46 million Milestone-Based Fusion Development Program, which supports public-private partnerships. The DOE’s Innovation Network for Fusion Energy (INFUSE) funded a partnership between PPPL and Princeton Stellarators, the former name for Thea Energy. 

The planar coil stellarator was one of three invention disclosures submitted by Gates. The other two include Hammond and Zhu. One is a stellarator neutron source that can breed tritium with a capability of breeding medical isotopes, which can be used in diagnostic images, and the other is a permanent magnet stellarator. Princeton University filed national stage patent applications on all three technologies.