Researchers at the Department of Energy’s Princeton Plasma Physics Laboratory are using a stellarator they designed and built using permanent rare-earth magnets and a 3D-printed shell to help test new fusion power concepts. MUSE—the first stellarator built at PPPL in 50 years—took one year to construct and generated its first plasma in February 2023. The work that went into its design has already inspired a stellarator power plant concept being developed by a commercial spin-off, Thea Energy.

A team of engineers, physicists, and data scientists from Princeton University and the Princeton Plasma Physics Laboratory (PPPL) have used artificial intelligence (AI) to predict—and then avoid—the formation of a specific type of plasma instability in magnetic confinement fusion tokamaks. The researchers built and trained a model using past experimental data from operations at the DIII-D National Fusion Facility in San Diego, Calif., before proving through real-time experiments that their model could forecast so-called tearing mode instabilities up to 300 milliseconds in advance—enough time for an AI controller to adjust operating parameters and avoid a tear in the plasma that could potentially end the fusion reaction.

Princeton Stellarators Inc. (PSI) and Type One Energy Group are two of the eight fusion developers selected by the Department of Energy in late May to receive a total of $46 million in funding to kick off a public-private Milestone-Based Fusion Development Program aimed at developing fusion pilot plant designs and resolving related scientific and technological challenges within five to 10 years. The DOE’s selections cover an array of plasma confinement concepts, including the magnetic confinement stellarators being developed by PSI and Type One more than 70 years after the stellarator was first envisioned.

Nuclear Newswire previously took a close look at two of the DOE’s picks: Realta Fusion and Zap Energy (“innovative concept”) and Focused Energy and Xcimer Energy (inertial fusion). Here, we’ll examine how PSI and Type One are engineering solutions to the fusion plasma confinement challenge. Both companies are benefiting from recent advances in computing power and high-temperature superconducting (HTS) magnets. It’s in plans for design, manufacturing, assembly, and control of their stellarators that they differ.

A key component needed for the National Spherical Torus Experiment–Upgrade (NSTX-U), the flagship fusion facility currently under repair at the Department of Energy’s Princeton Plasma Physics Laboratory (PPPL), has been delivered to the lab’s New Jersey campus.

Tokamak Energy’s ST40, which achieved plasma temperatures of 100 million °C earlier this year. (Photo: Tokamak Energy)

Tokamak Energy on October 26 announced plans to construct a high field spherical tokamak using high-temperature superconducting (HTS) magnets. Dubbed the ST80-HTS, the machine would demonstrate multiple technologies required to achieve commercial fusion energy, the company says. Tokamak Energy plans to complete the ST80-HTS in 2026 to demonstrate spherical tokamak operations and inform the design of its successor, a fusion pilot plant called ST-E1 that the company says could deliver electricity into the grid in the early 2030s and produce up to 200 MWe.

Temperature milestone: Earlier this year, the company’s ST40 spherical tokamak reached the commercial fusion energy plasma temperature threshold of 100 million °C with what was reported as the highest triple product (an industry measure of plasma density, temperature, and confinement) of any private fusion energy company. The ST40 achieved those results with a plasma volume of less than one cubic meter, which is 15 times less volume than any other tokamak that has achieved the same threshold.

The DIII-D National Fusion Facility now boasts a unique automated system that allows for a quick reversal of the direction of its magnetic field, expanding the range of possible fusion experiments while reducing downtime. General Atomics, which operates the DIII-D for the Department of Energy’s Office of Science, announced the new Toroidal Field Reversing Switch (TFRS) on July 26.

A wager struck by two plasma physicists 34 years ago was finally fulfilled in June during the opening day of the 48th European Physical Society Division of Plasma Physics, when Robert Goldston, former director of the Department of Energy’s Princeton Plasma Physics Laboratory (PPPL), virtually presented a plaque to his friend and colleague Jean Jacquinot, former director of the Joint European Torus (JET), EUROfusion's flagship fusion experiment based at the Culham Centre for Fusion Energy in the United Kingdom. Their bet, and JET’s record-breaking achievements in 2021, were celebrated in an article published by PPPL on July 8.

The Department of Energy announced awards for 18 Innovation Network for Fusion Energy (INFUSE) projects on July 6 that link private fusion energy developers with DOE national laboratories (and, in a first for the program, with U.S. universities) to overcome scientific and technological challenges in fusion energy development. The 18 selected projects include representation from 10 private companies, three national labs, and eight universities.

According to the Department of Energy’s Princeton Plasma Physics Laboratory, recent simulations and analysis demonstrate that the design of its flagship fusion facility, the National Spherical Torus Experiment Upgrade (NSTX-U), which is currently under repair, could serve as a model for an economically attractive next-generation fusion pilot plant.

The Department of Energy has selected eight private industry projects for fusion energy collaboration with DOE national laboratories. The awards are provided through the Innovation Network for Fusion Energy (INFUSE), which focuses on five areas of research: enabling technologies; materials; diagnostics; modeling and simulation; and experimental capabilities.

Researchers at the Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have developed a new model of how heat flows within plasmas. According to PPPL, the model could improve insights into the behavior of plasmas and may help engineers avoid the conditions that could lead to heat loss in future fusion facilities.

PPPL physicist Dan Boyer. (Photo: Amber Boyer/Kiran Sudarsanan)

Researchers at the Department of Energy’s Princeton Plasma Physics Laboratory are using machine learning to predict electron density and pressure profile shapes on the National Spherical Torus Experiment-Upgrade (NSTX-U), the flagship fusion facility at PPPL that is currently under repair.

The hope is that such predictions, generated by artificial neural networks, could improve the ability of NSTX-U researchers to optimize the components of experiments that heat and shape the fusion plasma.

“This is a step toward what we should do to optimize the actuators,” said PPPL physicist Dan Boyer, author of the paper, “Prediction of electron density and pressure profile shapes on NSTX-U using neural networks,” published by Nuclear Fusion, a journal of the International Atomic Energy Agency. “Machine learning can turn historical data into a simple model that we can evaluate quickly enough to make decisions in the control room or even in real time during an experiment.”

Research led by scientists at the Department of Energy's Princeton Plasma Physics Laboratory (PPPL) provides new evidence that particles of boron, the main ingredient in Borax household cleaner, can coat internal components of doughnut-shaped plasma devices known as tokamaks and improve the efficiency of the fusion reactions, according to an article published on Phys.org on April 2.

The NSTX-U “umbrella.” Photo: Elle Starkman/ PPPL Office of Communications

The Department of Energy on September 8 announced funding for research at the National Spherical Tokamak Experiment Upgrade (NSTX-U), an Office of Science user facility at the DOE’s Princeton Plasma Physics Laboratory in Princeton, N.J.

Total planned funding is $17 million for the NSTX-U work over five years in duration. As much as $6 million in fiscal year 2020 dollars and out-year funding could be available this year, contingent on congressional appropriations and satisfactory progress.

The initiative will support experiments, data analysis, and computer modeling and simulation of plasma behavior. A major focus will be on the start of laying the scientific groundwork for a next-generation facility through better understanding of the behavior of plasmas in spherical tokamaks, the DOE said.

PPPL physicists Raffi Nazikian (left) and Qiming Hu, with a figure from their research. Photo: PPPL/Elle Starkman

Stars contain their plasma with the force of gravity, but here on earth, plasma in fusion tokamaks must be magnetically confined. That confinement is tenuous, because tokamaks are subject to edge localized modes (ELM)—intense bursts of heat and particles that must be controlled to prevent instabilities and damage to the fusion reactor.

Researchers at the Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) and at General Atomics (GA) recently published a paper in Physical Review Letters explaining this tokamak restriction and a potential path to overcome it. They have developed a new model for ELM suppression in the DIII-D National Fusion Facility, which is operated by GA for the DOE. PPPL physicists Qiming Hu and Raffi Nazikian are the lead authors of the paper, which was announced on August 10 by PPPL.