PPPL is collaborating with private industry on cutting-edge fusion research aimed at achieving commercial fusion energy. This work, enabled through a public-private DOE grant program, supports efforts to develop high-performance plasmas that fuel fusion reactions. In one such project PPPL is working in coordination with MIT’s Plasma Science and Fusion Center (PSFC) and Commonwealth Fusion Systems, a start-up spun out of MIT that is developing a tokamak fusion facility called SPARC. Its features include its compact size and new high-temperature superconducting magnets whose powerful fields aim to confine plasma more tightly than existing superconducting magnets can do.

The goal of the project is to predict the leakage of fast “alpha” particles produced by fusion reactions in SPARC. These particles can create a largely self-heated or “burning plasma” that maintains fusion reactions — a major goal of fusion energy research. However, leakage of alpha particles could slow or halt the reactions and damage the interior of the SPARC facility.

“We found that the alpha particles are indeed well confined in the SPARC design,” said PPPL physicist Gerrit Kramer, who collaborates through the DOE Innovation Network for Fusion Energy (INFUSE) program that PPPL physicist Ahmed Diallo serves as deputy director. Kramer worked closely with researcher Steven Scott, a consultant to Commonwealth Fusion Systems and former long-time physicist at PPPL.

Kramer and colleagues found that misalignment of the SPARC magnets will increase losses of fusion particles leading to increased power striking the walls. Their calculations will provide guidance to the SPARC engineering team about how well the magnets must be aligned to avoid excessive power loss and wall damage. Proper alignment will enable studies of plasma self-heating for the first time and development of improved techniques for plasma control in future fusion power plants.

A key hurdle facing fusion devices called stellarators — twisty facilities that seek to harness on Earth the fusion reactions that power the sun and stars — has been their limited ability to maintain the heat and performance of the plasma that fuels those reactions. Now collaborative research by scientists at PPPL and the Max Planck Institute for Plasma Physics (IPP) in Greifswald, Germany, have found that the Wendelstein 7-X (W7-X) facility in Greifswald, the largest and most advanced stellarator ever built, has demonstrated a key step in overcoming this problem.

The cutting-edge facility, built and housed in Greifswald with PPPL as the leading U.S. collaborator, is designed to improve the performance and stability of the plasma that fuels fusion reactors. Recent research on the W7-X aimed to determine whether design of the advanced facility could temper the leakage of heat and particles from the core of the plasma that has long slowed the advancement of stellarators. “That is one of the most important questions in the development of stellarator fusion devices,” said PPPL physicist Novimir Pablant

whose work validates an important aspect of the findings. The research, combined with findings of Max Planck scientists demonstrates that the advanced design does in fact moderate the leakage.

“I recall my excitement seeing Novi’s raw data in the control room right after the shot,” said Max Planck physicist Andreas Dinklage. “I immediately realized it was one of the rare moments in a scientist’s life when the evidence you measure shows that you’re following the right path. But even now there’s still a long way to go.”

A further benefit of the W7-X design is that it reveals where most of the leakage in the W7-X stellarator now comes from. “This allows us to determine how much turbulent transport is going on in the core of the plasma,” Pablant said. “The research marks the first step in showing that high-performance stellarator designs such as W-7X are an attractive way to produce a clean and safe fusion reactor.”

World-class expertise in confining and stabilizing the plasma that fuels fusion reactions has brought two new public-private collaborations to PPPL. The new awards, made by the DOE’s Innovation Network for Fusion Energy (INFUSE) program, will bring together PPPL physicist Walter Guttenfelder with Britain’s Tokamak Energy, and PPPL’s Zhirui Wang and Dylan Brennan with General Fusion of Canada.

“These partnerships recognize PPPL’s world-class skill in modeling fusion plasmas,” said Ahmed Diallo, a PPPL physicist and deputy director of the INFUSE program. “The goal of INFUSE is to leverage the capabilities of national laboratories to enhance private fusion development.”

The private developers are joining with PPPL for modeling analysis. Tokamak Energy, a 2009 spinoff from Britain’s Culham Centre for Fusion Energy, is developing a compact spherical tokamak with high-temperature superconducting magnets that can reduce the size of future fusion reactors. The company has turned to Guttenfelder to model the sources and strength of the microturbulence that causes heat to escape from tokamaks.

General Fusion, founded in 2003, is developing a facility called a magnetized target fusion (MTF) machine that uses pistons to compress plasma tightly enough to produce fusion energy. A key requirement of this technique is for the plasma to remain stable during compression. The company is turning to PPPL’s Wang and Brennan, physicists on the forefront of stability theory, to apply advanced theory to prevent instabilities from forming during compression scenarios.

Wang and Brennan will modify and apply a leading computer code for analyzing plasma instabilities and will provide technical support for application of that code and another one to experiments. The two projects bring to six the number of INFUSE collaborations with private industry that PPPL has been awarded since the DOE launched the program in 2019.

From plasma technologies to fight the COVID-19 pandemic to heat-resistant Earth reentry vehicles, U.S. researchers are exploring state-of-the-art projects at the new Princeton Collaborative Low Temperature Plasma Research Facility (PCRF). The joint venture of PPPL and Princeton University provides access to world-class diagnostics, computational tools, and expertise in plasma physics for characterizing low temperature plasmas (LTP) — a rapidly expanding source of innovation in fields ranging from electronics to health care to space exploration.

“All of us at PCRF are very pleased with the impressive results of the first solicitation, which demonstrated a remarkable user demand for PCRF research resources and our expertise,” said PPPL physicist Yevgeny Raitses, principal investigator for the facility.

Here is a look at some first-round collaborations conducted by PPPL and Princeton scientists in the innovative facility:

• Mikhail Shneider, a Princeton University researcher and co-principal investigator of the PCRF, is exploring the breakdown of plasma in liquid with Texas A&M University-Kingsville. Such breakdown is crucial to the design of pulsed power systems that deliver high-voltage power for uses ranging from food processing to water contamination.

• PPPL researcher Sophia Gershman and the New Jersey Institute of Technology (NJIT) are developing innovative low temperature plasma devices for the disinfection and sterilization of surfaces and air from bacteria and viruses such as COVID-19.

• Igor Kaganovich, a PPPL scientist and co-principal investigator of the PCRF, is overseeing a project with the University of Illinois at Urbana-Champaign that studies an obstacle that reduces the neutralization of laser-like ion beams. Such beams must be neutralized for applications that range from inertial confinement fusion to the production of superhot states of matter that are thought to exist in the core of giant planets like Jupiter.

• Princeton researcher Arthur Dogariu conducted a project at the University of Texas at Arlington that characterized the high-velocity flow of plasma in a wind tunnel-like device that tests the heat-resistance of innovative materials for space vehicle reentry to Earth.

• Shurik Yatom of PPPL is working with a team at Washington University in St. Louis to investigate the interaction of plasma with liquid for potential use in electrochemistry, a field with applications ranging from cell phone batteries to anti-corrosive metal plating.

• Raitses has conducted a project with physicist Kai-Mei Fu of the University of Washington in Washington State on low temperature magnetized plasma for processing materials such as diamond for quantum information network applications. He notes that response to the second round of solicitation, which ended last December, “has demonstrated an even greater demand for PCRF state-of-the art capabilities.”