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February 17, 2022

How the Princeton Plasma Physics Lab contributed to the new world record in clean fusion energy

By John Greenwald, Princeton Plasma Physics Laboratory Communications

Research by scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) has played a supporting role in the recent major advance in the production of fusion power at the Joint European Torus (JET) in the United Kingdom. In the recently disclosed breakthrough by the EUROfusion research consortium that contributes to JET, the largest and most powerful tokamak fusion facility in current use set an historic record in the production of experimental fusion energy.

That energy totaled 59 megajoules for five seconds, a fusion power output that averaged 11.8 million Watts. That production was more than two-and-a-half times the world record that JET previously set in 1997.

Fusion, the power that drives sun and stars, combines light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei, or ions, making up 99% of the visible universe — to generate massive amounts of energy. Scientists around the world are seeking to reproduce and control fusion on Earth for a virtually inexhaustible supply of safe and clean power to generate electricity. Tokamaks, doughnut-shaped magnetic fusion facilities, are the most widely used experimental devices in these efforts.

High-power fusion fuel

The new record came during a five-month campaign in which EUROfusion tested high-power fusion fuel that was last used in the 1990s and will next power ITER, the international tokamak under construction in France. The fuel combines the hydrogen isotopes deuterium and tritium (D-T) that ITER plans to use to prove the feasibility of producing controlled fusion energy. JET is currently the only tokamak in the world that can operate using the D-T fuel planned for ITER and future fusion power plants.

Studies conducted ahead of the JET experiments included those delivered by PPPL. “We provided and operated a diagnostic to measure the loss of energetic ions,” said Mario Podesta, the PPPL physicist who led the work. “Such ions produce fusion reactions and provide heat to the plasma and understanding why they are lost is the first step to improving their confinement.”

The results have proved essential. “The collaboration between PPPL and JET has been very important in order to study and characterize fast ions losses before the D-T campaign and I am convinced that the diagnostic managed by PPPL will provide key physics about energetic particles in D-T,” said Jeronimo Garcia, JET Task Force Leader responsible for the collaboration between JET and PPPL.

Garcia added that PPPL’s TRANSP computer code plays an important role in the analysis and prediction of plasmas with D-T. The TRANSP team, led by PPPL physicist Francesca Poli, continues working with the JET team on upgrades to the code that support the JET campaign in preparation for ITER operation.

Researchers from PPPL who contributed to the advance at JET (from top): Francesca Poli, Mario Podesta, Anna Teplukhina, Philip Bonofiglo. Photos by Elle Starkman/Office of Communications for Podesta, Poli and Teplukhina; Kate Yang for Bonofiglo.

PPPL became a pioneer user of D-T in 1991. Its Tokamak Fusion Test Reactor (TFTR) ran on the high-power fuel from 1991 to 1997, set a then-world record for producing fusion power in 1992 and now is dismantled. JET also began its D-T use in 1991 and in 1997 set the record eclipsed by its recent five-month campaign that ended last December and has now been reported.

The recent production of fusion power marks a major step toward the creation of safe and clean fusion energy to offset global climate change. “It’s clear we must make significant changes to address the effects of climate change, and fusion offers so much potential,” said Ian Chapman, CEO of the EUROfusion member UKAEA (United Kingdom Atomic Energy Authority) that operates JET in Britain’s Culham Centre for Fusion Energy on behalf of EUROfusion. “We’re building the knowledge and developing the new technology required to deliver a low carbon, sustainable source of baseload energy that helps protect the planet for future generations,” Chapman said.

JET has long been a testbed for ITER, which applauded the new results. “A sustained pulse of deuterium-tritium fusion at this power level — nearly industrial scale — delivers a resounding confirmation to all of those involved in the global fusion quest,” said Bernard Bigot, ITER Director-General. “For the ITER Project, the JET results are a strong confidence builder that we are on the right track as we move forward toward demonstrating full fusion power.”

JET will now follow up its D-T campaign from mid-2022 to 2023 before ITER starts operating in 2025. ITER will begin using the D-T combination in 2035 when its plans call for the production of “burning plasmas” — largely self-sustaining fusion reactions — that will produce 10 times more energy than will be required to heat the plasma to the roughly 150 million degree temperatures that can create fusion energy.

Additional researchers who worked on the JET collaboration include physicist Philip Bonofiglo, who has operated the PPPL diagnostic for studying fast ions in JET experiments for the past two years. Also collaborating was Anna Teplukhina, a former post-doctoral researcher at PPPL who ran TRANSP simulations and did analysis on fast ion transport.

Support for this research comes from the DOE Office of Science.

PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit

This story originally appeared on main Princeton University homepage and on the Princeton Plasma Physics website.