Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


New explanation for sudden heat collapses in plasmas can help create fusion energy


Scientists seeking to bring the fusion that powers the sun and stars to Earth must deal with sawtooth instabilities -- up-and-down swings in the central pressure and temperature of the plasma that fuels fusion reactions, similar to the serrated blades of a saw. If these swings are large enough, they can lead to the sudden collapse of the entire discharge of the plasma. Such swings were first observed in 1974 and have so far eluded a widely accepted theory that explains experimental observations.

Consistent with observations

PPPL physicist Stephen Jardin with figure from paper.

Photo and composite by Elle Starkman/PPPL Office of Communications.

Researchers at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have proposed a new theory to explain the swings that occur in doughnut-shaped tokamaks, or fusion facilities. The theory, created through high-fidelity computer simulations, appears consistent with observations made during tokamak experiments, the researchers said.

Understanding the process could prove vital to next-generation fusion facilities such as ITER, the international experiment under construction in France to demonstrate the practicality of fusion power.

Fusion combines light elements in the form of plasma -- the hot, charged state of matter composed of free electrons and atomic nuclei -- that generates massive amounts of energy. Scientists seeking to replicate fusion on Earth intend to provide a virtually inexhaustible supply of safe and clean power to generate electricity.

The recent findings demonstrate that when the pressure in the core of the plasma reaches a certain point, other instabilities can be excited that produce the sudden pressure and temperature drops.

These instabilities create jumbled -- or stochastic -- magnetic fields in the core of the plasma that cause the collapse, said physicist Stephen Jardin, lead author of a paper describing the process in Physics of Plasmas and highlighted in a featured American Institute of Physics publication called "SciLight."

"Most tokamak discharges exhibit sawteeth," Jardin said, "and we're trying to provide the theory of the physics behind them."

The new findings depart sharply from a long-held theory that causing the swings is an instability that leads to magnetic reconnection -- the breaking apart and snapping together of the magnetic field lines in plasma. "That theory has been around for over 40 years," Jardin said.

Motivating the new theory

Motivating the new theory is previous PPPL research that demonstrates how the instability that was thought to lead to magnetic reconnection can, in fact, self-stabilize the plasma. It does this by producing a localized voltage that prevents the current in the core of the plasma from peaking sufficiently to be subject to magnetic reconnection.

The new explanation holds that even though the magnetic reconnection is suppressed, an increase of heat in the core of the plasma can excite localized instabilities that act together to flatten the pressure and temperature during the sawtooth cycle.

Simulations produced by codes developed by Jardin and PPPL physicist Nate Ferraro, a coauthor of the paper, demonstrate this process. The new instabilities can grow very fast, consistent with the rapid collapse of heat seen in experiments that the traditional theory cannot explain.

This advanced model provides a new way to understand sawtooth phenomena. Looking ahead, the scientists want to explore the applicability of the model to tasks such as describing the evolution of "monster sawteeth" and using high powered Radio Frequency antennas to control sawtooth swings. "We want to develop a simulation model of a whole tokamak plasma," Jardin said, "and this new theory of the sawteeth is an important part of the effort."


Coauthors of the paper include Isabel Krebs, a former post-doctoral physicist at PPPL now at the Dutch Institute for Fundamental Energy Research (DIFFER), who developed the theory that the instability thought to cause temperature collapse could serve to stabilize the plasma. Support for the new research comes from the DOE Office of Science and the SciDAC Center for Tokamak Transient Simulations. Researchers developed the new simulations at the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility at Lawrence Berkeley National Laboratory.

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

Media Contact

John Greenwald


John Greenwald | EurekAlert!
Further information:

More articles from Power and Electrical Engineering:

nachricht Impact assessment of F-gas free medium voltage switchgear
30.06.2020 | Fraunhofer-Institut für Energiewirtschaft und Energiesystemtechnik IEE

nachricht Hot patterns in cold space
25.06.2020 | Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: ILA Goes Digital – Automation & Production Technology for Adaptable Aircraft Production

Live event – July 1, 2020 - 11:00 to 11:45 (CET)
"Automation in Aerospace Industry @ Fraunhofer IFAM"

The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM l Stade is presenting its forward-looking R&D portfolio for the first time at...

Im Focus: AI monitoring of laser welding processes - X-ray vision and eavesdropping ensure quality

With an X-ray experiment at the European Synchrotron ESRF in Grenoble (France), Empa researchers were able to demonstrate how well their real-time acoustic monitoring of laser weld seams works. With almost 90 percent reliability, they detected the formation of unwanted pores that impair the quality of weld seams. Thanks to a special evaluation method based on artificial intelligence (AI), the detection process is completed in just 70 milliseconds.

Laser welding is a process suitable for joining metals and thermoplastics. It has become particularly well established in highly automated production, for...

Im Focus: A structural light switch for magnetism

A research team from the Max Planck Institute for the Structure of Dynamics (MPSD) and the University of Oxford has managed to drive a prototypical antiferromagnet into a new magnetic state using terahertz frequency light. Their groundbreaking method produced an effect orders of magnitude larger than previously achieved, and on ultrafast time scales. The team’s work has just been published in Nature Physics.

Magnetic materials have been a mainstay in computing technology due to their ability to permanently store information in their magnetic state. Current...

Im Focus: Virtually Captured

Biomechanical analyses and computer simulations reveal the Venus flytrap snapping mechanisms

The Venus flytrap (Dionaea muscipula) takes only 100 milliseconds to trap its prey. Once their leaves, which have been transformed into snap traps, have...

Im Focus: NASA observes large Saharan dust plume over Atlantic ocean

NASA-NOAA's Suomi NPP satellite observed a huge Saharan dust plume streaming over the North Atlantic Ocean, beginning on June 13. Satellite data showed the dust had spread over 2,000 miles.

At NASA's Goddard Space Flight Center in Greenbelt, Maryland, Colin Seftor, an atmospheric scientist, created an animation of the dust and aerosols from the...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Aachen Machine Tool Colloquium AWK'21 will take place on June 10 and 11, 2021

07.04.2020 | Event News

International Coral Reef Symposium in Bremen Postponed by a Year

06.04.2020 | Event News

Latest News

Rice lab's bright idea is pure gold

30.06.2020 | Physics and Astronomy

Scientists devise gentle technique to study heart tissue functioning

30.06.2020 | Life Sciences

Analysis of complex geometric models made simple

30.06.2020 | Information Technology

Science & Research
Overview of more VideoLinks >>>