X Marks the Spot: Researchers Confirm Novel Method for Controlling Plasma Rotation to Improve Fusion Performance

Reprinted from T. Stoltzfus-Dueck et al., Phys. Rev. Lett. 114, 245001 (2015). Copyright 2015 by the American Physical Society. Representative plasma geometries, with the X-point location circled in red

Such a method could prove important for future facilities like ITER, the huge international tokamak under construction in France that will demonstrate the feasibility of fusion as a source of energy for generating electricity. ITER's massive size will make it difficult for the facility to provide sufficient rotation through external means.

Rotation is essential to the performance of all tokamaks. Rotation can stabilize instabilities in plasma, and sheared rotation – the difference in velocities between two bands of rotating plasma – can suppress plasma turbulence, making it possible to maintain the gas's high temperature with less power and reduced operating costs.

Today's tokamaks produce rotation mainly by heating the plasma with neutral beams, which cause it to spin. In intrinsic rotation, however, rotating particles that leak from the edge of the plasma accelerate the plasma in the opposite direction, just as the expulsion of propellant drives a rocket forward.

Stoltzfus-Dueck and his team influenced intrinsic rotation by moving the so-called X-point – the dividing point between magnetically confined plasma and plasma that has leaked from confinement – on the Tokamak à Configuration Variable (TCV) in Lausanne, Switzerland. The experiments marked the first time that researchers had moved the X-point horizontally to study plasma rotation. The results confirmed calculations that Stoltzfus-Dueck had published in a 2012 paper showing that moving the X-point would cause the confined plasma to either halt its intrinsic rotation or begin rotating in the opposite direction. “The edge rotation behaved just as the theory predicted,” said Stoltzfus-Dueck.

A surprise also lay in store: Moving the X-point not only altered the edge rotation, but modified rotation within the superhot core of the plasma where fusion reactions occur. The results indicate that scientists can use the X-point as a “control knob” to adjust the inner workings of fusion plasmas, much like changing the settings on iTunes or a stereo lets one explore the behavior of music. This discovery gives fusion researchers a tool to access different intrinsic rotation profiles and learn more about intrinsic rotation itself and its effect on confinement.

The overall findings provided a “perfect example of a success story for theory-experiment collaboration,” said Olivier Sauter, senior scientist at École Polytechnique Fédérale de Lausanne and co-author of the paper.

Along with the practical applications of his research, Stoltzfus-Dueck enjoys the purely intellectual aspect of his work. “It’s just interesting,” he said. “Why do plasmas rotate in the way they do? It's a puzzle.”

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. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single 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, please visit science.energy.gov.

Contact Information
Raphael Rosen
rrosen@pppl.gov
Phone: 609-243-3317

Media Contact

Raphael Rosen newswise

All latest news from the category: Physics and Astronomy

This area deals with the fundamental laws and building blocks of nature and how they interact, the properties and the behavior of matter, and research into space and time and their structures.

innovations-report provides in-depth reports and articles on subjects such as astrophysics, laser technologies, nuclear, quantum, particle and solid-state physics, nanotechnologies, planetary research and findings (Mars, Venus) and developments related to the Hubble Telescope.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors