Nav: Home

New turbulent transport modeling shows multiscale fluctuations in heated plasma

February 13, 2018

WASHINGTON, D.C., February 13, 2018 -- Researchers at the DIII-D National Fusion Facility, a DOE Office of Science user facility operated by General Atomics, used a "reduced physics" fluid model of plasma turbulence to explain unexpected properties of the density profile inside a tokamak experiment. Modeling plasma's turbulent behavior could help scientists optimize the tokamak performance in future fusion reactors like ITER.

Applying heat in a tokamak produces many interesting phenomena such as changes in plasma rotation and density. DIII-D researchers modeled how different types of heating, like microwaves that produce electron heating or neutral beams that produce ion heating, influences the plasma density, behavior of impurities and turbulent transport. The different heating methods drive turbulence at the long (ion) scales and much shorter (electron) scales that are at the frontier of turbulence computer simulations.

Their findings, reported this week in Physics of Plasmas, from AIP Publishing, showed that heating the electrons in a fusion reactor caused important changes in density gradients within the plasma. Their "trapped gyro-Landau fluid" (TGLF) model predicted that adding heat excited turbulence, at wavelengths between the ion and electron scales, and would produce a particle pinch that modifies the plasma's overall density profile. Additionally, in this paper, researchers used their reduced transport model to predict impurity transport in a fusion reactor.

Brian Grierson, a Princeton Plasma Physics Laboratory physicist working as a researcher at the DIII-D National Fusion Facility in San Diego, said that "when you heat the plasma, you don't just change the temperature, you change the type of turbulence that exists, and that has secondary implications on the transport of plasma density and the plasma rotation."

Generally, heat flowing from the hot plasma center to the cold plasma edge drives turbulent diffusion, which should act to flatten the density gradient. "But the fascinating thing is that sometimes applying heat in a fusion reactor causes it to produce a density gradient rather than flatten it," Grierson said. This density peaking is significant because the fusion reaction between deuterium and tritium particles in a tokamak increases as the density of the plasma increases. In other words, he said, "fusion power is proportional to the [plasma] density squared."

Grierson credits Gary Staebler, a co-author on the paper, as the General Atomics theoretician behind TGLF, the model tested in this paper. TGLF is a reduced physics model of the "full physics" gyrokinetic code GYRO for turbulent transport, which must be run on supercomputers. Using this more cost-effective TGLF model, researchers were able to execute the code with various experimental measurement and inputs hundreds of times to quantify how uncertainties in the experimental data affect the theoretical interpretation.

Going forward, Grierson hopes that these findings will help inform research to advance the fusion community's understanding of extremely small-scale fluctuations and impurity transport within a plasma.

"We need to understand transport under ion and electron heating to confidently project to future reactors, because fusion power reactors will have both ion and electron heating," Grierson said. "This result identifies what we need to investigate with the computationally challenging full physics simulations to verify the interaction of particle, momentum and impurity transport with heating."
This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-AC02-09CH11466, DE-FC02-04ER54698, DE-FG02-08ER54999, DE-FG02-07ER54917, DE- FG03-97ER54415, DE-FG02-04ER54235 and DE-FG02- 08ER54984.

The article, "Multi-scale transport in the DIII-D ITER baseline scenario with direct electron heating and projection to ITER," is authored by B.A. Grierson, Gary Staebler, Wayne M. Solomon, George R. McKee, Christopher Holland, Max E. Austin, Alessandro Marinoni, Lothar Schmitz, Robert I. Pinsker, and the DIII-D Team. The article appeared in the journal Physics of Plasmas Feb. 13, 2018 (DOI: 10.1063/1.5011387) and can be accessed at


Physics of Plasmas is devoted to the publication of original experimental and theoretical work in plasma physics, from basic plasma phenomena to astrophysical and dusty plasmas. See

American Institute of Physics

Related Plasma Articles:

Table top plasma gets wind of solar turbulence
Scientists from India and Portugal recreate solar turbulence on a table top using a high intensity ultrashort laser pulse to excite a hot, dense plasma and followed the evolution of the giant magnetic field generated by the plasma dynamics.
Getting the biggest bang out of plasma jets
Capillary discharge plasma jets are created by a large current that passes through a low-density gas in what is called a capillary chamber.
Neptune: Neutralizer-free plasma propulsion
Plasma propulsion concepts are gridded-ion thrusters that accelerate and emit more positively charged particles than negatively charged ones.
UCLA researchers discover a new cause of high plasma triglycerides
People with hypertriglyceridemia often are told to change their diet and lose weight.
Where does laser energy go after being fired into plasma?
An outstanding conundrum on what happens to the laser energy after beams are fired into plasma has been solved in newly-published research at the University of Strathclyde.
New feedback system could allow greater control over fusion plasma
A physicist has created a new system that will let scientists control the energy and rotation of plasma in real time in a doughnut-shaped machine known as a tokamak.
PPPL scientist uncovers physics behind plasma-etching process
PPPL physicist Igor Kaganovich and collaborators have uncovered some of the physics that make possible the etching of silicon computer chips, which power cell phones, computers, and a huge range of electronic devices.
Calculating 1 billion plasma particles in a supercomputer
At the National Institutes of Natural Sciences National Institute for Fusion Science (NIFS) a research group using the NIFS 'Plasma Simulator' supercomputer succeeded for the first time in the world in calculating the movements of one billion plasma particles and the electrical field constructed by those particles.
Anti-tumor effect of novel plasma medicine caused by lactate
Nagoya University researchers developed a new physical plasma-activated salt solution for use as chemotherapy.
Clarifying the plasma oscillation by high-energy particles
The National Institute for Fusion Science has developed a new code that can simulate the movement of plasma and, simultaneously, the movement of particles circulating at high speeds.

Related Plasma Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#513 Dinosaur Tails
This week: dinosaurs! We're discussing dinosaur tails, bipedalism, paleontology public outreach, dinosaur MOOCs, and other neat dinosaur related things with Dr. Scott Persons from the University of Alberta, who is also the author of the book "Dinosaurs of the Alberta Badlands".