Nav: Home

Tracking major sources of energy loss in compact fusion facilities

June 11, 2019

A key obstacle to controlling on Earth the fusion that powers the sun and stars is leakage of energy and particles from plasma, the hot, charged state of matter composed of free electrons and atomic nuclei that fuels fusion reactions. At the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL), physicists have been focusing on validating computer simulations that forecast energy losses caused by turbulent transport during fusion experiments.

Researchers used codes developed at General Atomics (GA) in San Diego to compare theoretical predictions of electron and ion turbulent transport with findings of the first campaign of the laboratory's compact -- or "low-aspect ratio" -- National Spherical Torus Experiment-Upgrade (NSTX-U). GA, which operates the DIII-D National Fusion Facility for the DOE, has developed codes well-suited for this purpose.

Low-aspect ratio tokamaks are shaped like cored apples, unlike the more widely used conventional tokamaks that are shaped like doughnuts.

State-of-the-art codes

"We have state-of-the-art codes based on sophisticated theory to predict transport," said physicist Walter Guttenfelder, lead author of a Nuclear Fusion paper that reports the findings of a team of researchers. "We must now validate these codes over a broad range of conditions to be confident that we can use the predictions to optimize present and future experiments."

Analysis of the transport observed in NSTX-U experiments found that a major factor behind the losses was turbulence that caused the transport of electrons to be "anomalous," meaning that they spread rapidly, similar to the way that milk mixes with coffee when stirred by a spoon. The GA codes predict the cause of these losses to be a complex mix of three different types of turbulence.

The observed findings opened a new chapter in the development of predictions of transport in low-aspect ratio tokamaks -- a type of fusion facility that could serve as a model for next-generation fusion reactors that combine light elements in the form of plasma to produce energy. Scientists around the world are seeking to replicate fusion on Earth for a virtually inexhaustible supply of power to generate electricity.

Researchers at PPPL now aim to identify the mechanisms behind the anomalous electron transport in a compact tokamak. Simulations predict that such energy loss stems from the presence of three distinct types of complex turbulence -- two types with relatively long wavelengths and a third with wavelengths a fraction of the size of the larger two.

The impact of one of the two long-wave types, which is typically found in the core of low-aspect ratio tokamaks as well as in the edge of the plasma in conventional tokamaks, must be fully taken into account when predicting low-aspect ratio transport.

Challenge to simulate

However, the combined impact of all three types of turbulence is a challenge to simulate since scientists normally study the different wavelengths separately. Physicists at the Massachusetts Institute of Technology (MIT) have recently performed multi-scale simulations and their work highlights the significant supercomputer time such simulations require.

Researchers must now test additional simulations to achieve more complete agreement between predictions of transport and experiments on plasmas in low-aspect ratio tokamaks. Included in these comparisons will be measurements of turbulence taken by University of Wisconsin-Madison coauthors of the Nuclear Fusion paper that will better constrain predictions. Improved agreement will provide assurance of energy-loss predictions for present and future facilities.
-end-
Support for this work comes from the DOE Office of Science. The National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility, enabled the simulations. NSTX-U diagnostic equipment from the University of Wisconsin-Madison provided data from experiments.

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 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 energy.gov/science (link is external).

DOE/Princeton Plasma Physics Laboratory

Related Plasma Articles:

Plasma-driven biocatalysis
Compared with traditional chemical methods, enzyme catalysis has numerous advantages.
How bacteria protect themselves from plasma treatment
Considering the ever-growing percentage of bacteria that are resistant to antibiotics, interest in medical use of plasma is increasing.
A breakthrough in the study of laser/plasma interactions
Researchers from Lawrence Berkeley National Laboratory and CEA Saclay have developed a particle-in-cell simulation tool that is enabling cutting-edge simulations of laser/plasma coupling mechanisms.
Researchers turn liquid metal into a plasma
For the first time, researchers at the University of Rochester's Laboratory for Laser Energetics (LLE) have found a way to turn a liquid metal into a plasma and to observe the temperature where a liquid under high-density conditions crosses over to a plasma state.
How black holes power plasma jets
Cosmic robbery powers the jets streaming from a black hole, new simulations reveal.
Give it the plasma treatment: strong adhesion without adhesives
A Japanese research team at Osaka University used plasma treatment to make fluoropolymers and silicone resin adhere without any adhesives.
Chemotherapeutic drugs and plasma proteins: Exploring new dimensions
This review provides a bird's eye view of interaction of a number of clinically important drugs currently in use that show covalent or non-covalent interaction with serum proteins.
The coming of age of plasma physics
The story of the generation of physicists involved in the development of a sustainable energy source, controlled fusion, using a method called magnetic confinement.
Intense microwave pulse ionizes its own channel through plasma
More than 30 years ago, researchers theoretically predicted the ionization-induced channeling of an intense microwave beam propagating through a neutral gas (>103 Pa) -- and now it's finally been observed experimentally.
Plasma thruster: New space debris removal technology
A Japanese and Australian research group has discovered new technology to remove space debris using a single propulsion system in a helicon plasma thruster.
More Plasma News and Plasma Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.