Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The long and short of plasma turbulence

11.11.2015

Scientists use supercomputer to model plasma turbulence, and solve a 50-year-old mystery

For more than 60 years, fusion scientists have tried to use "magnetic bottles" of various shapes and sizes to confine extremely hot plasmas, with the goal of producing practical fusion energy. But turbulence in the plasma has, so far, confounded researchers' ability to efficiently contain the intense heat within the core of the fusion device, reducing performance. Now, scientists have used one of the world's largest supercomputers to reveal the complex interplay between two types of turbulence known to occur in fusion plasmas, paving the way for improved fusion reactor design.


Plasma turbulence in conditions with long wavelength turbulence (top) are compared with those exhibiting long and short wavelength turbulence (bottom). The top condition is representative of the standard model. The bottom model demonstrates the clear impact of capturing long and short wavelength turbulence simultaneously.

Credit: N. T. Howard

Years of careful research have shown that fusion devices are plagued by plasma turbulence. The turbulence quickly pushes heat from the hot fusion core to the edge, cooling the plasma in the process and reducing the amount of fusion energy produced.

While turbulence has been identified as the culprit, the measured heat losses in many fusion devices are still commonly higher than scientists' leading theories of turbulence. Thus, even after more than half a century of research, the origin of this "anomalous" heat loss in experimental fusion plasmas remained a mystery.

To tackle this problem, scientists had to create a model that captured the different types of turbulence known to exist in fusion plasmas. This turbulence can roughly be grouped into two categories: long wavelength turbulence and short wavelength turbulence.

Most prior research has assumed a dominant role for long wavelength turbulence, often neglecting short wavelength turbulence altogether. Although scientists were aware they were missing the contributions of the small eddies, simulation of all the turbulence together was too challenging to undertake...until now.

Using one of the world's largest supercomputers (the NERSC Edison system) and experimental data obtained from the Alcator C-Mod tokamak, scientists from the University of California, San Diego and the Massachusetts Institute of Technology recently performed the most physically comprehensive simulations of plasma turbulence to date.

These simulations capture the spatial and temporal dynamics of long and short wavelength turbulence simultaneously, revealing never before observed physics phenomena. Contrary to many proposed theories, long wavelength turbulence was found to coexist with short wavelength turbulence, in the form of finger-like structures known as "streamers" (Figure 1).

In many experimental conditions, the large scale turbulent eddies were found to interact strongly with the short wavelength turbulence, transferring energy back and forth. Most significantly, these simulations demonstrated that interactions between long and short wavelength turbulence can increase heat losses tenfold above the standard model, matching a wide variety of experimental measurements, and likely explaining the mystery of "anomalous" heat loss in plasmas.

Pushing the limits of supercomputing capabilities has changed scientists' understanding of how heat is pushed out of fusion plasmas by turbulence, and may help explain the 50-year-old mystery of "anomalous" heat loss. The study, currently submitted to the journal Nuclear Fusion, required approximately 100 million CPU hours to perform. For comparison, this is approximately the same as the latest MacBook Pro running for the next 3,000 years.

Ultimately, these results may be used to inform the design of fusion reactors, allowing for improved performance, and hopefully pushing us closer to the goal of practical fusion energy.

###

Contact: N. T. Howard, (617) 253-4785, nthoward@psfc.mit.edu

Abstracts: NI3.00001 The Role of ITG/TEM/ETG Cross-Scale Coupling in Explaining Experimental Electron Heat Flux and Profile Stiffness
9:30 AM-10:00 AM, Wednesday, November 18, 2015
Session NI3: MFE Transport and Turbulence
9:30 AM-12:30 PM, Wednesday, November 18, 2015
Room: Oglethorpe Auditorium

Media Contact

Saralyn Stewart
stewart@physics.utexas.edu
512-694-2320

 @APSphysics

http://www.aps.org 

Saralyn Stewart | EurekAlert!

More articles from Physics and Astronomy:

nachricht Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials
17.01.2018 | Universität des Saarlandes

nachricht Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Gran Chaco: Biodiversity at High Risk

17.01.2018 | Ecology, The Environment and Conservation

Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials

17.01.2018 | Physics and Astronomy

Fraunhofer HHI receives AIS Technology Innovation Award 2018 for 3D Human Body Reconstruction

17.01.2018 | Awards Funding

VideoLinks
B2B-VideoLinks
More VideoLinks >>>