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Primeur weekly 2017-07-31

Focus

ECMWF at the heart of weather and climate modelling as global challenge of societal relevance with game changing prediction capability through exascale ...

NVIDIA hits the top 10 in the TOP500 and Green500 lists with multi-tasking GPUs - NVIDIA Vice President Ian Buck explains ...

Exascale supercomputing

Oak Ridge National Laboratory acquires D-Wave 2000Q Cloud services to accelerate hybrid computing applications ...

Crowd computing

Dark ecology project will use past weather radar data to trace bird migrations ...

Quantum computing

Tiny dancer atoms could prove a hit with quantum computer scientists ...

Qubitekk licenses ORNL single-photon source approach for quantum encryption ...

Ultracold molecules hold promise for quantum computing ...

University of Sydney and Microsoft forge global quantum computing partnership ...

Focus on Europe

Prof. Jan de Boer joins Board of Directors at Netherlands eScience Center ...

Hardware

Cray to expand storage portfolio through strategic transaction and partnership with Seagate ...

Stampede2 storms out of the Corral in support of U.S. scientists ...

Nick Nystrom appointed Interim Director of PSC ...

CSIRO has chosen Dell EMC to build a new scientific computing capability, kicking off a new generation of research ...

One Stop Systems named one of San Diego's fastest growing companies ...

Applications

High risk of unprecedented rainfall in the United Kingdom simulated by Met Office supercomputer ...

NIH awards $9.3 million for further development of PHENIX structural biology software ...

Inaugural Collaborative Science Call yields six proposals melding genomics and supercomputing ...

Stampede supercomputer skyrocketed science ...

IBM combines All-Flash and storage software optimized for Hortonworks ...

PPPL researchers perform first basic-physics simulation of the impact of recycled atoms on plasma turbulence ...

Catch of the day: A net full of trees ...

Liquid electrolyte contacts for advanced characterization of resistive switching memories ...

PPPL researchers perform first basic-physics simulation of the impact of recycled atoms on plasma turbulence


Physicist Daren Stotler. Photo by Elle Starkman/Office of Communications.
24 Jul 2017 Princeton - Turbulence, the violently unruly disturbance of plasma, can prevent plasma from growing hot enough to fuel fusion reactions. Long a puzzling concern of researchers has been the impact on turbulence of atoms recycled from the walls of tokamaks that confine the plasma. These atoms are neutral, meaning that they have no charge and are thus unaffected by the tokamak’s magnetic field or plasma turbulence, unlike the electrons and ions - or atomic nuclei - in the plasma. Yet, experiments have suggested that the neutral atoms may be significantly enhancing the edge plasma turbulence, hence the theoretical interest in their effects.

In the first basic-physics attempt to study the atoms' impact, physicists at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have modelled how the recycled neutrals, which arise when hot plasma strikes a tokamak's walls, increase turbulence driven by what is called the "ion temperature gradient" (ITG). This gradient is present at the edge of a fusion plasma in tokamaks and represents the transition from the hot core of the plasma to the colder boundary adjacent to the surrounding material surfaces.

Researchers used the extreme-scale XGC1 kinetic code to achieve the simulation, which represented the first step in exploring the overall conditions created by recycled neutrals. "Simulating plasma turbulence in the edge region is quite difficult", stated physicist Daren Stotler, who took over authorship of the paper, published inNuclear Fusionin July, once PPPL computational scientist Jianying Lang joined Intel Corp. in California. "Development of the XGC1 code enabled us to incorporate basic neutral particle physics into kinetic computer calculations, in multiscale, with microscopic turbulence and macroscale background dynamics", he stated. "This wasn't previously possible."

The results, reported in July in the journalNuclear Fusion, showed that neutral atoms enhance ITG turbulence in two ways:

  • First, they cool plasma in the pedestal, or transport barrier, at the edge of the plasma and thereby increase the ITG gradient.
  • Next, they reduce the sheared, or differing, rates of plasma rotation. Sheared rotation lessens turbulence and helps stabilize fusion plasmas.

Going forward, researchers plan to compare results of their model with experimental observations, a task that will require more complete simulations that include other turbulence modes. Findings could lead to improved understanding of the transition of plasmas from low confinement to high confinement, or H-mode - the mode in which future tokamaks are expected to operate. Researchers generally consider lower recycling, and hence fewer neutrals, as conducive to H-mode operation. This work may also lead to a better understanding of the plasma performance in ITER, the international fusion facility under construction in France, in which the neutral recycling may differ from that observed in existing tokamaks.

This research was performed under the supervision of PPPL physicist C.S. Chang. Modelling was done on the Titan supercomputer at the Oak Ridge Leadership Computing Facility and the Edison supercomputer at the National Energy Research Scientific Computing Center with support from the DOE Office of Advanced Scientific Computing Research and the DOE Office of Science (FES).

PPPL, on Princeton University's Forrestal Campus in Plainsboro, New Jersey, 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.
Source: Princeton Plasma Physics Laboratory - PPPL

Back to Table of contents

Primeur weekly 2017-07-31

Focus

ECMWF at the heart of weather and climate modelling as global challenge of societal relevance with game changing prediction capability through exascale ...

NVIDIA hits the top 10 in the TOP500 and Green500 lists with multi-tasking GPUs - NVIDIA Vice President Ian Buck explains ...

Exascale supercomputing

Oak Ridge National Laboratory acquires D-Wave 2000Q Cloud services to accelerate hybrid computing applications ...

Crowd computing

Dark ecology project will use past weather radar data to trace bird migrations ...

Quantum computing

Tiny dancer atoms could prove a hit with quantum computer scientists ...

Qubitekk licenses ORNL single-photon source approach for quantum encryption ...

Ultracold molecules hold promise for quantum computing ...

University of Sydney and Microsoft forge global quantum computing partnership ...

Focus on Europe

Prof. Jan de Boer joins Board of Directors at Netherlands eScience Center ...

Hardware

Cray to expand storage portfolio through strategic transaction and partnership with Seagate ...

Stampede2 storms out of the Corral in support of U.S. scientists ...

Nick Nystrom appointed Interim Director of PSC ...

CSIRO has chosen Dell EMC to build a new scientific computing capability, kicking off a new generation of research ...

One Stop Systems named one of San Diego's fastest growing companies ...

Applications

High risk of unprecedented rainfall in the United Kingdom simulated by Met Office supercomputer ...

NIH awards $9.3 million for further development of PHENIX structural biology software ...

Inaugural Collaborative Science Call yields six proposals melding genomics and supercomputing ...

Stampede supercomputer skyrocketed science ...

IBM combines All-Flash and storage software optimized for Hortonworks ...

PPPL researchers perform first basic-physics simulation of the impact of recycled atoms on plasma turbulence ...

Catch of the day: A net full of trees ...

Liquid electrolyte contacts for advanced characterization of resistive switching memories ...