Feb. 2, 2021 — Multi-institutional researchers led by physicist C.S. Chang of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have been granted millions of supercomputer node-hours to investigate issues crucial to the success of ITER, the international tokamak under construction in France to demonstrate the feasibility of fusion power. The two-year award from the DOE’s Innovative and Novel Computational Impact on Theory and Experiment (INCITE), selected in competition with science and engineering research from around the world, enables the team to extend its previous INCITE work into areas of critical interest for next-step fusion facilities.

Fusion, the power that drives the sun and stars, combines light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei that makes up 99 percent of the visible universe — to generate massive amounts of energy. ITER represents doughnut-shaped magnetic fusion facilities called “tokamaks” that aim to create and control fusion on Earth for a virtually inexhaustible supply of power to generate electricity.

Supercomputer hours

The new INCITE award provides the team from four national laboratories, two universities, and a consulting firm with 0.9 million node-hours on the Summit supercomputer at the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory, and 1.3 million node-hours on Theta at the Argonne Leadership Computing Facility at Argonne National Laboratory.

On both supercomputers, researchers will run the state-of-the-art XGC code developed at PPPL, in collaboration with members of Chang’s Scientific Discovery through Advanced Computing (SciDAC) team at national laboratories, universities and a consulting firm. XGC is a high-fidelity plasma turbulence code that is equipped to model the complicated tokamak boundary physics in realistic geometry.  The goal will be to predict the minimum power needed to transition the plasma from low- to high-confinement on ITER and to predict the height and shape of the “pedestal” at the edge of the plasma together with the width of the heat load that will strike the divertor plates that accept waste heat from the tokamak.

New edge physics

The research aims to find new edge physics that will govern the plasma performance in ITER and predict how the processes that drive present-day tokamaks can be extrapolated to ITER in accordance with the new physics. Of particular interest is the footprint of the exhaust heat on the  surface of the tokamak divertor plates.  ITER operations that can produce 10 times more energy than the input energy could exhaust 100 megawatts  of heat on the divertor plates. If the width of the peak heat-flux is too narrow, it could seriously damage the divertor plates.

“The collaborative XGC team includes not only U.S. researchers, but also European Union and Asian researchers,” Chang said.  “The new physics and simulation capability will also strengthen the edge component of the Exascale Computing Whole Device Modeling Application project (ECP-WDMApp)” — a PPPL-led program to develop the first complete model of a fusion plasma as part of the DOE’s Exascale Computing Project.

Members of this research team include PPPL physicists Michael Churchill, Michael Cole, Stephane Ethier, Robert Hager, Seung-Hoe Ku, Benjamin Sturdevant, and others. Collaborating members include Mark Adams, Lawrence Berkeley National Laboratory; Luis Chacon, Los Alamos National Laboratory; Scott Klasky and Sarat Sreepathi, Oak Ridge National Laboratory; Scott Parker, University of Colorado; Mark Shephard, Rensselaer Polytechnic Institute; and Aaron Scheinberg, Jubilee Development.

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 single largest 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, visit energy.gov/science.

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Source: John Greenwald, PPPL