Grant-winning PPPL scientists lead fusion to the edge

A center based at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) has won a highly competitive $12.25 million grant to develop computer codes to simulate a key component of the plasma that fuels fusion energy. The five-year DOE award could produce software that helps researchers design and operate facilities to create fusion as a clean and abundant source of energy for generating electricity.

The grant comes from the Department's Scientific Discovery through Advanced Computing (SciDAC) program supported by the DOE Office of Science.

"The DOE grant is terrific for the Laboratory because it allows us to work in the forefront of the simulation of the edge region of fusion plasmas," said PPPL Director Stewart Prager. "This code could go a long way toward modeling and understanding this pivotal region."

The grant will go to PPPL's Center for Edge Physics Simulation (EPSI) headed by C.S. Chang, a principal research physicist at the Laboratory. The award will fund an advanced computer simulation of the complex and turbulent conditions at the edge of the plasma, the hot, electrically charged gas that scientists confine inside magnetic fields in facilities called tokamaks. Controlling the little-understood plasma edge is crucial for maintaining the confinement so that fusion can take place.

The task of confinement has many everyday parallels. "If you want to confine soup, the bowl should not leak, wobble or be broken by the heat," said Chang, who joined PPPL in April, 2011, from the Korea Advanced Institute of Science and Technology and the Courant Institute of Mathematical Sciences at New York University.

The EPSI team consists of leading physicists, mathematicians and computer scientists from 11 U.S. research institutions, together with PPPL participants. Collaborating institutions include: DOE's Oak Ridge National Laboratory; Brown University; the University of Colorado at Boulder; the University of Texas at Austin; Rensselaer Polytechnic Institute; the Massachusetts Institute of Technology; the California Institute of Technology; the University of California at San Diego; Columbia University; Lehigh University; and Rutgers University.

PPPL participants include staff physicists Stephane Ethier, Seung-Hoe Ku, Jianying Lang and Daren Stotler, and postdoctoral fellows Devon Battaglia and Robert Hager.

The EPSI team will work on Titan, a Cray XK6 and one of the world's fastest scientific supercomputers, which is housed at the DOE's Oak Ridge National Laboratory. Titan is expected to have a peak performance of more than 20 petaflops—the technical term for a million billion calculations a second. The machine will have the combined power of well over two million home computers and the ability to perform in one day what a single desktop device would take more than 5,000 years to complete. The EPSI team also will work on Hopper, a Cray XE6 supercomputer at the DOE's E.O. Lawrence Berkeley National Laboratory.

The new computer code will build on software created by a previous Chang-directed center, the Center for Plasma Edge Simulation. The new code will seek to model the harsh pressure, temperature, density and flow conditions that mark the edge of intensely hot fusion plasmas, and cause them to grow unstable, leak from their magnetic confinement and damage tokamak walls.

The EPSI researchers will test their model against data gleaned from actual fusion experiments to see if the model's predictions are accurate. "If the code proves to be validated for all the relevant aspects of today's experiments, then we would have the confidence to project it for the future," Chang said.

The validated model could serve as a guide to developers of next-generation fusion facilities, which will need to confine hot plasmas at temperatures of over 100 million degrees and cope with extreme heat fluxes against their walls. Such facilities include ITER, the huge tokamak that the European Union, the United States and five other countries are building in Cadarache, France. Plans call for ITER to produce 500 million watts of fusion energy for up to 500 seconds by the late 2020s.

Efforts such as the EPSI project will thus serve as a pathway to fusion power.

Provided by Princeton Plasma Physics Laboratory