This NSF award to Princeton University funds U.S. researchers participating in a project competitively selected by the G8 Research Councils Initiative on Multilateral Research through the Interdisciplinary Program on Application Software towards Exascale Computing for Global Scale Issues. This is a pilot collaboration among the U.S. National Science Foundation, the Canadian National Sciences and Engineering Research Council (NSERC), the French Agence Nationale de la Recherche (ANR), the German Deutsche Forschungsgemeinschaft (DFG), the Japan Society for the Promotion of Science (JSPS), the Russian Foundation for Basic Research (RFBR),and the United Kingdom Research Councils (RC-UK), supporting collaborative research projects selected on a competitive basis that are comprised of researchers from at least three of the partner countries.
The fusion of light nuclides forms the basis of energy release in the universe, which can potentially be harnessed and used as a clean and sustainable supply of energy on Earth. In order to build the scientific foundations needed to develop fusion energy, a key need is the timely development of an integrated high-physics-fidelity predictive simulation capability for magnetically confined fusion plasmas. An associated central physics challenge is understanding, predicting, and controlling instabilities caused by the unavoidable spatial variations (gradients) in a magnetically-confined thermonuclear plasma. One consequence is the occurrence of turbulent fluctuations (microturbulence) which can significantly increase the transport rate of heat, particles, and momentum across the confining magnetic field in a tokamak device such as ITER -- a multi-billion dollar international experimental device being built in Cadarache, France and involving the partnership of 7 governments representing over half of the world?s population. Microturbulence can severely limit the energy confinement time for a given machine size and therefore it?s performance and economic viability. Understanding and possibly controlling the balance between these energy losses and the self-heating rates of the actual fusion reaction is key to achieving the efficiency needed to help ensure the practicality of future fusion power plants.
Accurate calculations of turbulent transport are vitally important and can only be achieved through advanced simulations. The current U.S. project uses ab initio particle-in-cell (PIC) global (3D) codes to solve the nonlinear equations underlying gyrokinetic theory with excellent scaling to more than 100,000 processor cores having already been demonstrated. It is planned that these codes will be deployed at the two supercomputing centres involved in this G8 project (Argonne National Laboratory in the U.S. and Juelich Supercomputing Centre in Germany), where state-of-the-art HPC systems are operative. In order to move in a timely manner to producing simulations with the highest possible physics fidelity, it is expected that computing at the exascale will be necessary to achieve the ultimate goal of computational fusion research ? an integrated predictive simulation capability that is properly validated against experiments in regimes relevant for practical fusion energy production.