Lunch & Learn: Simulations at the petascale and beyond for fusion energy sciences with William Tang

Fusion donut

Imagine harnessing the power of the sun within a magnetic bottle. Unlike hydrogen bombs, which are essentially uncontrolled fusion reactions, scientists for decades have been pursuing the peaceful challenge of safely harnessing fusion energy, a potentially efficient and environmentally attractive energy source. Progress in addressing this scientific grand challenge, suggested William Tang, the Director of the Fusion Simulation Program at the Princeton Plasma Physics Laboratory (PPPL) has benefited substantially from advances in super-computing. At the March 10 Lunch ‘n Learn, Tang noted that such capabilities continue to progress at a remarkable rate, from tera-to-petascale today, and to exascale in the near future.

If we can create the conditions for fusion to occur, says Tang, bringing deuterium and tritium together at very high temperatures, the reaction produces alpha particles, fast neutrons, and an energy multiplication of 450:1. It would then be possible to use that energy to heat the burning plasma in a self-sustaining reaction.


The Federal Government recognizes the importance of the effort, as evident, for example, in the Department of Energy document, “Facilities for the Future: A Twenty-Year Outlook.” Current Presidential Science Advisor John Holdren has commented that it is important to shrink the time scale for achieving fusion energy deployment by increasing appropriate investments in fusion research and development.

Tang pointed out that major progress achieved over the years in magnetic fusion research has led to ITER – a multi-billion dollar burning plasma experiment currently under construction in Cadarache, France. Seven governments (EU, Japan, US, China, Korea, Russia, and India) that represent over half of the world’s population are collaborating on this international effort led by the EU. Up to the present, laboratory experiments have produced 10 megawatts of power for approximately 1 second. The goal for ITER is to produce 500 million Watts of heat from fusion reactions for more than 400 seconds. A successful ITER experiment would demonstrate the scientific and technical feasibility of magnetic fusion energy.

Tang emphasized that the burning plasma experiment is a truly dramatic step forward in that the fusion fuel will be sustained at high temperature by the fusion reactions themselves. Worldwide experimental data and computational projections indicate that ITER can likely achieve its design performance. Indeed, notes Tang, temperatures in existing experiments have already exceeded what is needed for ITER.

Tang expressed the hope that American investments in Fusion Energy development will be able to keep pace with those of foreign countries and that it will be possible to deal effectively with political and associated financial constraints to achieve the kind of sustained support that the highly challenging research efforts will require. This will be essential for attracting, training, and assimilating bright young people that are needed to move the program forward.


The ITER effort will clearly require strong research and development efforts to harvest the scientific knowledge, which Tang pointed out entails a proper integration of advanced computation with experimental data acquisition and analysis together with fundamental plasma theory. Progress will be significantly aided by the accelerated development of computational tools and techniques to support the acquisition of the scientific understanding needed to develop predictive models which can prove superior to empirical extrapolations of experimental results. This provides the key motivation for the Fusion Simulation Program (FSP) – a new U.S. Department of Energy initiative supported by its Offices of Fusion Energy Science and Advanced Scientific Computing Research — that is currently in the program definition/planning phase.

Tang expects that the FSP will make unique contributions to the fusion program by addressing the integration challenges for multi-scale physics problems that are currently being mostly treated in isolation. The FSP approach will involve carrying out a rigorous and systematic validation program — that would enhance confidence in the reliability of the associated predictive models developed to improve our capabilities for reliable scenario modeling for ITER and for future devices.

Tang added that even more powerful super-computers at the “exascale” range and beyond will help meet the formidable future challenges of designing a demonstration fusion reactor (DEMO) after ITER. With ITER and leadership class computing being two of the most prominent current missions of the U.S. Department of Energy, whole device integrated modeling, which can achieve the highest possible physics fidelity, is a most worthy exascale-relevant project for producing a world-leading realistic predictive capability for fusion. This should prove to be of major benefit to U.S. strategic considerations for Energy, Ecological Sustainability, and Global Security.

WilliamMTang.jpgWilliam Tang is the Director of the Fusion Simulation Program at the Princeton Plasma Physics Laboratory (PPPL), the U. S. Department of Energy (DoE) national laboratory for fusion research. He is a Fellow of the American Physical Society, and on October 15, 2005, he received the Chinese Institute of Engineers-USA (CIE-USA) Distinguished Achievement Award. The CIE-USA, which is the oldest and most widely recognized Chinese-American Professional Society in North America, honored him “for his outstanding leadership in fusion research and contributions to fundamentals of plasma science.” He has been a Principal Research Physicist at PPPL and Lecturer with Rank & Title of Professor in the Department of Astrophysical Sciences since 1979, served as Head of the PPPL Theory Department from 1992 through 2004, and was the Chief Scientist at PPPL from 1997 until 2009. He also played a prominent national leadership role in the formulation and development of the DoE’s multi-disciplinary program in advanced scientific computing applications, SciDAC (Scientific Discovery through Advanced Computing). For the next two years he will be the PI (Principal Investigator) leading a national multi-disciplinary, multi-institutional team of plasma scientists, computer scientists, and applied mathematicians from 6 national laboratories, 2 private industry companies, and 9 universities to carry out the program definition and planning of DoE’s Fusion Simulation Program (FSP).

In research activities, Dr. Tang is internationally recognized for his leading role in developing the requisite mathematical formalism as well as the associated computational applications dealing with electromagnetic kinetic plasma behavior in complex geometries. He has over 200 publications – with more than 125 peer-reviewed papers in Science, Phys. Rev. Letters, Phys. Fluids/Plasmas, Nuclear Fusion, etc. and an “h-index” or “impact factor” of 42 on the Web of Science, including over 5300 total citations. He has guided the development and application of the most widely recognized codes for realistically simulating complex transport dynamics driven by microturbulence in plasmas and is currently the Principal Investigator of a multi-institutional DoE INCITE Project on “High Resolution Global Simulations of Plasma Microturbulence.” The INCITE (Innovative and Novel Computational Impact on Theory and Experiment) Program promotes cutting-edge research that can only be conducted with state-of-the-art super-computers. Prof. Tang has also been a key contributor to teaching and research training in Princeton University’s Department of Astrophysical Sciences for over 30 years and has supervised numerous successful Ph.D. students, who have gone on to highly productive scientific careers. Examples include recipients of the prestigious Presidential Early Career Award for Scientists and Engineers (PECASE) in 2000 and 2005.

A podcast and the presentation are available.

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