G8 NuFuSE NSF Project Outcome Report 1128080

Submitted  By:     William Tang – Principal Investigator

Title:

G8 Initiative:  G8 Research Councils Initiative on Multilateral Research Funding

Objectives:

The overall goal of the G8 NuFuSE Project was to significantly improve computational modelling capabilities that enhance the predictive capabilities needed to help build the scientific foundations required to develop fusion power.  In order to address key physics challenges commensurate with “path to exascale” progress in supercomputers, we focused on delivering new high-physics-fidelity predictive simulation capability for magnetically-confined fusion energy (MFE) plasmas.

An associated goal was to help contribute to producing a new interdisciplinary international community of fusion scientists capable of utilizing modern HPC resources at the extreme scale to help accelerate progress in understanding fusion grade plasmas.

Significant Results: 

New results delivered by our NSF-supported G8 NuFuSE project deals with new physics findings in the core region of the plasma -- with the key result that more efficient confinement may be achievable in large burning plasmas such as ITER.  For over a decade, both experimental observations and theoretical simulations of turbulent losses of fusion-grade tokamak plasmas have indicated that energy confinement degrades as the size of the tokamak increases in the  so-called “Bohm regime.” However, these earlier simulations have also predicted that for sufficiently large tokamaks there will be a turnover point into a “Gyro-Bohm regime,” where the losses become independent of system size.  For burning plasma devices such as ITER, it is of key importance that systems can operate in this favorable Gyro-Bohm regime.  A modern gyro-kinetic code (GTC-P) capable of utilizing world-leading HPC platforms – such as the  “Mira” and “Sequoia” BG/Q supercomputers in the U.S. and the “K-computer” in Japan – has been developed by the Princeton-University-led team to achieve unprecedented phase-pace resolution enabled by successfully running on over 1.5 million processors. Associated physics studies in the plasma core region have been carried out with the discovery that the magnitude of turbulent losses in the Gyro-Bohm regime can be up to 50% lower than indicated by earlier much lower-resolution simulations and that the Bohm to Gyro-Bohm transition is much more gradual as the plasma size increases.  This finding was made possible only after going to high-resolution, long-time scale simulations needed to achieve the physics fidelity enabled by computing at extreme scales. 

Associated Award:

The International Data Corporation (IDC) announced during the SC'13 Conference that William Tang (Princeton U/PPPL), Bei Wang (Princeton U), and Stephane Ethier (PPPL) have received a "High Performance Computing (HPC) Innovation Excellence Award" for using high-end supercomputing resources to carry out advanced simulations for the first time of confinement physics in large-scale magnetic fusion energy (MFE) plasmas with unprecedented phase-space resolution and long temporal duration to deliver important new scientific insights.  This research was enabled by the new GTC-Princeton (GTC-P) code, developed to use multi-petascale capabilities on world-class systems such as the IBM BG-Q "Mira" at DOE-SC's Argonne Leadership Computing Facility and NNSA's "Sequoia" at the Lawrence Livermore N...

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