Sabbagh to Lead $3 Million International Grant on Sustained Tokamak Operation

Columbia Engineering

APAM senior research scientist and adjunct professor Dr. Steven A. Sabbagh will lead a new joint international grant from the US Department of Energy (DOE) to study high performance tokamak plasma disruption prediction and avoidance in the long-pulse Korea Superconducting Tokamak Advanced Research (KSTAR) located in Daejeon, South Korea. APAM associate research scientist Dr. Young-Seok Park will be lead researcher on the project for Columbia. This effort, which directly addresses one of two Tier 1 (highest priority) elements of the US magnetic fusion program as defined by the DOE, is a joint international effort comprised of three US institutions (Columbia University, the Princeton Plasma Physics Laboratory (PPPL), and the Massachusetts Institute of Technology (MIT)) and the National Fusion Research Institute in Daejeon, South Korea. Dr. Sabbagh is lead principal investigator (PI) for the overall project and institutional PI for Columbia, with Dr. Steven D. Scott and Dr. Earl S. Marmar as institutional PIs for PPPL and MIT, respectively. The present grant covering three years totals $3.3 million for all three institutions, 53% of which will fund Columbia researchers. Drs. Sabbagh and Park will conduct the research full time at PPPL in close coordination with Dr. Sabbagh’s present Columbia U. group research on this topic on the US DOE National Spherical Torus Experiment – Upgrade (NSTX-U), including Dr. John (Jack) Berkery and Dr. James M. Bialek of APAM, and two newly-appointed APAM post-doctoral researchers. The project also aims to bring in an APAM student.

The prediction and avoidance of tokamak disruptions, which stop plasma operation in the device, comprise a present “grand challenge” problem facing magnetic fusion in this leading magnetic confinement system. The research is of critical importance to the field, and while challenging, the goals of this exciting research are tractable and rewarding.

The present expanded research effort is enabled by the prudent guidance and strong support of the DOE to create joint research efforts, including national and international partners, to tackle such high priority research issues. The present work builds on the successful, award-winning Columbia APAM group effort at PPPL to allow analysis of data from multiple tokamak devices, leveraging the advanced, unique capabilities of the high performance, long pulse superconducting KSTAR device (at high aspect ratio) and low aspect ratio (“spherical”) plasmas in NSTX-U. These devices represent the greatest range of aspect ratio of high performance tokamaks in the world today, allowing plasma theory to be validated over a wide range of this important device parameter. The devices also have world-class diagnostics and multi-megawatt auxiliary heating systems. The present research is the natural progression of past research by Columbia APAM scientists, evolving the research by directly applying the plasma stability, transport, and control physics knowledge gained in the past decade to disruption event characterization and forecasting (DECAF).

The new grant is organized into three elements:

1) Analysis of the chains of events leading to disruptions in a long pulse, high performance superconducting tokamak, and forecasting the onset of such events. This effort includes the important effort of collecting the present set of excellent diagnostic data on KSTAR into more advanced plasma equilibrium, stability, and transport analyses required to support DECAF analysis.

2) Improvements and additions to certain key diagnostics required for equilibrium, stability, and transport analysis, especially the addition of a background light polychrometer for the KSTAR Motional Stark Effect (MSE) diagnostic, built by our PPPL and MIT partners. An existing 10 channel system will be shipped to KSTAR to improve the present MSE system on the device, especially as the pulse length goes beyond 50 seconds, and the auxiliary heating power is doubled to 12 MW within 3 years. Research under the present grant by PPPL and MIT will also build 15 additional polychrometer channels to fully support the present MSE system on KSTAR.

3) Instability control for disruption avoidance will be implemented and supported in KSTAR in a manner similar to the successful research conducted by the Columbia group at PPPL over the past decade. Control efforts will feature multi-sensor control, and advanced algorithms including a physics model-based state-space controller to maintain global MHD stability.

This effort will produce exciting, new, and greatly needed data in conjunction with our strong international partners at NFRI, utilizing and building or collaborative research and extending the reach of Columbia APAM researchers around the globe.

Photo (above): APAM senior research scientist and adjunct professor Dr. Steven A. Sabbagh (left) and APAM associate research scientist Dr. Young-Seok Park (right)