Sabbagh to lead $7.6 million international grant on sustained tokamak operation

Oct 03 2019 | By Dr. Steven A. Sabbagh

APAM senior research scientist and adjunct professor Dr. Steven A. Sabbagh will lead an expanded joint international grant from the U.S. Department of Energy (DOE) to study high performance tokamak plasma disruption prediction and avoidance in the long-pulse Korea Superconducting Tokamak Advanced Research (KSTAR) device located in Daejeon, South Korea. The expanded grant research will add further physics studies, real-time data acquisition, and plasma control to the device to understand how plasma disruptions can be largely eliminated in a tokamak. The granted funding expands past support by 130%. APAM associate research scientist Dr. Young-Seok Park will be lead researcher on the project for Columbia. This effort, which directly addresses a Tier 1 (highest priority) element of the U.S. magnetic fusion program as defined by the DOE, is a joint international effort comprised of three U.S. institutions (Columbia University, the Princeton Plasma Physics Laboratory (PPPL), and Nova Photonics, Inc.) 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. Mario Podesta and Dr. Fred Levinton as institutional PIs for PPPL and Nova Photonics, respectively. The present grant covering three years exceeds $7.6 million for all three institutions, with the Columbia research component increasing by 63% compared to past funding. Drs. Sabbagh and Park will conduct the research full time at PPPL in close coordination with Dr. Sabbagh’s present Columbia U. group researchers, including Dr. John (Jack) Berkery and Dr. James M. Bialek of APAM, two APAM post-doctoral researchers Dr. Yanzheng Jiang and Dr. Jae Heon Ahn, and two APAM graduate students Juan Riquezes and Jalal Butt. The project also aims to bring in a new APAM post-doctoral researcher.

The prediction and avoidance of tokamak disruptions, which stop plasma operation in the device, comprise a present “grand challenge” problem facing magnetic fusion for 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 a joint research effort, 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 tokamak”) plasmas in NSTX at PPPL and the Mega-Ampere Spherical Tokamak (MAST) at the Culham Centre for Fusion Energy (CCFE). 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 four 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 a full supporting physics research effort using the present set of excellent diagnostic data on KSTAR to produce advanced plasma equilibrium, stability, and transport analyses required to support DECAF analysis. These supporting capabilities were constructed during our prior research effort on KSTAR funded by the DOE.

2) Reduction and/or direct implementation of these physics models to allow their use in real-time for disruption prediction during the long-pulse operation of the KSTAR device (~ 100 seconds).

3) Implementation and analysis of real-time diagnostic capabilities on KSTAR for disruption prediction and avoidance. This effort will bring significant new capabilities allowing real-time measurements of key plasma parameters such rotation profile, magnetic field pitch angle and internal magnetic perturbation profiles, electron temperature and electron temperature fluctuation profiles, evolution and decomposition of rotating magnetohydrodynamic modes, and energetic particle-driven mode onset and evolution. These measurements will allow the physics models to assess how close the plasma state is from being disrupted.

4) Creation and implementation of control algorithms that will steer the plasma away from possible disruption to preferred, sustained operational states.

This multi-institutional effort by Columbia U. APAM, PPPL, and Nova Photonics researchers will create a world-leading capability on the KSTAR device, uniquely produced by a united group effort. It further extends the reach of our international team of Columbia APAM researchers and students on devices 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)


The Columbia University APAM research team on tokamak plasma disruption prediction and avoidance: From the left in each row, bottom to top: Dr. James Bialek, Dr. Yanzheng Jiang, Prof. Steven A. Sabbagh, Mr. Jalal Butt, Dr. Young-Seok Park, Dr. Jack Berker