World’s Largest Fusion Energy Tokamak Device Endorses Sabbagh Research Group Solution Enabling Sustained Fusion Production
The tokamak magnetic confinement concept was chosen for the International Tokamak Experimental Reactor (ITER) device (https://www.iter.org), the world’s largest fusion energy device of its kind, now being constructed in the south of France. A key goal of the device is to generate 500 MW of fusion power in its plasma for long pulses, representing an anticipated ten-fold return on the input heating power, paving the way toward bringing virtually limitless, carbon-free, and environmentally-benign power to humanity in a next-step fusion energy pilot plant.
A long-standing grand challenge problem in tokamak fusion energy research and development is the prediction and avoidance of plasma disruptions which stop plasma operation in the device, and create transient electromagnetic and thermal forces that may damage the device. An applied research approach named disruption event characterization and forecasting (DECAF), pioneered by APAM senior research scientist and adjunct professor Steven A. Sabbagh, is a leading solution to this critical applied plasma physics issue producing high accuracy disruption prediction in both large database analysis and real-time application [S.A. Sabbagh, et al., Physics of Plasmas 30 (2023) 032506]. The unique DECAF approach has U.S. and international patents pending.
Recently, plasma control management of the $22 billion dollar ITER Project, led by Dr. Peter de Vries, has endorsed the implementation and use of DECAF for real-time disruption prediction and avoidance in ITER, along with associated physics analysis. Dr. Sabbagh leads U.S. Department of Energy (DOE) multi-institutional grants supporting DECAF research through an international effort comprised of four U.S. institutions (Columbia University, the Princeton Plasma Physics Laboratory (PPPL), Nova Photonics, SapientAI) and international collaborations with the Korea Institute of Fusion Energy (KFE) and the UK Atomic Energy Authority.
Prof. Sabbagh’s present Columbia research group includes APAM associate research scientist Dr. Veronika Zamkovska, post-doctoral researchers Dr. Guillermo Bustos-Ramirez, Dr. Joseph Jepson, Dr. Hankyu Lee, and students Mr. Juan Riquezes, Mr. Matt Tobin, Mr. Frederick Sheehan, and Mr. Grant Tillinghast. More than half of the group visited ITER Headquarters during the summer to attend and make presentations at the 3rd IAEA Technical Meeting on Plasma Disruptions and their Mitigation, visit the ITER experimental site, and meet with the ITER control group (Figure 1).
Figure 1: (left) Dr. Veronika Zamkovska, Mr. Matt Tobin, Prof. Steven A. Sabbagh, Dr. Guillermo Bustos-Ramirez, and Dr. Hankyu Lee in the ITER Council Chamber, and (right) in the ITER Assembly Hall adjacent to the ITER Tokamak Building.
Prof. Sabbagh and the visiting Columbia research team met extensively with the leadership and members of the three main branches of the ITER Plasma Control Team to discuss details of DECAF and how to best implement it on ITER and use it for analysis (Figure 2). These meetings, spanning several days, were the first in-person meetings between DECAF Group members and the ITER Plasma Control Team on DECAF research and implementation on ITER. Initial remote discussions have been conducted remotely over many preceding months.
Figure 2: Head of the ITER Control Team Physics Group, Dr. Peter de Vries, guiding Columbia DECAF Research Group Team Members and some ITER Plasma Control Team Members
DECAF research presents a new paradigm in the pursuit of a high accuracy solution to tokamak plasma disruption prediction and avoidance, which is required to meet the lofty goal of greater than 98% accuracy in the predictive performance of the underlying physics models over the entire databases of large auxiliary-heated tokamaks located around the world (e.g. the Korea Superconducting Tokamak Advanced Research (KSTAR) at KFE in South Korea, the Mega-Ampere Spherical Tokamak (MAST) and it’s upgrade MAST-U in the UK, the National Spherical Torus Experiment at PPPL, and the DIII-D National Fusion Facility at General Atomics in San Diego). Access to 9 such databases presently exists, with others continuing to be added, representing a petabyte-scale data store – a modern-day “big data” problem. Addressing such a problem requires full automation of all steps, so that physics models can be repeatedly validated against entire device databases. Validation of physics models at that scale is transformative in the field of magnetic confinement fusion, and required to reach the high accuracy goals disruption prediction and avoidance, with the required physical understanding of the analysis to provide confident extrapolation to future devices. DECAF research also expanded to real-time implementation on the KSTAR device with dedicated experiments producing 100% accuracy of magnetohydrodynamic (MHD)-induced plasma disruptions, published at the IAEA Fusion Energy Conference in 2023. At present, DECAF physics models are broadening in depth and scope at a rapid rate, with the analysis itself now having sufficient “intelligence” to point out problems in present models, or the need for new physical models (part of the “DECAF workflow”). Such topics include tokamak plasma density limits produced by loss of energy balance, microturbulence, and other reasons, fast magnetic field reconnection dynamics and related physics, resistive MHD mode stability and triggering, and MHD mode coupling and locking. A manifestation of this rapid physics model expansion is the record number of presentations (14) shown by the DECAF group at the 2024 American Physical Society Division of Plasma Physics Meeting in Atlanta, GA. DECAF research will continue to introduce new topical physics areas as needed in the pursuit of producing a solution for the tokamak plasma disruption prediction and avoidance challenge.
Steven A. Sabbagh
November 2024