Tokamak Energy Ltd Path to Fusion: ST40 Results, Li Technology Development, Next Steps
Abstract: The combination of the high b, which has been achieved in STs, and high TF that can be produced by HTS TF magnets, opens a path to lower-volume fusion reactors. High field spherical tokamak ST40 (design parameters: R=0.4-0.6m, R/a=1.6-1.8, Ipl=2MA, Bt=3T, k=2.5, tpulse~1-2sec, 2MW NBI, 2MW ECRH/EBW, DD and DT operations) is the first prototype on this path and is now operating. Overview of ST40 and main recent results will be given. Proposals for the next step TE.Ltd devices and technology development, e.g. Li technologies, will be presented.
Recent studies (Segal et al, NF 2021) have shown potential advantages of a pulsed fusion reactor over a conventional steady-state reactor and pulsed ST reactors have even more advantages due to possibility of high bootstrap current, stronger increase in the confinement with the toroidal field, good stability, and lower requirements on the volt-second capability of the central solenoid for the plasma current sustainment. However, discharges in both pulsed and steady-state reactors may be limited and, even in relatively short pulses, unexplained fast disruptions have been observed which can be attributed to dust generation, flaking of depositions on the vessel wall, formation of hot spots and other plasma-wall interaction phenomena.
The minimum pulse duration to get to a sustained burn should not be less than 10 min, but commercially attractive pulsed reactor should have a pulse duration of 1.5 – 2 h. Although tens of minutes or even 2 h discharges are far from typically assumed steady-state pulse durations, the limitations mentioned above may be serious show-stoppers and research in the plasma-wall interaction area is urgently needed to be advanced.
Bio: Mark Koepke is Vice President-R&D at Tokamak Energy Inc and Professor of Physics at West Virginia Univ. He received his PhD in experimental plasma physics in 1984 from the Univ. Maryland and spent time at NASA-Goddard, Lawrence Livermore National Laboratory, and the University of Washington before launching the plasma physics program at West Virginia Univ. in 1987. He served simultaneously as Acting Director of the Research Division, Team Lead for Discovery Science and Joint Programs, and Senior Scientific Coordinator for Basic Plasma Science in the Office of Fusion Energy Sciences, U.S. DOE (2009-2011). Dr. Koepke held visiting appointments in Kiel, Greifswald, Innsbruck, Stockholm, Oxford, and Sandia National Labs. He is Visiting Professor/Academic Visitor at Univ. Strathclyde, Imperial College, and SLAC and is Mercator Fellow at Ruhr Univ. – Bochum. He is a Fellow of the APS, JSPS (Japan), and Institute of Physics (UK), Former Chair of DIII-D Program Advisory Committee, Former Chair of U.S. Burning Plasma Organization Council, Past Chair of Omega Laser User Group, Former Secretary of APS-Gaseous Electronics Conference (presently a member of GEC ExCom), Former APS-DPP Chair, Past Chair of DOE-SC-FESAC, Affiliated Member of DOE-NNSA Center for Astrophysical Plasma Properties (2017-19) and Affiliated Member of DOE-SC Center for Predictive Control of Plasma Kinetics (since 2009). From 2005-2011, he represented the U.S. on Commission 16: Plasma Physics of the International Union of Pure and Applied Physics (IUPAP) and is U.S. Deputy Editor of the journal Plasma Physics and Controlled Fusion. His main research interests include frontier science experiments on DIII-D (General Atomics), TJ-II (CIEMAT), and LAPD (UCLA), Theta/Z Pinch Pulsed-Power Science, basic plasma physics (wave-particle interactions, instabilities, turbulence-induced energy transport, dynamical complexity), space-related Q-machine experiments, Dust/Granule/Nanoparticle Tribology and dusty plasmas (ExoMars lander’s Dust Suite), driven-oscillator spatiotemporal phenomena, low-temperature plasma science, and plasma diagnostic techniques. Sixteen PhD theses have been completed under his supervision across this topical range.
