Achievement of Field-Reversed Configuration Plasma Sustainment via 10 MW Neutral-Beam Injection on the C-2U Device

1 EX/P3-41 Achievement of Field-Reversed Configuration Plasma Sustainment
via 10 MW Neutral-Beam Injection on the C-2U Device
H. Gota,1 M.W. Binderbauer,1 T. Tajima,1,2 S. Putvinski,1 M. Tuszewski,1 D. Barnes,1
S. Dettrick,1 E. Garate,1 S. Korepanov,1 A. Smirnov,1 M.C. Thompson,1 E. Trask,1 X. Yang,1 L. Schmitz,3 Z. Lin,2 A.A. Ivanov,4 T. Asai,5 and the TAE Team
1Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, CA 92688, USA 2Department of Physics and Astronomy, UCI, Irvine, CA 92697, USA 3Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095, USA 4Budker Institute of Nuclear Physics, Novosibirsk, 630090, Russia
5College of Science and Technology, Nihon University, Tokyo 101-8308, Japan
E-mail contact of main author: hgota@trialphaenergy.com
Abstract. Tri Alpha Energy’s experimental program has demonstrated reliable field-reversed configuration (FRC) formation and sustainment, driven by fast ions via high-power neutral-beam (NB) injection. The world’s largest compact-toroid device C-2U was upgraded from C-2 with the following key system upgrades: increased total NB input power from ~4 MW (20 keV hydrogen) to 10+ MW (15 keV hydrogen) with tilted injection angle; enhanced edge-biasing capability inside of each end divertor for boundary/stability control. C- 2U experiments with those upgraded systems have successfully demonstrated dramatic improvements in FRC performance and sustained advanced beam-driven FRCs with a macroscopically stable and hot plasma state for up to 5+ ms, in which the plasma diamagnetism in the best discharges has reached record lifetimes of over 11 ms, timescales twice as long as C-2. Our zero-dimensional power balance analysis shows substantial improvements in equilibrium and transport parameters, in which electron energy confinement time strongly correlates with electron temperature. The demonstrated sustainment of beam-driven FRCs in C-2U is an extraordinary achievement for the FRC and innovative confinement concepts communities, and may lead to intriguing possibilities for fusion reactors.
1. Introduction
A field-reversed configuration (FRC) is a high-beta compact toroid (CT) which has closed- field-line and open-field-line regions of poloidal axisymmetric magnetic field with no or small self-generated toroidal magnetic field [1,2]. The FRC topology is generated by the plasma's own diamagnetic currents, which are of sufficient strength to reverse the exterior magnetic field, and only requires solenoidal coils located outside of a simply connected vacuum vessel. The averaged beta value of FRCs is nearly unity: <β> = 2μ0<p>/Be2 ~90%, where μ0 is permeability of free space, <p> is the average plasma pressure, and Be is the external magnetic field. The edge layer outside of the FRC separatrix coalesces into axial jets beyond each end of the FRC, providing a natural divertor, which may allow extraction of energy without restriction. Another attractive feature of the FRC is its potential for a fusion reactor with low-cost construction due to the simple geometry, and FRCs may also allow the use of advanced, aneutronic fuels such as D-3He and p-11B.