Equilibrium properties of hybrid field reversed configurations

International Atomic Energy Agency Nuclear Fusion Nucl. Fusion 57 (2017) 076018 (7pp) https://doi.org/10.1088/1741-4326/aa6dcd
Compact toroid injection fueling in a large eld-reversed con guration
T. Asai1, T. Matsumoto1, T. Roche2, I. Allfrey2, H. Gota2, J. Sekiguchi1, T. Edo1, E. Garate2, Ts. Takahashi1, M. Binderbauer2 and T. Tajima2,3
1 College of Science and Technology, Nihon University, Tokyo 101-8308, Japan
2 Tri Alpha Energy, Inc., Rancho Santa Margarita, CA 92688, United States of America
3 Department of Physics and Astronomy, University of California, Irvine, CA 92697,
United States of America
E-mail: asai.tomohoiko@nihon-u.ac.jp
Received 15 December 2016, revised 7 March 2017 Accepted for publication 19 April 2017
Published 18 May 2017
Abstract
A repetitively driven compact toroid (CT) injector has been developed for the large eld- reversed con guration (FRC) facility of the C-2/C-2U, primarily for particle refueling. A CT is formed and injected by a magnetized coaxial plasma gun (MCPG) exclusively developed for the C-2/C-2U FRC. To refuel the particles of long-lived FRCs, multiple CT injections are required. Thus, a multi-stage discharge circuit was developed for a multi-pulsed CT injection. The drive frequency of this system can be adjusted up to 1 kHz and the number of CT shots per injector is two; the system can be further upgraded for a larger number of injection pulses. The developed MCPG can achieve a supersonic ejection velocity in the range of ~100 km s−1. The key plasma parameters of electron density, electron temperature and the number of particles are ~5 × 1021 m−3, ~30 eV and 0.5–1.0 × 1019, respectively. In this project, single- and double-pulsed counter CT injection fueling were conducted on the C-2/C-2U facility by two CT injectors. The CT injectors were mounted 1 m apart in the vicinity of the mid-plane. To avoid disruptive perturbation on the FRC, the CT injectors were operated at the lower limit of the particle inventory. The experiments demonstrated successful refueling with a signi cant density build-up of 20–30% of the FRC particle inventory per single CT injection without any deleterious effects on the C-2/C-2U FRC.
Keywords: eld-reversed con guration, compact toroid injection, refueling, magnetized coaxial plasma gun
(Some gures may appear in colour only in the online journal)
1. Introduction
A repetitively driven compact toroid (CT) injector [1] has been developed for the large eld-reversed con guration (FRC) facility of the C-2/C-2U [2], primarily for particle refueling. Pursuit of the FRC as a fusion reactor is motivated by its highly favorable technological features: extremely high β (>50%), natural divertor capabilities and axial mobility allowing sepa- ration of the start-up and con nement functions [3]. Recently, high con nement performance of the FRC was achieved at the C-2/C-2U facility by neutral beam injection (NBI)
Figure 1. A schematic view of the developed CT injector.
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