EX_P3-37_a2

1
EX/P3-37
Compact Toroid Injection Fueling
on a Large-sized Field-Reversed Configuration
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., CA 92688, USA
3 Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
E-mail contact of main author: asai.tomohoiko@nihon-u.ac.jp
Abstract. A repetitively driven compact toroid (CT) injector has been developed for large-sized field-reversed configuration (FRC) facility of the C-2/C-2U primarily for 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 injection is required. Thus, a multi-stage discharge circuit has been developed for multi-pulsed CT injection. Drive frequency of this system can be adjusted up to 1 kHz and the number of CT shots per injector is 2; the system can be further upgraded for larger number of injection pulses. The developed MCPG has achieved supersonic ejection velocity in the range of ~100 km/s. 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 CT injection fueling have been conducted on the C-2/C-2U facility by two CT injectors. The CT injectors are mounted 1 m apart on the vicinity of midplane. To avoid disruptive perturbation on the FRC, the CT injectors have been operated at the lower limit of particle inventory. The experiments demonstrated successful fueling with significant 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.
1. Introduction
A repetitively driven compact toroid (CT) injector [1] has been developed for large-sized field-reversed configuration (FRC) facility of the C-2/C-2U [2] primarily for refueling. Pursuit of the FRC as fusion reactor is motivated by highly favorable technological features: extremely high b (>50%), a natural divertor, and axial mobility allowing separation of start- up and confinement functions [3]. Recently, high confinement performance of FRC has been achieved on the C-2/C-2U facility by neutral beam injection (NBI) [4]. However, development of effective fueling method remains as a significant task of FRC fusion reactor core. In this work, repetitively driven CT injector with the rate up to 1kHz by multi-stage discharge circuit has been developed [5]. In this paper, we report the proof of concept experiments of CT injection has been performed on the C-2/C-2U. CT injection with the frequency at 0.5kHz has successfully demonstrated with a fueling rate of 20 - 30% in total particle number per single CT injection [6, 7].
2. Experimental Setup
A magnetized coaxial plasma gun (MCPG) has been developed exclusively for C-2/C-2U device primarily for fueling. The developed MCPG has been optimized on a test chamber which has a transverse field coil to simulate external magnetic field of C-2U device. The