Compact toroid injection fueling in a large field-reversed configuration

Abstract

A repetitively driven compact toroid (CT) injector has been developed for the large fieldreversed configuration (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 × 10 21 m −3 , ~30 eV and 0.5-1.0 × 10 19 , respectively. In this project, singleand 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 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.

Performance Improvement of a Magnetized Coaxial Plasma Gun by Adopting Iron-Core Bias Coil and Pre-Ionization Systems

“…It also reached approximately 140 km/s in dCoil = 0 case. From edge probe measurements, the electron density is lower than the typical value (∼ 5 × 10 15 cm −3 ) of the CT injector developed for the C-2U FRC [3]. Figure 6 shows the typical ion temperature T i at 0.276 and 0.172 MPa gas pressure operations with the PI system.…”

“…MCPG-type CT injectors had been developed as a particle refueling system for C-2/C-2U field-reversed configuration (FRC) experiments [1][2][3]. The CT injection demonstrated successful refueling with a significant build-up of author's e-mail: asai.tomohiko@nihon-u.ac.jp * ) This article is based on the presentation at the 26th International Toki Conference (ITC26).…”

“…The CT injection demonstrated successful refueling with a significant build-up of author's e-mail: asai.tomohiko@nihon-u.ac.jp * ) This article is based on the presentation at the 26th International Toki Conference (ITC26). 20 -30 % of the total particle number per single CT injection without any disruptive effects on the target plasma [3].…”

Behavior of a Tracer-Containing Compact Toroid in a Transverse Magnetic Field

“…The CT injection experiments demonstrated a success- ful refueling with the density build-up of 20% -30% for the FRC particle inventory without any serious effects. The CT parameters of electron density, electron temperature, and ejection velocity are ∼5 × 10 21 m −3 , ∼30 eV, and ∼100 km/s, respectively [5]. Using the CT injector, the TCCT could be accelerated to enough velocity to penetrate the confinement field.…”

“…To realize tracer injection into MCPs, an ejected TCCT must penetrate a confinement magnetic field without the separation of tracer ions from a CT. In this experiment, we generated and accelerated a TCCT using a CT injector that had successfully demonstrated particle fueling on a large field-reversed configuration (FRC) device C-2/C-2U [5]. This CT injector can eject a deuterium CT with enough velocity to penetrate a confinement field of an FRC.…”