Development of a magnetized coaxial plasma gun for compact toroid injection into the C-2 field-reversed configuration device

• Published in: Review of scientific instruments 2016-05, Vol.87 (5), p.053512-053512
• Main Authors: Matsumoto, T., Sekiguchi, J., Asai, T., Gota, H., Garate, E., Allfrey, I., Valentine, T., Morehouse, M., Roche, T., Kinley, J., Aefsky, S., Cordero, M., Waggoner, W., Binderbauer, M., Tajima, T.
• Format: Article
• Language: English
• Subjects: ACCELERATION; Coated electrodes; COMPACTS; Configurations; CYLINDRICAL CONFIGURATION; Ejection; ELECTRODES; ELECTRON DENSITY; Electron energy; ELECTRON TEMPERATURE; ELECTRONS; FIELD-REVERSED THETA PINCH DEVICES; GAS INJECTION; INJECTION; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; LENGTH; MAGNETIC FIELDS; Magnetism; PARTICLES; Plasma; PLASMA GUNS; PLASMA RINGS; Poloidal flux; Scientific apparatus & instruments; TUNGSTEN
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.4952581

A compact toroid (CT) injector was developed for the C-2 device, primarily for refueling of field-reversed configurations. The CTs are formed by a magnetized coaxial plasma gun (MCPG), which consists of coaxial cylindrical electrodes and a bias coil for creating a magnetic field. First, a plasma ring is generated by a discharge between the electrodes and is accelerated by Lorenz self-force. Then, the plasma ring is captured by an interlinkage flux (poloidal flux). Finally, the fully formed CT is ejected from the MCPG. The MCPG described herein has two gas injection ports that are arranged tangentially on the outer electrode. A tungsten-coated inner electrode has a head which can be replaced with a longer one to extend the length of the acceleration region for the CT. The developed MCPG has achieved supersonic CT velocities of ∼100 km/s. Plasma parameters for electron density, electron temperature, and the number of particles are ∼5 × 1021 m−3, ∼40 eV, and 0.5–1.0 × 1019, respectively.