Sho Watanabe

Stable confinement of toroidal electron plasma in an internal conductor device Prototype-Ring Trap

A pure electron plasma has been produced in an internal conductor device Prototype-Ring Trap (Proto-RT). The temporal evolution of the electron plasma was investigated by the measurement of electrostatic fluctuations. Stable confinement was realized when the potential profile adjusted to match the magnetic surfaces. The confinement time varies as a function of the magnetic field strength and the neutral gas pressure, and is comparable to the diffusion time of electrons determined by the classical collisions with neutral gas. Although the addition of a toroidal magnetic field stabilized the electrostatic fluctuation of the plasma, the effects of the magnetic shear shortened the stable confinement time, possibly because of the obstacles of coil support structures.

RT-1 Project: Magnetosphere-Like Plasma Experiment

The Ring Trap-1 (RT-1) is a novel plasma device designed to explore various effects of plasma flow in the most universal and fundamental magnetosphere-like configuration. A super-conducting ring magnet, levitated in the vacuum chamber, produces a dipole magnetic field that traps high-temperature plasma. Plasma is produced by electron cyclotron heating using an 8.2GHz microwave. The mechanism of plasma confinement is based on the theory of high-beta equilibrium that is self-organized in a flowing plasma. Realization of such a configuration in a laboratory system, which is known to exist in some astronomical systems, may open a way to the advanced-fuel fusion. Analyses of the equilibrium and stability pose interesting theoretical and experimental challenges.

Confinement of Toroidal Non-neutral Plasma in Proto-RT

In contrast to linear configurations for non‐neutral plasmas, toroidal devices allow us to trap charged particles without the use of a plugging electric field. Thus it has a potential ability to confine high‐energy particles or to simultaneously trap multiple particles with different charges. In spite of the relatively long history of the study in pure toroidal magnetic field devices, toroidal non‐neutral plasmas are attracting renewed interest with the use of magnetic surface configurations. Possible applications of toroidal traps for non‐neutral plasmas are formation of matter‐antimatter plasmas, investigation on the fundamental properties of exotic plasmas including pair (equal mass) plasmas, and experimental test on the equilibrium and stability of flowing plasmas. As an initial test on non‐neutral plasmas in the toroidal magnetic‐surface geometry, formation and confinement properties of pure electron plasma have been investigated at Prototype‐Ring Trap (Proto‐RT) device with a dipole magnetic field. ...