Confinement of Pure-Electron Plasmas in a Toroidal Magnetic-Surface Configuration

Abstract

A pure-electron plasma has been confined in a toroidal magnetic-surface configuration for as long as classical diffusion time due to neutral collisions. By controlling the potential of the internal conductor, long-term stable confinement of electrons has been achieved in a toroidal geometry.

Measurement of the Density Profile of a Toroidal Non-neutral Plasma with a Wall-Probe Array

“…In RT-1, the levitated superconducting coil was covered by a stainlesssteel case that was charged up to certain voltages V c by the formation of an electron plasma, though direct measurements of V c were not carried out. In previous experiments in Proto-RT [8] with a mechanically supported dipole field coil, we found V c to be typically 20 % lower than −V acc according to the measurements by a 100 MΩ high impedance voltage probe. Because the dipole field coil in RT-1 was levitated and electrically insulated from the chamber, it is quite probable that the coil was charged up in the same manner as in Proto-RT.…”

“…Azimuthal symmetry of the system is essential to conserve the canonical author's e-mail: saito@ppl.k.u-tokyo.ac.jp angular momentum of particles and to realize good confinement [6]. Langmuir probes are useful tools for measuring local plasma parameters [7][8][9]11] during electron injection, but they cause serious disturbance and cannot be used in the stable confinement phase of plasmas, especially those consisting of small numbers of particles such as antimatters. Perturbation-free diagnostics of density profile information is, therefore, strongly required for experiments on toroidal non-neutral plasmas.…”

“…A pure electron plasma can be confined in RT-1; the density is of the order of 10 11 m −3 , and the confinement time is longer than 400 s [3]. A toroidal system [4][5][6][7][8][9][10][11][12][13][14] has merits in trapping various kinds of charged particles including antimatters [15][16][17][18]. In our previous experiment on the Proto-RT device [6][7][8], we measured the internal electric potential by inserting probes and showed that an appropriate control of the potential of the internal ring produces closed equi-potential surfaces aligned with the magnetic surfaces, achieving good confinement.…”

Formation of high-β plasma and stable confinement of toroidal electron plasma in Ring Trap 1

“…Inward pinch of particles is one of the key issues for particle injection process of toroidal non-neutral plasmas as well as for the formation of high temperature fusion plasma. In contrast to the widely used linear configurations for non-neutral plasma trap, 14 toroidal geometries [15][16][17][18][19][20][21][22] can trap charged particles independently of its electric signs. 17 It can then in principle confine plasmas of arbitrary neutrality including multispecies antimatter particles.…”

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

“…[1][2][3][4][5][6] The early experiments aimed at the storage or acceleration of heavy ions 2 or creation of high-current relativistic electron beams 3 in a pure toroidal magnetic field configuration. In recent years, it has been recognized that the toroidal geometries might be suitable for various kinds of non-neutral plasmas, 7,8 such as the mixtures of antimatters 9 or streaming non-neutralized plasmas for the investigation of new relaxation states of plasmas with strong flow. 7 At present, experiments of toroidal nonneutral plasmas on internal conductor devices, 7 a "partial" torus trap, 10,11 a stellarator, 9 and a helical system 12 are in progress or under construction.…”