Equilibrium of non-neutral plasma in toroidal geometry with applied electric field

Abstract

The equilibrium and stability of non-neutral plasma in toroidal geometry with applied electric field is studied. The calculations are done in a large aspect ratio, thin ring approximation, using a circuit model. Toroidal corrections to the I= 1 (I is the poloidal mode number) mode are obtained. These corrections reduce the I= 1 cylindrical diocotron frequency. It is shown that under certain conditions, the external electric field can stabilize dissipative I= 1 diocotron oscillations.

Electron plasma confinement in a partially toroidal trap

“…It seems more likely however, that the presence of the applied horizontal electric field introduces a new mode of oscillation not present in the cylindrically symmetric trap. Bhattacharyya and Avinash [5] predict a mode with characteristic frequency in the range of ER/RB 0 , where ER is the magnitude of the vacuum horizontal electric field. The experimentally measured frequency is proportional to 11B (Fig.…”

“…Under certain restrictions, the equilibria are also expected to be stable [5,6,7]. Experiments confirm the existence of equilibria [8,9,10,11], but to date, no experiment has tested the theory closely.…”

“…Successful trapping requires application of a horizontal electric field as predicted by Bhattacharyya and Avinash [5], although the magnitude of the applied field is significantly larger than theory predicts for a high aspect ratio electron plasma. Drift orbit calculations suggest that typical electron energies are in the range of 100-200 eV.…”

“…An electric field in the +P direction exerts an inward force on the plasma opposing the outward hoop and tire tube forces. Bhattacharyya and Avinash [5] investigated not only the required magnitude of the horizontal electric field, but the index of variation in the horizontal field required to avoid certain macroscopic instabilities (involving axisymmetric rigid displacements). The experimental design discussed below incorporates horizontal field electrodes that permit a test of theoretical predictions like those of Bhattacharyya and Avinash.…”

PoloidalE×BDrift Used as an Effective Rotational Transform to Achieve Long Confinement Times in a Toroidal Electron Plasma

“…Vertical drifts are managed and confinement achieved in toroidal plasmas (e.g., in tokamaks) by employing a rotational transform or poloidal component of the magnetic field. Non-neutral plasmas (i.e., plasmas with a single sign of charge [1]), on the other hand, are predicted to exhibit stable equilibria in a purely toroidal magnetic field [2][3][4][5][6][7]. A handful of electron plasma experiments over more than three decades generally support these predictions, but they fail to confine plasmas for more than about 100 s [8][9][10][11][12][13][14].…”