Further research of the collisional instability. An extensive study of growth and a notable influence of the boundaries

Abstract

In a cylindrical geometry, a low-pressure magnetized argon plasma is lit, using the rf upper hybrid resonance. As a radial dc electric field is formed, a perpendicular drift velocity is obtained on the charged particles and a collisional instability is raised. The description, study and identification of that wave were given in the last published work from NCSR 'Demokritos', both experimentally and theoretically. Since then, the research has been continued and significant results have been obtained concerning the fields of plasma parameters, wave further understanding, growth research and boundaries' strong influence. The aim of the present paper is to inform that the rising instability has many of the characteristics of drift instabilities that are caused by the density gradient, as well as the ability of it's frequency to overcome the ion gyro-frequency. In addition, it gives an answer to the well-known problem of the need to consider a small component of the wave vector in the parallel direction, in order the wave to rise through the electron-neutral collisions' proceedings; a strong influence of cavity length on wave amplitude has been observed and measured.

Nonlinear wavy phenomena into plasma: some cases of stabilization and control of chaotic behaviors

“…A drift wave occurrence is persistent and an extensive research has been carried out in Plasma Laboratory of 'Demokritos' [9,10,21,22]. These waves fall into three frequency ranges, and are propagated azimuthally but sometimes have an axial component.…”

“…The first group with the lowest frequency (≈17 KHz) is studied and listed as drift wave, caused by the rf electric field gradient [9,21]. The middle group of frequencies (≈70 KHz) is studied later and listed as collisional instability [10,22]. The third group with the highest frequencies (≈280 KHz) has not been identified yet.…”

“…The plasma production keeps the following factors and the physical parameters unchanged: the plasma cavity is always constituted by a metallic closed cylinder, with a fixed inner radius (r = 3 cm) and its axis is placed along the external homogeneous magnetic field B. The length of the cylinder depends on the experimental purpose; however, its values vary between 40 cm and 140 cm; in this paper, in order to avoid the boundaries influence, the plasma column length remained unchanged at 70 cm [22]. The rf power for the plasma's maintenance is produced by a magnetron generator operating at 2.45 GHz; this wavy power is entered into the cavity by a metallic antenna fastened on the circular base centre, along the cylindrical axis, so that a coaxial line is formed with the external conductor.…”