Influence of external magnetic field on dust acoustic waves in a capacitive RF discharge

Abstract

This paper reports experiments on self-excited dust acoustic waves (DAWs) andits propagation characteristics in a magnetized rf discharge plasma. The DAWs are spontaneously excited in dusty plasma after adding more particles in the confining potential well and found to propagate in the direction of streaming ions. The spontaneous excitation of such low-frequency modes is possible due to the instabilities associated with streaming ions through the dust grain medium. The background E-field and neutral pressure determine the stability of excited DAWs. The characteristics of DAWs strongly depend on the strength of external magnetic field. The magnetic field of strength B < 0.05 T only modifies the characteristics of propagating waves in dusty plasma at moderate power and pressure, P = 3.5 W and p = 27 Pa, respectively. It is found that DAWs start to be damped with increasing the magnetic field beyond B > 0.05 T and get completely damped at higher magnetic field B ∼ 0.13 T. After lowering the power and pressure to 3 W and 23 Pa respectively, the excited DAWs in the absence of B are slightly unstable. In this case, the magnetic field only stabilizes and modifies the propagation characteristics of DAWs while the strength of B is increased up to 0.1 T or even higher. The modification of the sheath electric field where particles are confined in the presence of the external magnetic field is the main cause of the modification and damping of the DAWs in a magnetized rf discharge plasma. K E Y W O R D Sdust acoustic wave, magnetized dusty plasma, magnetized plasma, RF discharge, superconducting magnet 1The presence of submicron to micrometre-sized particles in a plasma makes it more complex because these particles alter the dynamics of the plasma species (electrons and ions) as well as they exhibit their own dynamics. Such medium, which consists of three charged species namely electrons, ions, and charged solid particles, is termed as a dusty plasma or complex plasma. In the background of a low-temperature plasma, energetic electrons impinge on the surface of the solid particle and charge their surface negatively up to 10 3 -10 5 times of an electron charge [1] to balance the fluxes of electrons and ions. After the density of negatively charged dust particles crosses a critical value, then long-range coulombic interaction among the dust particles turnsThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Perspective: The dusty plasma experiments a learning tool for physics graduate students

“…3(a). Similar to the well-known mediums, dusty plasma medium also supports very low frequency (< 100 Hz) acoustic modes (DAW) [10][11][12]41,46,47 . This novel feature of dusty plasma attracts undergraduate and postgraduate students to understand the wave motion in any medium (gas, liquid, and solid) by performing experiments on dust-acoustic waves in dusty plasma device.…”

“…This novel feature of dusty plasma attracts undergraduate and postgraduate students to understand the wave motion in any medium (gas, liquid, and solid) by performing experiments on dust-acoustic waves in dusty plasma device. The excitation of dust-acoustic waves in dusty plasma device is possible in direct current (DC) discharge as well as in radio-frequency (RF) discharge configurations 10,41,[46][47][48][49][50]…”

Rotational properties of annulus dusty plasma in a strong magnetic field

“…They observed the inversion of rotation at lower magnetic field strength and a slow increase of the angular frequency after B > 0.1 T. Karasev et al 23 reported a rotating dust cluster and shell structure in the presence of a strong magnetic field. Apart from DC discharges, some interesting features of 3D dusty plasmas, as damping of dust-acoustic waves 24 and counter-rotating dust torus 25 have been reported in recent experiments by Choudhary et al in rf discharge. Melzer et al 26 investigated the effect of a strong magnetic field (B > 5 T) to a dust cluster confined by a ring shaped electrode in a rf discharge.…”

Magnetized dusty plasma: On issues of its complexity and magnetization of charged dust particles

“…There are few dusty plasma devices based on permanent magnet [ 52 ] and superconducting electromagnet [ 53–55 ] to conduct dusty plasma studies with strong magnetic field (few Tesla). Researchers are continuously working to explore the effect of strong magnetic field on low‐temperature plasma and dusty plasma phenomena such as patterns formation, [ 56,57 ] imposed structure formation, [ 58 ] computational modeling of dust charging, [ 59 ] study of dust acoustic modes, [ 60,61 ] vertical oscillation of dust grain, [ 62 ] rotational and vortex motion, [ 25,63 ] crystallization and melting of dust grain medium, [ 64 ] Mach cone formation, [ 65 ] dusty plasma crystal as tunable terahertz (THz) filter, [ 66 ] etc. Despite having interesting experimental results on strongly magnetized dusty plasma, there are still many challenges to achieve magnetization conditions of charged dust grains and understand the experimentally observed results at kinetic level.…”