Rotational properties of annulus dusty plasma in a strong magnetic field

Abstract

The collective dynamics of an annulus dusty plasma formed between a co-centric conducting (non-conducting) disk and ring configuration is studied in a strongly magnetized radiofrequency (rf) discharge. A superconducting electromagnet is used to introduce a homogeneous magnetic field to the dusty plasma medium. In the absence of the magnetic field, the dust grains exhibit thermal motion around their equilibrium position. The dust grains start to rotate in the anticlockwise direction with increasing magnetic field (B > 0.02 T), and the constant value of the angular frequency at various strengths of the magnetic field confirms the rigid body rotation. The angular frequency of dust grains linearly increases up to a threshold magnetic field (B > 0.6 T) and after that its value remains nearly constant in a certain range of magnetic field. Further increase in magnetic field (B > 1 T) lowers the angular frequency. Low value of the angular frequency is expected by reducing the width of the annulus dusty plasma or the input rf power. The azimuthal ion drag force due to the magnetic field is assumed to be the energy source which drives the rotational motion. The resultant radial electric field in the presence of a magnetic field determines the direction of rotation. The variation of floating (plasma) potential across the annular region at given magnetic field explains the rotational properties of the annulus dusty plasma in the presence of a magnetic field.

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

“…The propagation characteristics of dust acoustic modes in low-temperature direct current (DC) and rf plasma [15][16][17]32,[74][75][76][77] were explained based on the available theoretical models. [20,67,78,79] Recently, Choudhary et al [60] and Melzer et al [61] conducted experimental studies on self-excited dust acoustic waves (DAWs) in the presence of external magnetic field and observed the damping as well as modification in propagation parameters at higher magnetic field. The role of external magnetic field on propagation characteristics of DAWs in capacitive coupled discharge is shown in Figure 1.…”

“…In the last 25 years, a wide spectrum of experimental and theoretical studies has been devoted to explore the collective response of dusty plasma in the form of various dynamical structures/phenomena such as dust acoustic waves, [15,16,[19][20][21][22][23] rotational and vortex motion, [24][25][26][27][28][29][30][31] crystallization and phase transition, [32][33][34][35] instability driven modes, [36][37][38][39][40] and voids. [41][42][43] The major objectives of these theoretical and experimental studies of dusty plasma were to understand the dust-plasma interaction and naturally occurring dusty plasmas, control the nano-to micron-sized dust impurities in semiconductor processing industries, explore the role of impurities on the characteristics of ambient plasma in astrophysical systems, establish it as a model system to understand the complex physical systems at a microscopic level, lower the hazardous effect of solid particles on plasma confinement in fusion devices and resolve the issues of air pollution by particulate of different sizes.…”

“…There are few dusty plasma devices based on permanent magnet [52] and superconducting electromagnet [53][54][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.…”

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

“…Apart from the vortex motion, dust grain medium can also be used to demonstrate the rigid rotational motion of any medium. In the presence of a weak magnetic field (B < 0.05 T), dust particles in either DC or RF discharge configuration exhibits the rigid rotational motion 20,60 . It provides a platform to learn the rotational motion of many-body systems by estimating the angular frequency of rotating particles.…”

“…8(b)). A constant angular frequency variation along radial direction indicates the rigid rotational motion of medium 60 . Thus, dusty plasma experiments at the graduate level may introduce students to the concepts of rotational motion of many-body system and vortex flow in fluids.…”