Propagation characteristics of dust–acoustic waves in presence of a floating cylindrical object in the DC discharge plasma

Abstract

The experimental observation of the self−excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object are investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in the background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at lower pressure.The excitation of such low frequency wave is a result of the ion-dust streaming instability in the dust cloud. The characteristics of the propagating dust acoustic wave get modified in presence of a floating cylindrical object of radius larger than the dust Debye length. Instead of propagating in the vertical direction, the DAWs are found to propagate obliquely in presence of the floating object (kept either vertically or horizontally). In addition, horizontally aligned floating object gives rise to form a wave structure in the cone shaped dust cloud in the sheath region. The change in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.

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

“…It has been discussed that dust grains absorb free electrons and reduce the density of free electrons in a plasma. It has been noticed in earlier studies as well in present study that the electrostatic probes modify the dynamics of dust grains in a local region [5,53,54] and cannot be used to measure the plasma parameters and E-field during the wave motion. It has been assumed that plasma parameters are not strongly affected by the dust grains if P h < 1 and plasma parameters can be used to estimate the dusty plasma parameters.…”

“…The results of the collective phenomena of dusty plasma are predicted theoretically and experimentally in the form of linear and non-linear waves such as longitudinal dust acoustic waves (DAWs) [2][3][4][5] dust acoustic transverse waves, [6][7][8] dust lattice waves, [9][10][11] dust acoustic solitary waves, [12,13] and dust acoustic shock waves [14][15][16] as well as dust vortices. The results of the collective phenomena of dusty plasma are predicted theoretically and experimentally in the form of linear and non-linear waves such as longitudinal dust acoustic waves (DAWs) [2][3][4][5] dust acoustic transverse waves, [6][7][8] dust lattice waves, [9][10][11] dust acoustic solitary waves, [12,13] and dust acoustic shock waves [14][15][16] as well as dust vortices.…”

“…The results of the collective phenomena of dusty plasma are predicted theoretically and experimentally in the form of linear and non-linear waves such as longitudinal dust acoustic waves (DAWs) [2][3][4][5] dust acoustic transverse waves, [6][7][8] dust lattice waves, [9][10][11] dust acoustic solitary waves, [12,13] and dust acoustic shock waves [14][15][16] as well as dust vortices. [20] In low-temperature discharges (DC or RF), the DAWs are excited in the dust grain medium which is confined in a strong electric field (E) of the cathode sheath [5,13] or anodic plasma [3] or rf sheath [21][22][23] or diffused plasma. [20] In low-temperature discharges (DC or RF), the DAWs are excited in the dust grain medium which is confined in a strong electric field (E) of the cathode sheath [5,13] or anodic plasma [3] or rf sheath [21][22][23] or diffused plasma.…”

“…the dust grain medium to respond collectively similar to the plasma. The results of the collective phenomena of dusty plasma are predicted theoretically and experimentally in the form of linear and non-linear waves such as longitudinal dust acoustic waves (DAWs) [2][3][4][5] dust acoustic transverse waves, [6][7][8] dust lattice waves, [9][10][11] dust acoustic solitary waves, [12,13] and dust acoustic shock waves [14][15][16] as well as dust vortices. [17][18][19] The study of DAWs has a more than 25-year-old history.…”

“…[17][18][19] The study of DAWs has a more than 25-year-old history. [20] In low-temperature discharges (DC or RF), the DAWs are excited in the dust grain medium which is confined in a strong electric field (E) of the cathode sheath [5,13] or anodic plasma [3] or rf sheath [21][22][23] or diffused plasma. [17,19,24] Such low frequency dust acoustic modes are either excited by inherent instabilities such as ion-streaming instability and dust-dust instability [25][26][27][28] or externally forced triggered instabilities.…”