Reflection of ion-acoustic waves from bipolar potential structures

Abstract

Reflection of ion-acoustic waves from the ion sheath in front of the separation grid in a double-plasma device has been investigated experimentally. The plasma potential φ of the source plasma was controlled relative to that of the target plasma. When eφ < κΤe, where Τe is the electron temperature, no reflection was observed. The reason for this is that ions are drifting towards the grid with the Bohm velocity, i.e. the ion-acoustic velocity. When eφ > κΤe the reflected wave consists of the ion-acoustic wave and the ion beam mode. The reflection coefficient for the ion-acoustic wave is about unity. This high efficiency is due to reflection of the ions themselves.

Reflection of modified Korteweg–de Vries solitons in a negative ion plasma

“…[9][10][11][12][13][14][15][16][17][18][19][20][21][22] Linear ion acoustic waves were reflected from a positively biased solid metallic plate. 9 KdV solitons were reflected from a negatively biased metal plate.…”

“…11 Nakamura and Chutia have argued that there is an ion flow toward a negatively biased plate, the Bohm drift velocity, which in this plasma has the same velocity as the ion acoustic wave. 12 Therefore, an ion acoustic wave cannot propagate in the upstream direction from the plate. Hence, the reflected ion acoustic wave from a negatively biased plate cannot be detected.…”

“…A negatively biased metallic grid was found to reflect both ion acoustic waves and solitons. [11][12][13][14][15][16][17] The observation of the reflection of a linear ion acoustic wave was first observed from a biased grid. 13 Schott has shown that the reflected ion acoustic wave is a downstream wave that propagates on the ion beam coming from the other side of the grid.…”

Reflection and excitation of ion-acoustic waves in a multi-component plasma with negative ions

“…A negatively biased mesh grid has been found to reflect ion-acoustic waves (Nishida 1984;Schott 1986). In this case the reflection is considered to be caused by ions coming from the other side of the grid (Nakamura & Chutia 1989). Therefore no reflection has been observed for a negatively biased metallic plate, since ion-acoustic waves are totally absorbed (Jones & Alexeff 1966).…”