Residual dust charges in discharge afterglow

Abstract

An on-ground measurement of dust-particle residual charges in the afterglow of a dusty plasma was performed in a rf discharge. An upward thermophoretic force was used to balance the gravitational force. It was found that positively charged, negatively charged, and neutral dust particles coexisted for more than 1 min after the discharge was switched off. The mean residual charge for 200-nm-radius particles was measured. The dust particle mean charge is about -5e at a pressure of 1.2 mbar and about -3e at a pressure of 0.4 mbar .

Complex Plasma Afterglow

“…When using a model based on an abrupt transition from ambipolar to free diffusion when the Havnes parameter P H = 0.5, the residual charge is smaller (in absolute value) Q d res ≃ −7e but still far from experimental value. A dependance on the ambipolar to free diffusion transition is again seen with Q d res ≃ −14e when using Gerber and Gerardo data and Q d res ≃ −2e when using Freiberg and Weaver data which is close to experimental results [6].…”

“…Furthermore, in the first case, there is no tail in the positive region of the dust particle charge distribution as there is one in the second case. The second residual charge distribution is similar to the experimental one [6].…”

“…Recently the decharging of dust particles in complex plasma afterglow raises interest as well as the dust particle residual charge [5,6,7]. Indeed it has been observed that dust particles do keep residual electric charges when the power of a RF discharge is turned off.…”

“…which is approximately the diffusion length of the PKE-Nefedov reactor in which experiments on residual dust charge have been performed [5,6].…”

Self-Excited Instabilities in Plasmas Containing Dust Particles (Dusty or Complex Plasmas)

“…[24][25][26][27] This charge loss can be drastic for the plasma equilibrium and instabilities can appear due to the strong interdependence between the dust particle cloud and the plasma. Various types of low-frequency instabilities (from few Hz to few kHz) are observed (with various frequencies and shapes) either during dust particle growth process 20,[28][29][30] or once the dust cloud is completely formed.…”