Effect of Ionization on Void Formation in an RF Discharge under Microgravity Conditions

An analysis of the formation of a void in the PK3 setup in dusty plasma with 3.4-mu m-diameter melamine-formaldehyde particles-in an RF discharge in argon at a pressure of 12-50 Pa under microgravity conditions at the ISS is presented. The uniform state of the plasma can only be obtained at a voltage close to the discharge extinction voltage. The application of a low-frequency voltage of 20-50 Hz stabilizes the state of the dusty plasma and shifts the void formation threshold towards higher RF voltages. It is shown that the formation of a void is associated with non-local ionization of the plasma at the center of the discharge by fast electrons, which are heated in the near-electrode layers.

Automated summary

This study analyzes the formation of a void in the PK3 setup in a dusty plasma with 3.4-mu m-diameter melamine-formaldehyde particles, in an RF discharge in argon at a pressure of 12-50 Pa under microgravity conditions at the ISS. The uniform state of the plasma can only be achieved at a voltage close to the discharge extinction voltage. Applying a low-frequency voltage of 20-50 Hz stabilizes the dusty plasma state and increases the threshold for void formation at higher RF voltages. The formation of a void is associated with non-local ionization of the plasma in the center of the discharge by fast electrons heated in the near-electrode layers.