Oxygen negative ion production in a pulsed radiofrequency plasma source toward a dual gridded ion thruster

Development of a compact electric propulsion system is a key issue for long-term operation of small satellites. Representative electric propulsion devices such as gridded ion and Hall thrusters requires a neutralizer to prevent the charge up of the satellites by extracting ion beams. However, since electrons exhausted from the neutralizer have no significant momentum, the neutralizer does not contribute to the thrust generation. Here a pulse-modulated dual gridded ion thrusters consisting of positive and negative ion sources is proposed, where positive and negative ions are alternately extracted from two pulsed RF plasma sources. This concept utilizes efficient negative ion production in an after glow discharge, this work focuses on negative ion production in the after glow of the pulsed inductively-coupled plasma in oxygen. The results show negative ion current have a peak at about 100 mm downstream of the source and the peak position slightly changes with the working gas pressure.