Radio Frequency Microdischarge Neutraliser

Abstract

A new plasma propulsion experimental apparatus has been set up at the University of Auckland in collaboration with the Australian National University. The first research focuses on exploring the potential of a novel millimetric scale capacitively coupled, low power radio frequency plasma device as an alternative to hollow cathodes for primary plasma and electron source in conventional ion thruster technologies. The electron Pocket Rocket neutraliser, ePR, has inherent advantages over hollow cathodes: the driven electrode is not in contact with the plasma, which enables longer operational lifetime and the device can produce a high density plasma (∼1018 m−3 ) instantly (∼µs) compared to the several minutes required for hollow cathodes. In a preliminary study, two modes of operation have been identified for routine operational conditions ranging ∈ [2, 24]W and ∈ [0.7, 2.0] Torr. A high current mode gives electron currents in excess of 25 mA. There, current scales with input power, argon pressure and negative bias on an internal electrode which collects an equal amount of ion current. A low current mode has electron currents ∈ [1, 3.5] mA and occurs when the internal electrode is grounded. In this mode, current scales with input power and decreasing operational argon pressure. An electron current of 41 mA was achieved at 2.0 Torr and ∼50W with the ion electrode biased at −320 V.