1 Characterization of Near Field Plasma Environment of a Hollow Cathode Assembly

Cathode keeper erosion has been identified as a possible limit to thruster lifetimes. Therefore, it is important to characterize a cathode discharge at various operating conditions in order to identify potential erosion mechanisms. In this investigation the near field plasma environment of a hollow cathode assembly was examined under several operating conditions in the Isp Lab’s Xenon Test Facility (XTF) at Michigan Tech. This examination focused on the region within 3 cm of the cathode keeper orifice. In this paper the results from six operating conditions are summarized giving values of plasma potential, electron temperature and number density. It was found that electron density did not vary significantly with changes in xenon flow rate and discharge current. It was also found that as flow rate increased, electron temperature decreased, resulting in a shorter Debye length and a flatter potential structure near the orifice; as discharge current increased, electron temperature also decreased. Nomenclature AP = area of probe e = elementary charge ID = discharge current Ieo = electron saturation current IP = probe current k = Boltzmann’s constant mc = cathode mass flow rate me = mass of an electron ne = electron density n0 = number density Te = electron temperature VD = discharge voltage VP = probe voltage λD = Debye lengt