Effects of propellant species on the discharge characteristics of glow discharge hollow cathode

Hollow cathodes are the key sources of electrons for the operation of space electric thrusters. Traditionally, hollow cathodes utilize heating elements to raise the temperature of low work function materials to produce electrons. To accommodate the development of small satellites, researchers around the world have developed alternative neutralizer technologies such as radio frequency neutralizers, electron cyclotron resonance neutralizers, and coiled tungsten filaments cathode neutralizers to simplify the cathodes design and operation. In this work, a lower current glow discharge hollow cathode (GDHC) is developed, which can generate a discharge current of 10-100 mA. By testing with xenon, krypton, and argon propellants, it is found that GDHC has lower discharge voltage and power consumption with argon propellant. Simulation analysis reveals that during argon propellant discharge, the secondary electron emission coefficient on the cathode surface is larger, the electron density in the cathode sheath area is higher, and the high mobility of argon ions increases the conductivity within the cathode sheath. In addition, there are low and high extraction modes for GDHC electron extraction, depending on whether the keeper electrode absorbs or emits electrons.