Characterization of a circular arc electron source for a self-neutralizing air-breathing plasma thruster

Abstract

The paper presents an enhanced version of an arc electron source designed for air ionization applications in a self-neutralizing air-breathing plasma thruster. The arc electron source is specifically suited for the air-breathing plasma thruster, as it allows precise control of mean electron energy levels. This paper focuses on the ionization aspects of air-breathing thrusters through the development of axially magnetized arc electron sources. The sources consist of a circular and coaxial configuration of a metallic arc plasma source coupled with a positively biased grid to extract electrons and control mean electron energy. The average mean electron energy of electrons in the arc electron source is regulated by adjusting the bias voltage of the grid within the range of 0 V – 300 V. To investigate the behavior of ion current density and electron density concerning pressure and mean electron energy, the current probe and magnetic filter were utilized. It was demonstrated that the circular electron source leads to enhanced ionization of airflow by achieving plasma densities greater than 1018 m−3. By utilizing a high-speed camera for the circular arc electron source, the arc spot was seen to move azimuthally due to the magnetic field. Furthermore, scanning electron microscopy and a conductance measurement system were employed for the coaxial arc electron source to examine the deposition and conductance of the electron extraction grid. While the grid underwent deposition of about 600 microns, the conductance was observed to increase/saturate with time and bias voltage, indicating an electrically “self-healing material”.