Plume Control of a Cusped Field Thruster

Abstract

The cusped field thruster uses several permanent ring magnets of alternating polarity to create a multistage cusp magnetic topology. It has demonstrated a long lifetime because of reduced plasma losses to the discharge channel surface. However, the high beam divergence problem has not been solved in this type of thruster. The purpose of this technical note is to describe a plume control method to reduce its plume angle. The results show that the magnetic field intensity in the plume region and the shape of the last separatrix have great influence on plume divergence.Index Terms-Cusped field thruster, plasma plume. T HE cusped field thruster represents a new type of electric propulsion device incorporating cusped magnetic field profiles that keep high-energy ions away from the channel walls and mitigate erosion. Thus, its lifetime will be longer compared with some other type of electric propulsion devices [1]. Recently, the cusped field thruster has been paid much attentions by many organizations, such as Thales Research Institute's High Efficiency Multistage Plasma Thruster (HEMPT) [2], MITs Diverging Cusped Field Thruster (DCFT) [3], and Stanford University's Converging Cusped Field Thruster (CCFT) [4].The cusped field thrusters use strong permanent ring magnets of alternating polarity to form cusped magnetic field. The magnetic cusps trap and reflect energetic electrons within the discharge channel, leading to the enhancement of the propellant ionization. The strong magnetic field is used to magnetically shield plasma from the thruster wall so as to minimize ion bombardment and corresponding erosion. Meanwhile, the electron's movement toward the anode is strongly impeded due to this magnetic field configuration, which contributes to the formation of a steep electric field gradient for effective ion acceleration. Recent works on cusped Manuscript field thrusters have shown that they have great difference compared with the traditional Hall thrusters [2]-[4]. It has a potential advantage in lifetime, but is limited by a highly divergent plume structure, which means the majority of the ion current coalesce into a conical shell with a half angle of more than 40° [3]. The divergent plume reduces the efficiency and increases the possibility of plasma beam impingement on critical satellite hardware, such as solar cells.Therefore, the reduction of the plume divergence is one of the main aims of investigations toward the cusped field thruster. In cusped field thrusters, the electric potential distribution plays direct divergence, which is necessary to analyze the influence factors of influence on the plume shape. The electric potential is mainly depended on the electron conductivity distribution, i.e., the process of electron movement from hollow cathode to anode. The electrons are ejected from the hollow cathode in the plume region and transit into the channel to ionize atoms. Before getting into the discharge channel, the electrons have to transverse the magnetic field lines in the plume region. The strong magnetic fie...

Study on the ionization and acceleration of a microwave discharge cusped field thruster

“…Also, the magnetic intensity distribution affects the electron-conduction impedance in the plume region, and the effectiveness of the plasma confinement in the channel. On the other hand, the magnetic topology, especially for the exit magnetic separatrix, has a significant impact on the ion beam profile [24]. It has been demonstrated that the separatrix should be flat to the exit plane to produce a concentrated beam.…”

Experimental Investigation of the CFHT-27 Cusped-Field Hall Thruster Performance

“…This concept is also patented by Airbus Defence and Space GmbH (Hey et al 2019). Based on the original design of THALES, researchers in academia have also investigated this thruster concept; at MIT (Courtney 2008;Courtney and Martinez-Sanchez 2007;Gildea et al 2013;Matlock et al 2010), at Stanford University (MacDonald et al 2012), and at Harbin Institute of Technology (Liu et al 2014a;b;Ma et al 2015;Zhao et al 2013). In this type of Hall thruster, unlike a single region of radial magnetic field of a typical Hall thruster, multiple regions of radial magnetic field are created by adopting alternating polarity permanent magnets.…”