Particle‐in‐Cell Simulations for Ion Thrusters

Zhao

et al. 2014

Physics of Plasmas

The multi-cusped field thruster is a kind of electric thruster adopting a cusped magnetic field to achieve a potentially longer lifetime. It is observed in some experiments that the main electric potential drop forms near the exhaust plane, but the formation mechanism of the electric field in this kind of thrusters is not fully clear yet. Based on the analysis of the electron movement, a 2D Particle-in-Cell plus Monte Carlo model is built to reveal the difference of the constraint to electrons between the central leak path and the lateral region of the thruster. Electron trajectories from cathode are analyzed furthermore. It is found that the central leak path inside the discharge channel may play a significant role in the formation of the main electric potential drop near the exhaust plane.

mentioning

confidence: 89%

mentioning

confidence: 98%

Study of the electric field formation in a multi-cusped magnetic field

Zhao

et al. 2014

Physics of Plasmas

“…Therefore, the main potential drop is formed in the plume region. Recent laser-induced fluorescence experiment and other PIC simulation results have also validated the peak axial electric field occurring somewhat downstream of the thruster exit, after the last separatrix in the plume of the thruster [5], [6].A separatrix is the line that separates the magnetic field lines that bend upstream at the axis of symmetry from those bend downstream, i.e., the flux line with zero magnetic flux. Fig.…”

mentioning

confidence: 92%

mentioning

confidence: 94%

Plume Control of a Cusped Field Thruster

IEEE Trans. Plasma Sci.

Zhao

Chen

et al. 2015

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...

“…The generated ions are accelerated by the mainly axial electric field near the exit and spurted out of the thruster, thus forming the thrust. 2 The laser-induced fluorescence (LIF) experiments [3][4][5] and Particle-in-Cell (PIC) simulations 6,7 have validated that the main acceleration region locates near the downstream of the thruster exit. Meanwhile, as the electrons are strongly confined by the mainly axial magnetic field in the discharge channel, the main ionization region can be established near the axis of the ultimate stage, as shown in figure 1.…”

Section: Introductionmentioning

confidence: 97%

Effects of magnetic field strength in the discharge channel on the performance of a multi-cusped field thruster

Gao

et al. 2016

AIP Advances

The effects of magnetic field in plume region on the performance of multi-cusped field thruster Physics of Plasmas 22, 103502 (2015) The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field strength in the discharge channel were investigated. Four thrusters with different outer diameters of the magnet rings were designed to change the magnetic field strength in the discharge channel. It is found that increasing the magnetic field strength could restrain the radial cross-field electron current and decrease the radial width of main ionization region, which gives rise to the reduction of propellant utilization and thruster performance. The test results in different anode voltage conditions indicate that both the thrust and anode efficiency are higher for the weaker magnetic field in the discharge channel. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license