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Prior experiments have demonstrated that the pole in a magnetically shielded Hall thruster sputters and erodes visibly, in contrast with that in an unshielded thruster. To determine the reason for this, a particle-in-cell simulation was conducted, and the difference between shielded and unshielded thrusters in terms of plasma behavior near the exit plane was studied. The results show that in the case of the magnetically shielded thruster, the ion flux peak is on the magnetic pole face with higher ion energy, indicating severer erosion at the pole. By contrast, the flux peak of the unshielded thruster is on the head face of the channel wall, indicating severer bombardment at the wall and milder erosion at the pole. Therefore, pole erosion occurs in the magnetically shielded thruster, and channel head face erosion can be observed in the unshielded thruster. In addition, the simulation results indicate that the greater the outward shift of the magnetic field, the severer the pole erosion. [ABSTRACT FROM AUTHOR]

To improve the performance of thrusters by using two permanent ring-shaped magnets to push a magnetic field downward, we propose an annular–cylindrical combined-channel Hall thruster and numerically study its performance. The results indicate that, compared with simple annular channels, the annular–cylindrical combined channel can effectively increase the neutral gas density contained within it and increase the degree of ionization, efficiency, thrust, and specific impulse. Moreover, the sputtering zone of discharge channel is in front of the permanent magnets, i.e., wall erosion occurs upon ion bombardment during discharge. However, ions cannot bombard the permanent magnetic rings, thus guaranteeing a constant magnetic field and long discharge lifetime. [ABSTRACT FROM AUTHOR]

The structure of an azimuthal diversion rail causes the neutral gas in the Hall effect thruster to possess a certain circumferential velocity. Two different directions of the magnetic field can be formed in the discharge channel, where the direction of the magnetic field depends on the direction of the excitation current. The aim of this work is to study the effect of magnetic field directionality on the discharging characteristics of a Hall effect thruster with an azimuthal diversion rail. The experimental results demonstrate that a change in the magnetic field direction corresponds to a change in the electronic Hall drift direction. When the electronic Hall drift direction is opposite to the circumferential velocity of the neutral gas, its thrust, specific impulse, and efficiency are higher than the case in which the electronic Hall drift direction is in the same direction as that of the circumferential velocity of neutral gas. The increase in performances is due to the increase in the propellant utilization. The reasons for the increase in the propellant utilization are explained. The experimental result provides a guide for the selection of the direction of excitation current of the Hall effect thruster with an azimuthal diversion rail. [ABSTRACT FROM AUTHOR]

In order to increase the degree of ionization and improve the efficiency, the effects of different cylindrical outer wall lengths on the discharge characteristics of the annular-cylindrical combined channel Hall thruster are studied. The cylindrical outer wall is set to the following positions: 95% (with positive magnetic field gradient), and 100%, 95%, 90%, 75%, and 50% (with negative magnetic field gradient) of the maximum magnetic field. The ionization gain and wall energy loss under different positions are analyzed through numerical simulations. The simulation result shows that when the cylindrical outer wall is set to the position where it is 100%–90% of the maximum magnetic field (negative magnetic field gradient zone), the power deposition on the channel wall is small, the propellant utilization can be largely improved, and the comprehensive performance is optimal for the annular-cylindrical combined channel Hall thruster. [ABSTRACT FROM AUTHOR]

Hall thruster is an attractive type of electric propulsion that is being developed to replace the chemical propulsion deployed in many tasks on satellites. The research on Hall thrusters in China has gradually progressed from basic theory to engineering applications, especially with the experience of on-orbit flight tests in low earth and geostationary equatorial orbits. This paper discusses the progress of research on Hall thrusters in China in recent years. This includes the beam focusing, scaling, high specific impulse, long lifetime, and effective magnetic field excitation techniques, as well as the stabilization technique of low-frequency oscillation, along with other types of Hall thrusters, such as cylindrical Hall, double-stage Hall, cusped field, nested-channel Hall, and anode layer Hall thrusters. In conclusion, this paper discusses the programs intended for the future focusing on the development of thrusters, their application prospects, and their use in space applications. [ABSTRACT FROM AUTHOR]

The strength and shape of the magnetic field are the core factors in the design of the Hall thruster. However, Hall current can affect the distribution of static magnetic field. In this paper, the Particle-In-Cell (PIC) method is used to obtain the distribution of Hall current in the discharge channel. The Hall current is separated into a direct and an alternating part to calculate the induced magnetic field using Finite Element Method Magnetics (FEMM). The results show that the direct Hall current decreases the magnetic field strength in the acceleration region and also changes the shape of the magnetic field. The maximum reduction in radial magnetic field strength in the exit plane is 10.8 G for an anode flow rate of 15 mg/s and the maximum angle change of the magnetic field line is close to 3° in the acceleration region. The alternating Hall current induces an oscillating magnetic field in the whole discharge channel. The actual magnetic deformation is shown to contain these two parts. [ABSTRACT FROM AUTHOR]

The theoretical specific impulse of Hall thrusters using a krypton propellant is much higher than that of those using xenon. However, the actual benefits of this improvement are limited by the difficulty in achieving krypton atom ionization, and its efficiency is much lower than that of xenon. In this study, the anode specific impulse and anode efficiency of Hall thrusters using krypton propellant were improved by adding a small quantity of xenon. A dual-channel supply of xenon and krypton was achieved by optimizing the discharge channel structure based on the design of the aft-loaded magnetic field. The effects of the xenon and krypton supply method and xenon fraction on the discharge characteristics of the Hall thruster were investigated by conducting discharge experiments using the mixed propellant. The results indicated that injecting a small quantity of xenon significantly improved the ionization of krypton, improved the ionization and acceleration efficiency of the thruster, and fully utilized the high specific impulse characteristics of krypton. Furthermore, the addition of a small quantity of xenon also significantly increased the upper limit of the discharge voltage for stable operation using krypton from 500 V. At the maximum tested xenon fraction, the maximum discharge voltage was loaded to 900 V. At a discharge voltage of 800 V, the optimal anode efficiency and anode specific impulse increased by 4.5 % and 534 s, respectively, compared with those for pure xenon propellant (with an anode efficiency of 54 % and anode specific impulse of 3034 s). The results of this study are of great significance for the design of high-efficiency, high-specific-impulse, and low-cost Hall thrusters. • A dual-channel gas supply structure is proposed, which can supply two kinds of gases into the discharge channel individually. • Thruster performance is optimal when krypton is supplied downstream and auxiliary xenon is supplied upstream. • High-voltage operating ability under krypton is greatly improved with the assistance of a small quantity of xenon. [ABSTRACT FROM AUTHOR]

With the development of electric space propulsion and all-electric propulsion technologies, the application range of the Hall effect thruster (HET) has gradually expanded. As an important part of the HET, the magnetic field plays a decisive role in its performance. In the development of versatile HETs, it is necessary to comprehensively and thoroughly understand the effects of the magnetic field on the HET discharge characteristics. In this paper, a HEP-100X thruster with multiple degrees of freedom in terms of magnetic field control is used to study the effects of the peak magnetic field position on the thruster discharge characteristics. The results indicate that the peak magnetic field position can effectively control the main ionization zone position and affect the ionization rate. The thruster has the best comprehensive discharge performance when the peak magnetic field position is located near the channel exit. Further analysis reveals that the performance improvement is mainly due to the reduced ion loss on the wall surface and plume divergence half-angle, and the increased current utilization efficiency and voltage utilization efficiency. The HEP-100X shows the above trends under various flow conditions, and the anode efficiency is the highest when the anode flow is 50 sccm. In this condition, the propellant is sufficiently ionized and the ion loss on the wall surface is small. This research provides the necessary support for a comprehensive understanding of the role and significance of the magnetic field in the thruster discharge process, and has important significance for the design optimization of multifunctional Hall thrusters and subsequent research. [ABSTRACT FROM AUTHOR]

Hall thrusters generally use a U-shaped insulated wall to form an annular discharge channel. As high-power and high-specific-impulse Hall thrusters develop, the disadvantages of this conventional topology—in terms of material and mechanical strength, processing, and manufacturing—are gradually being exposed. Therefore, in this study, a new wall material was employed, and its effects were investigated numerically and experimentally. A boron nitride ceramic wall was retained in the strong discharge area owing to its excellent secondary electron emission characteristics; while a metallic wall was applied upstream of the channel, forming a segmented hybrid wall. A Hall thruster with an aft-loaded magnetic field, which offers a long lifetime, was adopted for this study. The particle-in-cell simulation shows that the length of the metallic wall has a significant impact on thruster performance. The same trend was observed in the experiments. Under the optimal metallic wall length, the anode efficiency is improved by approximately 4% compared to that of the ceramic-wall-only case. The physics involved is analyzed and qualified by comparing the simulated and measured results. The findings of this study provide valuable guidance for the optimal design of high-power, high-specific-impulse Hall thrusters. • Metal-ceramic hybrid channel wall improves high-voltage performance of Hall thrusters. • Optimal length of metallic segment exists and is strongly related to magnetic field. • Too long metallic segment augments electron wall loss and then ionization loss. [ABSTRACT FROM AUTHOR]