Low-power Cylindrical Hall Thruster Research Articles

Far-field plume characterization of a low-power cylindrical Hall thruster

A fully cylindrical Hall thruster prototype was tested in the power range of 30–300 W with the objective of understanding the behavior of the discharge as a function of input parameters. Various operating conditions were compared, including two magnetic field configurations, a set of propellant mass flow rates, and a range of discharge voltages. Plasma properties were measured in the plume, with a Langmuir probe, a retarding potential analyzer, and a Faraday cup. The experimental results showed that the mass flow rate strongly affects the ionization and, consequently, other related properties such as the plasma density, currents, and propellant utilization. The discharge voltage also appeared to influence the ion energy and propellant utilization. The performance accessible from the measured magnitudes is assessed, resulting in a maximum thrust efficiency of about 18% at 0.35 mg s−1 and 168 W.

Simulation of the effect of a magnetically insulated anode on a low-power cylindrical Hall thruster

The intersection point of the characteristic magnetic field line (CMFL) crossing the anode boundary with the discharge channel wall, and its influence on thruster performance and the energy and flux of ions bombarding the channel wall, have been studied numerically. The simulation results demonstrate that with the increase in distance from the crossover point of the CMFL with the channel wall to the bottom of the thruster channel, the ionization rate in the discharge channel gradually increases; meanwhile, the ion energy and ion current density bombarding the channel wall decreases. When the point of the CMFL with the channel wall is at the channel outlet, the thrust, specific impulse, and efficiency are at a maximum, while the ion energy and ion current density bombarding the channel wall are at a minimum. Therefore, to improve the performance and lifetime of the thruster, it is important to control the point of intersection of the CMFL with the channel wall.

Effect of vortex inlet mode on low-power cylindrical Hall thruster

This paper examines a new propellant inlet mode for a low-power cylindrical Hall thruster called the vortex inlet mode. This new mode makes propellant gas diffuse in the form of a circumferential vortex in the discharge channel of the thruster. Simulation and experimental results show that the neutral gas density in the discharge channel increases upon the application of the vortex inlet mode, effectively extending the dwell time of the propellant gas in the channel. According to the experimental results, the vortex inlet increases the propellant utilization of the thruster by 3.12%–8.81%, thrust by 1.1%–53.5%, specific impulse by 1.1%–53.5%, thrust-to-power ratio by 10%–63%, and anode efficiency by 1.6%–7.3%, greatly improving the thruster performance.

Effect of anode position on the performance characteristics of a low-power cylindrical Hall thruster

In this paper, the design of a new cylindrical Hall thruster (CHT) is presented. Its anode is separated from the gas distributor, which is made of ceramic. The effect of the anode position on the performance characteristics of the CHT was investigated by mounting a series of anodes with different radii inside the CHT. It is found that progressively positioning the anode away from the axis along the radial direction increases the ion current and reduces the electron current. Meanwhile, the peak energy in the ion energy distribution function increases, and the shape of the ion energy distribution function noticeably narrows; the ion beam in the plume converges. It is suggested that moving the anode away from the axis may strengthen the electron confinement, thus optimizing the ionization efficiency. Additionally, the electric field near the anode appears to deflect toward the axis, which may promote the collimation of the ion beam in the plume. As a result, the overall performance of the CHT is significantly enhanced in our proposed design.

A type of cylindrical Hall thruster with a magnetically insulated anode

In this paper, a type of magnetically insulated anode structure is proposed for the design of a low-power cylindrical Hall thruster. The magnetic field distribution in the channel is guided by the magnetically insulated anode, altering the intersection status of the magnetic field line passing through the anode and wall. Experimental and simulation results show that a high potential is formed near the wall by the magnetically insulated anode. As the ionization moves towards the outlet, the energy and flux of the ions bombarding the channel wall can be reduced effectively. Due to the reduction in the bombardment of the wall from high-energy ions, the thrust and specific impulse greatly increase compared with those of the non-magnetically insulated anode. For anode mass flow rates of 0.3 and 0.35 mg s−1 and discharge voltages in the 100–200 V range, the thrust can be increased by more than 33% and the anode efficiency can be improved by more than 7%. Meanwhile, the length of the sputtering area is clearly reduced. The starting position of the sputtering area is in front of the magnetic pole, which can effectively prolong the service life of the thruster.

Performance characteristics according to the radial position of gas distributor holes in a low-power cylindrical Hall thruster

The effect of radial position of gas holes in the distributor on the performance of cylindrical Hall thruster was investigated. A series of gas distributors with different radial positions (Rg) of holes were designed in the experiment. The results show that the larger Rg leads to the higher ion current and electron current; meanwhile, the beam angle in plume is narrowed. Nevertheless, the peak energy in ion energy distribution function increases, together with the narrowing of ion energy distribution function. As a result, the overall performance is enhanced. It is suggested that the growing of Rg could lead to the movement of the main ionization region towards anode, which could promote ion velocity and the clearer separation of acceleration region from ionization region. This work can provide some optimal design ideas to improve the performance of the thruster.

Performance characteristics of very low power cylindrical Hall thrusters for the nano-satellite “PROITERES-3”

Development of Hall thrusters for nano, small and low power satellites below 100 W is expected. In lowering Hall thruster power, the cylindrical type Hall thruster is more advantage than conventional coaxial-type Hall thrusters. In this study, a very low power cylindrical Hall thruster for nano-satellite “PROITERES-3” under development in Osaka Institute of Technology was designed, and the thruster performance was measured. As a result, a stable operation was achieved even with 10 W. The anode specific impulse and the anode thrust efficiency were 1570 s and 18.1%, respectively, with 66 W. Also, the discharge current oscillation was lower compared with that of SPT-type Hall thruster.

Performance of a Low-Power Cylindrical Hall Thruster

Recent mission studies have shown that a Hall thruster which operates at relatively constant thrust efficiency (45-55%) over a broad power range (300W - 3kW) is enabling for deep space science missions when compared with slate-of-the-art ion thrusters. While conventional (annular) Hall thrusters can operate at high thrust efficiency at kW power levels, it is difficult to construct one that operates over a broad power envelope down to 0 (100 W) while maintaining relatively high efficiency. In this note we report the measured performance (I(sub sp), thrust and efficiency) of a cylindrical Hall thruster operating at 0 (100 W) input power.

Electron cross-field transport in a low power cylindrical Hall thruster

Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are therefore more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been studied through the analysis of experimental data and Monte Carlo simulations of electron dynamics in the thruster channel. The numerical model takes into account elastic and inelastic electron collisions with atoms, electron-wall collisions, including secondary electron emission, and Bohm diffusion. It is shown that in order to explain the observed discharge current, the electron anomalous collision frequency νB has to be on the order of the Bohm value, νB≈ωc/16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant.