In this work, a force measurement system is proposed to measure the thrust of plasma microthruster with thrust magnitude ranging from sub-micro-Newtons to hundreds micro-Newtons. The thrust measurement system uses an elastic torsional pendulum structure with a capacitance sensor to measure the displacement, which can reflect the position change caused by the applied force perpendicular to the pendulum axis. In the open-loop mode, the steady-state thrust or the impulse of the plasma micro-thruster can be obtained from the swing of the pendulum, and in the closed-loop mode the steady-state thrust can be obtained from the feedback force that keeps the pendulum at a specific position. The thrust respond of the system was calibrated using an electrostatic weak force generation device. Experimental results show that the system can measure a thrust range from 0 to 200 μN in both open-loop mode and closed-loop mode with a thrust resolution of 0.1 μN, and the system can response to a pulse bit at the magnitude of 0.1 mN s generated by a micro cathode arc thruster. The background noise of the closed-loop mode is lower than that of the open-loop mode, both less than 0.1 / mN Hz in the range of 10 mHz to 5 Hz.

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Hall thrusters have been widely used in orbit correction and the station-keeping of geostationary satellites due to their high specific impulse, long life, and high reliability. During the operating life of a Hall thruster, high-energy ions will bombard the discharge channel and cause serious erosion. As time passes, this sputtering process will change the macroscopic surface morphology of the discharge channel, especially near the exit, thus affecting the performance of the thruster. Therefore, it is necessary to carry out research on the motion of the sputtering products and erosion process of the discharge wall. To better understand the moving characteristics of sputtering products, based on the hybrid particle-in-cell (PIC) numerical method, this paper simulates the different erosion states of the thruster discharge channel in different moments and analyzes the moving process of different particles, such as B atoms and B + ions. In this paper, the main conclusion is that B atoms are mainly produced on both sides of the channel exit, and B + ions are mainly produced in the middle of the channel exit. The ionization rate of B atoms is approximately 1%.

The definition of a magnetic shuttle is introduced to describe the magnetic space enclosed by two magnetic mirrors with the same field direction and high mirror ratio. Helicon plasma immersed in such a magnetic shuttle (mirror ratio 5) that can provide the confinement of charged particles is modeled using an electromagnetic solver. The perpendicular structure of the wave field along this shuttle is given in terms of stream vector plots, showing a significant change from midplane to ending throats, and the vector field rotates and forms a circular layer that separates the plasma column radially into core and edge regions near the throats. The influences of the driving frequency (f = 6.78 MHz–40.68 MHz), plasma density (nemax = 1016 m−3 to 1019 m−3), and field strength (B0max = 0.017 T–1.7 T) on the wave field structure and power absorption are computed in detail. It is found that the wave energy and power absorption decrease for increased driving frequency and reduced field strength and increase significantly when the plasma density is above a certain value. The axial standing-wave feature always exists, due to the interference between forward and reflected waves from ending magnetic mirrors. Distributions of wave energy density and power absorption density all show a shrinking feature from midplane to ending throats, which is consistent with the nature of the helicon mode that propagates along field lines. Theoretical analysis based on a simple magnetic shuttle and the governing equation of helicon waves shows consistency with computed results and previous studies. This hypothetical work is a valuable to guide the helicon physics prototype experiment, which is designed for the fundamental wave–particle interaction study in helicon plasma, to achieve high plasma density and energy absorption efficiency.

As a novel propulsion technology, ultrasonic electric propulsion is mainly applied to micro-satellite platforms (<10 kg). In this work, effects of vibration frequency and typical operating conditions on extraction process of charged droplets in ultrasonic electric propulsion are investigated by an ultra-high speed imaging technique. A long-distance microscope coupled with an ultra-high speed camera (NAC HX-6) is also used. A solution of formamide and lithium chloride is employed as propellant. Experimental results show that mean diameters of charged droplets are 43.3 ± 4.2 µm (120 kHz), 76.2 ± 5.8 µm (60 kHz), and 101.4 ± 7.1 µm (25 kHz), respectively. Besides, the theoretical diameter values are calculated, which are close to experimental ones and both values decrease with the increase of vibration frequency. Meanwhile, experimental results indicate that the diameter of charged droplets increases as the propellant flow rate rises, and such effect is obvious when the flow rate is ranging from 3 to 10 ml/h. It is also found that charged droplets are not uniformly accelerated and their motion directions are also divergent.