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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.

Ionic wind has been widely used in the fields of flow control, heat cooling, thruster, and so on. In this work, an investigation of ionic wind under different magnetic field configurations is processed. By changing the position relationship between the electrode and the magnetic field, the magnetic field configuration in the discharge region is modified. With the injection of different magnetic field configurations to the discharge region, the amplitude of Trichel pulse is decreased, and the pulse frequency is increased. Besides, the ionic wind velocities’ distribution is deflected and the electrical-to-kinetic energy conversion efficiency is enhanced. The mechanism is analyzed by considering the movement path of particles in the ionization region and drift region under different magnetic field configurations. These results illustrate that the magnetic field configuration would be a method to adjust the direction and improve the electrical-to-kinetic energy conversion efficiency of ionic wind. This method provides a feasible way to regulate the performance of ionic wind without additional energy consumption.

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.

A time-resolved optical measurement method is applied to examine the gas discharge process inside the discharge channel during a Hall thruster ignition. The results show that the excitation and ionization processes in the working gas begin near the exit of the channel and then propagate upstream along the channel. The change in energy of electrons moving toward the anode leads to the alternating dominance of ionization and excitation processes, which is the main reason for the changes in light intensity in different regions of the channel during the thruster startup.

In this paper, we investigated how magnetic field influenced Trichel discharges by performing a statistical analysis of the current amplitude and pulse interval of Trichel discharges at various magnetic field intensities. Experimental results indicate that the amplitude and pulse intervals always obey lognormal functions. As the magnetic field intensity increased, the current amplitudes almost decreased and the pulse intervals increased significantly. The paths of negative ions produced in the Trichel discharge were curved by the magnetic field, weakening their shielding effect. A magnetic field can enhance the possibility of Trichel discharge with small energy release. Moreover, the characteristics of the Trichel pulse could be controlled with only magnetic field and without any energy addition.

The effect of the tube materials on the characteristics of an argon atmospheric pressure cold plasma jet is investigated through a single-electrode configuration driven by ac power supply. Two kinds of tube materials, Pyrex glass and 95% alumina ceramic, are applied in the experiments. Results show that, with the change of tube material, both the discharge current and the plume length are barely affected, whereas the plume volume exhibits an enormous distinction. In comparison with the results obtained in the ceramic tube, the peak volume can increase by 65% in the glass tube, while the increment of the peak length is only 2%. Through the analysis, the difference in the thermal conductivity between the glass and the ceramic is regarded as the main reason.

Surrounded with distilled water, a classic argon atmospheric pressure discharge device is employed to study the propagation of the plasma. By examining the high-speed photographs, a phenomenon of interruption is found at different flow rates. At 3 L/min, the interruption appears only at the downward stage of the applied voltage after the plasma jet has run into the ambient air. As the flow rate reaches up to 15 L/min, however, the interruption can be obtained at a rather low applied voltage and exists in both the upward and downward stages. It is believed that the active species flowing from the upstream to the downstream region may be the main cause.

This paper illustrates a repetitive nanosecond volume discharge in the airflows at different velocities. The plasma images presented here show that the volume discharge modes vary with the changes of airflow speeds, and a diffuse and homogeneous volume discharge occurs at the airflow speed of 30 m/s. The discharge is promoted in the airflows at a lower velocity, and the discharge tends to be inhibited at a speed to 40 m/s. However, the inhibited mode disappears at higher repetitive frequency of the pulse.