Particle‐in‐cell simulation of the effect of curved magnetic field on wall bombardment and erosion in a hall thruster

Abstract

A curved, convex towards the channel bottom magnetic field is an important feature of an advanced Hall thruster that allows confining the plasma flow in the channel center, reducing the divergence angle of the ejected ion beam, and improving the discharge performance. In this article, the discharge behaviour of a Hall thruster in magnetic fields with different degrees of curvature is simulated with a particle‐in‐cell numerical method, and the effect of curved magnetic field on the ion bombardment and wall erosion and the associated mechanisms are studied and analysed. The results show that, as the curvature of the magnetic field increases, the propellant ionization becomes more confined at the channel center, the potential drop inside the channel decreases, and the acceleration region shifts outside the channel, which lead to the attenuation of the ion energy bombarding the wall and the deviation of the bombardment angle from the optimal sputtering angle. Conversely, the ion flux bombarding the wall near the channel exit increases. Nevertheless, the bombardment energy and angle are the dominant factors for the wall erosion, and the wall erosion rate clearly decreases with the increasing curvature of the magnetic field. These findings are closely related to the behaviour of electron conduction under a curved magnetic field; the relevant mechanisms are clarified in this article.

Influence of neutral gas supply position on wall erosion of Hall thruster studied by particle-in-cell simulation

“…Meanwhile, it can be found that the peak erosion rate under the lower and middle gas supply conditions is relatively close, and that the peak erosion rates of the inner and outer walls are about 6.3 mm/kh and 10.7 mm/kh respectively. Considering the order of magnitude, it is consistent with previous literature reports [32]. The peak erosion rate under the upper gas supply condition is relatively low, and the peak erosion rates on the inner and outer walls are 4.2 mm/kh and 7.5 mm/kh respectively, which are 33.3% and 29.9% lower than those under the other two conditions.…”

“…In terms of the angle dependence function, we use the Pencil model [8,32,35]; its function form is shown in equation (7). Here, the correlation coefficients are based on the erosion experimental results of BN, c 1 = 0.53, c 2 = 2.61, c 3 = 1.54 [32]. The distribution of the angular sputtering coefficient is shown in figure 3.…”

Review of Plasma-Induced Hall Thruster Erosion

“…Further plasma discharge model fidelity was attained with the advent of particle-in-cell (PIC) models that solve the equations of motion for super particles representing groups of individual particles. Like fluid modelers, most authors [37,[93][94][95][96][97][98] implementing PIC models for erosion calculation relied on simple theoretical fits of experimental data to determine sputtering yield. However, Cheng et al [99] developed a variation of the Yamamura and Tawara model based on physical considerations, and Cao et al [100] utilized the Huygens wavelet method to predict surface evolution.…”