Theoretical model of suppression of electron instability in hall thrusters by boundary feedback system

Abstract

Among plasma instabilities in Hall thrusters, large-scale electron instability of Rayleigh type holds one of the main positions. Its arising brings about redistribution of the electrical field in the acceleration layer that can increase losses of ions on the walls of the thruster. In the paper, the possibility of suppression of this instability by a boundary feedback system (BFS) is theoretically considered. The analysis is carried out with the use of hydrodynamic approximation. The eigenvalue problem is solved in assumption that the BFS creates an azimuthal distribution of the electrical potential on the surface of the anode, which is a function of the perturbation electrical field near the anode. From the solution of the eigenvalue problem, it follows that for the suppression of the electron instability, the transformation coefficient of the BFS should lie in the region limited by both a lower value and upper value, which depend on the length of the wave and distance between the anode and a maximum of the drift velocity.

Detection of the magnetic field parameters influence on discharge current fluctuations and optimal operation modes of the hall thruster

“…The proposed approach is significantly different from most known works [1,2,[4][5][6][7]11] in this scientific field. In them, the main attention is paid to the formal construction of mathematical models of fluctuations of plasma parameters in Hall thrusters and mathematical modeling without specific reference to the integral parameters of the thruster -thrust, specific impulse, efficiency.…”

“…On the basis of a critical analysis of existing works [1][2][3][4][5][6][7][8][9][10][11] tackling the problem of the occurrence of significant discharge current fluctuations in Hall thrusters, it is shown that their formation leads to a significant decrease in the main values of the thruster parameters -thrust, specific impulse, and efficiency. Thus, this issue has not yet been solved, and all Hall thruster developers face this problem.…”

“…However, the proposed recommendations did not look like a certain procedure that provides a solution to the problem of discharge current fluctuations. In work [2], in order to reduce the amplitude of fluctuations of the plasma parameters, it was proposed to place electric probes in the acceleration channel of the thruster, to which the voltage was applied in the opposite phase to the fluctuations of the discharge current. The effectiveness of the proposed procedure turned out to be quite low, which was associated with the problems of placing the probes in the channel and the issues related to matching the phases of fluctuations of the plasma parameters with the voltage on the probes.…”