Expansion of stable operation range of a Hall thruster

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A Hall thruster is one of the most promising electric propulsion systems. However this thruster has a serious problem : discharge oscillation. In our previous research, we found that the discharge is stabilized by propellant non-uniform feeding. In order to comprehend the mechanism of this method, we developed a numerical simulation code and observed the plasma in the thruster. As a result, we found that the stabilization was realized by the increment of the electron mobility in the thruster. However, this non-uniform feeding method decreases the thrust efficiency. This decrement of the efficiency is caused by two phenomena ; one is increment of the ion loss to the wall ; the other is increment of the electron current. In order to solve the first problem, we develop a wall guard made of an insulator. On the other hand, the 2^<nd> problem is difficult to solve because the electron current increases when the electron mobility increases. Therefore, we optimized a magnetic topology in the thruster in order that the electron mobility increases only in a part of the thruster. As a result, the discharge stabilization was realized without the decrement of the thrust efficiency.