This paper introduces a new concept for the magnetic field in a Hall-effect thruster. The Magnetic Interference Hall Accelerator (MIHA) uses independent magnetic circuit elements to put its peak magnetic field outside its exit plane. As a result, the zone of minimum electron mobility is outside its exit plane, as well as its ion acceleration zone. Wall-effects are reduced, and ion bombardment of the channel wall is moderated. The design and operating behavior of a MIHA prototype is detailed,

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... thrust is determined at several operating conditions. The plasma potential is measured, and verifies an external acceleration zone. Figure 1. Diagram of a Hall-effect thruster. inverse Hall parameter is close to the Bohm value, (ωτ ) −1 = 1/16. 7 However, in those regions where the magnetic field is strongest, the mobility approaches the value expected for classical diffusion. The reason for this behavior is a subject of debate, 8, 9 but it is usually attributed to fluctuations in the potential and/or electron-wall interactions. In either case, anomalous transport mechanisms cause the electron current to exceed its classical value. Anomalous transport reduces the thrust efficiency of the Hall-effect thruster; it reduces the ion current fraction. Less obvious though, is its impact on the Hall thruster's operational life. The Ion Energy Distribution Function (IEDF) is determined by the electrostatic potential, and again, the electron mobility. As a consequence, it is difficult to predict the rate that ions will collide with the ceramic channel. Since highenergy ion bombardment limits the life of the HET, it is difficult to design for increased life. Furthermore, optimizing for increased life is made more difficult by the location of the peak B. In the conventional Hall accelerator, the ion acceleration zone is near the peak magnetic field. Due to the design of the magnetic circuit, the peak magnetic field is inside the ceramic channel or very near its exit. As a result, it is guaranteed that high-energy ions will impact the channel wall and limit the life of the conventional Hall accelerator. This paper describes a concept for the magnetic field in the Hall-effect thruster that could simplify anomalous transport, reduce erosion due to ion bombardment, and lead to improved Hall thruster design. The Magnetic Interference Hall Accelerator, MIHA, pushes the minimum electron mobility outside the channel. As a result, the ion acceleration zone is outside the channel. Since the discharge is sustained in vacuum, high-energy ion bombardment of the ceramic channel is moderated, and electron-wall interactions are reduced. Since the electron mobility is "simplified", the design could allow for greater optimization of the magnetic field. The MIHA magnetic circuit is discussed, as well as a prototype design. The prototype is found to operate like a conventional Hall accelerator, and display several typical behaviors: the "breathing mode" oscillation at moderate discharge power, an increase in the discharge current with an increase in voltage, and a decrease in discharge current with an increase in the magnetic field. Unlike a conventional accelerator though, the wall material has a weak impact on the discharge. To demonstrate our findings, the general operating characteristics of a prototype MIHA thruster are detailed. Current-voltage characteristics, discharge current fluctuation spectra, and thrust measurements are provided. To demonstrate the movement of the acceleration zone to a point outside the exit plane, plasma potential measurements are provided.