抄録
Low-power Hall thruster flowfields were calculated using a simple one-dimensional model to understand plasma characteristics and ion acceleration processes and to predict thruster performance. The influences of magnetic field strength and acceleration channel length were mainly examined. The thruster model for calculation is the THT-IV low power thruster developed in Osaka University. Generally, ions were produced in an upstream region from the anode to some axial location of the acceleration channel, and then they were intensively accelerated in a region downstream just from the ionization region. With too short channel, ionization began downstream just from the anode, and then ion acceleration also occurred in the same region, resulting in poor ion flux and low thrust performance. In large channel length, the channel was long enough to produce a fully-ionized plasma, and efficient ion production and acceleration occurred. When the magnetic field strength increased in the channel, ionization occurred in a more upstream region, and ion acceleration began in the same region; that is, ionization and acceleration overlapped in the relatively long region. On the other hand, with a weak magnetic field ion production and acceleration, intensively and efficiently, occurred in their thin regions. Furthermore, we tried to include unclear anomalous electron diffusions by changing a Bohm diffusion coefficient at each high magnetic field strength in order to fit a calculated performance to the measured one. The calculated discharge current almost equaled the measured one, and the thrust characteristic also agreed well with the measured one.
