Particle Simulation of a Micro ICP Plasma Source for Miniature Ion Thruster

There has recently been an ongoing trend toward decreasing the mass, dimension, and overall complexity of spacecraft. Propulsion systems are no exception. We have developed an electrothermal-type microthruster so far, which can produce a relatively high thrust, and have investigated the thrust performance with an experimental and numerical approach. On the other hand, a microthruster with a high specific impulse, such as ion thruster, is also required. The micro ion thruster presented here uses a cylindrical micro ICP with a flat spiral coil for its ion source, the inner radius and the length of which are 3 mm and 6 mm, respectively. To investigate the plasma characteristics of the source, we have developed a particle simulation model (PIC/MC: Particle-in-Cell/Monte Carlo) for Ar gas as a propellant. The simulation results showed that the electron density obtained was $\sim 10^{17}$ m$^ {-3}$ at an Ar gas pressure of 4 mTorr with an absorbed power of 10 mW, producing a thrust of 50 $\mu$N and specific impulse of 7000 s.