Experimental Evaluation of Neutralization Phenomena with Visualized Ion Thruster

In order to evaluate neutralization phenomena of ion thrusters, ion beams and plasmas were observed with a two-dimensional visualized ion thruster and a miniature microwave neutralizer. This neutralizer was appropriated for this study because of the low consumption power, the low carrier gas flow rate, the low luminescence and the wide controllable range of emission current. Through the observation and electrical measurements, it was confirmed that imperfect neutralization affected the ion beam optics, caused stagnation of emitted ions, refluxed the ions into the grid system, and increased space potential in the downstream region resulting in the formation of “virtual anode.” Since the shapes of observed virtual anodes were semicircular, it was also confirmed that twoor three-dimensional evaluation is necessary for the more detail understandings of neutralization phenomena.