Measurement of a force imparted to a magnetic nozzle by electron diamagnetism

Abstract

An electron-beam plasma source consisting of a hot filament is installed near the throat of the magnetic nozzle immersed in a vacuum chamber. The low plasma potential of about 5 V is formed over the region of the measurement in the weakly ionized and partially magnetized argon plasma expanding along a magnetic nozzle; an electric field is much smaller than a pressure gradient, providing a force balance between the electron pressure and the magnetic pressure. This condition leads to a negligible electron E × B drift current and nearly pure diamagnetism. Measurement of the force exerted on the magnetic nozzle is performed by attaching only the solenoid to a pendulum thrust balance, clearly demonstrating the presence of the force induced by the purely diamagnetic current, which is the major contributor to the thrust generation in the magnetic nozzle plasma thruster. This indicates that the thrust can be generated only by the electrons expanding in the magnetic nozzle.