Current sheet formation in planar inductive pulsed plasma thrusters

Abstract

Formation of a well-defined, magnetically impermeable current sheet is central to the operation of pulsed plasma thrusters. Existing scaling laws for inductive pulsed plasma thrusters, however, are primarily derived from models that either overlook or greatly simplify the current sheet formation process. Data obtained from a compact, low discharge energy planar inductive pulsed plasma thruster were used to gain insight into the fundamental physics governing current sheet formation in these devices. It was found that the maximum inductive coupling and current density in the sheet scaled with the logarithm of the ratio of the resistive diffusion to ionization timescales. The ratio of these timescales was shown to describe the combined role of diffusion and ionization in influencing the electron population within the current sheet. When the ionization timescale was fast relative to the diffusive timescale, the thruster discharge was found to be much more effective at concentrating current in the sheet. A connection between the strength of the current sheet and the thruster design and operational parameters is derived and used to identify the parameter space over which efficient thruster operation is possible.