Abstract: An ion thruster has a hollow cathode assembly including a heater with an inner ceramic sleeve and an outer ceramic sleeve. The outer ceramic sleeve overlies the inner ceramic sleeve with a filament volume between the two sleeves. A wound filament has windings disposed within the filament volume, and a mass of ceramic powder fills the remaining portion of the filament volume between the windings of the filament. A cathode is disposed within the inner ceramic sleeve of the heater. The heater is assembled by preparing the filament and forming it into a wound cylinder, and then encapsulating it and the powder between the inner and the outer ceramic sleeves. The hollow cathode assembly may serve as a portion of a plasma source or as a portion of a charge neutralizer.

Abstract: An ion thruster includes a source of a plasma of ions and electrons, and an ion-optics system located in sufficient proximity to the source of the plasma to extract ions therefrom. The ion-optics system has at least two domed grids arranged in a facing-but-spaced-apart relationship to each other. Each grid has a local reference vector that is perpendicular to the surface of the grid and a reference plane perpendicular to the reference vector. Each of the grids is formed of anisotropic pyrolytic graphite having an “ab” crystallographic plane that lies substantially in the reference plane. In one form, the “ab” crystallographic plane lies coplanar with the reference plane at all locations on each domed grid made of pyrolytic graphite. In another form, the “ab” crystallographic plane has a constant orientation at all locations on the domed grid.