The Use of Boron Nitride for Improved Cold-Cathode Electron Field Emission Technology

Low-power Hall thrusters offer potentially important advantages for certain military applications but issues of lifetime and efficiency degradation at lower powers are issues hindering its utilization. A factor impacting efficiency is that the state-of-the-art techniques for electron generation used for neutralization (such as hollow cathodes operating on the same propellant as the thruster) do not scale down in mass, power, and propellant consumption as readily as the miniaturized thrusters themselves. This proposal out-lines the development of a field emitter cathode utilizing the chemically inert, tough, low work-function ma-terial Boron Nitride (BN) and corresponding testing of a low power Hall thruster to better understand cath-ode integration. The desirable characteristics of leading electron emission materials such as molybdenum tips and Carbon Nanotubes (CNT) are well known. However, the chemical reactivity of these materials, especially carbon, in oxidizing environments presents significant limitations with respect to their applica-tion in Hall thrusters and other propulsion technologies (both operational and handling factors). The propel-lantless nature of this approach eliminates the neutralizer as a degrading factor for efficiency and its supe-rior material properties offer the possibility of long lifetime operation.