Field electron emission in the atmospheric pressure range

Field emission is a well-known technology for generating electrons under vacuum conditions. Here we assess whether gated silicon field emitter microstructures, originally developed for use in space, can ionise air for electroaerodynamic propulsion and other applications. Electron range in air is compared to breakdown voltage over the atmospheric pressure range, to evaluate whether an operational region exists for which the geometry permits electrons to escape and ionise, whilst keeping the voltage low enough to avoid breakdown. An operational region is identified between 500–100 V for pressures corresponding to 0–20 km altitude. This offers low-power and low-mass operation in comparison to existing ionisation technologies. Carbon nanotube field emitters may offer enhanced performance over the silicon emitters. Field electron emission represents a new air ionisation technology which may be appropriate for light-weight, high-altitude aircraft propulsion.