Abstract
Electrons may be removed from the gas between a pair of plane parallel electrodes by being swept out by the field, by recombination, by attachment or by diffusion. At high enough frequencies diffusion is the most likely mechanism. This can be tested quantitatively by plotting the relation between EΛ and pΛ (E=electric field required to produce breakdown, p=gas pressure, Λ=`diffusion length' for the gap). It can also be tested qualitatively by observing the decrease of E with increasing gap width d. The electrodes must be properly profiled to avoid breakdown beginning at the edges.
The necessary observations of breakdown voltage, electrode spacing, electrode size and gas pressure are made for air, hydrogen, nitrogen and neon, at 9.5 Mc/s. The (EΛ,pΛ) plot gives a single line for ultra-high-frequency breakdown, and E decreases with increasing d in accordance with diffusion theory. Values of the ionizing efficiency η are calculated.