Effect of anode gas liberation on prebreakdown currents in vacuum

The effect on prebreakdown currents in vacuum of different gases introduced in the vessel is compared with the influence of gas desorbed from the anode surface. The experiments show that gases such as CO and N₂ reduce the pre-exponential factor in the Fowler-Nordheim equation. With anodic gas desorbed there may be a feedback to the emission current resulting in an apparent change of the slope of the Fowler-Nordheim plots. This can cause large apparent field enhancement factors beta , thus explaining unrealistically high values for metallic field emitters.