Behavior of prebreakdown emission centers with 200-kv 100-ns pulses applied to a vacuum gap

Using an electron-transparent anode (titanium foil), the behavior of prebreakdown emission centers on a cathode made of 12X18H10T stainless steel is studied for the case of vacuum gap excitation by 100-ns-wide voltage pulses with an amplitude of 200 kV. To raise the working electric field to 1 MV/cm or higher, the electrodes are preprocessed by a low-energy high-current electron beam in the surface melting mode. It is found that prebreakdown emission centers may be stable and unstable. The stable ones arise at an electric field strength of 0.4–0.6 MV/cm, and their activity grows with voltage up to breakdown. As the electric field increases, new unstable emission centers occur at sites other than those observed at the previous voltage pulse. Reasons for the appearance of unstable emission centers are discussed.