Secondary Electron Trajectories in High-gradient Vacuum Insulators with Fast High-voltage Pulses

Vacuum insulators composed of alternating layers of metal and dielectric, known as high-gradient insulators (HGIs), have been shown to withstand higher electric fields than conventional insulators. Generally, vacuum insulator failure is due to surface flashover, initiated by electrons emitted from the triple junction. These electrons strike the insulator surface and produce secondary electrons, which also strike the insulator surface to create more secondary electrons and lead to avalanche. Magnetic field from the external sources, the high-current electron beam, the conduction current in the transmission line or the displacement current in the insulator can deflect primary and secondary electrons’ trajectories either toward to or away from the insulator surface, and hence affect the performance of the high-voltage vacuum insulator. The displacement current effects are particularly interesting for short pulse applications. This paper presents the displacement current effects with various short applied voltage pulses on performance of high-gradient insulators. Optimal HGI configurations will also be discussed.
Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan