Electron Field Emission from Insulators Relevant to Anode-Initiated Flashover Development

Electron field emission from insulators is believed to contribute to the development of anode-initiated vacuum surface flashover, a breakdown mechanism which fundamentally limits electrical power transfer into vacuum environments. However, in part owing to the difficulty of separating insulator field emission from confounding physical effects, there has heretofore existed no direct experimental confirmation of its existence, and, by extension, no concrete description of its nature. This work reports the first direct measurements of insulator field emission, sampling a large parameter space including variations in pulse width, electric field magnitudes, types of insulator, and surface preparation methods. Emission is shown to be spatially nonuniform and highly statistical in nature, with estimates of the quantity of emitted electrons often varying by orders of magnitude between successive voltage applications to a given sample. Investigation of surface morphology, discussion of electronic states within the polymers, and the extension of previously suggested semiconductor emission phenomenology are used to explore the physical processes involved in insulator emission. The application of these results to the problem of anode-initiated flashover is discussed, both from a physics perspective and in terms of scalability to the insulator stacks of large-scale pulsed power machines, and avenues for future inquiry on the topic of insulator field emission are suggested.