Microwave Corona Breakdown in Strongly Inhomogeneous Fields
Paper in proceedings, 2009
We investigate the main physical properties of microwave corona breakdown in strongly inhomogeneous electric fields. The focus is put on numerical and approximate analytical calculations of the breakdown threshold in an exponential ionization profile, which is the basic form of the ionization profile caused by the field enhancement around irregular and curved conducting objects. The breakdown threshold is a value associated with a certain plasma density profile. We explain the major characteristics of the density profile, its dependance on pressure and the interplay of diffusion and attachment. For lower pressures the diffusion distributes the electrons from regions of high ionization frequency to regions of weak ionization, where the attachment acts as a sink. For high pressures the diffusion becomes negligible and the breakdown threshold is set by the equality of the ionization and attachment frequencies in the high field region.