Requirements for optimal performance and the consequences of using toroidal shaped electrodes in multichanneling switches

In many multi-channel switch designs, toroidal shaped electrodes are used to form the cascade breakdown section of a closing switch. Advantages of using toroidal electrodes include providing evenly graded electric fields from one gap to the next during charging and shaping the electric fields away from the mechanical connections that hold the electrodes in place. Often the inductance of arc channels is considered, but the inductance of electrodes must be considered when evaluating a multi-channeling switch. In typical geometries, electrode inductances are one to two orders of magnitude larger than of the inductance of the arcs themselves and may not be neglected. It is generally assumed that achieving more channels ad infinitum is desired to produce a low switching inductance. Calculations suggest this is not necessarily the case. Calculations also suggest that channel distribution, not simply the number of channels, strongly affect the operating inductance of the switch. For example, if one gap in the cascade section does not multi- channel, the bottleneck caused by this will dictate switch inductance, even if every other gap closes with many channels. Suggestions and supporting calculations are presented for minimizing arc inductance and electrode inductance of a toroidal arrangement. There must be the same number of channels from gap to gap to minimize the effects of arc inductance. The distribution of channels must be identical from gap to gap to minimize electrode inductance and azimuthal current flow on the electrodes with respect to the axial direction of the cascade section. Future work on optimizing fast, multi-channeling switch electrodes at the University of Missouri terawatt test stand (MUTTS) will be introduced.