Laboratory investigations of pulsed RF plasmas relevant to CW arc pluming at high-power aerials. Part 2: Relevance of scale-model studies based on pulsed RF techniques

The paper describes experiments which extend the observations of RF breakdown events in nonuniform fields reported in Part 1 of the paper. In particular, emphasis is given to examining the relevance of laboratory observations on pulsed RF discharges to the understanding of the `pluming¿ phenomenon occurring under CW conditions at high-power aerial arrays. This is achieved by examining the effects of various scaling factors on the breakdown characteristics using both scaled sphere-to-plane and scaled toroid-to-plane geometries. It is shown how the intrusion of objects with needle-point geometries can lead to dramatic reductions in the critical electric fields needed to initiate the unwanted `pluming¿ phenomeonon.