Pressure dependence of plasma structure in microwave gas breakdown

摘要

Recent studies of 110 GHz microwave discharges in air at atmospheric pressure have demonstratednformation of a large array of quarter-wavelength-spaced plasma filaments. Here we presentnmeasurements showing that as pressure is decreased from atmosphere to a few torr, the dischargentransitions from a well-defined array to a smeared-out array and finally to a diffuse plasma. Despitenthe distinct nature of breakdown phenomena at high microwave frequencies, the pressurendependence of the breakdown threshold field is seen to follow a Paschen-type curve. Data for air andnargon at 110 GHz are compared with previous low-frequency data. © 2010 American Institute ofnPhysics. u0004doi:10.1063/1.3462320