Fundamental Study of Atmospheric Rf Breakdown at 3.3 MHz

RF breakdown at a frequency of particular relevance to ionospheric heating-3.3 MHz, close to the low end of the applicable frequency range-is studied at centimeter sized gap distances and compared to literature for small gaps. Paschen's famous DC breakdown study utilizing two brass spheres of radius 1 cm was recreated following the original procedure, from which the data was used to compare to a study of RF breakdown. Through testing it was found that brass as an electrode material exhibits a large standard deviation in breakdown voltage and as such stainless-steel Bruce profile uniform electric field electrodes were substituted. Steel's resistance to surface ablation provided for extremely low standard deviation of measurements and hence good repeatability. Additionally, unlike brass, steel is not contaminated through reaction with gaseous elements such as carbon, oxygen and nitrogen. Electrodes were polished to remove any field enhancements and cleaned of polishing compound such that dielectric inclusions were largely avoided.