New types of electron beam generated electric discharge in dense gases: A “Fountain” and a “Thunderstorm”

The paper presents qualitative ideas and modeling resultson dynamics ofplasmas generated in air and other gases by injecting beams of high-energy electrons. Two distinct regimes are found, differing in a way that the excess negative charge brought in by the ionizing electron beam is removed. In the first regime, called a “fountain”, the charge is removed by the back current of plasma electrons towards the injection foil. In the second, called a “thunderstorm”, a substantial cloud of negative charge accumulates, and the increased electric field near the cloud causes a streamer to strike between the cloud and a positive or grounded electrode, or between two different clouds created by two different beams. A quantitative analysis, including electron beam propagation, electrodynamics, charge particle kinetics, and a simplified heat balance, is performed in 1D approximation. Effects of non-one-dimensionality are discussed qualitatively.