Electric expansion of the avalanche heads during the formation of high pressure pulsed avalanche discharges

A homogeneous pulsed high-pressure discharge can be created by strong preionization. The preionization mechanism must then start a sufficient density of avalanches so that their heads overlap before the critical stage at which streamers are formed. Earlier investigations of this ignition mechanism have been based on the assumption that the avalanche heads expand purely by diffusion. We propose here that the local electric field E-R, from the negative charges in the avalanche heads themselves, will enhance the expansion rate. A numerical model using simplified assumptions show that this electric expansion might decrease the required preionization density dramatically, possibly by more than two orders of magnitude. More detailed investigations are recommended in view of the importance of this type of discharges.