Behavior of streamers in liquids under step voltages in point-plane geometry

An attempt to identify gases generated during the propagation phase of streamers and to measure their volume is presented. The method used consists of producing a large number of streamers (thousands) in liquids (a blend of mono- and dibenzyltoluene, and phenylxylylethane) previously saturated with nitrogen and measuring the total electric charge, from which the mean energy of a streamer can be evaluated. The liquid samples are analyzed afterward by chromatography. This analysis shows the presence of decomposition products such as H/sub 2/, CH/sub 4/. C/sub 2/H/sub 2/, C/sub 2/H/sub 4/, and C/sub 2/H/sub 6/. The different mechanisms that could be involved in the prebreakdown phase are discussed. It is shown that fast streamers need much more energy to propagate, and their propagation seems to be governed mainly by dissociation and ionization in the liquid phase. Slow streamers seem to result from the vaporization of the liquid by heating. These results are confirmed by spectroscopic studies of the light emitted by streamers.<>