Simulation of Electrooptical Measurements of Prebreakdown Electric Fields in Polar Liquids Near Cathode Streamer

This article is devoted to the analysis of electrooptical studies of the prebreakdown stage in water and nitrobenzene in the submicrosecond range and the modeling of these processes. Computer simulation showed that in water at an unchanged permittivity $\varepsilon $ = 80, the field strength at the head of the cathode streamer did not exceed $E$ = 2 mV/cm. Considering the nonlinearity of the permittivity $\varepsilon $ = $\varepsilon (E)$ made it possible to estimate the strength of the same field as $E$ = 2.4–3.1 mV/cm. These values are close to the estimate of the dipole saturation strength in water ( $E_{S}$ = 3 mV/cm), and consideration of saturation does not lead to a sharp increase in the field. It should be emphasized that, in the case of an anode streamer, the calculated field strength was much larger than $E_{S}$ , which led to an anomalous increase in the field strength when the nonlinearity was taken into account. An electrooptical experiment in nitrobenzene was also analyzed. It was computed that the value of the field strength in front of the head of the moving cathode streamer is 2.7 mV/cm. Taking into account the possible saturation of dipoles leads to an $E_{\mathrm {S}}$ of $\sim $ 4 mV/cm. The closeness of the obtained values in water and nitrobenzene indicates the similarity of the mechanisms of formation of slow cathode streamers in various liquids.