Streamer propagation in cyclohexane: influence of a polyaromatic additive

This paper presents an experimental study of the influence of a polyaromatic additive (pyrene) on the propagation of positive streamers in cyclohexane. Experiments were carried out in gaps up to 5 cm over a wide voltage from the inception of streamers up large overvoltage. With pyrene, streamers are composed with a much larger number of branches than in pure cyclohexane. It is observed that the additive leads to slightly lower breakdown voltages, but also induces a large increase of the acceleration voltage (inception threshold of fast streamers). These results are explained by the macroscopic electrostatic properties of streamers, that depend on the streamer shape, and thus on their tendency to form branches. The transition to fast propagation modes occurs at higher voltage when streamers are more ramified.