Controlling branching in streamer discharge by laser background ionization

Takahashi, Eiichi*; Kato, Susumu*; Sasaki, Akira; Kishimoto, Yasuaki*; Furutani, Hirohide*

Positive streamer branching in atmospheric argon gas was controlled by a KrF laser irradiation. This laser irradiation changes the amount of background ionization before the streamer discharge. Initial electron density formed by the KrF laser was evaluated by measuring ionization current. Characteristic "feather like" branching structure was observed and was suppressed only for the irradiated region. The threshold of ionization density which can influence to the branching was evaluated to be 510/cm. This suppression behavior was explained by the relation between a size of avalanche head and mean initial electron distance. These experimental results support the origin of the feather like structure comes from the branching model of Loeb-Meek that is probabilistic merging of individual avalanches.