Initiation of breakdown in bubbles immersed in liquids: pre-existed charges versus bubble size

In this paper we report on results from a computational investigation of streamer evolution in bubbles immersed in liquids. We show that avalanche-to-streamer transition and streamer formation in the uniform electric field are determined by the applied external field, the parameter pR (pressure times bubble size), as well as by the location and amount of initial free charges inside the bubble. We found that streamers are not formed in bubbles with a rather small size, unless pre-existed or injected charges are large enough to initiate the breakdown. The present investigation relates the bubble size and the applied field to the minimal possible amount of charge in a bubble.