Atmospheric diffuse plasma jet formation from positive-pseudo-streamer and negative pulseless glow discharges

Atmospheric gas discharge is very likely to constrict into filaments and diffuse plasma formation is inefficient in most cases. Developing cost-efficient atmospheric diffuse plasma devices represents a significant challenge for high performance in biomedical decontamination and material processing. Here, we propose an alternative roadmap to produce a diffuse argon plasma jet by expanding and quenching the existing filamentary discharge at the initial or middle stage of streamer development. Possible mechanisms are summarized. With the gas flow velocity comparable to the ion drift one, enhancing ambipolar diffusion near the edge of the positive-streamer channel promotes the radial diffusion of newly-produced electrons, realizing the radial expansion of channel. Weakening electric field in front of the streamer head through head expansion and field offset, prevents the further development of streamer, leading to a positive-pseudo-streamer discharge. Reducing electric field in front of the negative-streamer head through ion compensation, impedes the initial growth of streamer, resulting in a negative pulseless glow discharge. The positive-pseudo-streamer and negative pulseless glow discharges function together to form the diffuse plasma jet. Streamer coupling theory is traditionally used to engineer the generation of diffuse plasmas in the regime preceding filamentary discharge, but this method remains inefficient. Here, an alternative route to cost-efficient diffuse plasma generation is proposed, involving the expansion and quenching of existing filamentary discharge.