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

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.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.

流光耦合理论传统上用于在丝状放电之前的阶段设计产生弥散等离子体，但该方法效率仍然不高。在此，提出了一种经济高效地产生弥散等离子体的替代途径，即对现有的丝状放电进行扩展和猝灭。大气气体放电很容易收缩成丝状，在大多数情况下弥散等离子体的形成效率较低。开发经济高效的大气弥散等离子体装置，对于实现生物医学净化和材料加工的高性能而言，是一项重大挑战。在此，我们提出一种替代路线，通过在流光发展的初始或中间阶段对现有的丝状放电进行扩展和猝灭，来产生弥散氩等离子体射流，并总结了可能的机制。当气体流速与离子漂移速度相当时，增强正流光通道边缘附近的双极扩散，可促进新产生电子的径向扩散，从而实现通道的径向扩展。通过流光头部扩展和场偏移来削弱流光头部前方的电场，可阻止流光进一步发展，从而产生正伪流光放电。通过离子补偿降低负流光头部前方的电场，会阻碍流光的初始增长，进而产生负无脉冲辉光放电。正伪流光放电和负无脉冲辉光放电共同作用，形成弥散等离子体射流。