The fundamental physics underlying non-thermal plasmas produced by pulsed discharges at atmospheric pressure is of great interest, especially considering the technological and environmental applications of these plasmas. Discharge dynamics is highly dependent on experimental conditions, such as the propagation medium and the voltage polarity. Herein, we investigate pulsed nanosecond discharges produced by a negatively polarized voltage in a medium of air in-contact with water. Electrical and optical characterization of the discharges is achieved using the appropriate probes and ultrafast imaging, respectively. The time-integrated images are acquired under varying conditions of applied voltage, and the discharge emission is shown to be a homogenous disk at voltages between −4 and −15 kV. When the voltage is increased (absolute value) beyond −15 kV, the homogeneous emission is superimposed with filaments. The temporal evolution of the discharge emission (1 ns integration time) shows that it remains homogeneous and has a ring-like ionization front. At higher voltages and during the falling period, the discharge reignites as filaments that significantly elongate and decrease in intensity until extinguishment. A comparison of discharge emissions obtained at positive and negative polarities indicates that the features of both may be controlled by manipulating the space charge formation dynamics.

在大气压力下由脉冲放电产生的非热等离子体的基本物理原理引起了人们的极大兴趣，特别是考虑到这些等离子体的技术和环境应用。放电动力学高度依赖于实验条件，例如传播介质和电压极性。在本文中，我们研究了在与水接触的空气介质中由负极化电压产生的脉冲纳秒放电。分别使用适当的探头和超快成像来实现放电的电学和光学表征。在所施加的电压的变化条件下获取时间积分图像，并且放电发射被示为在-4和-15kV之间的电压下的均匀盘。当电压增加（绝对值）超过-15 kV时，均匀发射与灯丝叠加。放电发射的时间演化（积分时间为1 ns）表明它保持均匀并且具有环状电离前沿。在较高的电压下和下降期间，放电会重新点燃，细丝会明显伸长并强度降低，直至熄灭。对正极性和负极性获得的放电发射的比较表明，可以通过操纵空间电荷形成动力学来控制两者的特征。放电重新点燃为细丝，细丝会明显伸长并降低强度，直至熄灭。对正极性和负极性获得的放电发射的比较表明，可以通过操纵空间电荷形成动力学来控制两者的特征。放电重新点燃为细丝，细丝会明显伸长并降低强度，直至熄灭。对正极性和负极性获得的放电发射的比较表明，可以通过操纵空间电荷形成动力学来控制两者的特征。