大气压直流激励空气等离子体羽发光的时空演化

在针-针电极结构的放电装置中以环境空气作为工作气体，大气压下产生了刷形等离子体羽。尽管使用的是直流电源，但放电发光呈现出脉冲性质，发光脉冲频率几乎不受气体流速的影响，但与电源输出功率成正相关关系。等离子体羽的长度与气体流速或者电源功率成正相关关系。通道出口附近，777.4 nm的氧原子谱线强度分布是非对称的，阴极附近处的谱线强度高于阳极附近处的谱线强度。远离通道出口位置，谱线强度逐渐趋于轴对称分布。电学特性和10 μs曝光高速影像结果表明，空气等离子体羽实际上是由拱形放电丝在远离通道出口的运动过程中叠加而成，同时放电从弧光放电丝向均匀辉光放电转化。

Spatio-Temporal Evolution of Air Plasma Plume Driven with a Direct-Current Voltage at Atmospheric Pressure

Using a plasma jet to compose two needle electrodes,a brush-shaped plasma plume is generated at atmospheric pressure with ambient air used as working gas.Although a direct-current power supply is used,the discharge shows a pulsed characteristic.The emission pulse frequency keeps constant with changing the gas flow rate,but it increases with the increasing of the output power.The length of the plasma plume increases with the increasing of the gas flow rate and the output power.According to the spatially resolved measurement of light emission (O Ⅰ,777.4 nm),the emission profile is non-symmetric near the outlet.The intensity near the cathode is greater than that near the anode.It tends to be near-symmetric with the location away from the outlet.The plume is analyzed in terms of sustaining voltage,evolution of current,light emission and fast photography of 10 μs.It can be found that the brush-shaped plume is actually a temporal superposition of moving arched discharge filament.As it moves away from the channel outlet,the discharge evolves from arc-shaped filament into a normal glow in one discharge cycle.