In this paper, the helium plasma jet generated by micro-hollow cathode discharge (MHCD) was studied. The MHCD was driven by a square-wave pulsed power source, and the characteristics of discharge and plasma jet were measured experimentally. The influences of the gas flow rate on the MHCD and the plasma jet were investigated. And the propagation mechanisms of the plasma jet were analyzed. The results show that within 100–1000 sccm of the gas flow rate, the breakdown delay time of the MHCD increases with the helium flow increasing. It is considered that the gas flow affects the density of seed electrons and thus the breakdown delay time. With the helium flow rate increasing, the whole plasma jet length increases firstly and then decreases. A detailed investigation shows that during one discharge pulse, two distinguishable propagation processes of the plasma jet are observed. It is found that the jet of the first stage is formed during the rising edge of the current pulse, while the other is generated after the discharge current becomes stable. The propagation velocity of jet in the first stage is on the order of several km s⁻¹, which is similar to that of the discharge evolution obtained by simulation. And the propagation speed of the jet in the second stage is on the order of several hundred m s⁻¹, which is close to the velocity of gas flow. The spatial–temporal distributions of light emission show that high-energy electrons can only be observed during the jet propagation in the first stage, and low-energy electrons can be detected in both the first and second stages. The results show that the electric field plays an important role on the jet propagation in the first stage, and the jet propagation during the second stage is mainly promoted by the thermal gas expansion.

本文研究了微空心阴极放电（MHCD）产生的氦等离子体射流。MHCD由方波脉冲电源驱动，并通过实验测量了放电和等离子体射流的特性。研究了气体流速对MHCD和等离子流的影响。并分析了等离子体射流的传播机理。结果表明，在气体流量的100–1000 sccm范围内，MHCD的击穿延迟时间随氦气流量的增加而增加。认为气流影响种子电子的密度，从而影响击穿延迟时间。随着氦气流速的增加，整个等离子流的长度先增大然后减小。详细研究表明，在一个放电脉冲中，观察到等离子体射流的两个不同的传播过程。发现在电流脉冲的上升沿期间形成第一级的射流，而在放电电流变得稳定之后产生另一级的射流。射流在第一阶段的传播速度约为几千米^-1，与通过模拟获得的放电变化相似。并且第二阶段中射流的传播速度为几百毫秒^-1的量级，其接近气流的速度。发光的时空分布表明，只有在第一阶段的射流传播过程中才能观察到高能电子，而在第一阶段和第二阶段都可以检测到低能电子。结果表明，电场在第一阶段的射流传播中起着重要作用，而第二阶段的射流传播主要是由热气体的膨胀促进的。