Measurements of the Propagation Velocity of an Atmospheric-Pressure Plasma Plume by Various Methods

The propagation behavior of atmospheric-pressure plasma plumes has recently attracted lots of attention. In this paper, five different methods are used to measure the propagation velocity of an atmospheric-pressure plasma plume. The first method, named the "current method," obtains the propagation velocity of the plasma plume by measuring the currents carried by the plasma plume at different positions. The second method, named the "voltage method," obtains the plume propagation velocity by measuring the plasma plume voltage potential at different positions along the plasma jet with a voltage divider. The third method, called the " charge method," which significantly interferes with the plume propagation, estimates the plume propagation velocity by measuring the charges deposited on the surface of a quartz tube. The fourth method, which is the noninterference method, obtains the plume propagation velocity by capturing the dynamics of the plasma plume with an intensified charge-coupled device camera. Finally, the fifth method estimates the plume propagation velocity based on the temporal optical-emission intensity measurement of the selected species by using a spectrometer. The advantage and disadvantage of each method are discussed. The experimental results show that plasma plume velocities obtained from the five methods have reasonable agreement with each other. They are all in the range of 104 m/s.