Distribution of Pressure Wave Generated by Atmospheric Plasma Jet Measured With Optical Wave Microphone

Plasma jets have been expected to be used in biomedical applications. There have been many reports on electrical and optical measurements about the plasma jets. From the practical point of view, one of the important observations on what the plasma jets emit is pressure waves because they can directly affect targets or penetrate into liquid, tissues, and so on. In this paper, we utilized a fiber-type optical wave microphone that works based on the Fraunhofer diffraction of phase objects and improves upon a conventional optical wave microphone with regard to signal-to-noise ratio to detect pressure waves generated inside the He plasma jets with the electrode configuration of the dielectric barrier discharge. The frequency of the applied voltage dependence on the generation of pressure waves from plasma jets was investigated at different He gas flow rates. The distribution of the pressure waves along the radius direction of plasma jets at different distances downstream from the plasma jet device was discussed.