A tomographic visualization of electric discharge sound fields in atmospheric pressure plasma using laser diffraction

The phase modulation of transparent gas can be detected using Fraunhofer diffraction technique, which we call optical wave microphone (OWM). The OWM is suitable for the detection of sonic wave from audible sound to ultrasonic wave. Because this technique has no influence on sound field or electric field during the measurement, we have applied it to the sound detection for the electric discharges. There is almost no research paper that uses the discharge sound to examine the electrical discharge phenomenon. Two-dimensional visualization of the sound field using the OWM is also possible when the computerized tomography (CT) is combined. In this work, coplanar dielectric barrier discharge sin different gases of Ar, N2, He were characterized via the OWM as well as applied voltage and discharge current. This is the first report to investigate the influence of the type of the atmospheric gas on the two-dimensional sound field distribution for the coplanar dielectric barrier discharge using the OWM with CT.