Observation of Microwave In-Liquid Plasma using High-Speed Camera

The behavior of 2.45 GHz microwave in-liquid plasma n-dodecane was observed using a high-speed camera. The system pressure before plasma generation was 1 or 100 hPa. The plasma was generated at the tip of a sharpened electrode, after which the plasma was found in a bubble in the liquid on the electrode. The plasma did not continuously emit light. The profile of light intensity varied between 1 and 100 hPa when the plasma faded. The behavior of the bubble by heat generation in the bubble was numerically simulated. To match experimental results, the heat generation was continued for 0.9 ms at 1 hPa and throughout the simulation at 100 hPa. The internal temperature ranged from 2,000 to 4,000 K, and the ratio of vapor n-dodecane to hydrogen produced by chemical reaction was at almost the same order at 1 hPa and approximately 1% at 100 hPa.