Visualizing Spatiotemporal Temperature Variation for Estimating H+aq Distribution by Pulsed Discharge Plasma Exposure

Positive pulsed discharge plasma is generated above a test liquid containing NaCl in Ar atmosphere, and H
⁺
distribution and a temperature variation in the liquid are, respectively, visualized by colorimetric methods using methyl red (MR) and microencapsulated thermotropic liquid crystals (MTLCs). The discharges generated above the liquid containing MR and MTLCs have almost the same characteristics in the waveforms of discharge voltage and current, and the appearance of discharges. The generation of H
⁺
and the temperature increase in the liquid are induced below the discharge area, and H
⁺
distribution and temperature-increased area expand similarly, by the plasma exposure. The spatiotemporal measurement of temperature distribution in the liquid is also observed with MTLCs using a sheet laser. It is found that temperature increase is measured just below the extremity of the discharge and distributes in a torus form and that no temperature increase occurs below the middle of the discharge area. Since good similarity is observed between the H
⁺
distribution and the temperature increase in the test liquid, H
⁺
distribution probably expands in a concentric configuration from the generation area with the plasma exposure time.