DC Breakdown Voltage of Carbon Dioxide Medium Under Needle to Plane Electrode

Summary form only given. Supercritical carbon dioxide has great importance in industrial uses as the extracting solvent of various useful ingredients, reaction solvent and reaction catalyst since it has unique characteristics such as high diffusivity (like a gas) and high solubility (like a liquid). On the other hand, electric discharge plasmas also have higher chemical reactivity. Therefore, the combination of SC CO₂ and electric discharge plasmas may offer a possibility of a new horizon in future reaction fields. This paper reports the experimental results on the dc corona onset voltage and the dc breakdown voltage in the pressure range of 1 to 10 MPa under the point-to-plane electrode. From experimental results of negative polarity voltage, (1) corona discharges preceding complete breakdown are observed more clearly in liquid and in supercritical fluid than in gas, (2) the estimated corona discharge onset voltage according to the streamer theory is in fairly good agreement with the measured breakdown voltage in the gas density region of 0.1-30 kg m^-3. The experimental results in the case of the application of positive dc voltage will be reported together at conference.