27.12 MHz plasma generation in supercritical carbon dioxide

An experiment was conducted for generating high-frequency plasma in supercritical carbon dioxide; it is expected to have the potential for applications in various types of practical processes. It was successfully generated at 6−20 MPa using electrodes mounted in a supercritical cell with a gap of 1 mm. Emission spectra were then measured to investigate the physical properties of supercritical carbon dioxide plasma. The results indicated that while the emission spectra for carbon dioxide and carbon monoxide could be mainly obtained at a low pressure, the emission spectra for atomic oxygen could be obtained in the supercritical state, which increased with the pressure. The temperature of the plasma in supercritical state was estimated to be approximately 6000−7000 K on the assumption of local thermodynamic equilibrium and the calculation results of thermal equilibrium composition in this state showed the increase of atomic oxygen by the decomposition of CO2.