Spectroscopic characteristics of pulsed arc discharge in high-pressure CO2 up to supercritical phase

This study describes spectroscopic measurement of pulsed arc discharge in high pressure CO
₂
including supercritical (SC) phase (1.6-8.1 MPa). A positive nanosecond pulsed voltage was applied to a needle-to-plane electrode. Spectral broadening of OI at 777 nm increased from gas to sub-critical phase and decreased around the critical condition of CO
₂
. The decrease was presumed to be caused by critical anomaly of thermal conductivity. In addition, spatial distribution of pulsed arc discharge emission intensity was processed from images taken. Basically, emission intensity was consistent with spectral broadening. Brightest emissions were observed in the SC phase (8.1 MPa).