Total radiation power of SF₆ gas blast arcs are measured by a photodetector which is composed of four photodiodes with different spectral sensitivities and designed for responding to radiation at wavelength ranging from 250 to 1, 800nm. The SF₆ gas flows along the arc column at 100l/min in our experiments. The arc plasmas are sustained with currents up to 10kA at the waveform frequency of 60Hz and up to 20kA at 120Hz. The radiation powers of 4, 000 to 8, 000kW/m are observed in 10kA arc plasma for both current frequencies. At the same time, a spectroscopic diagnoses are performed to monitor the arc temperature and diameter. Average temperature reaches more than 20, 000K in 10kA-class arc.
Theoretical calculations are carried out for emission coefficients in high temperature SF₆ gas contaminated with copper vapor. It is found that the emission coefficients are independent on admixture of the copper vapor at the high temperature above 15, 000K. The estimated total radiation powers based on the calculated emission coefficients are in good agreement with directly observed ones.