Transient behaviour of axial temperature distribution in post-arc channel after current zero around nozzle throat in flat-type SF6gas-blast quenching chamber

The decaying behaviour of the axial temperature distribution in the post-arc channel after current zero is measured around the nozzle throat in a flat-type SF 6 gas-blast quenching chamber. In the quenching chamber, iron is intentionally used as the electrode material. Two iron atom spectral lines at wavelengths 426 and 443 nm are detectable even up to 100 mu s after current zero for an arc with peak value of 5 kA. This is because the spectral lines for iron have higher radiation intensities than those for other species such as sulphur ions or copper atoms. From the radiation intensities measured at each of the five axial positions around the nozzle throat, the temperatures are estimated by means of the two-line method. The axial temperature distribution shows a local maximum at the nozzle throat up to a time of 20 mu s after current zero. However, the temperature at the nozzle throat decays more rapidly than at the other axial positions. At 100 mu s after current zero, the temperature at the nozzle throat reaches 3500 K, the lowest magnitude among the axial positions.