A method for the measurement of the cathode surface temperature for a high‐current free‐burning arc

A method using two‐wavelength pyrometry has been developed for the measurement of the cathode surface temperature of high‐current free‐burning arcs. The method measures the total thermal radiation flux emitted from the cathode and the surrounding plasma and subtracts the derived plasma component using a modified Abel‐inversion transformation. The effects associated with the plasma radiation reflected by the cathode are minimized by using measurements near the cathode edges. Experimental data are used to account for the dependency of the cathode emissivity on wavelength. In this paper the details of this technique are discussed and measurements of cathode surface temperature are presented for pure and thoriated tungsten cathodes.