Influence of CuCr electrode composition on 2D electron and metal vapor density distribution over vacuum arc

ShackHartmann-type laser wavefront sensors were utilized for the systematic investigation on Cr content dependence of 2D electron and metal vapor density distributions over vacuum arcs generated between CuCr electrodes, whose Cr content were 0 wt.%, 25 wt.%, 35 wt.%, 50 wt.% and 75 wt.%. The electron density was highest for the Cr25wt.% and Cr35wt.%, while the metal vapor density was lowest for the same CuCr electrode compositions. These experimental results demonstrated high consistency with previously reported CuCr composition dependence of electrode erosion rates, duration time of anode melting and residual charge after current zero. Furthermore, based on the present density data and previously proposed dielectric recovery processes, it was suggested that Cr25wt.% and Cr35wt.% are suitable for the interruption of intense-mode vacuum arcs; instead, Cr50wt.% and Cr75wt.% are useful for diffused arc interruption. The validity of this suggestion was supported by previous experimental studies reporting Cr content dependence of arc current interruption capacities and dielectric recovery speeds.