Ionization–Recombination Front in High-Current Vacuum Arc

Stable plumes with a distinct and bright shell were observed at the anode of the high-current vacuum arc burning during 10 ms at a current of up to 15 kA in peak. Spectrum-resolved imaging reveals the shell to be emitted mostly by neutral atoms. A shell is surrounded by a diffuse halo emitted by ions. The shell nature can be interpreted in terms of formation of the ionization-recombination front in the place of impact of the cathode and anode plasmas.