Some results of the spectroscopic study of a low-current (single spot) short vacuum arc in an axial magnetic field

Abstract

Measurements of spatial distribution of the intensity of radiation of different ionization sates of copper (CuI, CuII and CuIII) in a short (8 mm length) low-current vacuum arc with copper electrodes were carried out. The arc current I = 60 A = Is (Is - average current per cathode spot). That is, an arc with a single spot was investigated. The spatial and temporal resolutions are, respectively, 0.5 mm and 50 μs. Induction of the external axial magnetic field 0 ≤ B ≤ 0.1 T. The investigations showed that the state of the plasma and the shape of the channel of the short arc are determined not only by cathode process. In the near-anode region of the arc, changes take place both inside the channel and in the “coat” of low ionized plasma surrounding the arc. Interaction of high-speed ions of the cathode spot plasma jet with the anode forms a flow of atoms from that part of the surface to which the arc is attached. The atoms are ionized in the immediate vicinity of its surface. This increases the plasma concentration and decreases the average charge of ions in the near-anode part of the arc, in comparison with the average charge of the cathode spot plasma jet.