The distribution of metal vapor is very important for the successful interruption of the arc, which directly affects the dielectric strength after the arc is extinguished. The purpose of this article is to observe the distribution of copper metal vapor after the arc when the arc is extinguished at different times by means of plane laser-induced fluorescence(PLIF). A voltage of 100V is applied to a 10mm gap, and a 45Hz sinusoidal current is generated by triggering the arc ignition, and its peak current is 2kA. A reverse current with a rising time of 30μs forces the sinusoidal current to extinguish at different times in its half cycle. The plane laser with a center wavelength of 324.8nm is used to excite the copper atoms, and ICCD camera is used to record the copper atoms distribution from the induced fluorescence. A pair of cup-shaped axial magnetic field (AMF) contacts made of CuCr50 were used in the experiment. The experiment found that when the arc was extinguished at 7ms, the copper vapor density value reache a peak, which is 1.8×10 19 m -3 .

The distribution and dissipation of neutral atoms are crucial for understanding the dielectric recovery process after interrupting direct current (DC) vacuum arcs. This article aims to investigate the dissipation of copper atoms after a forced extinction of the vacuum arc experimentally, adopting the plane laser-induced fluorescence method. The change in the 2-D distribution of copper atoms with time is presented. The results show that the magnetic fields, the axial magnetic field (AMF), and the transverse magnetic field (TMF) have a limited effect on the initial density of copper atoms. For both the AMF and the TMF, the copper atom densities at current zero (CZ) vary in the range (6-8) × 10 17 m -3 when 3-kA vacuum arcs are forced to 0 in 0.2 ms. Contrary to the TMF case, in the AMF case, the evaporation on the anode after the CZ results in long-existing atoms near it. Consequently, the atom density of the TMF decays faster than that of the AMF, which indicates that a vacuum interrupter with the TMF contacts has a better performance when interrupting a DC load. The difference between the two magnetic fields originates from the arc control patterns. Namely, the AMF tends to keep vacuum arcs in a stable mode, which is unfavorable for a DC interruption; on the contrary, the TMF drives the vacuum arcs to move at high velocities resulting in faster dissipation of copper atoms after the CZ. In addition, the composition proportion of CuCr contacts has a limited effect on the diffusion of copper atoms when a low-vacuum arc is interrupted.

Vacuum arc cathode spots are centers of metal vapor evaporation, electron emission and plasma production. Arc properties are dominated by the behavior of the cathode spots. A systematic investigation on the density of copper metal vapor emitted from a single cathode spot is benefit for understanding the mechanism of vacuum arc discharge. The objective of this paper is to get the spatial density distribution of copper neutral atoms emitted from a single cathode spot in ~55A vacuum arc by planar Laser Induced Fluorescence (LIF) method. The experiments are conducted with CuCr10 (Cr weight of 10%) butt contacts in a demountable vacuum chamber. 2D distribution of copper metal vapor density is photographed by an intensified CCD cameral (i-CCD) with an exposure time of 50 ns. The uniform constant Axial Magnetic Field (AMF) within the inter-contacts region is supplied by Helmholtz coils. 2D copper vapor density distribution between two electrodes as well as the influence of external AMF on vapor density distribution are investigated. When the arc current is ~55 A, a typical cathode spot or two spots are observed in the experiments. Copper vapor density reaches the maximum value 6×10 19 m -3 in the center of cathode spot.