Two Dimensional Distribution Diagnostic of Copper Vapor in a Vacuum Arc by Laser-induced Fluorescence

It is important to obtain the information on the neutral metallic vapor during the arcing period for a better understanding of vacuum arc interruption process. In this work, the objective is to experimentally study the two dimensional distribution of copper vapor during arcing. A reverse current was injected at specific time points to force the 45 Hz sinusoidal arc current to be extinguished in a short time, avoiding the interference of intensive arc self-radiation. Meanwhile, the plane laser-induced fluorescence (PLIF) using a pulse laser with a central wavelength at 324.8 nm was adopted to excite the metallic vapor, and a iCCD camera recorded the distribution of the vapor from the induced fluorescence. In the experiments, a pair of cup-shaped axial magnetic field (AMF) contacts were used. The material was CuCr50 and the peak amplitude of the arc current was 3 kA. It is found that the peak value of the metallic vapor density occurred at about 8 ms while the current peak occurred approximate 3 ms in advance, and the highest density value can achieve up to 2.3×1020m-3. It is also found that the metallic vapor mainly accumulated on the anode surface under AMF during the arcing period, which became obvious when the current begins to drop.