The influence of axial magnetic filed distribution on high-current vacuum arc

The influence of the distribution of axial magnetic filed (AMF) was investigated experimentally with three pairs of specially designed testing electrodes generating conventional bell-shaped AMF profile and different saddle-shaped AMF distributions. The characteristics of high-current vacuum arc (HCVA) up to 20 kA (rms), e.g., the shape of arc column, and the distribution of cathode spots, was investigated with the aid of high-speed digital camera with exposure of 2 mus. Experimental results further manifested the distinct influence of AMF distribution on the characteristics of high-current vacuum arc. Saddle-shaped AMF could resist the constriction of high-current vacuum arc more efficiently than traditional bell-shaped AMF. Furthermore, cathode spots in saddle-shaped AMF distributed more uniformly than that in bell-shaped AMF. It was found that AMF in the central region of saddle-shaped AMF should not be too weak. Otherwise, cathode spots would be out of control in the central region as observed in experiments. The ldquooptimalrdquo minimal AMF in central region was estimated to be about 3-4 mT/kA.