Experimental investigation of vacuum arcs in nonuniform axial magnetic fields

Experiments were conducted in a detachable vacuum chamber with conventional cup-shaped axial magnetic field (AMF) electrodes and three types of AMF electrodes with different nonuniform AMFs. The radial distributions of the AMF were varied by introducing ferromagnetic material into the cup-shaped AMF electrodes. The vacuum arc column and the distribution of cathode spots were photographed with a high-speed charge coupled device (CCD) camera. Experimental results indicate that a nonuniform AMF with higher axial magnetic flux density at the contact periphery than that at the center (saddle.shaped AMF) can resist arc constriction and increase the cathode and anode utilization ratios more effectively than the ordinary bell-shaped AMF profile.