High-current vacuum arc appearance in nonhomogeneous axial magnetic field

The distribution of the spots over the cathode of a high-current vacuum arc stabilized by an axial magnetic field (AMF) has been investigated. AMF configuration has been varied from conventional "bell-shaped" to "magnetic barrier," where a substantial AMF is created on the electrode edge and virtually vanishes in the center. The complex effect of the AMF configuration on the behavior of cathode spots has been satisfactorily explained based on the Steenbeck minimum principle. It has been shown that the "magnetic barrier" represents an optimum AMF configuration, providing even current distribution and relatively low and stable arc voltage.