High-current vacuum arc appearance in nonhomogeneous axial magnetic field

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