Modeling the effects of an axial magnetic field on the vacuum arc

A quantitative two-dimensional model of a vacuum are in an applied magnetic field is presented. For the particular case, a uniform axial magnetic fiel d B-Z, it provides a unified condition for the two regimes of are voltage v ersus B-Z, i.e., the steeply falling voltage branch (low B-Z), and the slow ly rising voltage branch (high B-Z, which characterizes the diffuse are mod e). The transition to the high-B-Z regime is complete when the average mixi ng distance of the individual expanding cathode-spot plasma jets, measured from the cathode plane, is equal to the contact gap length. The model also predicts the observed smooth transition and minimum are voltage between the two branches, and the independence of the arc voltage on the arc current i n the high-B-Z regime. Calculated results are found to be in good agreement with reported experimental data from several independent investigations ov er a wide range of gap, B-Z and arc current I-ARC.