Influence of Axial Magnetic Field on Mass-to-Charge Composition of High-Current Vacuum Arc Plasmas with Cu-Cr Cathodes

Abstract

We have used the time-of-flight technique and a vacuum arc discharge source of metal ions in an axial magnetic field to study the mass-to-charge composition of the arc plasma. The cathode current density and the magnetic field induction near the cathode surface were typical for high-current vacuum interrupter chambers, about 1 kA/cm2 and 1.2 T, respectively. It has been shown that the mean charge states of copper and chromium ions depend on their percentage in the composite cathode material and elevates in the presence of an axial magnetic field. With the fraction of chromium increasing to 50 %, the mean charge state of copper ions lowers from 2.1 to 1.9, while that of chromium elevates from 1.73 to 2.18. The presence of a magnetic field also leads to an increased discharge burning voltage by a factor of about 2, from 34 V to 67 V, as well as to the appearance of atomic ions of hydrogen H+ , oxygen 02+ , and carbon C+ and molecular ions of hydrogen H2+ . Their total content in the plasma flux is about 20 %. The obtained results may be useful for studying the current interruption and dielectric strength recovery in switching devices based on a vacuum arc.