Angular Distribution of Ion Current Emerging From an Aperture Anode in a Vacuum Arc

The ion current distribution emerging from a vacuum arc between a Cu cathode and a conical ring anode was measured by a set of five probes. It was found that 1) the total ion current emerging through the anode was 8.5 percent of the arc current, 2) the measured ion distribution without a magnetic field was a slightly flattened cosinusoidal function, 3) with an axial magnetic field, the ion current distribution became peaked along the z axis, 4) the total ion current extracted through the anode aperture slightly increased with the magnetic field, and 5) an anode with a larger aperture exhibited less magnetic collimation.