Beam current density distribution of a vacuum arc ion source

The distribution of the beam current density for metal ion vacuum arc ion sources (MEVVA-type) lacks sufficient uniformity and its original form is similar to the Gaussian one. This is because of the plasma generation in a small space near the cathode spot. Further expansion of the plasma to the emission region does not improve this situation which poses a serious problem in creating a broad beam ion source. This article presents experimental results on the influence of various factors on the beam current density distribution. Experiments were carried out in Beijing with the MEVVA-IIA ion source. An additional magnetic field was applied to the arc gap and a small metal grid covering the emission electrode was used.