Mass-to-Charge State of Vacuum Arc Plasma With a Film-Coated Composite Cathode

We describe here our investigation of the mass-to-charge state of the plasma ions produced in a vacuum arc discharge with a composite cathode, which is a flat copper substrate coated with a hydrogen-saturated zirconium film of thickness 25-30 μm. It is shown that during the arc current pulse, the fractions of hydrogen and zirconium ions in the plasma decrease synchronously, while the copper ion fraction increases. The use of a film-coated cathode in a vacuum arc ion source allows generation of multicomponent gas and metal ion beams with a hydrogen ion fraction from several percent to several tens of percent. The lifetime of the cathode in terms of the total ion charge transported in the arc is as high as 1800 C.