Production of Multiply Charged Bismuth Ion Beams in a Vacuum Arc Ion Source with a Submicrosecond Pulse Duration

Vacuum arc ion sources are capable of generating pulsed ion beams of any solid-state conducting material and are used as injectors in heavy ion accelerators and technological implanters for surface modification of different materials. Without any special measures to increase the charge states of ions with typical arc discharge parameters, at an arc current amplitude of several hundred amperes and a pulse duration of several tens of microseconds, the charge states of ions in the beam do not exceed 5+, and the average ion charge is in the range from 1+ to 3+, depending on the cathode material. An increase in the charge states of vacuum arc plasma ions makes it possible to increase the ion energy in the extracted beam without a corresponding increase in the accelerating voltage or to form ions with a given energy at a significantly lower accelerating voltage. The charge states can be increased by increasing the amplitude of the discharge current and reducing its pulse duration. This article presents a study of the processes of generating beams of multiply charged heavy metal ions using bismuth ions as an example in a high-current vacuum arc with a kiloampere current amplitude at a submicrosecond pulse duration. By shortening the duration of the arc current pulse, the most probable charge state of ions in the extracted 18+ beam is formed, which is a record for bismuth.