VACUUM-ARC ION SOURCES FOR PARTICLE ACCELERATORS AND ION-IMPLANTATION

The vacuum arc is a prolific generator of highly ionized metal plasma. This method of plasma production can be used to advantage to construct a high current metal ion source. We have developed a succession of such metal vapor vacuum arc ion sources at Berkeley, initially for the production of intense beams of uranium ions for injection into the Bevalac heavy ion synchrotron for fundamental nuclear physics research, and also for the production of large area beams of a wide range of metal ion species for carrying out ion implantation for materials surface modification. The beam parameters can be attractive, and the source has provided a valuable addition to the spectrum of ion sources available to the experimenter. We have produced beams from 50 of the solid metals of the periodic table, with mean ion energy up to several hundred keV and with pulsed beam currents in the ampere range. Typically the source is repetitively pulsed with pulse length 250 microseconds and duty cycle of order 1%. We have recently, tested a dc embodiment from which a large area titanium beam with steady-state ion current 600 mA was produced. Separately we have used a 50 cm diameter set of beam formation grids to form a beam of area 1000 cm2 at an energy of 100 keV and a pulsed beam current of approximately 10 A. The source can also be seen as a tool for the study of vacuum arc plasmas, and we have studied vacuum arc ion charge state distributions in this way. Here we describe the general features and performance characteristics of the sources and their use for accelerator injection and ion implantation applications.