Alternate extraction and acceleration of positive and negative ions from a gridded plasma source

Abstract

By applying a square-wave voltage with frequencies between 10 kHz to 1 MHz to a set of grids terminating an ion–ion plasma source, we experimentally demonstrate the alternate extraction and acceleration of high energy (hundreds of eV) positive and negative ion beams. In addition, the ratio of positive-to-negative ion beam current can be controlled by adjusting the applied square-wave duty cycle. Temporally resolved floating potential measurements of a target show that the downstream potential can be controlled and sufficiently reduced at high applied frequencies (∼200 kHz), indicating that space-charge compensation can be achieved to prevent beam stalling.