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

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 (similar to 200 kHz), indicating that space-charge compensation can be achieved to prevent beam stalling.