[Granted] An ion source may include a chamber configured to house a plasma comprising ions to be directed to a substrate and an extraction power supply configured to apply an extraction terminal voltage to the plasma chamber with respect to a voltage of a substrate positioned downstream of the chamber. The system may further include a boundary electrode voltage supply configured to generate a boundary electrode voltage different than the extraction terminal voltage, and a boundary electrode disposed within the chamber and electrically coupled to the boundary electrode voltage supply, the boundary electrode configured to alter plasma potential of the plasma when the boundary electrode voltage is received.