An apparatus and method are provided. In one embodiment. an apparatus may include a main chamber, where the main chamber includes an electrode assembly. The electrode assembly may include a plurality of electrodes arranged between a chamber entrance and a chamber exit of the main chamber. The apparatus may include a beam tunnel, connected to the chamber entrance, configured to conduct an ion beam to the main chamber; and an electrostatic tuner, disposed in the beam tunnel, the electrostatic tuner comprising at least one tuner electrode, independently coupled to a tuner voltage assembly.