The flow of electrolyte and/or of ions is controlled by a diffuser element provided in a plating reactor, wherein, in one embodiment, the diffuser element comprises a mechanical adjustment mechanism to adjust the effective size of passages of the diffuser element. In another embodiment, the diffuser element comprises at least two patterns of passages that are movable relatively to each other so as to adjust an overlap and thus an effective size of the corresponding passages. Moreover, the path of ions within the plating reactor may be controlled by an electromagnetically driven diffuser element so that a required thickness profile on the workpiece surface may be obtained.