A plasma-based processing system and a corresponding operation method are proposed. One or more absorbers are positioned between a plasma generation volume inside the plasma chamber and a support structure configured to support the workpiece, and then a portion of plasma delivered from the plasma generation volume to the support structure (or the workpiece) is absorbed by the absorber(s). Further, the absorber(s) are made of electrical conductive material(s), and the structure of at least one absorber and/or the relative geometric relation between at least two absorbers is adjustable. Hence, the position(s) of the electric conductor(s) overlap(s) with the delivered plasma may be adjusted, and then the ion current distribution on the cross section of the delivered plasma may be modified correspondingly.