A chamber component configured to be coupled to a processing chamber is described. The chamber component comprises one or more adjustable gas passages through which a process gas is introduced to the process chamber. The adjustable gas passage may be configured to form a hollow cathode that creates a hollow cathode plasma in a hollow cathode region having one or more plasma surfaces in contact with the hollow cathode plasma. Therein, at least one of the one or more plasma surfaces is movable in order to vary the size of the hollow cathode region and adjust the properties of the hollow cathode plasma. Furthermore, one or more adjustable hollow cathodes may be utilized to adjust a plasma process for treating a substrate.