Also described as “tube or tunnel reactor”. Cylindrical plasma system through which the process gas flows in axial direction. With HF excitation by MHz radiation, one electrode is provided as a cylinder, the second as a plate in the centre of the cylinder. Usually, this second electrode also serves as a product carrier. This reactor design is preferably used for plasma etching processes where the substrate should not be exposed to direct bombardment with ions. Plasma etching in the barrel reactor with MHz excitation can achieve high etching rates.