Rf power is supplied to a vacuum processing module in that in the plasma processing module a time invariant impedance transform is performed by an impedance transform network in the plasma processing module and a time variable matching is performed by a matchbox connected to the impedance transform network. The impedance transform network includes an inductive element of a hollow conductor. A cooling medium is flown through the hollow conductor of the impedance transform network as well as through a part of the plasma processing module to be cooled and not being part of the impedance transform network at the plasma processing module.