Abstract: A method and an apparatus relate to an ignition an arc between an anode and a cathode of a plasma source which can be used for a substrate surface modification at environmental atmosphere conditions. The cathode is arranged at a spacing from the anode. This method and the apparatus may reduce the effort for the ignition of an arc of a plasma source and to make the ignition process safer. The method is such that a barrier discharge is ignited with a supplied gas by means of two electrodes which are arranged parallel to the longitudinal axis between the anode and the cathode and are connected to a high-voltage generator and are supplied with a radio frequency electric AC voltage on the ignition. When an electric DC voltage is applied to the anode and to the cathode, an arc can thereby be ignited by means of the charge carriers present between the anode and the cathode due to the barrier discharge.