The invention relates to a plasma source comprising an oscillator, which has an active element and a resonator connected to the active element. The resonator comprises a hollow body, a gas inlet, a gas outlet arranged at a distal end of the hollow body about a longitudinal axis of the hollow body, and a coil arranged along the longitudinal axis of the hollow body, the coil having an effective length of one quarter of a wavelength at a resonant frequency of the resonator. A distal end of the coil is arranged relative to the gas outlet such that a plasma section can form between the distal end of the coil serving as a first plasma electrode and the gas outlet of the hollow body serving as a second plasma electrode. At a proximal end of the hollow body, the coil is lead out of the interior of the hollow body through an electrically contact-free feedthrough, and a proximal end of the coil contacts the outside of the hollow body. On a first contact region located between the proximal end of the coil and the feedthrough, the coil is coupled to a first port of the active element, and on a second contact region located between the proximal end of the coil and the feedthrough, it is coupled to a second port of the active element.