An RF resonator cavity for accelerating charged particles is provided, wherein an electromagnetic RF field can be coupled into the RF resonator cavity. During operation, the RF field acts on a particle beam which traverses the RF resonator cavity. At least one intermediate electrode for increasing the dielectric strength is arranged in the RF resonator cavity along the beam path of the particle beam, wherein the conductivity of the intermediate electrode is limited such that upon coupling-in of the electromagnetic RF field at the operating frequency of the RF resonator cavity the intermediate electrode is at least partially penetrated by the coupled-in electromagnetic RF field.