Resonant effects in the longitudinal coupling impedance of a rectangular slot in a coaxial liner

We earlier developed a general analysis, based on a variational formulation, which includes both the realistic coaxial structure of the beam pipe and the effect of finite wavelength in the calculation of the coupling impedance of a rectangular slot in a liner wall of zero thickness. In the present paper we use this analysis to study the frequency dependence of the coupling impedance of a longitudinal rectangular slot. Resonant effects in the coupling impedance are discussed.