Endcaps for TE01 cavities in fountain frequency standards

Design of endcaps for TE₀₁ cavities in fountain frequency standards are discussed. Excitation of atoms in the TE₁₁ mode, below-cutoff waveguide due to mis-centering of the waveguide in the Ramsey cavity. The microwave cavity model is used in the junction between the coaxial waveguide (mode filter choke ) and the cylindrical cavity. New design of the choke for the cylindrical cavity using a coaxial waveguide with reduced inner conductor radius and a thin diaphragm with a smaller annular gap placed between the cavity and the coaxial waveguide. A design for choke structures which suppresses the unwanted (TM₁₁) mode which is normally degenerate in frequency with TE₀₁ mode.