Coupling Impedances of Azimuthally Symmetric Obstacles of   Semi-Elliptical Shape in a Beam Pipe
  The beam coupling impedances of small axisymmetric obstacles having a semi-elliptical cross section along the beam in the vacuum chamber of an accelerator are calculated at frequencies for which the wavelength is large compared to a typical size of the obstacle. Analytical results are obtained for both the irises and the cavities with such a shape which allow simple estimates of their broad-band impedances. 
Robert L. Gluckstern (UMD) and Sergey S. Kurennoy (LANL)