Impedance calculations of nonaxisymmetric transitions using the optical approximation

Abstract

In a companion report, we have derived a method for finding the impedance at high frequencies of vacuum chamber transitions that are short compared to the catch-up distance, in a frequency regime that-in analogy to geometric optics for light-we call the optical regime. In this report we apply the method to various nonaxisymmetric geometries such as irises/short collimators in a beam pipe, step-in transitions, step-out transitions, and more complicated transitions of practical importance. Most of our results are analytical, with a few given in terms of a simple one-dimensional integral. Our results are compared to wakefield simulations with the time-domain, finite-difference program ECHO, and excellent agreement is found. © 2007 The American Physical Society.