Design of a cylindrical corrugated waveguide for a collinear wakefield accelerator

Abstract

We present the design of a cylindrical corrugated waveguide for use in the A-STAR accelerator under development at Argonne National Laboratory. A-STAR is a high gradient, high bunch repetition rate collinear wakefield accelerator that uses a 1-mm inner radius corrugated waveguide to produce a 90 MV m^{-1}, 180-GHz accelerating field when driven by a 10-nC drive bunch. To select a corrugation geometry for A-STAR, we analyze three types of corrugation profiles in the overmoded regime with a/λ ranging from 0.53 to 0.67, where a is the minor radius of the corrugated waveguide and λ is the free-space wavelength. We find that the corrugation geometry that optimizes the accelerator performance is a rounded profile with vertical sidewalls and a corrugation period p≪a. Trade-offs between the peak surface fields and thermal loading are presented along with calculations of pulse heating and steady-state power dissipation. In addition to the TM_{01} accelerating mode, properties of the HEM_{11} mode and contributions from higher order modes are discussed.