Fabrication and testing of corrugated waveguides for a collinear wakefield accelerator

Abstract

Significant progress has been made at Argonne National Laboratory in the development of a compact wakefield accelerator based on a cylindrical corrugated waveguide with a 2-mm ID and fine corrugations on the wall. The fabrication process of 10-cm-long corrugated waveguide structures has been established and a high quality of the final product has been confirmed by precision metrology. Several samples have been tested using the electron beam at Brookhaven National Laboratory's Accelerator Test Facility. The frequency and group velocity of the fundamental monopole ${\mathrm{TM}}_{01}$ mode of sub-terahertz \ifmmode \check{C}\else \v{C}\fi{}erenkov radiation produced by a 1.5-ps-long electron bunch propagating in the corrugated waveguide, as well as the frequencies of the dipole ${\mathrm{HEM}}_{11}$ and the quadrupole ${\mathrm{HEM}}_{21}$ modes have been measured and found to be in good agreement with the design values calculated using CST Microwave Studio. The energy modulation of a 5-ps-long electron bunch caused by the self-induced wakefield has also been measured and found to be in good agreement with the calculated values.