Electron-beam driven dielectric wakefield accelerator experiments in the terahertz regime

Abstract

In recent years, there has been rapid experimental progress on using the self-fields of electron beams to drive accelerating gradients in dielectric lined cavities. The extension to sub-mm scaled cavities, producing terahertz frequencies, has allowed an accessible region to study high-gradient structures in many advanced accelerator facilities. In this paper, we present a broad review of such results as they pertain to dielectric wakefield acceleration (DWA). Issues that are discussed include the examination of breakdown in such structures and materials, as well as studies of in-line spectra generated by coherent Cherenkov radiation, which, for appropriate geometries, produce narrowband, tunable terahertz radiation. We examine measurements of higher-order mode excitations in these structures, which provide a novel characterization method as well as a tunable source of terahertz radiation. We describe DWA measurements including wakefield mapping, selective resonant mode excitation, and observation of energy modulation and acceleration made possible by electron beam manipulation schemes, such as drive-witness, pulse-train, and ramped beam generation. We present alternate materials and geometries such as 1D and 3D photonic-like structures. Finally, we conclude with preliminary results from the initial DWA experimental runs at the SLAC FACET facility. © 2012 American Institute of Physics.