Experimental characterization of electron beam driven wakefield modes in a dielectric woodpile Cartesian symmetric structure

TL;DR

This paper experimentally investigates THz wakefield modes in a 3D photonic woodpile structure, demonstrating control over wakefield excitation and suppression, which is promising for high-gradient dielectric accelerators.

Contribution

It provides the first experimental demonstration of selective wakefield mode control in a dielectric woodpile structure using elliptical drive beams.

Findings

Selective excitation and suppression of wakefield modes achieved.

Wakefield spectrum insensitive to beam offset.

Results align with theory and simulations.

Abstract

The use of photonic structures in the terahertz (THz) spectral region may enable the essential characteristics of confinement, modal control, and electric field shielding for very high gradient accelerators based on wakefields in dielectrics. We report here an experimental investigation of THz wakefield modes in a 3D photonic woodpile structure. Selective control in exciting or suppressing of wakefield modes with non-zero transverse wave vector is demonstrated by using drive beams of varying transverse ellipticity. Additionally, we show that the wakefield spectrum is insensitive to the offset position of the strongly elliptical beam. These results are consistent with analytic theory and 3D simulations, and illustrate a key advantage of wakefield systems with Cartesian symmetry, the suppression of transverse wakes by elliptical beams.