Parallel-Plate Waveguides for Terahertz-Driven MeV Electron Bunch Compression

TL;DR

This paper demonstrates a novel parallel-plate waveguide design for terahertz-driven electron bunch compression, achieving significant bunch length reduction with high field strengths and innovative waveguide modifications.

Contribution

It introduces a dispersion-free tapered PPWG for femtosecond electron bunch manipulation and presents a modified design for improved performance and reduced magnetic fields.

Findings

Achieved over 4x compression of 2.5 MeV electron bunches to 18 fs.

Demonstrated peak THz fields of at least 300 kV/cm with 0.9 μJ energy.

Validated the waveguide's effectiveness for ultrafast electron beam control.

Abstract

We demonstrate the electromagnetic performance of waveguides for femtosecond electron beam bunch manipulation and compression with strong-field terahertz (THz) pulses. The compressor structure is a dispersion-free exponentially-tapered parallel-plate waveguide (PPWG) that can focus single-cycle THz pulses along one dimension. We show test results of the tapered PPWG structure using electro-optic sampling (EOS) at the interaction region with peak fields of at least 300 kV/cm given 0.9 uJ of incoming THz energy. We also present a modified shorted design of the tapered PPWG for better beam manipulation and reduced magnetic field as an alternative to a dual-feed approach. As an example, we demonstrate that with 5 uJ of THz energy, the PPWG compresses a 2.5 MeV electron bunch by a compression factor of more than 4 achieving a bunch length of about 18 fs.