Cascaded Multi-cycle terahertz driven ultrafast electron acceleration and manipulation

TL;DR

This paper demonstrates the use of dielectrically-lined waveguides powered by multi-cycle THz pulses to achieve longer interaction lengths for electron acceleration, showing potential for reaching relativistic energies with existing THz sources.

Contribution

It introduces a novel approach of using multi-cycle THz pulses and dielectric waveguides for extended electron acceleration and demonstrates THz energy recycling in this context.

Findings

Successful acceleration, compression, and focusing in dielectric capillary stages.

First demonstration of THz energy recycling for electron acceleration.

Potential to reach relativistic energies with current THz sources.

Abstract

Terahertz (THz)-based electron acceleration and manipulation has recently been shown to be feasible and to hold tremendous promise as a technology for the development of next-generation, compact electron sources. Previous work has concentrated on structures powered transversely by short, single-cycle THz pulses, with mm-scale, segmented interaction regions that are ideal for acceleration of electrons in the sub- to few-MeV range where electron velocities vary significantly. However, in order to extend this technology to the multi-MeV range, investigation of approaches supporting longer interaction lengths is needed. Here, we demonstrate first steps in electron acceleration and manipulation using dielectrically-lined waveguides powered by temporally long, narrowband, multi-cycle THz pulses that co-propagate with the electrons. This geometry offers centimeter-scale single-stage interaction lengths and offers the opportunity to further increase interaction lengths by cascading acceleration stages that recycle the THz energy and rephase the interaction. We prove the feasibility of THz-energy recycling for the first time by demonstrating acceleration, compression and focusing in two sequential Al2O3-based dielectric capillary stages powered by the same multi-cycle THz pulse. Since the multi-cycle energy achievable using laser-based sources is currently a limiting factor for the maximum electron acceleration, THz energy recycling provides a key enabling factor for reaching relativistic energies with existing sources.