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 millimeter-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, an 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, narrow-band, multicycle THz pulses that copropagate 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 -based dielectric capillary stages powered by the same multicycle THz pulse. Since the multicycle THz energy achievable using laser-based sources is currently a limiting factor for the maximum electron acceleration, recycling the THz pulses provides a key factor for reaching relativistic energies with existing sources and paves the way for applications in future ultrafast electron diffraction and free-electron lasers.
- Received 5 July 2019
- Revised 25 October 2019
- Accepted 6 February 2020
DOI:https://doi.org/10.1103/PhysRevX.10.011067
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Terahertz-based electron acceleration has recently emerged as a promising candidate for next-generation compact electron sources. In these devices, pulses of terahertz radiation accelerate electrons across a relatively short distance. Although initial work in this field has demonstrated impressive capabilities for acceleration and beam manipulation, the electron energy gain is still limited by the short interaction distance and low terahertz energy for powering the device. Here, we demonstrate the first steps toward creating a scheme to overcome these hurdles.
Our setup uses dielectric-lined waveguides powered by narrow-band, long-duration terahertz pulses (known as multicycle pulses) that copropagate with the electrons. The terahertz phase velocity is matched with the electron speed, which enables effective beam manipulation across interaction lengths roughly a centimeter long in the nonrelativistic regime—about an order of magnitude greater than other methods. Moreover, we demonstrate a novel scheme of cascaded acceleration and manipulation by terahertz-energy recycling and rephasing the interaction, which offers the opportunity to further increase the interaction length.
Increased interaction length is important because the efficiency of current laser-based technologies for terahertz generation is still rather low, which requires high-power laser systems for electron acceleration to mega-electron-volt energies. Our cascading scheme will greatly lower the demand on the required laser system for electron acceleration in the nonrelativistic regime, opening new possibilities for the design of terahertz-based accelerators.