Beam by design: Laser manipulation of electrons in modern accelerators

TLDR

Accelerator‑based light sources such as storage rings and free‑electron lasers use relativistic electron beams to produce intense radiation across a wide spectral range, yet conventional techniques increasingly struggle to meet the growing demands of advanced research worldwide. This review focuses on laser‑based methods that manipulate and rearrange electron distributions—termed “beam by design”—to tailor radiation properties for modern accelerators. The authors survey laser‑driven techniques for creating micro‑ and nano‑structured electron beams, generating fully coherent X‑rays, mode‑locked pulse trains, orbital‑angular‑momentum light, attosecond/zeptosecond pulses, femtosecond pulses in storage rings, and enhancing source performance through beam conditioning, laser heating, emittance exchange, and diagnostics.

Abstract

Accelerator-based light sources such as storage rings and free-electron lasers use relativistic electron beams to produce intense radiation over a wide spectral range for fundamental research in physics, chemistry, materials science, biology and medicine. More than a dozen such sources operate worldwide, and new sources are being built to deliver radiation that meets with the ever increasing sophistication and depth of new research. Even so, conventional accelerator techniques often cannot keep pace with new demands and, thus, new approaches continue to emerge. In this article, we review a variety of recently developed and promising techniques that rely on lasers to manipulate and rearrange the electron distribution in order to tailor the properties of the radiation. Basic theories of electron-laser interactions, techniques to create micro- and nano-structures in electron beams, and techniques to produce radiation with customizable waveforms are reviewed. We overview laser-based techniques for the generation of fully coherent x-rays, mode-locked x-ray pulse trains, light with orbital angular momentum, and attosecond or even zeptosecond long coherent pulses in free-electron lasers. Several methods to generate femtosecond pulses in storage rings are also discussed. Additionally, we describe various schemes designed to enhance the performance of light sources through precision beam preparation including beam conditioning, laser heating, emittance exchange, and various laser-based diagnostics. Together these techniques represent a new emerging concept of "beam by design" in modern accelerators, which is the primary focus of this article