Sub-5-fs compression and synchronization of relativistic electron bunches enabled by a high-gradient $\alpha$-magnet and low-jitter photoinjector

TL;DR

This paper demonstrates a novel method for generating and synchronizing relativistic electron bunches with sub-5 femtosecond duration and femtosecond-level timing precision, advancing ultrafast science capabilities.

Contribution

It introduces a new approach combining a high-gradient alpha-magnet and a low-jitter photoinjector for simultaneous bunch compression and synchronization.

Findings

Achieved sub-5-fs rms electron bunch duration.

Demonstrated femtosecond-level synchronization.

Established a new regime in ultrafast electron beam control.

Abstract

Generating high-brightness relativistic electron bunches with few-femtosecond duration, while simultaneously achieving few-fs synchronization with ultrafast lasers, remains an outstanding challenge at the frontier of accelerator physics and ultrafast science. In this Letter, we present the beam physics and experimental demonstration of a new method that, for the first time, enables simultaneous control of bunch duration and synchronization with few-fs precision. Timing stabilization is achieved using a tailored high-gradient $\alpha$-magnet that optimizes the correlation between time of flight and momentum, together with a photocathode RF gun designed to suppress the effect of RF-to-laser timing jitter. Compression is realized by manipulating the time-momentum correlation in phase space, primarily through space-charge effects. Sub-5-fs rms bunch duration and synchronization are demonstrated. This method establishes a new regime in electron bunch control, unlocking new capabilities for ultrafast beam physics and applications.