Transient chirp reconstruction of electron beam via tightly focused chirped laser pulse

Abstract

Controlling the phase space of particle beams is essential for the generation of high-quality, ultrashort electron beams in plasma-based accelerators. Accurately diagnosing the transient energy chirp, which evolves rapidly at the onset of acceleration, presents a significant challenge. This paper introduces a novel method for reconstructing the transient energy chirp of ultrashort electron beams by employing tightly focused and chirped laser pulses. We investigate the conditions that enhance the modulation of electron-beam divergence and illustrate the reconstruction of transient chirp based on the intrinsic phase correlation of the modulated divergence as projected onto specific phase space coordinates. Additionally, we estimate the temporal delay between the laser and electron beam by applying a Fourier transform to the reconstructed divergence modulation in the frequency domain. This approach holds promise for optimizing accelerator performance and facilitates the probing of timing jitter in ultrafast electron diffraction with attosecond-level precision.