Temporal characterization of ultrashort linearly chirped electron bunches generated from a laser wakefield accelerator

TL;DR

This paper introduces a novel diagnostic method for analyzing the temporal profile and linear energy chirp of ultrashort electron bunches from laser wakefield accelerators, using spectral modulation techniques validated by simulations and experiments.

Contribution

A new spectral modulation technique for diagnosing the temporal structure and energy chirp of ultrashort electron bunches in laser wakefield acceleration.

Findings

Successfully reconstructed bunch profiles and energy chirp from spectral data.

Validated the method through particle-in-cell simulations and experimental results.

Demonstrated the ability to identify linear energy chirp in electron bunches.

Abstract

A new method for diagnosing the temporal characteristics of ultrashort electron bunches with linear energy chirp generated from a laser wakefield accelerator is described. When the ionization-injected bunch interacts with the back of the drive laser, it is deflected and stretched along the direction of the electric field of the laser. Upon exiting the plasma, if the bunch goes through a narrow slit in front of the dipole magnet that disperses the electrons in the plane of the laser polarization, it can form a series of bunchlets that have different energies but are separated by half a laser wavelength. Since only the electrons that are undeflected by the laser go through the slit, the energy spectrum of the bunch is modulated. By analyzing the modulated energy spectrum, the shots where the bunch has a linear energy chirp can be recognized. Consequently, the energy chirp and beam current profile of those bunches can be reconstructed. This method is demonstrated through particle-in-cell simulations and experiment.