Longitudinal phase-space reconstruction of laser wakefield accelerated electron beams via coherent transition radiation

We propose and numerically validate a scheme for reconstructing the longitudinal phase space of laser wakefield accelerated electron beams, based on measuring the coherent transition radiation spectrum in combination with dispersion manipulation. The final beam length after the chicane depends on the initial longitudinal beam properties and the deflection angle. By fitting the measured dependence of beam length on deflection angle to a theoretical model, key initial beam parameters are estimated, including the chirp, slice energy spread, and beam duration. This allows the longitudinal phase space distribution to be derived. Start-to-end simulations confirm that the method operates without direct laser–electron interaction, provides the potential for sub-femtosecond resolution, and effectively characterizes higher-order chirp components.