Speaker
Description
Laser and plasma wakefield accelerators are promising for many applications such as future TeV electron-positron colliders and X-ray free electron lasers (XFELs). These applications require high beam quality in terms of energy spread, emittance, and shot-to-shot stability. To achieve high beam quality, one needs to precisely diagnose the beam dynamics during acceleration. This is difficult owing to the highly nonlinear acceleration process and the sub-µm and sub-fs resolution requirements. Here, we report on a single-shot method for reconstructing the longitudinal phase space of electron beams in laser wakefield accelerators based on experimental observation of distinct periodic modulations in the angularly resolved spectra. The modulated spectra arise from the direct interaction between an ultra-relativistic electron beam and laser driver in the presence of the wakefield. A constrained theoretical model coupled with a genetic algorithm was used to recreate the experimental electron spectra and fully reconstruct the longitudinal phase-space distribution of the electron beam with a temporal resolution of ∼1.3 fs. The reconstructred phase-space provides the slice energy spread of the electron beam, which is critical for assessing the viability of applications such as XFELs. In our specific experiment, the root-mean-square slice energy spread is bounded at 9.9 MeV, corresponding to a 0.9-3.0% relative spread, despite a ~100% overall energy spread relative to the GeV average electron energy. Particle-in-cell simulations demonstrate that the reconstruction method can also be applied to electron beams from traditional accelerators, direct laser-electron interactions in vacuum, or beam-driven plasma wakefield accelerators.
| Working group | WG1 |
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