Temporal diagnostics of femtosecond electron bunches with complex structures using sparsity-based algorithm

Femtosecond electron bunches with complex temporal structures play a crucial role in THz generation, free-electron lasers and plasma wakefield accelerators. The ultrashort electron pulse duration can be reconstructed from the coherent transition radiation (CTR) spectrum based on prior knowledge. A weighted greedy sparse phase retrieval (WGESPAR) algorithm is developed to reduce the ambiguities for reconstructing the distribution of the beam current. This algorithm achieves better performance than iterative algorithms, especially for truncated noisy spectra of multibunch structures. Based on the WGESPAR algorithm, the complex temporal structures of femtosecond electron bunches generated from laser wakefield accelerators can be successfully reconstructed.