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

Abstract

Femtosecond electron bunches with complex temporal structures play a crucial role in terahertz generation, free-electron lasers, and plasma wakefield accelerators. However, diagnostics of electron beam current profiles with femtosecond resolution are still challenging. Coherent transition radiation (CTR) has been proven to have the capability to reconstruct current profiles based on prior knowledge or complete information of spectra. In this paper, a weighted greedy sparse phase retrieval (WGESPAR) algorithm is developed to reduce the ambiguities during reconstruction of complex current profiles. This algorithm can achieve better performance than the Kramers-Kronig method and the Bubblewrap algorithm in the case of reconstructing complex temporal structures from truncated noisy CTR spectra. Based on the WGESPAR algorithm, the complex temporal structures of femtosecond electron bunches generated from laser wakefield accelerators can be successfully reconstructed.