Speaker
Description
Attosecond science with ultrafast optical pulses has revolutionized our understanding of electron dynamics, enabling direct observation of charge migration, electron correlation effects, and field-driven phenomena on their intrinsic timescales. Recent advances in electron accelerator technologies at XFEL facilities have extended attosecond techniques into the hard X-ray regime [1,2], allowing matter to be probed with both attosecond temporal and angstrom spatial resolutions.
A key challenge in the generation and application of attosecond hard X-ray pulses is their temporal characterization. Current estimates of pulse duration rely on comparisons between measured spectra and theoretical simulations of the FEL process. However, such estimates are inherently uncertain, as the spectral width is strongly affected by the energy chirp of the lasing electron bunch and provides only a lower bound on the pulse duration.
In this presentation, we will present the direct experimental evidence of attosecond hard X-ray pulses, enabled by a new temporal diagnostics method [3]. Our approach leverages amplified spontaneous emission (ASE), which is a collective fluorescent process observable when tightly focused X-ray pulses irradiate 3d transition metal targets. By comparing the yield, angular divergence, and transverse correlation length of ASE to quantitative modelling of the ASE process, one can retrieve shot-to-shot pulse duration and transverse X-ray beam profile on the metal target.. We will discuss the underlying principles of this nonlinear diagnostic technique and its application to attosecond pulse characterization at European XFEL and SACLA.
[1] J. Yan et al., Nature Photon. 18, 1293 (2024).
[2] R. Robles et al., arXiv:2604.09969
[3] I. Inoue et al., arXiv:2506.07968
| Scientific Topics | Quantum Science |
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