Abstract
Dedicated simulations show that the application of time-domain ptychography to angular photo-electron streaking data allows shot-to-shot reconstruction of individual X-ray free electron laser pulses. Specifically, in this study, we use an extended ptychographic iterative engine to retrieve both the unknown X-ray pulse and the unknown streak field. We evaluate the quality of reconstruction versus spectral resolution, signal-to-noise and sampling size of the spectrogram.
Highlights
Time-domain ptychography refers to a specific class of iterative algorithms that reconstruct a complex valued waveform E(t) from a spectrogram, S(τ, ω ) ∝ Z∞dt E(t) P(t − τ ) e −iωt (1) −∞with a known or unknown gate, P(t)
We propose a combination of so-called angular streaking [8,9] with time-domain ptychography for the reconstruction of individual spontaneous emission (SASE) X-ray pulses on a shot-to-shot basis
We found that the rms error decreased with a slope of −0.25, which is reasonable because we added noise to the spectrogram and here, we expect a slope of −0.5 for pure statistical noise
Summary
Time-domain ptychography refers to a specific class of iterative algorithms that reconstruct a complex valued waveform E(t) from a spectrogram, S(τ, ω ) ∝. The real space image of an unknown object is reconstructed iteratively from a series of far-field diffraction measurements. Each of those is recorded after shifting the object or the coherent illumination beam in the object plane. Given the fluctuations that are typical of the electron acceleration as well as the stochastic nature of the self-amplification of spontaneous emission (SASE) nature of such sources, single shot measurement, not scanning, must be used for pulse characterization; no two pulses look alike at an FEL In this manuscript, we propose a combination of so-called angular streaking [8,9] with time-domain ptychography for the reconstruction of individual SASE X-ray pulses on a shot-to-shot basis. The main goal is to identify the minimum number of electron spectra and the required spectrometer resolution to achieve X-ray pulse reconstruction of sufficient quality
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