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K: Fachverband Kurzzeit- und angewandte Laserphysik

K 4: X-Ray Lasers

K 4.4: Talk

Wednesday, March 22, 2023, 11:45–12:00, HSZ/0403

Characterization of SASE FEL pulses with angular streaking — •Lars Funke¹, Kristina Dingel², Arne Held¹, Sara Savio¹, Lasse Wülfing¹, Niclas Wieland¹, Markus Ilchen³, and Wolfram Helml¹ — ¹Fakultät Physik, Technische Universität Dortmund, Germany — ²Intelligent Embedded Systems, Universität Kassel, Germany — ³Deutsches Elektronensynchrotron DESY, Hamburg, Germany

SASE free-electron-laser pulses pose a challenge in terms of temporal diagnostics, due to their intrinsic stochastic structure. Few methods allow directly resolving the full spectro-temporal information. In angular streaking, photoelectron momenta are linked to their birth phase by superimposing a circularly polarized infrared laser pulse. This principle allows reconstructing a pulse spectrogram shot-by-shot, enabling “stochastic experiments” by evaluating measurements as a function of derived quantities such as pulse duration or delay in a (stochastic) double pulse.

The analysis of angular streaking data involves disentangling the spectral and temporal contributions to the measurement for a single shot. In this talk, we present a current adaptation of the iterative Pacman algorithm and further, advanced reconstruction methods.

Furthermore, we show the application of these methods to data measured using angular streaking at the SQS instrument of European XFEL in June 2022. Statistical analysis of the reconstructed spectrograms allows providing diagnostic feedback with regard to different short-pulse FEL modes.