Open AccessWigner distribution of self‐amplified spontaneous emission free‐electron laser pulses and extracting its autocorrelation
Author(s) -
Serkez Svitozar,
Gorobtsov Oleg,
Rivas Daniel E.,
Meyer Michael,
Sobko Bohdana,
Gerasimova Natalia,
Kujala Naresh,
Geloni Gianluca
Publication year - 2021
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s160057752001382x
Subject(s) - physics , autocorrelation , free electron laser , chirp , laser , radiation , optics , spectral line , free electron model , electron , linear particle accelerator , spectral power distribution , beam (structure) , radiant intensity , cathode ray , computational physics , nuclear physics , quantum mechanics , statistics , mathematics
The emerging concept of `beam by design' in free‐electron laser (FEL) accelerator physics aims for accurate manipulation of the electron beam to tailor spectral and temporal properties of the radiation for specific experimental purposes, such as X‐ray pump/X‐ray probe and multiple wavelength experiments. `Beam by design' requires fast, efficient, and detailed feedback on the spectral and temporal properties of the generated X‐ray radiation. Here a simple and cost‐efficient method to extract information on the longitudinal Wigner distribution function of emitted FEL pulses is proposed. The method requires only an ensemble of measured FEL spectra and is rather robust with respect to accelerator fluctuations. The method is applied to both the simulated SASE spectra with known radiation properties as well as to the SASE spectra measured at the European XFEL revealing underlying non‐linear chirp of the generated radiation. In the Appendices an intuitive understanding of time–frequency representations of chirped SASE radiation is provided.