X-ray free electron lasers provide short, polarized, high-power pulses of x-ray radiation, where polarization properties are determined by the undulator magnetic field. We propose a cost-effective method to shape the polarization of FEL radiation on the sample both spatially, on a few-$\mu \mathrm{m}$ scale, and/or temporally on the 100-femtosecond scale. The method is based on coaxial superposition of two coherent radiation pulses with different frequencies emitted in two consequent undulators set to emit radiation with orthogonal polarization states. Its capabilities are demonstrated via numerical simulations for the SASE3 undulator line of the European X-ray Free-Electron Laser. Generation of x-ray free-electron laser pulses with shaped polarization may be interesting for studies of magnetism or ultrafast phenomena and will facilitate further developments of complex light engineering in the soft X-ray range.

We report on observations of single spike spectra (3–13% of events) upon employing a previously proposed method for single spike generation via harmonic conversion. The method was tested at the soft X-ray SASE3 undulator of the European XFEL. The first part of the undulator allows one to amplify bunching at the fundamental as well as the higher harmonics. The downstream undulator is tuned to a harmonic, the fourth in our case, to amplify pulses with a shorter duration. We estimate the generated pulse duration within such a subset of short pulses at a level of 650 as. Considering the demonstrated probability of single spike events, this method is attractive for high repetition-rate free electron lasers.

Over the next decade, the extremely brilliant fourth generation synchrotron radiation sources are set to become a key driving force in materials characterization and technology development. In this study, we present a conceptual design of a versatile “Materia” diffraction and imaging beamline for a low-emittance synchrotron radiation facility. The beamline was optimized for operation with three main principal delivery regimes: parallel collimated beam ∼1 mm beam size, micro-focus regime with ∼10 μm beam spot size on the sample, and nano-focus regime with <100 nm focus. All regimes will operate in the photon energy range of 10–30 keV with the key feature of the beamline being fast switching between them, as well as between the various realizations of diffraction and imaging operation modes while maintaining the target beam position at the sample, and with both spectrally narrow and spectrally broad beams up to the energy band ΔE/E of 5 × 10⁻². The manuscript presents the details of the principal characteristics selected for the insertion device and beamline optics, the materials characterization techniques, including the simulations of thermal load impact on the critical beamline optics components. Significant efforts were made to design the monochromators to mitigate the very high beam power load produced by a superconducting undulator source. The manuscript will be of interest to research groups involved in the design of new synchrotron beamlines.

Wavefront propagation codes play pivotal roles in the design of optics at synchrotron radiation sources. However, they usually do not account for the stochastic behavior of the radiation field originating from shot noise in the electron beam. We propose a computationally efficient algorithm to calculate a single statistical realization of partially coherent synchrotron radiation fields at a given frequency. This field can be consequently propagated from the source position downstream through an optical beamline to the sample position. The proposed algorithm relies on a method for simulating Gaussian random fields. We initially generate the radiation field as Gaussian white noise and then restrict it in both real and inverse space domains for a given radiation size and divergence. We exploit the assumption of quasi-homogeneity of the source. However, we show that the method is applicable with reasonable accuracy outside of this assumption. The proposed algorithm is consistent with other well-established approaches, and, in addition, it possesses an advantage in terms of computational efficiency. It can be extended to other types of sources that follow Gaussian statistics. Finally, the demonstration of the algorithm is well suited for educational purposes.

A scheme to generate wide-bandwidth radiation using a step-wise tapered undulator with a segmented structure is proposed. This magnetic field configuration allows to broaden the undulator harmonic spectrum by two orders of magnitude, providing 1 keV bandwidth with spectral flux density exceeding 10¹⁶ photons s⁻¹ mm⁻² (0.1% bandwidth)⁻¹ at 5 keV on the sample. Such a magnetic setup is applicable to superconducting devices where magnetic tapering cannot be arranged mechanically. The resulting radiation with broadband spectrum and flat-top shape may be exploited at a multipurpose beamline for scanning over the spectrum at time scales of 10–100 ms. The radiation from a segmented undulator is described analytically and derivations with numerical simulations are verified. In addition, a start-to-end simulation of an optical beamline is performed and issues related to the longitudinally distributed radiation source and its image upon focusing on the sample are addressed.

In this work, we propose to use a pinhole camera at high photon energies, specifically 200–300 keV, to measure ultra-small electron beam size by means of bending magnet radiation. We show that there is a sufficient photon flux at the detector position. Our theoretical analysis includes an examination of the applicability of the van Cittert-Zernike theorem for the bending magnet radiation generated by an ultralow emittance electron beam and a detailed analysis of the imaging properties of rectangular pinhole cameras. This led us to practical, universal formulas. We identify the optimal aperture size and resolution of the camera in the given geometry. The theoretical findings are further substantiated by wavefront propagation numerical simulations of partially coherent radiation. This study serves both as a practical guide for optical engineering and an educational resource for explaining the imaging properties of pinhole cameras. Published by the American Physical Society 2024