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Innovative, low-loss, and compact optical systems are essential to meet the experimental requirements of emerging novel radiation sources. The microchannel plate (MCP), a metamaterial-based optical device, shows promising potential for shaping, condensing, and focusing soft x-ray radiation at synchrotron radiation (SR) facilities. This study highlights the impact of MCP optical devices on SR beam condensing capability and their sensitivity to the degree of coherence by investigating the profile of transmitted beams through single and double MCP optical devices. Transmitted diffraction patterns of soft x-ray SR radiation change with energy and radiation modes. At 92 eV, the double MCP-based device affects the beam divergence and degree of coherence more than the single MCP. Moreover, the double MCP device shows potential as a condensing optics at shorter wavelengths, i.e., 480 eV. Experiments were performed at the available end-station of the Circular Polarization beamline at the Elettra synchrotron facility in Trieste, using a high-vacuum chamber with a hexapod system, providing the precise movement necessary to align these diffractive optics. The findings contribute to the development of innovative optical systems for SR and free-electron laser beamlines, paving the way for advanced experiments in spectroscopy, microscopy, and imaging in a wide energy range. [ABSTRACT FROM AUTHOR]

Copper (Cu), with its ability to exist in various oxidation states, notably Cu(I) and Cu(II), plays a crucial role in diverse biological redox reactions. This includes its involvement in pathways associated with oxidative stress in neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Transmissible Spongiform Encephalopathies. This paper offers an overview of X‐ray Absorption Spectroscopy (XAS) studies designed to elucidate the interactions between Cu ions and proteins or peptides associated with these neurodegenerative diseases. The emphasis lies on XAS specificity, revealing the local coordination environment, and on its sensitivity to Cu oxidation states. Furthermore, the paper focuses on XAS applications targeting the characterization of intermediate reaction states and explores the opportunities arising from recent advancements in time‐resolved XAS at ultrabright synchrotron and Free Electron Laser radiation sources. [ABSTRACT FROM AUTHOR]

The development of novel coherent and brilliant sources, such as soft X-ray free electron laser (FEL) and high harmonic generation (HHG), enables new ultrafast analysis of the electronic and structural dynamics of a wide variety of materials. Soft X-ray FEL delivers high-brilliance beams with a short pulse duration, high spatial coherence and photon energy tunability. In comparison with FELs, HHG X-ray sources are characterized by a wide spectral bandwidth and few- to sub-femtosecond pulses. The approach will lead to the time-resolved reconstruction of molecular dynamics, shedding light on different photochemical pathways. The high peak brilliance of soft X-ray FELs facilitates investigations in a nonlinear regime, while the broader spectral bandwidth of the HHG sources may provide the simultaneous probing of multiple components. Significant technical breakthroughs in these novel sources are under way to improve brilliance, pulse duration, and to control spectral bandwidth, spot size, and energy resolution. Therefore, in the next few years, the new generation of soft X-ray sources combined with novel experimental techniques, new detectors, and computing capabilities will allow for the study of several extremely fast dynamics, such as vibronic dynamics. In the present review, we discuss recent developments in experiments, performed with soft X-ray FELs and HHG sources, operating near the carbon K-absorption edge, being a key atomic component in biosystems and soft materials. Different spectroscopy methods such as time-resolved pump-probe techniques, nonlinear spectroscopies and photoelectron spectroscopy studies have been addressed in an attempt to better understand fundamental physico-chemical processes. [ABSTRACT FROM AUTHOR]

EuPRAXIA is a leading European project aimed at the development of a dedicated, ground-breaking, ultra-compact accelerator research infrastructure based on novel plasma acceleration concepts and laser technology and on the development of their users' communities. Within this framework, the Laboratori Nazionali di Frascati (LNF, INFN) will be equipped with a unique combination of an X-band RF LINAC generating high-brightness GeV-range electron beams, a 0.5 PW class laser system and the first fifth-generation free electron laser (FEL) source driven by a plasma-based accelerator, the EuPRAXIA@SPARC_LAB facility. Wiggler-like radiation emitted by electrons accelerated in plasma wakefields gives rise to brilliant, ultra-short X-ray pulses, called betatron radiation. Extensive studies have been performed at the FLAME laser facility at LNF, INFN, where betatron radiation was measured and characterized. The purpose of this paper is to describe the betatron spectrum emitted by particle wakefield acceleration at EuPRAXIA@SPARC_LAB and provide an overview of the foreseen applications of this specific source, thus helping to establish a future user community interested in (possibly coupled) FEL and betatron radiation experiments. In order to provide a quantitative estimate of the expected betatron spectrum and therefore to present suitable applications, we performed simple simulations to determine the spectrum of the betatron radiation emitted at EuPRAXIA@SPARC_LAB. With reference to experiments performed exploiting similar betatron sources, we highlight the opportunities offered by its brilliant femtosecond pulses for ultra-fast X-ray spectroscopy and imaging measurements, but also as an ancillary tool for designing and testing FEL instrumentation and experiments. [ABSTRACT FROM AUTHOR]

EuPRAXIA@SPARC_LAB is a new Free Electron Laser (FEL) facility that is currently under construction at the Laboratori Nazionali di Frascati of the INFN. The electron beam driving the FEL will be delivered by an X-band normal conducting LINAC followed by a plasma wakefield acceleration stage. It will be characterized by a small footprint and will deliver ultra-bright photon pulses for experiments in the water window to the user community. In addition to the soft-X-rays beamline already planned in the project, we propose the installation of a second photon beamline with seeded FEL pulses in the range between 50 and 180 nm. Here, we will present the FEL generation scheme, the layout of the dedicated beamline and the potential applications of the FEL radiation source in this low energy range. [ABSTRACT FROM AUTHOR]

A processing pipeline for diffraction data acquired using the `serial crystallography' methodology with a free-electron laser source is described with reference to the crystallographic analysis suite CrystFEL and the pre-processing program Cheetah. A detailed analysis of the nature and impact of indexing ambiguities is presented. Simulations of the Monte Carlo integration scheme, which accounts for the partially recorded nature of the diffraction intensities, are presented and show that the integration of partial reflections could be made to converge more quickly if the bandwidth of the X-rays were to be increased by a small amount or if a slight convergence angle were introduced into the incident beam. [ABSTRACT FROM AUTHOR]

Protein crystallization in cells has been observed several times in nature. However, owing to their small size these crystals have not yet been used for X-ray crystallographic analysis. We prepared nano-sized in vivo-grown crystals of Trypanosoma brucei enzymes and applied the emerging method of free-electron laser-based serial femtosecond crystallography to record interpretable diffraction data. This combined approach will open new opportunities in structural systems biology. [ABSTRACT FROM AUTHOR]

Abstract We are proposing a facility based on high gradient acceleration via X-band RF structures and plasma acceleration. We plan to reach an electron energy of the order of 1 GeV, suitable to drive a Free Electron Laser for applications in the so called water window (2–4 nm). A conceptual design of the beamline, from the photon beam from the undulators to the user experimental chamber, mainly focusing on diagnostic, manipulation and transport of the radiation is presented and discussed. We also briefly outline a user end station for coherent imaging, laser ablation and pump-probe experiments. [ABSTRACT FROM AUTHOR]

The Trypanosoma brucei cysteine protease cathepsin B (TbCatB), which is involved in host protein degradation, is a promising target to develop new treatments against sleeping sickness, a fatal disease caused by this protozoan parasite. The structure of the mature, active form of TbCatB has so far not provided sufficient information for the design of a safe and specific drug against T. brucei. By combining two recent innovations, in vivo crystallization and serial femtosecond crystallography, we obtained the room-temperature 2.1 angstrom resolution structure of the fully glycosylated precursor complex of TbCatB. The structure reveals the mechanism of native TbCatB inhibition and demonstrates that new biomolecular information can be obtained by the "diffraction-before-destruction" approach of x-ray free-electron lasers from hundreds of thousands of individual microcrystals. [ABSTRACT FROM AUTHOR]