Ultra-high Brilliance Research Articles

Turning European XFEL raw data into user data

The European X-ray Free Electron Laser is a research facility located close to Hamburg, offering X-ray pulses with ultra-high brilliance and femtosecond duration at megahertz repetition rates. The detection systems necessary to unlock the full scientific potential made possible by this machine poses considerable challenges both in terms of data volume and rate, as well as the interpretation of their recorded signal. To provide optimal data quality, expert and detector-specific knowledge not easily accessible to external facility users is essential, and its implementation must cope with the generated volumes. We therefore aim to perform these preparatory processing steps and offer users a dataset suitable for further analysis as the primary data product. This work describes the machinery and workflows providing this data to users in an automatic, configurable and reproducible manner, both online during the experiment, and offline for scientific analysis afterward on the way to publication.

Single-pulse characterization of the focal spot size of X-ray free-electron lasers using coherent diffraction imaging.

The characterization of X-ray focal spots is of great significance for the diagnosis and performance optimization of focusing systems. X-ray free-electron lasers (XFELs) are the latest generation of X-ray sources with ultrahigh brilliance, ultrashort pulse duration and nearly full transverse coherence. Because each XFEL pulse is unique and has an ultrahigh peak intensity, it is difficult to characterize its focal spot size individually with full power. Herein, a method for characterizing the spot size at the focus position is proposed based on coherent diffraction imaging. A numerical simulation was conducted to verify the feasibility of the proposed method. The focal spot size of the Coherent Scattering and Imaging endstation at the Shanghai Soft X-ray Free Electron Laser Facility was characterized using the method. The full width at half-maxima of the focal spot intensity and spot size in the horizontal and vertical directions were calculated to be 2.10 ± 0.24 µm and 2.00 ± 0.20 µm, respectively. An ablation imprint on the silicon frame was used to validate the results of the proposed method.

High-order vortex harmonics generation by bi-circular Laguerre-Gaussian laser fields with relativistic plasmas

Vortex beams with ultra-high brilliance can greatly enrich the light and matter interaction process and even shed light on the unexpected information in relativistic nonlinear optics. Thus, we propose a scheme for relativistic intense vortex harmonic radiation by use of bi-circular Laguerre–Gaussian lasers irradiating relativistic plasmas. Three-dimensional particle-in-cell simulation results show that the emitted harmonics own controllable spin and orbital angular momentum simultaneously, which can be attributed to the vortex mirror model and the related conservation laws. Meanwhile, the conversion efficiency of harmonic generation can be tuned through adjusting the intensity ratio of the two driving field components.

Isotope-selective radiography and material assay using high-brilliance, quasi-monochromatic, high-energy photons.

We demonstrate the possibility to directly detect microgram amounts of the isotope 7Li using a quasi-monochromatic high-energy photon beam. The isotope selective detection is based on a witness scatterer absorbing and re-emitting photons via nuclear resonance fluorescence. This enables the detection of isotopes with microgram accuracy at long distances from the actual sample. Further, we demonstrate that the technique can deliver quantitative information without specific knowledge of the photon flux and no spectral capabilities or knowledge of the resonance fluorescence cross section. Detection of low-atomic-weight isotopes screened by heavy shielding is also shown. The techniques described are applicable to all next-generation, ultrahigh brilliance, laser-Compton light sources currently under construction.

Ultrahigh brilliance quasi-monochromatic MeV γ-rays based on self-synchronized all-optical Compton scattering.

Inverse Compton scattering between ultra-relativistic electrons and an intense laser field has been proposed as a major route to generate compact high-brightness and high-energy γ-rays. Attributed to the inherent synchronization mechanism, an all-optical Compton scattering γ-ray source, using one laser to both accelerate electrons and scatter via the reflection of a plasma mirror, has been demonstrated in proof-of-principle experiments to produce a x-ray source near 100 keV. Here, by designing a cascaded laser wakefield accelerator to generate high-quality monoenergetic e-beams, which are bound to head-on collide with the intense driving laser pulse via the reflection of a 20-um-thick Ti foil, we produce tunable quasi-monochromatic MeV γ-rays (33% full-width at half-maximum) with a peak brilliance of ~3 × 1022 photons s−1 mm−2 mrad−2 0.1% BW at 1 MeV. To the best of our knowledge, it is one order of magnitude higher than ever reported value of its kinds in MeV regime. This compact ultrahigh brilliance γ-ray source may provide applications in nuclear resonance fluorescence, x-ray radiology and ultrafast pump-probe nondestructive inspection.

A high-energy, high-flux source of gamma-rays from all-optical non-linear Thomson scattering

γ-Ray sources are among the most fundamental experimental tools currently available to modern physics. As well as the obvious benefits to fundamental research, an ultra-bright source of γ-rays could form the foundation of scanning of shipping containers for special nuclear materials and provide the bases for new types of cancer therapy.However, for these applications to prove viable, γ-ray sources must become compact and relatively cheap to manufacture. In recent years, advances in laser technology have formed the cornerstone of optical sources of high energy electrons which already have been used to generate synchrotron radiation on a compact scale. Exploiting the scattering induced by a second laser, one can further enhance the energy and number of photons produced provided the problems of synchronisation and compact γ-ray detection are solved.Here, we report on the work that has been done in developing an all-optical and hence, compact non-linear Thomson scattering source, including the new methods of synchronisation and compact γ-ray detection. We present evidence of the generation of multi-MeV (maximum 16–18MeV) and ultra-high brilliance (exceeding 1020photonss−1mm−2mrad−2 0.1% BW at 15MeV) γ-ray beams. These characteristics are appealing for the paramount practical applications mentioned above.

The sub-micron resolution X-ray spectroscopy beamline at NSLS-II

Abstract For many research areas such as life, environmental, earth or material sciences, novel analytical resources have to be developed for an advance understanding of complex natural and engineered systems that are heterogeneous on the micron to the tenths of microns scale. NSLS-II at BNL will be a synchrotron radiation source with an ultra-high brilliance delivering a high current (500 mA). One of the 1st six NSLS-II beamlines will be the Sub-micron Resolution X-ray spectroscopy beamline (SRX), dedicated as an analytical tool to study complex systems on a sub-micron length scale. SRX will comprise two branches thanks to a canted setup with two undulators: the first branch using Kirkpatrick–Baez mirrors as focusing optics will cover the energy range of 4.65–23 keV, allowing for XANES experiments from the Ti to the Rh K-edge. Thanks to a horizontally deflecting double crystal monochromator with maximum stability, a set of slits located on the secondary source, and two sets of complementary and quickly interchangeable KB mirrors, spectroscopy with very high spectral and spatial resolution will be achieved. The spot size will almost fully cover a range from 60×60 to 1300×500 nm2, providing an attractive adaptability of the observation scale. A 1.5 m long IVU21 will serve as a light source. The expected high flux in a sub-micron-spot (5×1012 and 7×1013 ph s−1 at maximum and lowest resolutions) will open new possibilities for spectromicroscopy of trace elements. The 2nd canted undulator will serve as an independent light source for the second branch designed for experiments with X-ray energies in the range of 2–15 keV. Using Fresnel zone plates, the spatial resolution aimed for is around 30 nm with up to 7×109 ph s−1 in the spot. This branch would be attractive for many biological applications from life and environmental science due to low-Z elements of interest within that energy range. In both experimental stations, X-ray fluorescence will be used for imaging, spectroscopy, tomography and μ-diffraction experiments.

Methods in carbon K-edge NEXAFS: Experiment and analysis

Near-edge X-ray absorption spectroscopy (NEXAFS) is widely used to probe the chemistry and structure of surface layers. Moreover, using ultra-high brilliance polarised synchrotron light sources, it is possible to determine the molecular alignment of ultra-thin surface films. However, the quantitative analysis of NEXAFS data is complicated by many experimental factors and, historically, the essential methods of calibration, normalisation and artefact removal are presented in the literature in a somewhat fragmented manner, thus hindering their integrated implementation as well as their further development. This paper outlines a unified, systematic approach to the collection and quantitative analysis of NEXAFS data with a particular focus upon carbon K-edge spectra. As a consequence, we show that current methods neglect several important aspects of the data analysis process, which we address with a combination of novel and adapted techniques. We discuss multiple approaches in solving the issues commonly encountered in the analysis of NEXAFS data, revealing the inherent assumptions of each approach and providing guidelines for assessing their appropriateness in a broad range of experimental situations.

New energy recovery linac source of synchrotron X-rays

Introduction Cornell University and Jefferson Laboratory physicists have been studying the properties of a new type of synchrotron radiation machine, called an Energy Recovery Linac (ERL), based on a superconducting linac configured for energy recovery with a return ring. A high energy, high current ERL could produce electron beams of order 10 microns in diameter. These could be used as an ultra-high brilliance x-ray source with many desirable characteristics, including: transversely coherent, diffraction-limited hard x-ray beams, very short (~100 fs) frequent (1 – 2 GHz) pulses, no limits on beam lifetime, and very flexible modes of operation. This combination of characteristics opens up new possibilities and could significantly advance the state of the art in x-ray research.

Synchrotron radiation time gate quartz device for nuclear resonant scattering

A synchrotron radiation time gate with X-cut quartz resonator has been constructed for use on nuclear resonant scattering at ultrahigh brilliance beam lines. The purpose is to discriminate the electronic scattered prompt (zero time) from the time delayed nuclear scattered photons. The special feature of this device is the possibility of adjusting the time modulation width of the gate without changing the frequency.