Diffraction-limited Storage Rings Research Articles

Structural dynamics probed by X-ray pulses from synchrotrons and XFELs

This review focuses on how short X-ray pulses from synchrotrons and XFELs can be used to track light-induced structural changes in molecular complexes and proteins via the pump–probe method. The upgrade of the European Synchrotron Radiation Facility to a diffraction-limited storage ring, based on the seven-bend achromat lattice, and how it might boost future pump–probe experiments are described. We discuss some of the first X-ray experiments to achieve 100 ps time resolution, including the dissociation and in-cage recombination of diatomic molecules, as probed by wide-angle X-ray scattering, and the 3D filming of ligand transport in myoglobin, as probed by Laue diffraction. Finally, the use of femtosecond XFEL pulses to investigate primary chemical reactions, bond breakage and bond formation, isomerisation and electron transfer are discussed.

Using a pre-kicker to ensure safe extractions from the HEPS storage ring

The High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited storage ring light source under construction. The swap-out injection is adopted with the depleted bunch recycled via high-energy accumulation in the booster. The extremely high beam energy density of the bunches with an ultra-low emittance (about 30 pm horizontally and 3 pm vertically) and high bunch charges (from 1.33 to 14.4 nC) extracted from the storage ring could cause hazardous damage to the extraction Lambertson magnet in case of extraction kicker failure. To this end, we proposed the use of a pre-kicker to spoil the bunches prior to extraction, significantly reducing the maximum beam energy density down to within a safe region while still maintaining highly efficient extractions. The main parameters of the pre-kicker are simulated and discussed.

Research on vacuum properties of CuCrZr UHV flanges for the Hefei Advanced Light Facility

Hefei Advanced Light Facility (HALF), one of the Diffraction-Limited Storage Rings (DLSR), requires low-impedance flanges to be welded with Oxygen-free with Ag (OFS) vacuum chamber. In this paper, CuCrZr alloy as flange material and spring energized metal C-ring sealing structure are proposed. Two types of CuCrZr flanges have been designed, which are chain clamp and bolted flange, respectively. Chain clamp flanges are planed for compact areas, due to its small axial dimension. Bolted flanges with better positioning ability are designed to place in sections without space limitation. A series of leak rate and outgassing rate measurements were performed, and force and finite element analyses were carried out. Leak rates of both two flanges are lower than 5×10−13Pam3s−1 after 10 times seal-changing tests and 15 times same-seal bakeout cycles. Required fastening torques of chain clamp and bolted flange are 5–7 N m and 3–5 N m, respectively, in order to achieve sealing. The outgassing rate of CuCrZr is about an order of magnitude less than that of stainless steel after bakeout to 250 °C. The simulation results indicate that stress on the CuCrZr flange is far lower than metal C-ring due to the large deformation of the seal.

Laser-driven resonant magnetic soft-x-ray scattering for probing ultrafast antiferromagnetic and structural dynamics

Time-resolved resonant magnetic scattering in the soft-x-ray range is a powerful tool for accessing the spatially resolved and element-specific spin dynamics in magnetic materials. So far, the application of this photon-demanding technique was limited to large-scale facilities. However, upgrades to diffraction-limited storage rings supporting only x-ray pulses beyond 100 ps, and the shift of x-ray free-electron lasers toward attosecond pulses aggravate the competition for beamtime in the picosecond time window, which is of utmost relevance for magnetism research. Here we present the development of a lab-based instrument providing sufficient photon flux up to 1.5 keV photon energy covering the soft-x-ray resonances of transition and rare-earth metal atoms. Our setup features the mandatory tunability in energy and reciprocal space in combination with sub-10 ps temporal resolution, exploiting the broadband emission of a laser-driven plasma x-ray source, which is monochromatized to about 1 eV bandwidth by a reflection zone plate. We benchmark our approach against accelerator-based soft-x-ray sources by simultaneously probing the laser-induced magnetic and structural dynamics from an antiferromagnetically coupled Fe/Cr superlattice. Our development lays the foundation for laser-driven resonant scattering experiments to study ultrafast ordering phenomena of charges, spins, and orbitals.

“Spiral COSAMI” — A Multi-Undulator Compact Source for Actinic Mask Inspection in the extreme ultraviolet range

A compact electron storage ring provides a bright, stable and reliable source of extreme ultraviolet (EUV) radiation for metrology applications in semiconductor industry. The COSAMI concept (COmpact Synchrotron for Actinic Mass Inspection) applied design principles and technology of modern diffraction limited light source storage rings to an EUV facility operating at 13.5 nm wavelength. Since floor space is an important issue in an industrial environment, we propose a lattice configuration where three (or more) recirculation turns are stacked vertically. We present a facility, called Spiral-COSAMI, which simultaneously serves multiple (three or more) EUV beamlines within about the same floor space of the original COSAMI, and using the same type of injector and the same set of diagnostics, radio-frequency and pulsed magnet devices. The increased period of revolution of the multiple turns mitigates the problem of ion trapping and relaxes specifications of injection kickers.

Intra-beam scattering and beam lifetime in a candidate lattice of the soft X-ray diffraction-limited storage ring for the upgraded SSRF

Intra-beam scattering and beam lifetime in a candidate lattice of the soft X-ray diffraction-limited storage ring for the upgraded SSRF

Design study of APS-U-type hybrid-MBA lattice for mid-energy DLSR

In recent years, a new generation of storage ring-based light sources, known as diffraction-limited storage rings (DLSRs), whose emittance approaches the diffraction limit for the range of X-ray wavelengths of interest to the scientific community, has garnered significant attention worldwide. Researchers have begun to design and build DLSRs. Among various DLSR proposals, the hybrid multibend achromat (H-MBA) lattice enables sextupole strengths to be maintained at a reasonable level when minimizing the emittance; hence, it has been adopted in many DLSR designs. Based on the H-7BA lattice, the design of the Advanced Photon Source Upgrade Project (APS-U) can effectively reduce emittance by replacing six quadrupoles with anti-bends. Herein, we discuss the feasibility of designing an APS-U-type H-MBA lattice for the Southern Advanced Photon Source, a mid-energy DLSR light source with ultralow emittance that has been proposed to be built adjacent to the China Spallation Neutron Source. Both linear and nonlinear dynamics are optimized to obtain a detailed design of this type of lattice. The emittance is minimized, while a sufficiently large dynamic aperture (DA) and momentum acceptance (MA) are maintained. A design comprising 36 APS-U type H-7BAs, with an energy of 3 GeV and a circumference of 972 m, is achieved. The horizontal natural emittance is 20 pm·rad, with a horizontal DA of 5.8 mm, a vertical DA of 4.5 mm, and an MA of 4%, as well as a long longitudinal damping time of 120 ms. Subsequently, a few modifications are performed based on the APS-U-type lattice to reduce the maximum value of damping time from 120 to 44 ms while maintaining other performance parameters at the same level.

Bridging the gap of storage ring light sources and linac-driven free-electron lasers

High-gain free-electron lasers (FELs) are driven by short, high-charge density electron beams as only produced at dedicated single pass or recirculating linear accelerators. We describe new conceptual, technical, and modeling solutions to produce subpicosecond, up to $\ensuremath{\sim}100\text{ }\text{ }\ensuremath{\mu}\mathrm{J}$-energy extreme ultra-violet and soft x-ray FEL pulses at high- and tunable repetition rates, from diffraction-limited storage ring light source. In contrast to previously proposed schemes, we show that lasing can be simultaneous to the standard multibunch radiation emission from short insertion devices, and that it can be obtained with limited impact on the storage ring infrastructure. By virtue of the high-average power but moderate pulse energy, the storage ring-driven high-gain FEL would open the door to unprecedented accuracy in time-resolved spectroscopic analysis of matter in the linear response regime, in addition to inelastic scattering experiments.

Conceptual design and theoretical analysis of a system: The reference network of alignment

As a fourth-generation light source based on a diffraction-limited storage ring, Hefei Advanced Light Facility (HALF) has higher requirements for the alignment of magnets in terms of accuracy, efficiency and reliability. In this paper, we propose a system called the Reference Network of Alignment (RNA) that can achieve a transverse alignment accuracy of the magnets of ±20μm along a 100 m straight section of the accelerator. We first present the concept underlying the design of the RNA system. The girder assembly on which several common axis magnets are fixed forms the independent unit, and a long stretched wire is used as a straightness reference. A theoretical analysis of our system is then presented based on strict mathematical models that center on the combining method of the wire position sensors, the hydrostatic leveling sensors, and two-axis inclination sensors, for which the positions and orientations are known relative to each other. Finally, we perform a simulation of the RNA system using the Monte Carlo method. The results show that it is credible to assume that the RNA system can achieve an alignment installation accuracy of 20 μm and a displacement monitoring accuracy of 15 μm.

Simulations of applications using diaboloid mirrors

The diaboloid is a reflecting surface that converts a spherical wave to a cylindrical wave. This complex surface may find application in new Advanced Light Source bending-magnet beamlines or in other beamlines that now use toroidal optics for astigmatic focusing. Here, the numerical implementation of diaboloid mirrors is described, and the benefit of this mirror in beamlines exploiting diffraction-limited storage rings is studied by ray tracing. The use of diaboloids becomes especially interesting for the new low-emittance storage rings because the reduction of aberration becomes essential for such small sources. The validity of the toroidal and other mirror surfaces approximating the diaboloid, and the effect of the mirror magnification, are discussed.

In-line holography with hard x-rays at sub-15 nm resolution

X-ray in-line holography is well suited for three-dimensional imaging, since it covers a large field of view without the necessity of scanning. However, its resolution does not extend to the range covered by coherent diffractive imaging or ptychography. In this work, we show full-field holographic x-ray imaging based on cone-beam illumination, beyond the resolution limit given by the cone-beam numerical aperture. Image information encoded in far-field diffraction and in holographic self-interference is treated in a common reconstruction scheme, without the usual empty beam correction step of in-line holography. An illumination profile tailored by waveguide optics and exactly known by prior probe retrieval is shown to be sufficient for solving the phase problem. The approach paves the way toward high-resolution and dose-efficient x-ray tomography, well suited for the current upgrades of synchrotron radiation sources to diffraction-limited storage rings.

Scanning Compton X-ray microscopy.

X-ray microscopy offers the opportunity to image biological and radiosensitive materials without special sample preparations, bridging optical and electron microscopy capabilities. However, the performance of such microscopes, when imaging radiosensitive samples, is not limited by their intrinsic resolution, but by the radiation damage induced on such samples. Here, we demonstrate a novel, to the best of our knowledge, radio-efficient microscope, scanning Compton X-ray microscopy (SCXM), which uses coherently and incoherently (Compton) scattered photons to minimize the deposited energy per unit of mass for a given imaging signal. We implemented SCXM, using lenses capable of efficiently focusing 60 keV X-ray photons into the sub-micrometer scale, and probe its radio-efficient capabilities. SCXM, when implemented in high-energy diffraction-limited storage rings, e.g., European Synchrotron Radiation Facility Extremely Brilliant Source and PETRA IV, will open the opportunity to explore the nanoscale of unstained, unsectioned, and undamaged radiosensitive materials.

Simultaneous ambient pressure x-ray photoelectron spectroscopy and grazing incidence x-ray scattering in gas environments

We have developed an experimental system to simultaneously measure surface structure, morphology, composition, chemical state, and chemical activity for samples in gas phase environments. This is accomplished by simultaneously measuring x-ray photoelectron spectroscopy (XPS) and grazing incidence x-ray scattering in gas pressures as high as the multi-Torr regime while also recording mass spectrometry. Scattering patterns reflect near-surface sample structures from the nano-scale to the meso-scale, and the grazing incidence geometry provides tunable depth sensitivity of structural measurements. Scattered x rays are detected across a broad range of angles using a newly designed pivoting-UHV-manipulator for detector positioning. At the same time, XPS and mass spectrometry can be measured, all from the same sample spot and under ambient conditions. To demonstrate the capabilities of this system, we measured the chemical state, composition, and structure of Ag-behenate on a Si(001) wafer in vacuum and in O2 atmosphere at various temperatures. These simultaneous structural, chemical, and gas phase product probes enable detailed insights into the interplay between the structure and chemical state for samples in gas phase environments. The compact size of our pivoting-UHV-manipulator makes it possible to retrofit this technique into existing spectroscopic instruments installed at synchrotron beamlines. Because many synchrotron facilities are planning or undergoing upgrades to diffraction limited storage rings with transversely coherent beams, a newly emerging set of coherent x-ray scattering experiments can greatly benefit from the concepts we present here.

Thallium sorption by soil manganese oxides: Insights from synchrotron X-ray micro-analyses on a naturally thallium-rich soil

Thallium (Tl) is a highly toxic trace metal. It occurs mostly as soluble monovalent Tl(I) and less frequently as poorly soluble trivalent Tl(III). Laboratory studies have shown that vacancy-containing hexagonal birnessites can sorb Tl with a very high affinity via a mechanism that involves the oxidation of Tl(I) to Tl(III) and strong complexation of Tl(III), whereas other manganese (Mn) oxides bind Tl(I) non-oxidatively and with lower sorption affinity. Information on the mode of Tl uptake by natural Mn oxides in soils, on the other hand, is still limited. In this study, we characterized the association of Tl with Mn oxides and Tl (redox) speciation in a naturally Tl-rich soil using micro-focused synchrotron X-ray absorption near edge structure (XANES) spectroscopy and X-ray fluorescence (XRF) chemical imaging. The results show that most soil Tl was Tl(I) associated with micaceous clay minerals in the soil matrix. High levels of Tl in soil Mn concretions, on the other hand, were mostly identified as Tl(III), suggesting that oxidative Tl uptake by vacancy-containing hexagonal birnessite was the main process of Tl accumulation in soil Mn concretions. The spectroscopic results in combination with chemical extractions and published sorption isotherms for Tl on synthetic Mn oxides suggest that the formation and transformation of natural Mn oxides in soils and sorption competition of Tl with major and trace metal cations determine the extent and mode of Tl uptake by soil Mn oxides. Methodologically, this study compares classical micro-XRF element mapping combined with point XANES analyses for spatially-resolved element speciation with high-resolution chemical imaging of entire sample areas, which is of great interest for the geochemical community in light of diffraction-limited storage ring upgrades to many synchrotron lightsources.

A conceptual design study of generating locally-round beam in a diffraction-limited storage ring using skew quadrupole triplets

Diffraction-limited storage rings (DLSRs), with sub-100pm⋅rad electron emittances approaching the diffraction limit for hard X-rays, would provide unprecedented transverse coherence and much higher brightness than currently operational light sources to the synchrotron radiation scientific community. Instead of typical flat beam, some individual synchrotron light users prefer round beam, a beam with equivalent emittances between the horizontal and vertical planes, for the reasons of fully transverse coherent X-ray radiation and better photon–electron phase space match, and so on. To meet the requirements of different experimenters, obtaining a locally-round beam will be a significant subject in DLSR studies. We investigate the approaches of realizing locally-round beam in a storage ring, by means of a local emittance equalization of the transverse planes. In this paper, a novel method is proposed to achieve locally-round beam, performed with a combination of skew quadrupoles in insertion section of the storage ring. Theoretical analysis and application of this method to achieve a locally-round beam at DLSRs, particularly to High Energy Photon Source (HEPS) storage ring, are presented.

A novel kind of nonlinear kicker for the Hefei Advanced Light Facility

The Hefei Advanced Light Facility (HALF) is a vacuum ultraviolet (VUV) and X-ray diffraction-limited storage ring light source. Because of its extremely small dynamic aperture, an injection scheme with a nonlinear kicker (NLK) was considered for the HALF. This magnet was designed with ferrite cores to achieve a higher excitation efficiency and a small gap shield in the central area for a flat magnetic field. In this paper, the design parameters, calculations and measurements of the kicker are described, and further optimization of the magnet structure is discussed.

Design of a diffraction-limited storage ring lattice using longitudinal gradient bends and reverse bends

Diffraction-limited storage ring (DLSR) light sources are being developed towards the goal of reaching the diffraction-limited emittances. To reduce the emittances, multi-bend achromat (MBA) lattices with many bend unit cells are used in DLSR designs. The bend unit cell with the combination of longitudinal gradient bend (LGB) and reverse bend (RB) can achieve much lower emittance, which has produced the SLS-2 7BA lattice (Streun et al., 2018). In this paper, a 6BA lattice with LGB/RB unit cells is designed for a DLSR with an energy of 2.2 GeV and 20 periods. An ultra-low natural emittance of 36 pm⋅rad is achieved for the designed DLSR, and the beta functions at straight sections are also relatively low so as to enhance the radiation brightness of insertion devices. The optimized dynamic aperture is relatively large, larger than 4 mm in the horizontal direction, and the momentum aperture is also reasonable. Besides, the intra-beam scattering effect is estimated and discussed.

Constraint handling in constrained optimization of a storage ring multi-bend-achromat lattice

In the design of multi-bend achromat (MBA) lattices for diffraction-limited storage rings (DLSRs), usually, many magnet parameters need to be adjusted, and the constraints to be satisfied can be stringent. When using an evolutionary algorithm to optimize such a complicated lattice, there can be only few or even none of lattice solutions satisfying the constraints in the early evolution stage of the algorithm, which may significantly affect the optimization result. Therefore, the techniques for constraint handling in an evolutionary algorithm will be important for better optimizing MBA lattices. In this paper, three typical constraint handling methods that are incorporated into a multi-objective particle swarm optimization algorithm are used to optimize a hybrid 7BA lattice for a 2.2 GeV DLSR. In this lattice optimization, the impacts of the population size of the algorithm and the constraint condition on the optimization result are studied for these methods, and comparisons are also made among these methods. It is shown that, in general, the penalty function method is a better constraint handling method for optimizing MBA lattices. From the optimization result obtained by the penalty function method, a lattice with a natural emittance of about 84 pm⋅rad is selected, which has large dynamic aperture and momentum aperture.

Extremely bright coherent synchrotron radiation production in a diffraction-limited storage ring using an angular dispersion-induced microbunching scheme

Generation of extreme bright coherent synchrotron radiation in a short wavelength range is of remarkable interest in the synchrotron light source community. In this paper, a novel technique is adopted to produce the coherent radiation which uses an angular dispersion to enhance the micro-bunch by a tiny amplitude of energy modulation. This scheme can be inserted in a long straight section of a storage ring. A lattice design of an extreme-low emittance storage ring with 3.5 GeV energy is presented in this paper, which employs a higher order achromat (HOA) concept. We show the design results for the multi-bend achromat (MBA) lattice with an emittance of 20 pm-rad in about 900-meter circumference. Numerical simulations demonstrated that this angular dispersion induced micro-bunch scheme can be used to generate coherent radiation near soft x-ray region, the repetition rate can reach 10 kHz and the spectral brightness can reach 3*10^24phs/s/mm^2/mrad^2/0.1%BW.

Design of the HEPS booster lattice

The high energy photon source (HEPS) is a diffraction-limited storage ring light source being built in China. Along with the deeper studies of booster and the evolution of the lattice design and injection scheme of the storage ring, four versions of the booster lattices have been proposed from the project proposal stage. Unlike the design of the storage ring, in the booster design, more effort was made to realize stable and reliable operation rather than advanced performance. A FODO structure lattice and the “high-energy accumulation” scheme was adopted in the HEPS booster design. To find the ultimate performance of the lattice, a multi-objective genetic algorithm (MOGA) and particle swarm optimization (PSO) were used to optimize the emittance and the dynamic aperture. In the latest booster lattice design, the emittance was reduced to 16.3 nm rad. At the same time, the single-bunch charge limit was increased by minimizing the average vertical beta function and reducing the chromaticity. Through multi iterations with the hardware system, the current lattice was basically frozen and can be used as a basis for related physics studies, hardware and engineering design of the booster. In the future, more detailed physical studies will be performed based on this lattice.