Diffraction-limited Storage Rings Research Articles

Applications of vertical damping wigglers in an X-ray diffraction limited storage ring

This study presents a lattice design for an X-ray diffraction limited storage ring (DLSR) light source with a circumference of 864 m and achieving an ultralow natural emittance of 25.6 pm·rad (N-IBS). However, the ultra-low emittance and long damping times lead to significant intra-beam scattering (IBS) effects. To address this issue, the study explores the implementation of vertical damping wigglers (VDWs) to decrease damping times, reduce beam horizontal emittance, and generate vertical emittance to achieve a “round beam” in the 864mDLSR. Through theoretical analysis and accelerator toolbox (AT) simulations, the impacts of VDWs with varied parameters were investigated, and the optimal period length, peak field, and total length were determined. Additionally, the twelve quadrupole magnets in both the front and rear cells of the VDWs were employed to correct linear optics. The findings demonstrate that VDWs could significantly reduce the beam's equilibrium emittance and damping times of the 864mDLSR. Furthermore, a comparison between the spectral brightness and flux of the 864mDLSR with and without VDWs revealed that the 864mDLSR employing VDWs yielded higher brightness and flux.

Generating high repetition rate X-ray attosecond pulses in a diffraction limited storage ring

To steer and track electron motion in atoms, molecules, and nanostructures, light pulses with attosecond duration and high repetition rate are required. In this paper, we use the angular dispersion-induced microbunching scheme and a few-cycle laser within a straight section (a few meters) of a diffraction-limited storage ring to generate a coherent high-flux attosecond pulse in the water window region. Simulation results based on the Southern Advanced Photon Source indicate that the proposed method can generate a chirp-free Fourier transform limited pulse with a minimum duration of 50 as, a maximum repetition rate of a few MHz, and a maximum average flux of about 4.4times 10^{11} photons/s/1%Bw.

Conceptual design of a beamline for classical XAFS spectroscopy at the future ultra low emittance storage ring PETRA IV

Conceptual design of a beamline for classical XAFS spectroscopy at the future ultra low emittance storage ring PETRA IV

Polarization switching of segmentally helical undulators in a diffraction-limited storage ring

Polarization switching of segmentally helical undulators in a diffraction-limited storage ring

The high level applications for the HEPS Linac

The High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited storage ring based light source, which is under construction in Beijing, China. The HEPS accelerator consists of a Linac, a booster, a storage ring and three transfer lines. Installation and high-power conditioning of the Linac has been completed. For beam commissioning and measurements of the HEPS Linac, it is necessary to develop high level applications (HLAs). The development of the Linac HLAs, based on the framework named Python accelerator physics application set(Pyapas), has been completed. All the applications are physics quantity based, including measurement applications, control applications and monitoring applications. All the applications have been tested and verified on virtual accelerator. The results show the validity of the algorithm and indicate that the developed applications could meet the requirements of Linac commissioning. All the applications have been deployed to the actual machine environment and communication and control test with hardware system have been completed.

Electromagnetic design study of a superconducting longitudinal gradient bend magnet based on the HALF storage ring

The National Synchrotron Radiation Laboratory is planning to build a 2.2 GeV diffraction-limited storage ring, the Hefei Advanced Light Facility (HALF), with a 6BA lattice structure and a large number of longitudinal gradient bends (LGBs). In order to increase the radiated photon energy to the hard X-ray band and to reduce the natural emittance, a superconducting longitudinal gradient bend (SLGB) magnet is planned to be used on HALF in the future, which requires a magnetic field integral of 0.40 T·m over a length of 0.46 m and a peak field of about 5 T. A SLGB has many structural parameters, such as the geometric parameters of the superconducting coils and the thickness of the yoke, etc. Their influence on the magnetic field distribution has been studied, although the computation of the 3D magnet model is very slow. Considering the longitudinal field variation, the vertical gap limitation, the field homogeneity requirement and the critical current of the superconducting wire, a method is developed to simplify the 3D magnet simulation by a corresponding 2D model, so that the longitudinal magnetic field profile of a 3D model can be approximately calculated in a 2D model with faster speed. Due to the faster calculation speed of 2D models, a Mathematica-based optimization program is developed and relatively good structural parameters for the HALF SLGB are found by the program. The simulation results show that the physical design requirements can be well met. The electromagnetic design for the HALF SLGB magnet is based on the current JC level of NbTi superconductor due to its excellent mechanical performance.

Selected advances in small-angle scattering and applications they serve in manufacturing, energy and climate change.

Innovations in small-angle X-ray and neutron scattering (SAXS and SANS) at major X-ray and neutron facilities offer new characterization tools for researching materials phenomena relevant to advanced applications. For SAXS, the new generation of diffraction-limited storage rings, incorporating multi-bend achromat concepts, dramatically decrease electron beam emittance and significantly increase X-ray brilliance over previous third-generation sources. This results in intense X-ray incident beams that are more compact in the horizontal plane, allowing significantly improved spatial resolution, better time resolution, and a new era for coherent-beam SAXS methods such as X-ray photon correlation spectroscopy. Elsewhere, X-ray free-electron laser sources provide extremely bright, fully coherent, X-ray pulses of <100 fs and can support SAXS studies of material processes where entire SAXS data sets are collected in a single pulse train. Meanwhile, SANS at both steady-state reactor and pulsed spallation neutron sources has significantly evolved. Developments in neutron optics and multiple detector carriages now enable data collection in a few minutes for materials characterization over nanometre-to-micrometre scale ranges, opening up real-time studies of multi-scale materials phenomena. SANS at pulsed neutron sources is becoming more integrated with neutron diffraction methods for simultaneous structure characterization of complex materials. In this paper, selected developments are highlighted and some recent state-of-the-art studies discussed, relevant to hard matter applications in advanced manufacturing, energy and climate change.

Non-equilibrium magnetic compression for picosecond-long X-ray pulses at a diffraction limited storage ring light source

Picosecond-long x-ray pulses of moderate intensity and high repetition rate are highly sought after by the light sources community, e.g. for time-resolved investigations of matter in the linear response regime. We investigate the upgrade of a diffraction-limited storage ring light source to a short X-ray pulse scheme. Short pulses are emitted by electron bunches magnetically compressed in the injection chain, with no impact on the simultaneous standard emission from long bunches. The ultimate performance, limits and operational aspects of the scheme are discussed in terms of soft X-ray undulator emission.

Optimization of dynamic aperture by using non-dominated sorting genetic algorithm-II in a diffraction-limited storage ring with solenoids for generating round beam

Optimization of dynamic aperture by using non-dominated sorting genetic algorithm-II in a diffraction-limited storage ring with solenoids for generating round beam

Refractive axicon for X-ray microscopy applications: design, optimization, and experiment.

In a full-field transmission X-ray microscopy (TXM) setup, a condenser X-ray optical element is used to illuminate the sample by condensing the X-ray beam delivered by the synchrotron storage ring. On-going and future upgrades of synchrotron facilities to diffraction-limited storage rings will pose new challenges to these TXM setups, such as much smaller X-ray beams on the condenser. Here, we demonstrate that a refractive axicon can be used as an X-ray beam shaper to match the ring-shaped aperture of the condenser. Aiming at more efficient use of the incoming X-ray intensity, we explore several axicon designs both analytically and with numerical simulations. The axicons were produced by two-photon polymerization 3D printing on thin silicon nitride membrane substrates. The first characterization of the axicon was carried out at the TOMCAT beamline of the Swiss Light Source (Switzerland).

Requirements and limitations of the pulsed wire technique for measuring short-period long undulators’ magnetic field

The pulsed wire method is an attractive option to measure the magnetic field in insertion devices, mainly for those with restricted access (e.g., small gaps, in-vacuum/cryogenic environments, etc.). Besides first and second field integrals, experiments have proved the feasibility of reconstructing the magnetic field profile. Undulators with a small gap and short period are — and are planned to be — used at diffraction-limited storage rings and free-electron lasers. This contribution outlines the pulsed wire system’s requirements to perform magnetic field reconstruction in such undulators. We examine the main expected limitations, particularly the dispersive, finite pulse-width, discretization error, and sag effects. Furthermore, we present the current status of developing the pulsed wire system at the European XFEL.

A WISER way for simulating the performance of gratings.

Soft X-ray monochromators for synchrotron radiation sources have been continuously developed over the years, improving energy resolution and stability. Great effort has been made in improving the surface quality of the optics involved, reaching values permitting diffraction-limited images. Still, one problem has not been solved, nor fully understood, yet: groove placing errors. Nowadays, these are one of the major factors responsible for resolving the power reduction of diffraction-gratings-based X-ray monochromators. Despite decades of use of gratings, there is not yet a universally established method for predicting and simulating the effect of groove placing errors on monochromator performance. This is especially important in the new scenario of high-coherent X-ray sources, i.e. diffraction-limited storage rings and free-electron lasers. To address this problem, in this article an approach based on WISER (Wavefront propagatIon Simulation codE libRary) is presented. WISER is a physical optics simulation package, also available in the user-friendly Orange Synchrotron Radiation Suite - OASYS. Even though it was originally conceived to assess the focusing performance of X-ray mirrors in the presence of height defects, it perfectly simulates the performance of a periodic (or quasi-periodic) structure like a diffraction grating. In this article, the way to use WISER and its application to a specific case, e.g. the design of a monochromator for the upgrade of a beamline at the Advanced Light Source, are shown. A simple rule for estimating how well the grooves are placed on a grating, based on calculation of the Strehl ratio, is also presented.

Optimization of echo-enabled harmonic generation toward coherent EUV and soft X-ray free-electron laser at NSLS-II.

Prebunching via echo-enabled harmonic generation (EEHG) is an efficient way to reduce the radiator length and improve the longitudinal coherence as well as output stability in storage-ring-based free-electron lasers. We propose a conceptual design, which uses two straight sections to seed coherent extreme-ultraviolet (EUV) and soft X-ray emission with nearly MHz repetition rate. To take the large energy spread (10−3) of a storage ring into account and utilize the existing bending magnets between the two straight sections as the first chicane, we implement a special modeling tool, named EEHG optimizer. This tool has been successfully applied to maximize the prebunching with a reasonably low energy modulation, thereby generating intense coherent X-ray pulses within a short undulator length (a few meters) limited by the available space of a storage ring. Numerical simulations confirm that the optimized EEHG parameters can be directly applied to generate a 10 MW scale peak power with fully coherent ultrafast EUV to soft X-ray pulses based on the NSLS-II parameters. This method can be easily extended to other types of diffraction-limited storage rings.

Development of an autotuning magnet girder with high stability and accuracy

With the development of high-performance photon sources which have extremely low emittance, autotuning magnet girders have drawn more and more attention, especially for diffraction-limited storage rings and free-electron lasers. The biggest challenge is to simultaneously obtain high stability and high flexibility. In this paper, an autotuning magnet-girder prototype has been designed and developed. Topological optimization, multipoint supports, and locking systems have been applied for magnet-girder design to improve the stability. The modal analysis accords with the vibration test well. The natural frequency of the magnet-girder assembly is deduced as high as 45.6 Hz, which demonstrates good stability. Ball-cam movers have been chosen as adjustment mechanisms, and a closed-loop control scheme has been used to pursue high accuracy. The kinematic resolution is better than $1\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$, and the accuracy is better than $1\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ within the adjusting range of $\ifmmode\pm\else\textpm\fi{}5\text{ }\text{ }\mathrm{mm}$. Besides, it can eliminate most of the calibration, which can save much manpower and time. The tests demonstrate that the magnet girder can be used for beam-based girder alignment with high stability and high accuracy.

Linearly and circularly polarized radiation with a low on-axis heat load from an asymmetric magnet pole undulator

The heavy heat load on optical components from the normal planar undulator has become a serious problem in the synchrotron radiation light source, especially for generating the low-energy photon in a high-energy storage ring and/or a diffraction-limited storage ring. The asymmetric magnet pole undulators have different period lengths between the upper and lower magnet poles. Taking the advantage of the asymmetric magnet pole undulators in building various magnetic fields, this paper proposes a new class of undulators to obtain the specific magnetic fields which can scatter the electron velocity away from the undulator axis. It consists of four magnet arrays and has a similar structure compared to the DELTA/APPLE-X undulator; however, each couple of magnet arrays has a different period length with the period ratio of ${n}_{1}:{n}_{2}$. Taking the one-to-two and two-to-three period ratios as examples, a novel Figure 8 undulator and a novel Knot undulator are demonstrated. The polarization state can be flexibly switched from the linear polarization to the circular polarization by tuning the phase shifts of magnetic fields, with the on-axis heat load greatly suppressed. The heat-load suppressions of linear polarization at two predetermined orthogonal directions are almost the same and fully effective. Analysis and simulations of undulator designs with the corresponding radiation characteristics are reported.

Study of the third-order parametric resonance induced by RF phase modulation and its effectiveness in improving injection efficiency

The on-axis swap-out injection scheme is promising for diffraction-limited storage rings, mainly because it can significantly reduce the requirement of dynamic aperture. However, this scheme requires the injection of full-charge bunches. Therefore, it may suffer from the reduction of injection efficiency caused by the so-called “injection transient instability” when high-charge bunches are needed. The idea of implementing RF modulation in a booster before extraction, driving the second-order parametric resonance to suppress the “injection transient instability” in the storage ring, was proposed and demonstrated previously. Here, we mainly present studies of third-order parametric resonance driven by RF phase modulation. Derivation of the modulated Hamiltonian around the third-order parametric resonance, the coordinates of both stable and unstable fixed points, and the ‘island tune’ are presented in detail. To double check the correctness of the theoretical results, numerical tests and tracking studies were carried out and presented. Furthermore, the results from comprehensive simulations are presented to demonstrate the improvement of injection efficiency by the proper settings of the RF phase modulation.

Generating coherent and ultrashort X-ray pulses via HHG-seeding in storage rings.

The generation of fully coherent and femtosecond time-scale radiation pulses in the X-ray regime is one of the most common demands of ring-based synchrotron light source users. In this paper, a method that utilizes the recent proposed angular dispersion induced microbunching technique to convert external light from high-harmonic generation (HHG) to coherent light at shorter wavelength is proposed. Numerical simulations using the practical parameters of a diffraction-limited storage ring demonstrate the generation of coherent pulse trains with photon energy as high as 2 keV, pulse duration as short as ∼10 fs and high peak brightness directly from an HHG source at 13 nm.

Prototype characterization of a charge-integration pixel detector readout chip with in-pixel A/D conversion

HYLITE (High dYmamic range free electron Laser Imaging deTEctor) is a hybrid pixel detector readout chip, which is designed for advanced light sources such as X-ray Free Electron Laser (XFEL) and diffraction-limited storage rings. It is a charge-integration readout chip which has three gains for different dynamic ranges and automatic gain-switching function. The full dynamic range covered by HYLITE is 1 ∼ 104 photons with an energy of 12 keV for each pixel in every shot. In-pixel ADC is designed to achieve front-end digitization and a 10 kHz continuous frame rate. HYLITE0.1 is the first prototype chip for functional verification that was produced in CMOS 0.13 μm technology. It consists of a pixel array with 6 × 12 pixels and a periphery with full standalone operation features. The size of each pixel is 200 μm × 200 μm. Three design variations of pixels with different integrating capacitance and structures were designed to optimize between area and performance. A 10-bit Wilkinson ADC is integrated in each pixel to digitize the outputs of the pre-amplifier. Therefore, analog signal transmission of long distance is avoided and a frame rate of 10 kHz can be achieved. In this paper, we present the design of HYLITE0.1 and the test results of this prototype chip.

X-ray in-line holography and holotomography at the NanoMAX beamline.

Coherent X-ray imaging techniques, such as in-line holography, exploit the high brilliance provided by diffraction-limited storage rings to perform imaging sensitive to the electron density through contrast due to the phase shift, rather than conventional attenuation contrast. Thus, coherent X-ray imaging techniques enable high-sensitivity and low-dose imaging, especially for low-atomic-number (Z) chemical elements and materials with similar attenuation contrast. Here, the first implementation of in-line holography at the NanoMAX beamline is presented, which benefits from the exceptional focusing capabilities and the high brilliance provided by MAX IV, the first operational diffraction-limited storage ring up to approximately 300 eV. It is demonstrated that in-line holography at NanoMAX can provide 2D diffraction-limited images, where the achievable resolution is only limited by the 70 nm focal spot at 13 keV X-ray energy. Also, the 3D capabilities of this instrument are demonstrated by performing holotomography on a chalk sample at a mesoscale resolution of around 155 nm. It is foreseen that in-line holography will broaden the spectra of capabilities of MAX IV by providing fast 2D and 3D electron density images from mesoscale down to nanoscale resolution.

A seven-bend-achromat lattice option for the HALF storage ring

The Hefei Advanced Light Facility (HALF) is a soft X-ray diffraction-limited storage ring being designed with an energy of about 2.2 GeV and an emittance goal of less than 100 pm·rad. The present HALF lattice is a modified hybrid six-bend-achromat (6BA) lattice with a long and a short straight section in each cell. In this paper, a 7BA lattice is designed for HALF as a promising option, which follows the main feature of hybrid 7BA lattice, but to have a compact configuration and lower emittance, all bends in this lattice are combined-function bends and reverse bends. The designed HALF storage ring has a circumference of 388.8 m and 20 identical cells. Two solutions with different betatron tunes are studied for this lattice. One with smaller tunes has better nonlinear dynamics performance allowing for off-axis injection, which has a natural emittance of 67 pm·rad. The other with larger tunes has very small beta functions at the straight section as well as lower natural emittance of 59 pm·rad, which can enhance the brightness of insertion device (ID) radiation. The intra-beam scattering effect and ID radiation properties are also presented in this paper.