Fourth-generation Storage Ring Research Articles

Design study of a low emittance complex bend achromat lattice

Light sources worldwide have experienced rapid growth in the last decades, pushing toward higher brightness with lower emittance to meet growing demands from the user community. The quest for higher brightness motivates the development of low-emittance ring lattices. At this point, all fourth-generation storage ring light sources employ variations of the multibend achromat (MBA) lattice. In this paper, we discuss an extension of this approach, known as complex bend achromat lattice in relation to the future NSLS-II upgrade. A detailed approach for the lattice design will be described and the developed lattice will be presented. The advantages of using our complex bend approach are evident in reaching a natural emittance as low as 23 pm at a beam energy of 3 GeV, providing a straight section of 8.4 m for long insertion devices, and acquiring a ratio of about 50% of free space with respect to the ring circumference. The design includes the use of permanent magnets largely reducing the need for power supplies. Our new approach provides an extension to the MBA concept for the next-generation light source lattice design. Published by the American Physical Society 2024

Synchrotron infrared nanospectroscopy in fourth-generation storage rings.

Fourth-generation synchrotron storage rings represent a significant milestone in synchrotron technology, offering outstandingly bright and tightly focused X-ray beams for a wide range of scientific applications. However, due to their inherently tight magnetic lattices, these storage rings have posed critical challenges for accessing lower-energy radiation, such as infrared (IR) and THz. Here the first-ever IR beamline to be installed and to operate at a fourth-generation synchrotron storage ring is introduced. This work encompasses several notable advancements, including a thorough examination of the new IR source at Sirius, a detailed description of the radiation extraction scheme, and the successful validation of our optical concept through both measurements and simulations. This optimal optical setup has enabled us to achieve an exceptionally wide frequency range for our nanospectroscopy experiments. Through the utilization of synchrotron IR nanospectroscopy on biological and hard matter samples, the practicality and effectiveness of this beamline has been successfully demonstrated. The advantages of fourth-generation synchrotron IR sources, which can now operate with unparalleled stability as a result of the stringent requirements for producing low-emittance X-rays, are emphasized.

Physics Design of a 200-MeV Electron Injector Linac With a Thermionic Electron Gun for the Korean Fourth-Generation Storage Ring Light Source

Physics Design of a 200-MeV Electron Injector Linac With a Thermionic Electron Gun for the Korean Fourth-Generation Storage Ring Light Source

Beam dynamics in the booster synchrotron of Korea-4GSR project

In recent years, there have been several projects in the world to design and construct a diffraction-limited light source which pushes an emittance of electron beams in a storage ring close to an emittance of photon beams in the X-ray region to enhance brilliance by two orders of magnitude. In line with this trend, the Korea fourth-generation storage ring (Korea-4GSR) project was launched in 2021 to establish a new light source in the Republic of Korea with an ultra-low emittance of 50 pmrad at a beam energy of 4 GeV. For the Korea-4GSR project, a compact linear accelerator for generating 200 MeV and a booster synchrotron is chosen as an injector. The booster synchrotron ramps beam energy from 200 MeV to 4 GeV and the lattice is designed based on the FODO concept. It is crucial in the booster to achieve high beam quality for injection efficiency into a storage ring. Since the quality of the extracted beam relies on an energy ramping profile, the ramping process is important to be optimized. This paper represents the result of our studies on the effect of the energy ramping profile in the evolutionary physical process in a booster synchrotron.

Optimization study for RF cavity and beam dynamics simulation in the electron linear accelerator using the multi-objective genetic algorithm

This work presents an optimization study on the RF cavity geometry design and beam dynamics of an electron injector linac for the Korea Fourth-Generation Storage Ring (Korea-4GSR). It is challenging to achieve an optimal design for a linac system due to the nonlinear nature of accelerator system and the associated beam dynamics with numerous knobs to control. To address this challenge, we employed the Multi-Objective Genetic Algorithm (MOGA) for efficient optimization. Through the utilization of MOGA, we effectively optimized the electron linac for the Korea-4GSR. The optimized design yielded a horizontal normalized rms emittance of approximately 3.79 mm-mrad and an energy spread of about 307.37 keV, which met design requirements of the Korea-4GSR. This approach facilitated the design of an electron linac tailored for the Korea-4GSR with enhanced efficiency and effectiveness.

Benchmark study and thermal-load analysis for soft X-ray beamline of Korea fourth-generation storage ring

Benchmark study and thermal-load analysis for soft X-ray beamline of Korea fourth-generation storage ring

Search for dark sector by repurposing the UVX Brazilian synchrotron

We propose the first Search for Dark Sector at the Brazilian Synchrotron Light Laboratory, site of Sirius, a fourth-generation storage ring. We show that UVX, Sirius predecessor, can be a promising dark sector detector, SeDS, with unprecedented sensitivity. The search is based on a 1-3 GeV positron beam impinging on a thick target leading the e^+ e^- rightarrow gamma A' reaction, followed by a missing mass spectrum event reconstruction. We show that SeDS has the potential to probe dark photons with masses up to 55 MeV and kinetic coupling down to epsilon ^2 sim 10^{-12}. Therefore, such experiment would constitute the best dark photon probe worldwide in the 10{-}55 MeV mass range, being able to probe an unexplored region of parameter space.

Demonstration of machine learning-enhanced multi-objective optimization of ultrahigh-brightness lattices for 4th-generation synchrotron light sources

Fourth-generation storage rings enabled by multi-bend achromat lattices are being inaugurated worldwide and many more are planned for the next decade. These sources deliver stable ultra-high brightness radiation with unmatched levels of transverse coherence by virtue of their highly advanced magnetic lattices. Optimization of these challenging and strongly nonlinear lattices with many degrees of freedom bounded by extensive sets of constraints and multiple often conflicting optimization goals is highly demanding and requires application of the most advanced numerical tools available to the community. While multi-objective genetic algorithms have been very successful in supporting these optimization efforts, the algorithms suffer from a fundamental limitation of their stochastic nature: an exceedingly vast number of candidate lattices, most of which eventually are rejected, has to be fully evaluated. This comes at immense computational cost and thus drives excessive runtime despite use of large supercomputing clusters. We therefore propose to employ deep learning techniques and iterative retraining of neural networks to massively accelerate such lattice evaluation, thereby allowing lattice optimization to rely on far fewer a priori assumptions, open up to larger search ranges, and include right from the start and in parallel multiple error distributions to find truly global optima, all while completing a full optimization campaign in weeks rather than months. In this paper we present the neural network designs, the deep learning approach, iterative retraining procedures, and demonstrate how these machine learning techniques can be incorporated into existing state-of-the-art optimization workflows with only minimal changes applied to the optimization pipeline itself and none at all to the employed tracking codes.

Beam focus modifications by cropping partially coherent X-ray beams

We simulate the focusing of a partially coherent X-ray beam emitted by an undulator in a fourth-generation storage ring by performing a coherent mode decomposition and wave optics propagation. The focus position is shifted, and its size is enlarged when an entrance slit crops the beam. This is the usual case when a slit is used to select the coherent fraction. The pairing of two focusing elements (mirrors, lenses or transfocators) to ensure a fixed focal position is also analyzed. Our results show that the image of a partially coherent source, such an undulator in a low-emittance storage ring, is a non-trivial function of the aperture used to control the coherence fraction.

Multi-objective optimization of longitudinal injection based on a multi-frequency RF system for fourth-generation storage ring-based light sources

In the fourth-generation storage ring light sources (4GLSs), associated with the extremely strong nonlinearities inherent in the multi-bend achromat design, the dynamic acceptance is usually small and it is difficult to implement traditional off-axis local-bump injection. To release the requirement on dynamic acceptance, on-axis longitudinal injection schemes have been explored. In this paper, we present a multi-objective optimization of longitudinal injection with a multi-frequency RF system, based on the parameters of the Southern Advanced Photon Source, a 4GLS proposed in China. We show that by treating the optimal bunch lengthening condition as an optimizing objective rather than a condition that must be satisfied, a plethora of feasible candidate solutions can be found, showing different trade-offs among multi-objectives. From these candidate solutions, one can find an optimal RF parameter setting that is most adapted to a specific 4GLS physics design and the available technical level of injection kicker. Especially, it would be feasible to realize longitudinal injection within a static bucket enabled by a double-frequency RF system, suggesting an attractive longitudinal injection option for 4GLSs.

A fast and lightweight tool for partially coherent beamline simulations in fourth-generation storage rings based on coherent mode decomposition.

A new algorithm to perform coherent mode decomposition of undulator radiation is proposed. It is based on separating the horizontal and vertical directions, reducing the problem by working with one-dimension wavefronts. The validity conditions of this approximation are discussed. Simulations require low computer resources and run interactively on a laptop. The focusing with lenses of the radiation emitted by an undulator in a fourth-generation storage ring (EBS-ESRF) is studied. Results are compared against multiple optics packages implementing a variety of methods for dealing with partial coherence: full two-dimension coherent mode decomposition, Monte Carlo combination of wavefronts from electrons entering the undulator with different initial conditions, and hybrid ray-tracing correcting geometrical optics with wave optics.

Impact of Carbon N-Doping and Pyridinic-N Content on the Fuel Cell Performance and Durability of Carbon-Supported Pt Nanoparticle Catalysts.

Cathode catalyst layers of proton exchange membrane fuel cells (PEMFCs) typically consist of carbon-supported platinum catalysts with varying weight ratios of proton-conducting ionomers. N-Doping of carbon support materials is proposed to enhance the performance and durability of the cathode layer under operating conditions in a PEMFC. However, a detailed understanding of the contributing N-moieties is missing. Here, we report the successful synthesis and fuel cell implementation of Pt electrocatalysts supported on N-doped carbons, with a focus on the analysis of the N-induced effect on catalyst performance and durability. A customized fluidized bed reduction reactor was used to synthesize highly monodisperse Pt nanoparticles deposited on N-doped carbons (N-C), the catalytic oxygen reduction reaction activity and stability of which matched those of state-of-the-art PEMFC catalysts. Operando high-energy X-ray diffraction experiments were conducted using a fourth generation storage ring; the light of extreme brilliance and coherence allows investigating the impact of N-doping on the degradation behavior of the Pt/N-C catalysts. Tests in liquid electrolytes were compared with tests in membrane electrode assemblies in single-cell PEMFCs. Our analysis refines earlier views on the subject of N-doped carbon catalyst supports: it provides evidence that heteroatom doping and thus the incorporation of defects into the carbon backbone do not mitigate the carbon corrosion during high-potential cycling (1-1.5 V) and, however, can promote the cell performance under usual PEMFC operating conditions (0.6-0.9 V).

Collimator irradiation studies in the Argonne Advanced Photon Source at energy densities expected in next-generation storage ring light sources

The Advanced Photon Source (APS) team is building a fourth-generation storage ring (4GSR), replacing the present double-bend achromat lattice with a multibend achromat system thereby allowing the production of ultrabright x-ray beams. The new lattice enables a 2-order-of-magnitude reduction in horizontal beam emittance and a factor of two increase in beam current. The result is an electron beam of very high energy and power densities. Initial predictions suggest many common ultrahigh-vacuum-compatible materials struck by the full-intensity electron beam will be damaged. Two experimental beam abort studies have been conducted on collimator test pieces in the present APS SR to inform the design of a fully-functional machine protection system for APS 4GSR operations at 200 mA. A comprehensive suite of diagnostics was utilized during the studies. The diagnostics used in these experiments are not new, but employed in different ways to obtain unique data sets. With these sets now in hand, we are developing new numerical tools to guide collimator design using pelegant [M. Borland, elegant: A flexible SDDS-compliant code for accelerator simulation, Technical Report No. LS-287, Advanced Photon Source, 2000; Y. Wang and M. Borland, Implementation and performance of parallelized elegant, in Proceedings of the 2007 Particle Accelerator Conference, http://cern.ch/AccelConf/p07/PAPERS/THPAN095.PDF, pp. 3444--3446], mars [N. V. Mokhov and S. I. Striganov, Fermilab-conf-07/008-ad, AIP Conf. Proc. 896, 50 (2007)], and flash [B. Fryxell et al., flash: An adaptive mesh hydrodynamics code for modeling astrophysical thermonuclear flashes, Astrophys. J. Suppl. Ser. 131, 273 (2000); P. Tzeferacos et al., Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma, Nat. Commun. 9, 591 (2018)].

Storage rings in Korea as synchrotron radiation source

Remarkable progress has been made in photon beam brightness from storage rings. From the early 90’s, third-generation storage rings (3GSRs) have been put into operation and have provided very bright photon beams using insertion devices. Fourth-generation storage rings (4GSRs) that exploit the multi-bend achromat lattice concept may be able to surpass the brightness and coherence that have been attained using present third-generation storage rings. Recently, a 4GSR project was officially approved to meet the increasing demand from the growing user community in Korea. This paper describes progress in the development of storage rings in Korea, including the status and the plans for PLS-II, and the results on the conceptual design for Korea-4GSR.

Characteristics of Photon Beam and Preservation of Coherence in Fourth-Generation Light Sources

Fourth-generation storage rings (4GSRs) that exploit the multi-bend achromat lattice concept may be able to surpass the brightness and coherence that are attained using the present third-generation storage rings. This paper presents the characteristics of photon beams and an analysis of their coherence properties in Korea-4GSR to represent 4GSRs.

Beam-based characterization of higher-order-mode driven coupled-bunch instabilities in a fourth-generation storage ring

Longitudinal coupled-bunch instabilities are driven by monopole higher-order modes (HOMs) in the active and passive radio-frequency (rf) cavities at the MAX IV 3 GeV electron storage ring. By combining different beam and rf-based techniques, we have performed a systematic survey of the properties of these resonant modes as a function of cavity temperatures and fundamental mode frequency. This information was then used to setup a HOM model that allowed us to infer optimized temperature ranges for the cavities. An important feature of the optimization method is that it takes into account not only the need to minimize the growth rates (given by the resistive component of the sum of HOM impedances) from each individual cavity but also aims to minimize the total reactive component of the impedance of HOMs that are present in more than one cavity. The resulting small real coherent tune shifts allow the coupled-bunch modes driven by these HOMs to be effectively Landau damped. Further optimization of the cavity temperatures was performed by minimizing the measured electron beam energy spread within the temperature ranges defined by the HOM model. The optimum temperature search was performed at 300 mA stored beam current and in multi-bunch mode using the RCDS (Robust Conjugate Direction Search) algorithm and succeeded in bringing the electron energy spread to within 10% of the zero current value determined solely by quantum excitation and radiation damping.

Comparison of photon beam characteristics of Korea-4GSR with PLS-II

The Korea fourth-generation storage ring (Korea-4GSR), with 4-GeV beam energy and 58-pm-rad emittance has been designed by the Pohang Accelerator Laboratory. The evaluated brilliance and coherence are approximately 100 times higher in the hard X-ray region in Korea-4GSR than in the third-generation storage ring at PLS-II. The coherence properties and preservation of coherence through beamline optical elements were studied using SPECTRA code and hybrid method. Result of this paper show essential information for planning experiments and designing beamlines using ultimate low emittance storage ring.

Investigation of the damping wiggler effect and application on the PAL fourth-generation storage ring.

An investigation of the damping wiggler effect to reduce the emittance in the Pohang Accelerator Laboratory (PAL), a fourth-generation storage ring (4GSR) that uses a multi-bend achromat, is presented. A 4GSR lattice which has reduced emittance and increased dynamic aperture to amplify the synergy with two existing light sources (PLS-II and PAL-XFEL) at PAL is described.

Transparent top-up injection into a fourth-generation storage ring

The reduction of transient stored beam perturbations generated by top-up injection into storage rings has since long been a topic of intense research and development in the synchrotron radiation community. The issue is particularly relevant to present and future fourth-generation storage rings, for which beam stability is a crucial performance parameter. In this paper, we report on the design and commissioning of a novel multipole injection kicker (MIK) that has successfully demonstrated high injection efficiency as well as outstanding transparency, with levels of residual disturbances to the stored beam well below the beam size in both the horizontal and vertical planes.

Characteristics of the Synchrotron Radiation of Fourth-Generation Storage Rings

Fourth-generation storage rings (4GSR) based on multi-bend achromat (MBA) lattices promise to deliver stable X-ray beams with higher brightness and coherence than existing third-generation light sources. The basic ingredient in achieving higher brightness is a further reduction of the electron beam emittance in storage rings dedicated to light sources. These 4GSR lattices can lead to 1 to 2 orders of magnitude reductions in the beam emittance by employing a MBA, where many dipoles per cell are used to keep the dispersion function low inside the dipoles. Moreover, these low emittance beams are transported to the beam-line through the insertion device or center-bend, which is a permanent magnet with a 2 T magnetic field. In this paper, we will introduce the characteristics of the synchrotron radiation of 4GSR compared to present third-generation sources, PLS-II.