arXiv subjects

Yi Jiao

Publications and source records attributed to Yi Jiao.

At least 19 recordsLinked to original sources

arXiv2026

Booster-based beam recycling for swap-out injection at the High Energy Photon Source

Fourth-generation synchrotron light sources employ ultralow-emittance storage rings with stringent injection requirements. On-axis swap-out injection alleviates the dependence on storage-ring dynamic aperture, but high-charge operation requires an efficient injector architecture capable of producing high-charge replacement bunches. This paper presents the accelerator physics design and performance analysis of a booster-based beam-recycling swap-out injection scheme implemented at the High Energy Photon Source (HEPS). In this approach, the full-energy booster serves as both an injector and a high-energy accumulator. An extracted storage-ring bunch is returned to the booster, merged with a low-charge bunch previously injected from the linac and accelerated to full energy. Following high-energy damping, the merged bunch is reinjected into the original storage-ring bucket. The scheme avoids the need for a dedicated accumulator ring while enabling high-charge bunch replacement. The recycling scheme was commissioned through staged machine studies. Full recycling-chain simulations, commissioning studies, and measured performance analysis are presented. The measured results characterize the recycling operation and quantify the transmission efficiency and performance limitations of the complete recycling loop. These results demonstrate the feasibility of the booster-based beam-recycling architecture and establish its operational basis for high-charge swap-out injection in future fourth-generation synchrotron light sources.

physics.acc-ph↗

arXiv2026

Two-dimensional beam compression for sub-femtosecond electron beam generation

Sub-femtosecond electron beams are powerful probes of ultrafast electronic, atomic, and nuclear dynamics, and promising drivers for ultrashort radiation generation from the extreme-ultraviolet to gamma-ray regimes. However, producing such beams at hundred-MeV energies with pC-level charge remains challenging. Here we develop a two-dimensional beam-compression scheme based on transverse--longitudinal coupling, in which dispersive beam optics convert the small transverse emittance of modern electron beams into an ultrashort bunch length. Linear analysis and particle tracking show that, after the dominant longitudinal and energy-spread contributions are cancelled, the compressed bunch length is governed primarily by transverse beam quality and collective-effect growth. We further derive and verify a scaling model that captures collective-effect-induced bunch-length degradation and provides a charge--energy operating map for sub-femtosecond compression. Start-to-end simulations of a realistic injector-to-compressor beamline produce a 200 MeV, pC-level bunch with a bunch length of 0.45 fs and a peak current of about 3.5 kA. Jitter studies over a broad range of beam energies show that the output bunch-length distribution narrows and then varies only weakly with increasing energy. These results suggest a feasible route toward compact, high-energy attosecond electron beam sources and may provide a basis for future sub-femtosecond radiation sources based on undulator emission or inverse Compton scattering.

physics.acc-ph↗

arXiv2026

High-Harmonic Coherent Pulse Generation in a Storage Ring Using Multiple-Echo-Enabled Harmonic Generation

Fourth-generation storage-ring light sources have achieved transverse emittances approaching the diffraction limit at x-ray wavelengths, while their longitudinal coherence remains limited. Existing laser-modulation schemes can induce strong microbunching, but most storage-ring implementations produce only one useful coherent output from a given longitudinal region during each revolution, thereby underutilizing the intrinsic multi-user capability of storage rings. We propose a multiple-echo-enabled harmonic generation (multi-EEHG) scheme that applies successive excitation--echo cycles to the same longitudinal slice of a stored bunch within one revolution, enabling coherent-radiation delivery to multiple beamlines at different wavelengths. A general formulation of the n-stage EEHG bunching factor and a corresponding optimization procedure are derived. As an example, a triple-EEHG configuration is designed for the SAPS storage ring. Simulations demonstrate coherent radiation at multiple wavelengths with single-pulse photon numbers up to $10^9$, corresponding to an enhancement of approximately three orders of magnitude over synchrotron radiation for the same spectral bandwidth, while achieving few-meV bandwidth without a monochromator. The proposed scheme offers a scalable approach for multi-beamline coherent operation in next-generation storage-ring light sources.

physics.acc-ph↗

arXiv2024

Self-Cancelation of Coherent Synchrotron Radiation Kicks Using a Non-Symmetric S-shape Four-Bend Chicane

High peak current electron beams are essential for x-ray free-electron lasers (FELs), and generally realized through multi-stage compression with symmetric C-shape four-bend chicanes. However, the coherent synchrotron radiations (CSR), emitted for wavelengths longer than or comparable to the length of the electron bunch during the compression, may degrade the beam quality and finally affect the FEL performance. In this Letter, we show that zero net CSR kick cannot be achieved in a symmetric C-chicane by using an explicit point-kick analysis of the CSR effects, which is responsible for significant emittance growth when pursuing a peak current of $\gtrsim$ 10 kiloamperes. A four-bend chicane with non-symmetric S-shape geometry that can self-cancel the CSR kicks is proposed to effectively suppress the emittance growth. Compared to the symmetric C-chicane, beams with three times higher peak current and similar emittance growth can be achieved with the S-chicane for typical FEL operation parameters. We believe that this study provides a viable way of producing high quality and short intense electron beams, benefiting future development of FELs and other types of accelerator-based scientific facilities.

physics.acc-ph↗

arXiv2024

Development of high-level applications for High Energy Photon Source booster

The High Energy Photon Source (HEPS), is the first fourth-generation storage ring light source being built in the suburb of Beijing, China. The storage ring was designed with the emittance lower than 60 pm.rad with a circumference of 1.36 km and beam energy of 6 GeV. Its injector contains a 500 MeV S-band Linac and a 454 m booster which was designed as an accumulator at the extraction energy. In the energy ramping control design of HEPS booster, the ramping process was programed to be able to stop and stay at any energy between the injection energy and the extraction energy. This feature enables us to conduct energy-dependent machine studies and ramping curve optimization. The beam commissioning of HEPS Linac finished in June, 2023. And the beam commissioning of booster started in the end of July, 2023. In November 17, main target values proposed in the preliminary design report has been reached. The high-level applications (HLAs) are essential tools for beam commissioning. The development of HLAs, which are based on the framework named Python accelerator physics application set (Pyapas), started in the end of 2021. The HEPS physics team spent more than one year to develop and test the HLAs to meet the requirements of beam commissioning of the booster. Thanks to the modular design, the principle based on physical quantities, and the ability of running simulation models online from the Pyapas, the development efficiency and reliability of the HLAs have been greatly improved. In particular, the principle based on physical quantities allows us to control the beam more intuitively.

physics.acc-ph↗

arXiv2024

A method for reversing the laser modulation in a Storage ring

The pursuit of coherent radiation generation remains a key direction in the advancement of storage ring light sources. Despite the potential of laser modulation in achieving this goal, it leads to a significant decline in the quality of the electron beam. Efforts to mitigate this decline have resulted in the proposal of demodulation schemes. However, implementing modulation and demodulation within the storage ring presents significant challenges due to dynamical and spatial constraints within straight sections. In this study, we propose a straightforward and easily implementable method for achieving reversible laser modulation in a storage ring. Notably, our approach circumvents the need for special storage ring requirements, such as lengthy straight sections or bypass section. Simulation results demonstrate a substantial restoration of beam quality following demodulation. This innovative scheme holds great promise for the realization of high repetition rate coherent storage ring light sources.

physics.acc-ph↗

arXiv2024

Analytical formulas of coherent-synchrotron-radiation induced microbunching gain and emittance growth in an arbitrary achromatic four-bend chicane

Coherent synchrotron radiations (CSR) emitted by a high-brightness electron beam during transport in a bending magnet is a double-edged sword in electron accelerators. While CSR contributes to a stronger radiation field than the incoherent radiation, it simultaneously leads to degradation of the electron beam quality. Specifically, CSR effects manifest in increases of the beam energy spread and the projected emittance, and amplification of the microbunching instability. This paper presents analytical formulas for the CSR-induced microbunching instability gain and for the induced emittance growth in an arbitrary achromatic four-bend chicane with inclusion of both the steady-state and transient CSR effects. The analytical formulas are compared and show good agreement with Vlasov calculations and particle tracking simulations. The obtained analytical formulas are then applied to evaluate the CSR effects in the design of a general achromatic four-bend bunch compressor chicane, providing a quick estimate on the microbunching gain and the induced emittance growth. From the widely adopted symmetric C-shape chicane to a non-symmetric S-shape chicane, our analytical formulas offer insight into the evolution of the microbunching gain and the emittance growth with the variations of design parameters. In comparison to particle tracking simulations currently employed for CSR effect analyses, the analytical formulas presented in this paper significantly reduce the evaluation time, enabling systematic study of parametric dependencies with inclusion of CSR effects within specified design parameter ranges.

physics.acc-ph↗

arXiv2024

Suppressing Coherent Synchrotron Radiation Effects in Chicane Bunch Compressors

The most significant advances in the accelerator-based light sources (i.e., x-ray free electron lasers) are driven by the production of the high final peak current in the last several decades. As a prerequisite to attain the proposed high brightness, the symmetric C-chicane bunch compressor is typically exploited due to its simplicity, efficiency, and natural dispersion-free feature at all orders. However, during bunch compression for a high peak current requirement, a main contributing factor to the transverse emittance degradation is the emission of the coherent synchrotron radiation (CSR). Suppressing this effect is necessary to preserve the beam phase-space quality. To this end, this paper presents an analysis of one-dimensional CSR point-kick and derives the cancellation conditions in terms of compression factor. The CSR cancelation conditions indicate an asymmetric geometric design. We demonstrate concrete schemes for asymmetric C- and S-chicanes, and verify the CSR cancelation conditions using integration methods and ELEGANT simulations. Furthermore, the proposed asymmetric C- and S-chicanes can drastically suppress the emittance growth compared with the symmetric ones with identical bunch compression goals.

physics.acc-ph↗

arXiv2022

Machine learning-based direct solver for one-to-many problems on temporal shaping of relativistic electron beams

To control the temporal profile of a relativistic electron beam to meet requirements of various advanced scientific applications like free-electron-laser and plasma wakefield acceleration, a widely-used technique is to manipulate the dispersion terms which turns out to be one-to-many problems. Due to their intrinsic one-to-many property, current popular stochastic optimization approaches on temporal shaping may face the problems of long computing time or sometimes suggesting only one solution. Here we propose a real-time solver for one-to-many problems of temporal shaping, with the aid of a semi-supervised machine learning method, the conditional generative adversarial network (CGAN). We demonstrate that the CGAN solver can learn the one-to-many dynamics and is able to accurately and quickly predict the required dispersion terms for different custom temporal profiles. This machine learning-based solver is expected to have the potential for wide applications to one-to-many problems in other scientific fields.

physics.acc-ph↗

arXiv2022

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.

physics.acc-ph↗

arXiv2021

Data-driven Chaos Indicator for Nonlinear Dynamics and Applications on Storage Ring Lattice Design

A data-driven chaos indicator concept is introduced to characterize the degree of chaos for nonlinear dynamical systems. The indicator is represented by the prediction accuracy of surrogate models established purely from data. It provides a metric for the predictability of nonlinear motions in a given system. When using the indicator to implement a tune-scan for a quadratic Henon map, the main resonances and their asymmetric stop-band widths can be identified. When applied to particle transportation in a storage ring, as particle motion becomes more chaotic, its surrogate model prediction accuracy decreases correspondingly. Therefore, the prediction accuracy, acting as a chaos indicator, can be used directly as the objective for nonlinear beam dynamics optimization. This method provides a different perspective on nonlinear beam dynamics and an efficient method for nonlinear lattice optimization. Applications in dynamic aperture optimization are demonstrated as real world examples.

physics.acc-ph↗

arXiv2021

Machine learning enabled fast evaluation of dynamic aperture for storage ring accelerators

For any storage ring-based large-scale scientific facility, one of the most important performance parameters is the dynamic aperture (DA), which measures the motion stability of charged particles in a global manner. To date, long-term tracking-based simulation is regarded as the most reliable method to calculate DA. However, numerical tracking may become a significant issue, especially when lots of candidate designs of a storage ring need to be evaluated. In this paper, we present a novel machine learning-based method, which can reduce the computation cost of DA tracking by approximately one order of magnitude, while keeping sufficiently high evaluation accuracy. Moreover, we demonstrate that this method is independent of concrete physical models of a storage ring. This method has the potential to be applied to similar problems of identifying irregular motions in other complex dynamical systems.

physics.comp-ph↗

arXiv2021

Design Study of APSU 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 (HMBA) 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 H7BA lattice, the design of the Advanced Photon Source Upgrade Project (APSU) can effectively reduce emittance by replacing six quadrupoles with antibends. Herein, we discuss the feasibility of designing an APSU type HMBA 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 APSU type H7BAs, 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 APSU type lattice to reduce the longitudinal damping time from 120 to 44 ms while maintaining other performance parameters at the same level.

physics.acc-ph↗

arXiv2016

Statistical analysis of the limitation of half integer resonances on the available momentum acceptance of a diffraction-limited storage ring

In a diffraction-limited storage ring (DLSR), the momentum acceptance (MA) might be limited by the half integer resonances (HIRs) excited by focusing errors, associated with the large detuning terms from the strong focusing and strong sextupoles required for an ultralow emittance. Taking the High Energy Photon Source (HEPS) as an example and through statistical analysis, we found that the horizontal HIRs have stronger impact on dynamics than the vertical ones; and the probability of MA reduction caused by a HIR is closely correlated with the level of the beta beats at the same plane, but independent of the error sources. For the HEPS design, to reach a small MA-reduction probability of about 1%, the rms amplitude of the beta beats at the nominal tunes should be kept below 1.5% horizontally and 2.5% vertically. The presented analysis can provide useful reference for other DLSR designs.

physics.acc-ph↗

arXiv2016

Feasibility study of online tuning of the luminosity in a circular collider with the robust conjugate direction search method

The robust conjugate direction search (RCDS) method has high tolerance to noise in beam experiments. It has been demonstrated that this method can be used to optimize the machine performance of a light source online. In our study, taking BEPCII as an example, the feasibility of online tuning of the luminosity in a circular collider is explored, through numerical simulation and preliminary online experiments. It is shown that the luminosity that is artificially decreased by a deviation of beam orbital offset from optimal trajectory can be recovered with this method.

physics.acc-ph↗

arXiv2015

Improving the nonlinear performance of the HEPS baseline design with genetic algorithm

The baseline design for the High Energy Photon Source has been proposed, with an emittance of 60 pm.rad within a circumference of 1.3 kilometers. Nevertheless, the nonlinear performance of the design needs further improvements to enlarge both the dynamic aperture and the momentum acceptance. In this study, genetic optimization of the linear optics is performed, so as to find all the possible solutions with weaker sextupoles and hence weaker nonlinearities, while keeping the emittance at the same level as the baseline design. These obtained solutions enable us to explore the dependence of nonlinear dynamics on the working point. The result indicates that with the same layout, it is feasible to obtain much better nonlinear performance with a delicate tuning of the magnetic field strengths and a wise choice of the working point.

physics.acc-ph↗

arXiv2015

ESRF-type lattice design and optimization for the High Energy Photon Source

A new generation of storage ring-based light source, called diffraction-limited storage ring (DLSR), with emittance approaching the diffraction limit for multi-keV photons by means of multi-bend achromat lattice, has attracted worldwide and extensive studies. Among various DLSR proposals, the hybrid multi-bend achromat concept developed at ESRF predicts an effective way of minimizing the emittance and meanwhile keeping the required sextupole strengths to an achievable level. For the High Energy Photon Source planned to be built in Beijing, an ESRF-type lattice design consisting of 48 hybrid seven-bend achromats is proposed to reach emittance as low as 60 pm.rad with a circumference of about 1296 m. Sufficient dynamic aperture promising vertical on-axis injection and moderate momentum acceptance are achieved simultaneously for a promising ring performance.

physics.acc-ph↗

arXiv2014

Suppression of the emittance growth induced by coherent synchrotron radiation in triple-bend achromats

The coherent synchrotron radiation (CSR) effect in a bending path plays an important role in transverse emittance dilution in high-brightness light sources and linear colliders, where the electron beams are of short bunch length and high peak current. Suppression of the emittance growth induced by CSR is critical to preserve the beam quality and help improve the machine performance. It has been shown that the CSR effect in a double-bend achromat (DBA) can be analyzed with the two-dimensional point-kick analysis method. In this paper, this method is applied to analyze the CSR effect in a triple-bend achromat (TBA) with symmetric layout, which is commonly used in the optics designs of energy recovery linacs (ERLs). A condition of cancelling the CSR linear effect in such a TBA is obtained, and is verified through numerical simulations. It is demonstrated that emittance preservation can be achieved with this condition, and to a large extent, has a high tolerance to the fluctuation of the initial transverse phase space distribution of the beam.

physics.acc-ph↗