The bunch-coupled instability of a beam moving under the influence of space charge forces and narrow-band impedance is analyzed through eigenvalue analysis of the Vlasov equation. When the space charge force is weak compared to synchrotron oscillations, chromaticity suppresses the bunch-coupled instability. However, as the space charge force becomes dominant, the oscillation mode of the bunch transitions from synchro-beta oscillations to a mode dependent solely on the longitudinal coordinate z, independent of momentum deviation, resulting in a weakening of the instability suppression effect.

As a prerequisite to achieve the desired high peak current in free electron lasers, multi-stage symmetric C-chicane compressors are essentially required and widely utilized. However, during the bunch compression process, coherent synchrotron radiation (CSR) effects may lead to evident transverse emittance dilution and eventually prevent achieving a higher peak current. In this paper, we present a general model of a four-bend chicane and conduct an explicit point-kick analysis of the coherent synchrotron radiation (CSR) effects. These yield two novel steady state CSR-immune chicanes that feature non-symmetric C-shape and S-shape layouts, respectively.

Plasma accelerators provide large accelerating gradients, but can also suffer strong transverse instabilities if operated at high power-transfer efficiency. This paper presents a full mapping of the parameters that govern the strength of the beam-breakup instability in beam-driven plasma accelerators. We find that the previously proposed efficiency–instability relation provides a lower bound on the strength of the instability. While it is possible to operate close to this lower bound, the strength is orders of magnitude higher in other parts of the parameter space.

In this study, a novel linear accelerator (linac) embedded in a coaxial high-power microwave source is proposed. This design not only takes advantage of coaxial geometry in high-power microwave generation, but also improves system-level compactness by sharing infrastructure between the microwave source and the accelerating structure. As an example of principle demonstration, a standing-wave linac integrated with an X-band coaxial backward wave oscillator is presented in detail. This work serves as a foundational study on integrated accelerator concepts, offering a pathway toward more efficient, scalable, and versatile particle acceleration systems.

A novel permanent magnet-based accelerator magnet is presented, featuring nested, independently rotatable Halbach rings that provide fully tunable multipole fields with no energy consumption. Its openable, modular design allows easy installation around existing beamlines and seamless conversion between dipole, quadrupole, or higher-order configurations. With precise control over field strength and orientation, including polarity reversal, this compact, maintenance-free device offers a versatile and scalable solution for modern accelerator optics.

In this paper, we develop and benchmark accurate numerical models of betatron radiation emitted in plasma wakefield acceleration (PWFA) experiments. Using Liénard-Wiechert potentials, we compute radiation spectra based on particle trajectories obtained from idealized blowout fields, the quasi-static particle-in-cell (PIC) code QuickPIC, and the fully self-consistent PIC code OSIRIS. We validate our models against analytical benchmarks and EPOCH’s QED-based simulations, and present predictions for experimental conditions relevant to SLAC FACET-II plasma photocathode setups.

Exotic, short-lived radioactive ion beams provide insights into nuclear structure and stellar nucleosynthesis, but their transport through complex beamlines traditionally demands labor-intensive, expert-driven tuning. We introduce an AI-assisted transport system utilizing Bayesian optimization that learns in situ, achieving comparable transmission rates while significantly reducing manual tuning time. Validated at a working radioactive-ion-beam facility, our approach demonstrates real-world advantages over manual tuning methods. This adaptable framework can enhance radioactive beam facilities globally, enabling faster and more reliable access to rare nuclear species.

Free-electron lasers (FELs) providing sub-10 fs resolution require ultrashort electron beams with excellent phase space and timing stability, which depends on highly stable RF fields in the accelerating cavities located at the bunch compressors. This paper presents the next-generation of RF controls with attosecond resolution, which outperforms state-of-the-art short-term stability of RF fields in SRF cavities by more than one order of magnitude. This novel application of the carrier suppression interferometer extends conventional heterodyne methods.

In ring-based accelerators, the high-order one-turn transport map - when represented as a transposed square matrix - exhibits a distinctive structural property: the top-right subblocks are zero. This inherent sparsity facilitates the iterative, order-by-order construction of approximate invariants of motion. The fluctuations of these invariants provide a quantitative measure of chaos and can be utilized to guide the nonlinear lattice optimization efficiently.

The beam loss mitigation and its localization, especially at high intensity proton synchrotrons are extremely serious issues, which in most cases go far beyond the designed constraints causing high machine activation and personal dose to the radiation workers. This work is a breakthrough in minimizing and well localizing the beam loss based on systematic beam tests and numerical simulations at the highest beam power of 1 MW at the 3-GeV rapid cycling synchrotron of J-PARC. The beam loss power is even less than 0.1 kW, remarkably lower than the design limit of 4 kW, perfectly localized at the designated area to realize a sustainable operation with a record high of 99\% availability.

In storage rings with extremely small global phase slippage, the bunch length can vary significantly around the ring due to the impact of the partial phase slippage, which leads to the breakdown of the adiabatic approximation. We have studied coherent synchrotron radiation (CSR) induced microwave instability (MWI) beyond adiabatic approximation and presented a general formula for the instability threshold. Our results show that depending on the distribution of the partial phase slippage, the instability threshold of a real lattice can be increased by a factor of two or even more compared to the classical prediction.

We present a simple yet insightful model for analyzing electron microbunch dynamics in laser modulator cavities of steady-state microbunching (SSMB) storage rings, incorporating finite cavity losses, external laser injection, and the build-up of coherent undulator radiation over multiple turns. By combining beamline transfer matrices with a low-gain FEL oscillator model, this approach enables quick estimation of key dynamical quantities relevant to practical SSMB implementations. Applying this simple model to three representative SSMB schemes, we find all remain feasible under proper design parameters in the presence of cavity-induced beam-radiation interactions.

Angular streaking experiments allow for measurements on the attosecond timescale, but the time of flight (TOF) detectors used are prone to noise and failure. These limitations make it challenging to interpret the data and extract beam properties. In this article, we introduce a method to reduce noise and reconstruct up to three failed TOF detectors from an array of 16. The approach is trained on simulated data, achieves evaluation times suitable for online use during live experiments, and is demonstrated on real-world experimental data.

Symplectic simulation of space‑charge effects is important for long-term stability study of high-intensity accelerators. We introduce a U‑Net–based generative adversarial model that predicts the transverse space‑charge Hamiltonian directly from the particle distribution, delivering over an order‑of‑magnitude speed‑up compared to a physical model while maintaining symplectic structure. A Gaussian‑smoothed spline of the predicted Hamiltonian yields low‑noise force fields for accurate one‑step symplectic kicks, and integration into JuTrack demonstrates the model’s ready applicability for efficient, physics‑informed beam dynamics studies.