Additive manufacturing of pure copper enables the production of complex RF cavities with features such as internal cooling channels. We report the successful demonstration of proton-beam acceleration in an additively manufactured pure-copper Interdigital H-mode structure (IH-DTL). The 433 MHz six-gap cavity accelerated 1.4 MeV protons to 2.212 MeV at 25 kW RF power, realizing an effective accelerating gradient of 5.6 MV/m while reaching cavity peak fields up to 68 MV/m without RF breakdown. With RF performance and vacuum operation on par with conventionally manufactured IH-type cavities, this experiment demonstrates the viability of additive manufacturing for future efficient linac structures.

Attosecond electron beams are essential for investigating ultrafast dynamics with atomic-scale resolution. However, conventional compression methods struggle to reach the sub-femtosecond regime without severe charge loss. We propose a novel multi-dimensional phase-space manipulation technique combining pulse-front-tilted photoemission, THz-driven chirping, and an angular dispersion beamline. This method effectively exchanges transverse emittance for robust attosecond longitudinal compression, paving the way for unprecedented resolution in ultrafast sciences.

We present a two-color XFEL scheme based on a self-seeding configuration. In this scheme, a chirped electron beam first generates a chirped x-ray pulse in the initial undulator. The electron beam is then directed through a chicane, while the chirped x-ray pulse is sent through a multilayer-based two-color filter to produce a two-color seed. Finally, the seed is amplified to saturation by the electron beam in the second undulator, yielding ultrashort two-color x-ray pulses that are separated both spectrally and temporally. This work offers a novel approach for the generation of ultrashort two-color XFEL pulses.

The electron–positron Future Circular Collider (FCC-ee) is an ambitious post-LHC project at CERN, designed to deliver collisions at four interaction points along a 91-km ring. At the experimental insertions, multiple radiation sources produce a challenging radiation environment exposing detectors and machine equipment. This work presents a comprehensive FLUKA model of the FCC-ee experimental insertions, characterizing the full radiation environment and identifying dominant sources in each region for the two extreme operational modes, at the Z pole and at the t$\overline{\mathrm{t}}$ threshold. The results crucially support the machine design, informing shielding strategies and technology choices.

Crab cavities are essential to the HL-LHC upgrade to restore geometrical luminosity loss at the main interaction points. Amplitude noise from their low-level RF systems drives both emittance growth and transverse beam tail evolution. In this CERN SPS experiment we demonstrate that crab cavity amplitude noise produces emittance growth with an unexpected dependence on octupole induced tune spread through beam-coupling impedance, while reducing the heavy-tail population of the beam profile. Through dedicated simulations we quantitatively reproduce both effects, establishing a validated framework to predict crab cavity noise impact in future operation.

The 3.8 nC/J low divergent electron bunch with energy up to 25 MeV is generated at 10 Hz by the 1.3 TW femtosecond laser pulse. The particles source is based on the efficient coupling of the pulse with an under-critical plasma slab formed by a nanosecond prepulse-induced breakdown of a thin, liquid ethanol microjet. The acceleration mechanism involves complex interplay between Direct Laser Acceleration (DLA) and Self-Modulated Laser Wakefield Acceleration (SM-LWFA) in the plasma density profile. Simple liquid target design has the advantage of robustness and suitability for long-term operation in vacuum for future kHz repetition rate laser-plasma applications.

Measuring neutron-capture cross sections on radioactive nuclei is one of the main open challenges in nuclear astrophysics, yet no existing technique can reach most of the relevant isotopes. We present the conceptual design of a free-neutron target driven by a supercompact cyclotron, optimized for integration into a low-energy ion storage ring using readily available technologies. Monte Carlo simulations show that the design enables a proof-of-concept demonstration at the CRYRING storage ring and is scalable to high neutron densities at future dedicated facilities, opening the path toward direct neutron-induced reaction measurements in inverse kinematics on stored radioactive beams.

This paper details the design, fabrication, and tuning methodology of a s-band cryogenic traveling-wave high-gradient accelerating structure with β = 0.3, targeting a theoretical accelerating gradient of 60 MV/m. For the first time, this work establishes a framework for tuning cryogenic traveling-wave copper cavities and for implementing conduction cooling in high-gradient, low-β copper cavities. These developments are significant for future high-gradient ultracompact linacs intended for hadron therapy and other applications.

This work introduces a systematic and deterministic approach to designing the linear set up of multi-bend achromat lattices with distributed sextupoles based on their substructures. The method reveals key parameter dependencies, prepares a relaxed starting point for nonlinear optimization and reduces reliance on computationally intensive optimization algorithms. Applied to the BESSY III design, it leads to a physically motivated baseline lattice. The approach efficiently provides a transparent foundation for further nonlinear optimization.

The Super Tau-Charm Facility requires an injector capable of delivering high-charge and high-brightness electron beams. We present a segmented design strategy that employs multi-objective optimization in the low-energy section mainly to restrain space-charge effects, followed by sophisticated beam manipulation in the high-energy section mainly to mitigate wakefield effects. This approach reduces design complexity and is capable of yielding a 2 GeV beam with 0.22% energy spread and normalized emittance below 6.5 μmrad. The lattice supports both 8.5 nC swap-out and 1.5 nC off-axis injection without hardware intervention, providing a versatile platform for future high-intensity colliders.

We present a new embedded structure for nanocrystalline soft magnetic alloy (MA) cores in proton/heavy-ion synchrotron RF cavities. The design uses ribbons of different thicknesses in distinct radial regions, effectively transferring power loss from inner thicker ribbons to thinner ribbon regions, overcoming the drawback of conventional cores fabricated from uniformly thick ribbons, where power loss concentrates in inner diameters. The embedded structure effectively improves temperature distribution and increases shunt impedance, as validated by numerical simulations and experiments. These results provide a theoretical foundation for the performance optimization of MA cores.

Dynamic detuning, encompassing dynamic Lorentz force detuning (LFD) and Microphonics, significantly restricts the operational stability of superconducting radio-frequency (SRF) cavity modules. This paper proposes a novel semi-analytical method for calculating the dynamic detuning of SRF cavities, reducing computation time by several orders of magnitude compared to transient f inite element analysis (FEA). A key advancement of this method is the incorporation of a correction term for high-frequency mechanical modes, which enhances simulation accuracy relative to conventional approaches that neglect them.

Beam trajectory control in free-electron lasers relies on static response matrices (RM) that become outdated as machine conditions drift, degrading correction performance. We propose an online dictionary learning method that continuously refines the RM during routine operation with modest data requirements. Simulations demonstrate that this approach achieves a root-mean-square error of 0.2 m/rad or lower for RM elements using only ~1000 trajectory–excitation data pairs. Online experiments at the Shanghai Soft X-ray Free-Electron Laser confirm robust orbit stabilization with correction precision better than 0.01 mm, enabling real-time trajectory correction in low-repetition-rate linacs.

Scientists have successfully developed two new methods that act as real-time “heart monitors” for high-power particle accelerators, allowing continuous and safe measurement of particle beams without interrupting particle accelerators. To prevent dangerous beam losses, operators must constantly track the beam’s current (intensity) and phase (precise timing relative to driving radio-frequency waves). Traditionally, acquiring these details required either dedicating machine time for offline phase scans or running the machine in a risky “open-loop” mode with radio frequency (RF) feedback turned off. To solve this problem, the newly developed Virtual Open-Loop and Steady-State algorithms mathematically analyze the existing RF signals that power the accelerator, accurately extracting the beam-induced signature while the feedback loops remain fully active. Tested successfully at the European Spallation Source, these noninvasive techniques accurately parse out both beam current and phase using zero additional hardware. This breakthrough provides a crucial real-time diagnostic tool for the safe and efficient operation of the next generation of high-power accelerators worldwide.

Next-generation particle accelerators facilities will require diagnostic systems that can operate at multi-GHz repetition rates. We have designed and tested an ionizing-particle detection system that achieves a 4-5 GHz response rate over a dynamic range of over 1000. The system consists of a novel compact signal path mated to a co-designed custom IC, all developed by the collaboration that authored the article. The resulting ionizing particle detection system is the best-performing fast particle detection system ever built. In addition to accelerator physics, this system could find application in high energy physics, advanced laser system development, and fusion energy science.

The crab-waist collision scheme now defines the world’s highest-luminosity circular colliders, from SuperKEKB today to future machines such as FCC-ee and CEPC. Such colliders require collimators placed very close to the beam core, making them dominant impedance sources that can drive the transverse mode-coupling instability (TMCI). Using electromagnetic and particle-tracking simulations, this work shows how collimator jaw geometry controls the vertical dipolar wakefield. Hollowed, exponentially tapered jaws, especially in a one-sided layout, reduce the dipolar kick factor and raise the TMCI threshold by up to ~90% in the SuperKEKB Low Energy Ring, used here as a case study.

Schottky effects in photoinjectors are neglected in most computational codes due to minimal impact. However, for applications such as high brightness high charge photoinjectors in future colliders such as FCC-ee, these field effects on the photocathode surface become significant. We explore the charge production limitations under ultrafast illumination that arise directly from these surface field effects. By self consistently coupling microscopic barrier dynamics with macroscopic space field and charge effects, a new model captures complex collective dynamics while remaining exceptionally computationally efficient, enabling real time simulation and injector tuning.

Nonlinear resonances are known to significantly influence stability boundaries, producing island chains and separatrix intersections that are difficult to capture analytically over a wide parameter range. This work introduces a perturbative construction of approximate invariants directly from symplectic one-turn maps. Unlike isolated-resonance normal forms, the method yields a generic invariant expression and can track changes in phase-space topology across different machine configurations. Applications to Fermilab lattices show that the resulting invariant accurately describes nonlinear trajectories and can be used for stability estimates.

In high-intensity proton accelerators, beam quality is strongly affected by space-charge effects, especially in the low energy beam transport (LEBT) region, where space-charge compensation (SCC) is essential for maintaining beam quality. In this work, we combine detailed simulations and experiments to study SCC dynamics in the LEHIPA LEBT, using PIC-MCC modelling along with dedicated diagnostics. A novel Particle Monitor Probe captures the time evolution of SCC, while a Retarding Field Analyzer measures the degree of compensation. In addition, a multiwire profiler is used to measure beam profiles under varying gas pressure, providing a comprehensive picture of the process.