In accelerators, especially in the low-energy range, stray particles significantly affect the performance parameters of the accelerator. The generation and movement of these stray particles have not been thoroughly studied. This paper introduces a Beam Monte Carlo Collision Code based on SIMION (BMCCS) to address this issue and provides three examples to illustrate its application. This code offers highly effective guidance for ion source and accelerator tube arcing, neutral beam generation, and ion implantation purity.

At the Photo Injector Test Facility at DESY in Zeuthen (PITZ), proof-of-principle experiments have showcased a high-peak, high-average-power single-pass THz FEL. Using electron beams with 17 MeV/c energy, a bunch charge of up to 2.4 nC and a bunch length much longer than the radiation wavelength, narrowband 3 THz radiation with a pulse energy of more than 0.1 mJ was obtained using an LCLS-I undulator. Unlike the typical XFEL mechanism, the THz FEL is initiated from coherent spontaneous emission rather than shot noise, emphasizing the critical role of the local bunching factor in achieving this performance.

Accelerator-based light sources are increasingly recognized as promising candidates for EUV lithography applications. This research proposes a regenerative amplifier free-electron laser EUV source with harmonic lasing, driven by a superconducting energy-recovery linac. In our simulations, this approach achieves an average EUV output power of approximately 2 kW using an electron beam with an energy of ~330 MeV, which significantly reduces the required electron energy and facility size relative to other accelerator-based proposals.

Machine learning is used to create a virtual pulse reconstruction diagnostic (VPuRD) tool for the analysis of longitudinal phase space electron beam data. The tool can be used as a noninvasive, efficient alternative to currently used single shot methods for free electron laser pulse characterization and can enable precise single shot measurements of pulse power.

Recent achievements in the operational deployment of efficient particle steering by means of bent crystals via planar channeling in the Large Hadron Collider renewed the interest in their exploitation for advanced accelerator and high-energy physics concepts. The results presented in this work show that incorporating an additional degree of freedom in the design of future goniometers could enable the operational deployment of axial channeling. This breakthrough paves the way for more efficient beam collimation and particle steering applications, with potential benefits for high-energy physics experiments and future accelerator designs.

We present a novel method to minimize radiative depolarization in electron storage rings. Groups of vertical orbit bumps are constructed that achieve simultaneous polarization, orbit, and optics control, motivating the name “Best Adjustment Groups for ELectron Spin” (BAGELS). Applied in simulations of the 18 GeV Electron Storage Ring of the Electron-Ion Collider, BAGELS increases the asymptotic polarization by nearly 2x in the 1 interaction point case and over 3x in the 2-IP case. BAGELS is also used to construct knobs for global coupling correction and for generating a vertical beam size match at the IP, with minimal impacts on the polarization, orbit, and optics.

Microbunched electron cooling (MBEC), a type of coherent electron cooling, has been under consideration as a candidate for the strong hadron cooling component of the Electron Ion Collider (EIC). Most treatments of this scheme have been based on simplified models for the space charge effect in which particles are approximated by charged disks. Although such models capture a good portion of the underlying physics, they lack the fidelity of a rigorous analysis that explicitly treats the hadron and electron beams as collections of point charges. In this paper we present such a rigorous, three-dimensional (3D) model, from a theory and a simulation perspective.

Theory and simulations revealed that low-energy positrons experience transverse expansion and quality degradation in vacuum-plasma transition regions due to the defocusing wakefields. To mitigate this effect, a wide driving electron beam is proposed to reduce the defocusing force in the transition zone. This work highlights critical challenges in nonuniform plasma environments and provides a practical strategy to preserve positron beam quality during acceleration, advancing the feasibility of plasma-based positron accelerators.

The cascade-line generator is a more compact Tesla-type generator with double pulse width and double stored energy compared with conventional single-line generators. We present a design for a 20-GW 40-ns generator of this type which is only about 4.5 m in length and 1 m in diameter.

This paper proposes an efficient and universal approach based on an equivalent circuit model for designing couplers in any travelling-wave (TW) structures including accelerating and deflecting structures. By leveraging the local reflection, this approach directly provides the coupling coefficient and frequency deviation, allowing the coupler to be optimized within just a few iterations. It significantly simplifies the overall design process while maintaining a high accuracy for both TW accelerating and deflecting structures.

A novel RF pulse compression mechanism utilizing a 3-dB hybrid and a single resonant cavity has been developed. To validate this innovative approach, we have designed an RF cavity system employing the TE₁₃₂ mode. The proposed configuration offers both enhanced fabrication feasibility and reduced production costs compared to conventional designs.

In hadrontherapy, gantries are used to deliver ion beams from different directions, enhancing the treatment quality and robustness. This paper presents the magnetic design of scanning magnets for the EuroSIG project, which aims to develop a novel superconducting gantry for hadrontherapy. The design focuses on optimizing magnet configurations and power converter compatibility. Simulations were conducted to assess field quality and beam deflection, as well as the effects of hysteresis and eddy currents. These studies confirm the feasibility of the design, supporting the development of a prototype scanning magnet.

Plasma can support extremely high-gradient strong electromagnetic fields, making it suitable not only for laser acceleration but also for short-distance manipulation of the charged particle beams. Straight capillary discharge plasma lenses have previously garnered widespread attention from researchers for their excellent focusing capabilities. In this letter, we present the first experimental demonstration of plasma-based deflection and focusing of laser-accelerated proton beams. This work is of great significance for the development of compact beam transport systems.

Laser-driven ion accelerators (LDIAs) offer ultra-high accelerating gradients, but their large divergence and broad energy spread pose significant transport challenges to use in applications. This study presents the design and simulation of compact, permanent-magnet beam transport systems to deliver laser-accelerated protons for applications in radiobiology, materials science, and high-energy-density physics. Using high-order particle tracking, we evaluated a number of transport configurations to optimize different parameters such as beam size, intensity, and energy. The tools and designs presented here will enable laser-driven ion accelerator facilities to better serve diverse user needs.

Acoustically driven crystalline undulators provide a method for generating brilliant, narrowband and tunable γ radiation, allowing for γ-ray sources with applications in nuclear physics, materials science, and biomedicine. Ultrarelativistic positrons channeling through a crystal that is periodically bent by a tens of MHz acoustic wave (AW) follow sinusoidal trajectories imposed by the spatially varying E-field of the bent lattice planes. Undulation results in the emission of directional and narrowband γ-rays, while brilliance and photon energy are controlled by the frequency and intensity of the AW. The demonstrated source can be developed for use at high-energy facilities.

A Shannon entropy analysis in Poincar apose maps was used as a measurable chaos indicator to define the online optimization objective for tuning the nonlinear dynamics of the National Synchrotron Light Source-II storage ring. Regularizing chaotic beam motion in phase space improved the off-axis injection efficiency by enlarging the degraded dynamic aperture.

Coupled-bunch instabilities can limit the performance of electron storage rings with higher harmonic cavities. This work unifies recent theories on longitudinal instabilities in double-rf systems and provides new insights into the periodic transient beam loading (PTBL)/mode-1 instability. The framework explains its dependence on azimuthal mode interactions and resistance to Landau damping, with predictions matching recent experimental data for the first time. The developed models were implemented in the open-source package pycolleff.

Reinforcement learning was used to optimize the injection of a particle beam into a synchrotron. The aim of the study is that an agent trained on a model adjusts eleven currents in quadrupoles and steerers of the physical injection beam line in such a way that a favorable contour (position and width) for the injection is achieved at the injection site. The contour measured with a luminescent screen and camera (see image) is one of the inputs for the agent.

Researchers developed an unsupervised machine learning framework to detect anomalies in superconducting RF (SRF) cavities at Jefferson Lab’s CEBAF accelerator. Tested for three months before a shutdown, it identified hardware failures and noise sources affecting performance. Unlike manual review, it detects beam disruptions missed by standard fault alerts. Enabled by fast-sampled RF signals (5,000 Hz vs. 1 Hz), it captures transient effects. Using principal component analysis (PCA), it builds daily, adaptive models without labeled data, automating a tedious process and reducing downtime, ultimately maximizing beam availability for nuclear physics experiments.