Symplecticity of the transfer maps is important for reliable evaluation of space-charge dominated beams in accelerators. Unfortunately, most simulation codes that include collective effects, such as space charge, do not use canonical phase-space variables and therefore are not symplectic in the presence of electromagnetic fields. In this paper, we present a numerical method to extract symplectic transfer maps using particle tracking simulation code IMPACT-T for space-charge dominated beams. We demonstrate this method by obtaining symplectic transfer maps in the photo-injector (113 MHz SRF gun) section of the Coherent electron Cooling (CeC) Proof of Principle (POP) experiment.

Xsuite is a Python toolkit for modelling and simulation of particle accelerators, which has been developed at CERN together with collaborators from other institutes over the past four years. The code has reached a mature development stage and has become the workhorse for several studies and applications, allowing the gradual replacement of legacy tools like Sixtrack, COMBI, PyHEADTAIL. This contribution provides an overview of the code capabilities and illustrates examples in different areas of accelerator science, including low-energy hadron rings for medical applications, high-intensity hadron accelerators, synchrotron light sources, high-energy hadron and lepton colliders.

The auto differentiable simulation is a type of simulation that outputs of the simulation contain not only the simulation result itself, but also its derivatives with respect to many input parameters. It provides an efficient method to study the sensitivity of the simulation result with respect to the input parameters and can be used in some gradient based optimization methods for fast parameter design optimization. In this paper, we report on the development of a fast auto differentiation module that can be used in many simulation codes.

The design and operation of modern accelerators demand advanced simulation tools capable of addressing complex challenges. Differentiable simulations are particularly valuable, as they enable gradient-based optimization techniques that significantly reduce computational costs and efficiently tackle high-dimensional problems. The PyTorch-based simulation code Cheetah was developed to combine high-speed, differentiable simulations with seamless integration into machine learning workflows. In this work, we present recent updates to Cheetah, developed collaboratively by DESY, KIT, SLAC, and LBNL, which extend its capabilities and enhance its performance. Key advancements include support for vectorized execution, enabling simultaneous simulations across large parameter spaces; the addition of space charge modeling and higher-order transfer maps for more accurate beam dynamics; and expanded support for multiple particle species and additional accelerator components, broadening its applicability to other systems. By enabling faster, more precise, and scalable simulations, Cheetah is poised to become a valuable tool for meeting the growing demands of the accelerator physics community.

FLUKA simulations of beamlines are important for un- derstanding numerous different aspects of accelerators, in- cluding beam losses, particle backgrounds, activation and shielding. Creating a beam-line simulation using FLUKA is a time consuming and potentially error prone process. This paper describes a set of python tools called pyflubl (Python FLUKA beam-line) which can create a FLUKA simulation using input from MAD-X, MAD8, Transport or BDSIM. pyflubl is based on multiple stable and advanced python packages created to make BDSIM (Geant4) beamline simu- lations as simple as possible, these are pymadx (an interface to MAD-X output), pymad8 (an interface to MAD8 out- put), pybdsim (interface to BDSIM) and most importantly pyg4ometry (a geometry engine for Monte Carlo geometry creation). The magnetic fields required for FLUKA are im- plemented in C++ via BDSIM, thus keeping fields consistent between Geant4 and FLUKA beamline simulations. This paper describes pyflubl design and implementation and ex- ample results for an idealised electron beam-line. Particular attention is given to geometry, fields and scoring.

BDSIM (Beam Delivery Simulation) is a Monte Carlo particle tracking tool for accelerator beamline modelling. It integrates particle transport with detailed geometry and physics using Geant4 for precise modelling of particle-matter interactions in 3D models of particle accelerators. Primarily for energy deposition studies and beam loss simulations, BDSIM allows a high degree of control and customisation, and is ideal for understanding and enhancing the performance of beamline designs. BDSIM has numerous modelling applications, including high-energy physics facilities, particle detection experiments, synchrotron light sources, medical accelerators, and novel acceleration experiments. Here, we present recent developments of BDSIM. This includes improved custom inverse-Compton scattering processes for laserwire and polarimeter simulations and extending the process to model polarization & electron spin; improved acceleration including transverse focussing in RF elements with implementation of 3D transverse magnetic and electric modes; custom elements for modelling muon cooling channels; and updates to interfacing with Xsuite via improved code couplings and BDSIM distribution methods.

AtomicAndPhysicalConstants.jl is a Julia package designed to provide atomic and physical constants including the speed of light, subatomic particle properties, atomic isotope properties, etc. Values are obtained from CODATA (Committee on Data of the International Science Council), NIST (National Institute of Standards and Technology), and PDG (Particle Data Group) datasets for physical constants, atomic and subatomic particles for scientific computations, particularly in fields such as particle and accelerator physics. Key features include a macro for users to access and customize units for constants, dynamic updates to integrate the latest scientific data, and compatibility with Julia's Unitful.jl library for convenient unit manipulation. These capabilities make the package ideal for applications requiring rigorous physical accuracy and reproducibility.

Longitudinal tomography is widely used in the CERN synchrotrons as an essential beam diagnostics tool. In recent years, more complex applications of phase space tomography, such as voltage calibration and multi-bunch tomography, have been explored. For these applications, large numbers of reconstructions are required, and computation time has a significant impact on usability. The current implementation is Python based, with the numerically intensive components written in C++. To further increase performance, a GPU-accelerated version has been developed using CuPy and CUDA. The most computationally demanding parts of the algorithm can now be run on the GPU, whilst maintaining the Python interface for maximum flexibility. Performance benchmarks showed speedups up to a factor of 35 in the scope of the entire application and even higher values when only considering the computationally intensive parts. This contribution discusses the implementation of GPU tomography as well as the additional performance improvements it enables.

Intra-beam scattering (IBS) has recently gained significant interest in the community of free electron lasers (FELs), as it is believed to produce an increment in the sliced energy spread (SES), which is detrimental to FEL performance. To control and contain this phenomenon, it is important to include IBS in the design phase of an FEL through appropriate numerical simulation. Most existing codes that simulate IBS were developed for long-term tracking in circular lattices, assuming Gaussian bunches. Unfortunately, this assumption doesn’t capture the rapid bunch evolution of electron bunches in photoinjectors. To address this limitation, the tracking code RF-Track has recently been updated to include IBS, using a novel hybrid-kinetic Monte Carlo method. This paper presents benchmarks performed to verify the implementation. The predicted SES increment in the beam due to IBS using RF-Track has been compared against a kinetic approach used in a different tracking code and, secondly, against a semi-analytical model. The results showed a good agreement, setting RF-Track as a tool to understand and control the SES growth in photoinjectors and, in particular, in FEL.

The SEALab facility in Berlin is home to an R\&D superconducting radio-frequency (SRF)photoinjector setup and beamline. Designed to support multiple varied applications - ranging from Energy Recovery Linac (ERL) to Ultrafast Electron Diffraction (UED) and Electron-Beam Water Treatment (EBWT) - SEALab requires flexible, high-precision tuning to support these diverse beam modes. These applications span over three orders of magnitude in bunch charge, emittance, and current, alongside sub-picosecond pulse lengths. This makes injector setup and tuning a significant challenge. With the world's first beam achieved at SEALab from a Na-K-Sb cathode in our SRF gun, a suite of beam dynamics models has been developed to support understanding of the beam behaviours in the gun, where no observations are possible, and operation of the commissioning process. This is comprised of a first-order analytical model, particle-in-cell (PIC) ASTRA simulations, and a machine-learning surrogate model trained for current commissioning operation ranges. These models are coupled with a Multi-Objective Bayesian Optimisation (MOBO) algorithm to enable rapid tuning across multiple beam modes. This combination of surrogate modelling and optimisation algorithm reduces optimisation timescales from hundreds of hours to minutes, allowing near-real-time tuning for the accelerator. This work presents the modelling framework, its validation, and its application to SEALab's many-mode optimisation challenges.

Structure-based wakefield accelerators (SWFA) have been identified as a candidate technology for future applications ranging from free electron lasers to colliders. However, achieving the desired beam energy and quality requires meter-scale structures with tight tolerances, placing constraints on structure and beam characteristics to minimize emittance growth and combat transverse instabilities. High fidelity and self-consistent simulations over these lengths necessitate enormous computational resources, making parametric studies of novel structures or instability-mitigation schemes unfeasible with standard practices. We present a technique for decomposing high dimensional wakefield systems into a set of lower dimensional components, capable of accurately reconstructing the structure response in a fraction of the time. We discuss the approach and implementation of this technique using Green’s Functions for common structure geometries. We demonstrate the potential for significant reduction in computation times and memory footprint using such representations. Finally, we discuss the application of machine learning in generating these representations for novel structure geometries.

Alternative configurations around the ATLAS experiment are investigated aiming to reduce muon rates at forward physics experiments such as FASER and SND@LHC. The Geant4 toolkit BDSIM is used to propagate muons through a model of a section of the LHC and the TI12 tunnel, where the FASER experiment is located. We compare the muon rates in BDSIM with FASER data collected during dedicated tests in the LHC. Results show a significant worsening of the background with the non-nominal polarity configuration of the triplet quadrupoles, used in 2024. The horizontal crossing angle further increased the background, however a partial mitigation of approximately 10% was found using a set of orbit corrector magnets. Additionally, nominal triplet polarity was favorable for both vertical and horizontal crossing angles. This work served as benchmark of simulations that will be used to validate future configurations.

Symplecticity of the transfer maps is important for reliable evaluation of space-charge dominated beams in accelerators. Unfortunately, most simulation codes that include collective effects, such as space charge, do not use canonical phase-space variables and therefore are not symplectic in the presence of electromagnetic fields. In this paper, we present a numerical method to extract symplectic transfer maps using particle tracking simulation code IMPACT-T for space-charge dominated beams. We demonstrate this method by obtaining symplectic transfer maps in the photo-injector (113 MHz SRF gun) section of the Coherent electron Cooling (CeC) Proof of Principle (POP) experiment.

The 7th International School on Beam Dynamics and Accelerator Technology (ISBA24) held in Chiangmai University during November 1-9, 2024, encompasses seven days opportunities where the foundation of accelerator physics is applied during hands-on sessions with simulation software including ASTRA, ELEGANT, Opera-3D and CST Studio Suite. Opera-3D, a finite element-based Maxwell’s equations solver, is known for its powerful low frequency simulation capabilities and is appropriate for magnet design. Instructed by two lecturers from Synchrotron Light Research Institute, 15 students from China, Japan, India and Thailand were trained on the Opera-3D software fundamentals in the application of magnet design for particle accelerator. The students showcase their knowledge in the group assignments including the design of H-shape dipole, C-shape dipole and combined horizontal and vertical corrector with success. Thanks to the generous support of the ISBA24 sponsors and Sigma Solutions Co., Ltd., who provided the software licenses during the school. This article reports on the completion of the ISBA24 Opera-3D hands-on session provided to graduate students and young researchers from the Asian region.

Space charge limited (SCL) emission is of fundamental importance to vacuum electronic devices, where the self-field of emitted charges limits the maximum current density being emitted from a cathode surface. Traditional modeling of SCL emission using the Child-Langmuir law primarily focuses on electron dynamics, neglecting the role of ions, which can significantly influence emission dynamics. In this work, we extend a previously developed simple SCL algorithm for implementing the Child-Langmuir law at the surface grid in particle-in-cell (PIC) simulations to study ion effects. The presence of ions introduces new dynamics, affecting the steady-state current, the evolution of surface electric fields, and the transient behavior of SCL emission. Using the 1-D electrostatic PIC code, XPDP1, developed by the Plasma Theory and Simulation Group (PTSG), we investigate these ion-induced modifications and test the influence of ions on the SCL emission algorithm. The extended algorithm ensures an accurate computation of the surface electric field via Gauss’s law to resolve the space charge contribution from both ion motion and electron emission, and the findings will be discussed in detail.

Graphical user interfaces (GUIs) are sought to support particle accelerator and beamline modeling for both conventional and advanced accelerator concepts. Downloaded over 1500 times in the last 22 years, G4beamline (available gratis from Muons, Inc.) has been used for diverse applications in science and industry, representing over 50M$ of economic activity. Its strengths include ease of use compared to its underlying CERN Geant4 package, flexibility in modeling beamline elements (as well as other systems such as particle detectors), and use of the well tested Geant4 libraries to track particles in electromagnetic fields and in matter: of particular importance in simulating muon cooling and muon colliders. Its current GUI interface is however rudimentary. A more comprehensive and modern GUI would enhance the program’s utility and user appeal, attracting a wider community of users in accelerator science and related fields. Another valuable feature would be “hooks” in the GUI interface for additional commonly used simulation programs such as MCNP and MAD-X, easing comparisons among alternative accelerator modeling tools by providing a common geometry description and output format.

Oriented bent crystal planes can deflect charged particles as strongly as a magnetic field exceeding 100 T. As a result, beam extraction from an accelerator using oriented crystals offers significant opportunities for diverse applications, ranging from beam tests for particle detector R&D to high-energy fixed-target experiments. However, designing these applications requires a universal simulation tool that accurately describes the physics of crystals, beam dynamics in an accelerator, and particle interactions with materials. We present a new simulation model realized using the BDSIM * , built on the Geant4 toolkit ** , to simulate particle transport in accelerators and their interactions with materials. The model includes a bent crystal as a new BDSIM accelerator component, leveraging the latest Geant4 features, G4ChannelingFastSimModel *** and G4BaierKatkov, to incorporate channeling physics and radiation losses, respectively. This model was applied to simulate the crystal-based extraction of 6 GeV electrons from the DESY II Booster Synchrotron ****. We present the calculated parameters of the extracted beam and discuss the feasibility of a proof-of-principle experiment.

Recently, many new light source projects have been developed based on the Multi-Bend Achromat (MBA) magnet lattice. In general, the dynamic aperture and transverse emittance of synchrotron light sources are sensitive to errors in magnet fields, alignment, and momentum. A realistic estimation of error tolerances is crucial for the successful construction of a fourth-generation synchrotron light source. In this paper, we present a realistic estimation of the error tolerances for a 4 GeV, 800-meter-long fourth-generation synchrotron light source, based on numerous simulations performed using the ELEGANT code in conjunction with an MCP server and an Agentic AI.

The 7th International School on Beam dynamics and Accelerator technology (ISBA24) took place over nine days, from November 1 to 9, 2024 at Chiang Mai University in Thailand. The school, part of the KEK-IINAS-NX series, was jointly hosted by Chiang Mai University and the Synchrotron Light Research Institute (SLRI). Out of 115 applicants who had submitted resumes and recommendation letters, 64 students from nine countries (Thailand, China, Japan, Indonesia, Korea, Taiwan, India, Germany, and Turkey) were selected to participate the school. During the ISBA24 school period, we opened four hands-on trainings with ASTRA, ELEGANT, CST, and OPERA codes to deepen students’ understanding of accelerator theory and improve their skills in accelerator design. All students chose one of the hands-on trainings according to their interests. In the ELEGANT hands-on training, approximately 20 students learned to use the ELEGANT code to design the various 4th generation synchrotron light sources with the Multi-Bend Achromat (MBA) magnet lattices. In this paper, we report details on the ELEGANT hands-on training conducted during ISBA24.