The Future Circular electron-positron Collider (FCC-ee) is a design study for a 90.7 km circumference high-luminosity and high-energy e+e- collider. In electron and positron machines, the Touschek effect can cause large transverse-to-longitudinal momentum exchange, leading to particle losses that can limit the beam lifetime and produce distinct beam loss patterns. A quantitative assessment of this mechanism is therefore essential to identify regions potentially exposed to Touschek-induced losses and to determine its impact on the beam lifetime relative to other lifetime-limiting processes. This paper presents a study of the Touschek effect in the FCC-ee, performed using a Monte Carlo Touschek-scattering simulation routine newly implemented in the Xsuite framework. The results include Touschek-lifetime estimates for the FCC-ee and an evaluation of the arising beam loss patterns. The performance of the FCC-ee beam collimation system to safely dispose of Touschek losses is also assessed.

Precise regulation of the bunch population in FCC-ee is required to maintain the charge imbalance between collision bunches within the 3-5% tolerance that preserves beamstrahlung limits, bunch-length stability, and avoids flip–flop behaviour. Laser-driven Compton backscattering (CBS) has been proposed as an active actuator for bunch-by-bunch intensity control. An Xsuite-based simulation framework is employed to track the beam over many turns, while the bunch population is continuously updated according to the CBS-induced particle removal. The modified bunch intensity is then propagated into the beam–beam interaction model, allowing the resulting impact on beam parameters and overall stability margins to be quantified.

The cooling process is one of the most critical challenges for the future Muon Collider, as muons are initially produced with a very large emittance that must be significantly reduced before acceleration. This cooling must occur rapidly, well within the muon lifetime. At low energies, collective effects such as space charge and intrabeam scattering can strongly influence emittance growth and must therefore be considered in the lattice design, which is currently under development. This work presents studies of space charge and intrabeam scattering effects within the first three cells of the latest Muon Collider final cooling lattice design evaluating their impact on emittance growth using the tracking code RF-Track.

A nanopatterned microbunching collaboration has been formed to test the production of electron microbunches by rotating transverse beamlets into the longitudinal plane using the emittance exchange (EEX) beamline of the Argonne Wakefield Accelerator (AWA).*-** This mechanism has been suggested, such as by the Compact X-ray Free-Electron Laser (CXFEL) group at Arizona State University, to hold the potential to make short-wavelength free-electron lasers (FELs) more compact. Our collaboration will pattern AWA’s 40 MeV electron beam with a TEM grid to produce micro-scale beamlets that will become mico-to-nano scale microbunches in the longitudinal plane. Characterizing an array of beamlets with a modulation period at the few micron scale and a low, single pC scale total charge presents challenges in achieving the necessary transverse resolution and signal strength. These proceedings will detail the diagnostics explored to characterize these transverse modulations. We will discuss the merits and challenges of each approach in relation to our application, and progress towards demonstrating these desired diagnostics.

We revisit the applicability of standard intrabeam scattering (IBS) theories to modern high-density, ultra-low-emittance beams in diffraction-limited storage rings. Classical IBS formalisms by Piwinski, Martini and Bjorken–Mtingwa are derived under assumptions of Gaussian phase-space distributions, small-angle diffusion and weak perturbations. For the parameter range of interest these premises fail: non-Gaussian cores and tails develop, longitudinal–transverse correlations become significant, and the IBS–Touschek continuum renders growth-rate predictions highly sensitive to the specific choice of Coulomb-log and tail-cut parameters. We quantify where these limitations are most severe for multi-bend achromat lattices and discuss consequences for reliable emittance and lifetime predictions in future high-brightness rings.

The SOLEIL II storage ring will be equipped with many in-vacuum undulators (IVUs) and superbends, which are vulnerable to gas scattering–induced beam losses due to their small vertical gaps. In this paper, gas scattering–induced beam losses in SOLEIL II are studied with tracking simulations. The results show that, without vertical scrapers, 53$\%$ of elastic scattering–induced losses happen at IVUs with 4 mm vertical gaps, posing a risk of damage to their magnets over 15 years of operation. Detailed tracking finds that most of these losses originate from scattering events in short range, e.g., within half a turn. This suggests that one vertical scraper located upstream of each IVU group could provide optimal collimation, protecting the IVUs while maintaining the beam lifetime. However, this scheme is not allowed due to space constraints. A second optimal vertical collimation scheme is proposed with 2 scrapers, which reduces the beam losses at IVUs by 40$\%$ while maintaining an elastic scattering lifetime of 40 hours. In contrast to elastic scattering, inelastic scattering leads to only minor beam losses and remains acceptable.

We proposed a novel method of using nuclear resonance fluorescence (NRF) as a probe for spectrum measurements. By utilizing the continuous tunability of an ICS source, NRF photons can be excited at different points across the spectrum. The shape of the energy spectrum can then be effectively scanned and reconstructed by recording the relative NRF yields at different energy points. The feasibility of the proposed method was validated by Geant4 simulations of measuring NRF photon emission from 56Fe irradiated by an ICS source. The simulation results showed high precision for quasi-monochromatic gamma ray spectrum measurements, with a normalized root mean square error (NRMSE) of less than 5%. To maintain a sufficient signal-to-noise ratio (SNR) during the measurement, the energy resolution of detectors is suggested to be less than 1% of the energy being measured. Given an energy tuning precision of Delta E, the minimum measurable width of the energy spectrum, in terms of standard deviation, can reach 0.85 Delta E.

SPring-8-II, a major upgrade of the third generation light source SPring-8, aims to achieve low emittance below 100 pm·rad and to reduce the power consumption of the light source machine. High magnetic field magnets for SPring-8-II naturally result in narrow bore diameters and are densely distributed. As a result, vacuum chambers along the entire storage ring are designed with narrow apertures, leading to low conductance, and space for vacuum equipment such as photon absorbers and vacuum pumps is limited. To meet these requirements, we employ small-diameter stainless steel chambers and discrete compact photon absorbers*. Non-Evaporable Getter (NEG) pumps are placed near photon absorbers to effectively evacuate photon stimulated desorption (PSD) gas. We simulated a pressure distribution within a SPring-8-II unit cell as a function of beam dose considering the degradation of a pumping speed of the NEG pump due to gas absorption. On the basis of these results, we evaluated the beam lifetime and formulated a commissioning strategy for increasing a stored current through systematic vacuum conditioning.

Neutron guide tubes are used to transport neutrons efficiently. However, it requires very precise alignment, which is costly and vulnerable to shocks from earthquakes and other incident. It also is very sensitive to the surface condition such as cracks or dusts on the mirror. We are developing a new type of neutron mirror by utilizing the deflection of neutrons in a gradient magnetic field. This paper presents experimental results obtained using neutron beams at SOFIA (MLF).

Very High Energy Electrons (VHEE) are an emerging radiotherapy modality offering magnetic steering and focusing for conformal treatments, with potential for compact, cost-efficient clinical systems. VHEE beams may also enable Ultra-High Dose Rate (UHDR) delivery for the FLASH effect, which can selectively spare healthy tissue while maintaining tumour toxicity. A key challenge is achieving transversely uniform VHEE dose at UHDR, as current magnets cannot scan large tumour volumes within FLASH timescales (~0.1 s). Conventional dual-scattering systems—using a pre-scatterer for magnification and a Gaussian scatterer for flattening—are unsuitable at VHEE energies, generating substantial photon contamination unless the beamline is greatly extended. This work replaces the pre-scatterer with a quadrupole lattice that magnetically enlarges the beam while reducing Bremsstrahlung. RF-Track and TOPAS simulations show that an optimised quadrupole-scatterer design produces a 75 mm uniform field and reduces photon yield by 94.5% compared with dual-scattering. BDSIM confirms the modelling. Experimental validation at CLEAR at CERN is in preparation, and an optimiser is being developed to design quad-scatterer systems for generic VHEE machines using existing quadrupoles. These results suggest that magnetic beam magnification upstream of a Gaussian scatterer is a promising route to FLASH-compatible VHEE therapy with reduced secondary radiation and improved dose conformity.

In theory, a 180° or 90° hybrid bridge can be used as a variable power divider and combiner. This study focuses on the related theoretical research, the Magic Tee and 3 dB bridge are selected as the required 180° and 90° hybrid bridges. Based on scattering matrix of the four-port microwave network, the relationship between the input and output amplitude and phase, the phase difference of the two output signals and the influence of the input amplitude or phase error on the output signals were deduced theoretically. The simulations were also conducted, and the results agreed with theory, which proved the theory correct. The variable power divider and combiner can be used in many applications and thus worth studying.

Small momentum offsets in the LHC can generate significant optics distortions, particularly at low $\beta$*. The beam energy carries a relative uncertainty of approximately $10^{-3}$, which is insufficient for precise optics control. To better understand the impact of energy on the optics, two beam-based techniques have been explored. The first applies a global linear response matrix between BPM phase advances and $\Delta p/p$; while effective in simulation, this method is sensitive and does not reproduce the response observed in the machine. We introduce a new approach based on the principle of Deep Lie Map Networks (DLMN), which fits turn-by-turn BPM trajectories to a differentiable tracking model. Using the single-pass forward differentiation capability of MAD-NG, derivatives of the orbit with respect to $\Delta p/p$ are computed directly within the symplectic tracking engine. The results reveal arc-by-arc variations consistent with dipole-induced orbit distortions, providing insight into orbit behaviour around the ring. The measured response also agrees with that observed in the machine, demonstrating that the DLMN offers a promising new method for analysing the effect of energy on the optics of the LHC.

Modeling of the beam dynamics of high intensity bunched beams including the effect of Coulomb collision is challanging. This is because the proper modeling of the collisionality must be consistent with the computation of the mean field. To model this process a Monte-Carlo- based PIC framework has been developed and implemented in the MICROMAP library in order to compute collisionality and space-charge mean fields with a fully 3D spectral Poisson solver. The aim of this development is to achieve reliable predictions of IBS-driven emittance growth and beam lifetime. In this proceeding we compare and discuss the results from the long-term beam tracking simulations using this modeling with the prediction of the analytical IBS predictions to assess the consistency and accuracy.

Simulations of particle beam dynamics in electron accelerators need to account for both internal space charge effects and transient electromagnetic waves scattered at chamber walls. Commonly, these effects are treated separately using very different simulation techniques. We have developed a coupling procedure to account for both effects simultaneously by using a scattered field formulation. Here, we combine two field solvers optimized to simulate either the internal beam dynamics assuming free space or the transient electromagnetic wave propagation. Previously, the coupling procedure was restricted to quasi-static beam behavior, as is sufficient for linear movement and emission from the gun. In this contribution we extend the approach to account for scattered synchrotron radiation wakefields from bent trajectories. We present computational studies of the scattered CSR effect created in bunch compressors, specifically the BC0 of the European XFEL. No restrictions are imposed methodologically on the surrounding geometry or on the flight path of the beam. Hence, our approach is much more general than CSR models used in the past, which assumed for example pre-defined trajectories in between two parallel plates and rigid bunches. At the same time, due to the de-coupled solvers, our method allows to compute particle-particle CSR fields inside the bunch using free-space assumptions, which reduces modeling complexity significantly.

To reliably and repeatably validate the electromagnetic behavior of the pickup prototypes designed for the Elettra 2.0 button-type beam position monitors, two different radio-frequency test fixtures have been developed. The first test fixture, based on a coaxial-line design that emulates the TEM excitation generated by a relativistic beam, allows to measure the transmission performance of the pickups up to 16 GHz. The second test fixture, employing an antenna-launcher design, extends the measurement range up to 40 GHz. This paper presents a comparison between measured and simulated data, with particular focus on the electromagnetic validation of the first 16 prototypes manufactured using glass as the dielectric material.

In many modern accelerators, intrabeam scattering (IBS) leads to measurable changes in a beam’s dimensions during operation. For a Gaussian beam, there are many well-known methods to calculate the growth rates. However, while growth rates are very useful, they generally do not provide insight into how IBS interacts with effects beyond linear dynamics. To avoid this limitation, we apply IBS kicks, with both damping and diffusion components, to macroparticles during element-by-element tracking. These kicks are derived from first principles and are chosen to give the same growth rates as traditional methods for a Gaussian beam, with no special form assumed for the covariance matrix of the distribution. The beam generally becomes non-Gaussian during tracking, but the kick is nevertheless approximated by that of a Gaussian beam with the same covariance matrix. This method of IBS simulation has been implemented in SciBmad, allowing for analysis of IBS effects in beams with nonlinear spin-orbit dynamics, synchrotron radiation, beam-beam interactions, and more. Furthermore, tracking with IBS kicks is parallelized on both the CPU and the GPU.

Precise 3D field measurements of large, complex magnet geometries are time-consuming and error-susceptible. For large magnets, it is common to record Hall probe data on a sparse grid, then use an interpolation algorithm to estimate field values at the remaining points. For common magnet geometries, such as quadrupoles and dipoles, linear interpolation often provides accurate results. However, for complex magnet geometries, this method can yield lower accuracy. In this paper, we present a method based on a locally Maxwell-consistent algorithm for sparse Hall probe measurements. Through the k-nearest neighbors algorithm, we locally fit the magnetic field with Tikhonov regularization. We test this method on a novel Compton spectrometer, capable of measuring single-shot, double-differential, energy-angle gamma spectra, ranging from 180 keV to 28 MeV. Using held-out validation, we demonstrate that we can reconstruct its magnetic fields with higher accuracy than linear interpolation and radial basis function (RBF) interpolation with cubic, thin plate spline, and quintic kernels. We also analyze the dependence of point sparsity on accuracy.

We present a new general analytic formula for radiation spectra of inverse Compton scattering due to a flat laser pulse at any scattering angle. Using the analytic solution for a flat laser pulse, we build an approximation of a Gaussian pulse as a series of flat pulses with varying field strengths. From this description we obtain an expression for the phase modulation between successive flat pulses due to changing field strength, which leads to ponderomotive broadening in the scattered spectra.

Intrabeam scattering (IBS) increases emittance and energy spread in low-emittance beams. In angular-dispersion-induced microbunching (ADM) beam lines, nanometre-scale density peaks cannot be represented reliably by a single smooth rms bunch length. This work separates the classical local IBS source from the microbunching spectrum: the former supplies the lattice and phase-space scattering kernel, whereas the latter modifies only the local pair-density weight. Rest-frame smoothing and a microbunching-dependent Coulomb-logarithm correction are introduced to exclude density structures below the collision resolution. For a 26 m branch line, the model gives single-pass microbunching-induced enhancements of 5.630% in the vertical-emittance source and 8.330% in the energy-spread-variance source. The additional source is concentrated in two intervals where the microbunching weight overlaps the local IBS kernel.

Traditional analytical models for intrabeam scattering (IBS) typically assume a Gaussian beam distribution in phase space. In this paper, we present an extended analytical IBS model that employs Hermite-Gaussian polynomials as basis functions to calculate the IBS diffusion coefficient for arbitrary phase space distributions. The generating function method is adopted to simplify the relevant calculations into a numerically solvable integral form. This approach retains the efficiency inherent to analytical models while ensuring calculation accuracy for non-Gaussian beam distributions.