arXiv subjects

Oliver Boine-Frankenheim

Publications and source records attributed to Oliver Boine-Frankenheim.

At least 19 recordsLinked to original sources

arXiv2026

Simulation of trapped non-neutral plasma dynamics with rotating wall compression

A spectral macroparticle simulation scheme is used to model non-neutral plasma dynamics in a Penning-Malmberg trap. This grid-free numerical scheme is well adapted to the specific geometry of trapped plasmas, with varying longitudinal and transverse profiles in a cylindrical conducting pipe. The cutoff spectral harmonics provide control over the trade-off between accuracy and noise smoothing, which is especially important in the three-dimensional case. We demonstrate the ability of this scheme to obtain the dispersion relation of the plasma modes from the inherent simulation noise, providing a valuable tool for understanding the plasma's behavior. In the presence of a rotating wall drive, we show that the numerical scheme can reproduce the time evolution of the driven eigenmodes, identify the onset of mode mixing with increasing drive amplitude and retrieve the compression rate dependency on the drive frequency, known from the weak drive regime of the rotating wall technique. To the authors' knowledge, such simulations have not been reported in the literature so far.

physics.plasm-ph↗

arXiv2026

Beam intensity and quality predictions for laser-accelerated ions after capture and transport

Laser-plasma acceleration produces ultrashort, high-brightness ion beams reaching tens of MeV, yet their large divergence and broad energy spread require dedicated capture elements for beam transport. Using laser-accelerated protons from the GSI PHELIX laser to the LIGHT beamline as a reference, we developed a framework to optimize and assess such combined capture and transport systems, with emphasis on injection into conventional accelerators. In addition to our numerical analysis we derive scaling laws linking transmission and chromatic emittance growth to the initial half-opening angle, showing that the present performance is primarily divergence-limited. We also estimate and predict the longitudinal bunch quality and quantify the divergence reduction needed to approach injector-relevant intensities.

physics.acc-ph↗

arXiv2026

Machine learning-based virtual diagnostics of dielectric laser acceleration

We present the development of a digital twin-based reconstruction framework for dielectric laser acceleration (DLA) based on machine-learning-assisted inversion of single-shot electron energy spectra. DLA as a promising candidate for compact electron accelerator designs using optical nearfields in dielectric nanostructures lacks on direct diagnostics on the laser-electron interaction. Thus, the outgoing electron energy distribution is one of the few experimentally accessible observables. To exploit this information, DLA interaction and mapping on the downstream spectrometer are treated as nonlinear measurement device whose response is described by the symplectic sixdimensional tracking code DLAtrack6D. This forward simulation model serves as a digital twin mapping laser-electron interaction parameters onto resulting energy spectra. For diagnostics, we are interested in the inverse mapping represented by a neural network trained by synthetic datasets generated with the forward simulation model. The reconstruction performance and parameter identifiability of the inverse model are evaluated for parameter ranges relevant to planned experiments at the ARES linac in the SINBAD facility at DESY. Simulation studies demonstrate that the method can recover pulse front tilt angles with an accuracy of about 1 deg and phase offsets with an RMSE of about 0.36 rad corresponding to a difference of 0.4 fs in arrival time. Training with noisy spectra further improves robustness against spectrometer noise. The trained surrogate model evaluates in the millisecond range, enabling shot-to-shot parameter estimation compatible with the 50 Hz repetition rate of ARES. The approach effectively transforms the DLA interaction region into a virtual in situ diagnostics for otherwise inaccessible laser parameters during experiment and provides a foundation for real-time monitoring and control of future DLA experiments.

physics.acc-ph↗

arXiv2025

Proceedings of the 14th International Computational Accelerator Physics Conference (ICAP24)

This is the proceedings of the 14th International Computational Accelerator Physics Conference, ICAP'24, which was held at the Lufthansa Seeheim Conference Hotel in Germany from October 2-5, 2024, hosted by TU Darmstadt and GSI Helmholtzzentrum für Schwerionenforschung. ICAP'24 has focused on advances in Computational Accelerator Physics and their application to existing machines and future facilities. It has provided a forum for researchers in modeling and simulation to exchange information and discuss new ideas that benefit a wide area of accelerator science and technology. Topics of the conference have included computational needs and challenges, beam dynamics and electromagnetic field calculations, code development and validation, data processing and visualization, high performance computing, machine learning and advanced optimization as well as emerging technologies that will impact computing for accelerator design.

physics.acc-ph↗

arXiv2024

Simulation of longitudinal Landau damping in bunches with space charge

For a single hadron bunch affected by longitudinal space charge in a stationary rf bucket we analyze the frequency spectrum close to the expected loss of Landau damping for the lowest order dipole mode. For different bunch intensity parameters we obtain the bunch oscillation spectrum from a conventional longitudinal particle tracking code with a grid-based space charge solver. We validate selected results against a grid-less space charge solver. We highlight the importance of the choice of the cut-off parameter $h_c$ in the space charge impedance for the long-term accuracy of grid-based schemes. For typical bunch parameters in an ion synchrotron at injection energies we find that the branching point, where the dipole mode frequency emerges from the incoherent synchrotron frequency spectrum, as well as the damping of the dipole mode do not depend on $h_c$, chosen well below the actual value for realistic beam pipes.

physics.acc-ph↗

arXiv2024

Beam-based Identification of Magnetic Field Errors in a Synchrotron using Deep Lie Map Networks

We present the first experimental validation of the Deep Lie Map Network (DLMN) approach for recovering both linear and non-linear optics in a synchrotron. The DLMN facilitates the construction of a detailed accelerator model by integrating charged particle dynamics with machine learning methodology in a data-driven framework. The primary observable is the centroid motion over a limited number of turns, captured by beam position monitors. The DLMN produces an updated description of the accelerator in terms of magnetic multipole components, which can be directly utilized in established accelerator physics tools and tracking codes for further analysis. In this study, we apply the DLMN to the SIS18 hadron synchrotron at GSI for the first time. We discuss the validity of the recovered linear and non-linear optics, including quadrupole and sextupole errors, and compare our results with alternative methods, such as the LOCO fit of a measured orbit response matrix and the evaluation of resonance driving terms. The small number of required trajectory measurements, one for linear and three for non-linear optics reconstruction, demonstrates the method's time efficiency. Our findings indicate that the DLMN is well-suited for identifying linear optics, and the recovery of non-linear optics is achievable within the capabilities of the current beam position monitor system. We demonstrate the application of DLMN results through simulated resonance diagrams in tune space and their comparison with measurements. The DLMN provides a novel tool for analyzing the causal origins of resonances and exploring potential compensation schemes.

physics.acc-ph↗

arXiv2024

Pulsed Electron Lenses for Space Charge Mitigation

To produce the intense, high-quality hadron beams required by future nuclear and high-energy physics experiments, synchrotrons need to overcome a most prominent intensity limitation i.e., space charge. This Letter characterizes the potential of pulsed electron lenses in detailed 3D tracking simulations, key to which is a realistic machine and space charge model. The space charge limit, imparted by betatron resonances, is shown to be increased by up to 50% using a low symmetric number of electron lenses in application to the FAIR SIS100 synchrotron. Conceptually, a 100% increase is demonstrated with a larger number of electron lenses, which is found to rapidly saturate near the theoretical 2D limit.

physics.acc-ph↗

arXiv2023

Modeling of a Liquid Leaf Target TNSA Experiment using Particle-In-Cell Simulations and Deep Learning

Liquid leaf targets show promise as high repetition rate targets for laser-based ion acceleration using the Target Normal Sheath Acceleration (TNSA) mechanism and are currently under development. In this work, we discuss the effects of different ion species and investigate how they can be leveraged for use as a possible laser-driven neutron source. To aid in this research, we develop a surrogate model for liquid leaf target laser-ion acceleration experiments, based on artificial neural networks. The model is trained using data from Particle-In-Cell (PIC) simulations. The fast inference speed of our deep learning model allows us to optimize experimental parameters for maximum ion energy and laser-energy conversion efficiency. An analysis of parameter influence on our model output, using Sobol and PAWN indices, provides deeper insights into the laser-plasma system.

physics.plasm-ph↗

arXiv2023

Identification of Magnetic Field Errors in Synchrotrons based on Deep Lie Map Networks

Magnetic field errors pose a limitation in the performance of synchrotrons, as they excite non-systematic resonances, reduce dynamic aperture and may result in beam loss. Their effect can be compensated assuming knowledge of their location and strength. Established identification procedures are based on orbit response matrices or resonance driving terms. While they sequentially build a field error model for subsequent accelerator sections, a method detecting field errors in parallel could save valuable beam time. We introduce deep Lie map networks, which enable construction of an accelerator model including multipole components for the magnetic field errors by linking charged particle dynamics with machine learning methodology in a data-driven approach. Based on simulated beam-position-monitor readings for the example case of SIS18 at GSI, we demonstrate inference of location and strengths of gradient and sextupole errors for all accelerator sections in parallel. The obtained refined accelerator model may support setup of corrector magnets in operation to allow more precise control over tunes, chromaticities and resonance compensation.

physics.acc-ph↗

arXiv2022

Landau damping of transverse head-tail instabilities with a pulsed electron lens in hadron synchrotrons

A pulsed electron lens produces a betatron tune shift along a hadron bunch as a function of the longitudinal coordinates, which is a longitudinal detuning. An example of transverse detuning are the tune shifts due to octupole magnets. This paper considers a pulsed electron lens as a measure to mitigate the head-tail instabilities. Using a detailed analytical description within a Vlasov formalism, the coherent properties of the longitudinal and transverse detuning are presented. The analytical predictions are compared with the results of the particle tracking simulations. A pulsed electron lens is demonstrated to be a source of tune spread with two components: a static one, leading to Landau damping; and a dynamic one, leading to an effective impedance modification, which we demonstrate analytically and in our particle tracking simulations. The effective impedance modification can be important for beam stability due to devices causing a longitudinal detuning, especially for nonzero head-tail modes. The Vlasov formalism is extended to include the combination of longitudinal and transverse detuning. As a possible application at the SIS100 heavy-ion synchrotron (FAIR at GSI Darmstadt, Germany), a combination of a pulsed electron lens with octupole magnets is considered.

physics.acc-ph↗

arXiv2022

Characterization and minimization of the half-integer stop band with space charge in a hadron synchrotron

In any hadron synchrotron, the half-integer resonance is among the strongest effects limiting the achievable maximum beam intensity. The heavy-ion superconducting synchrotron SIS100, currently under construction at GSI, should provide intense beams for the future FAIR experiments. Using SIS100 as an example, this paper develops a quantitative framework for characterizing the half-integer stop band for realistic, Gaussian-like distributed bunched beams. This study identifies the tune areas affected by the gradient-error-induced half-integer resonance for varying space charge strengths. A key insight of our analysis is that, for bunched beams a relatively small gradient error can result in a large half-integer stop band width. The achievable maximum bunch intensity, often referred to as space charge limit, is thus reduced significantly. This contrasts the findings in existing studies in literature based on more simplified beam distributions. The reason for discrepancy is identified in the increasing stop band width for Gaussian distributions when space charge becomes stronger, which appears on longer time scales as relevant for synchrotrons. The role of synchrotron motion in providing continuous emittance growth across the bunch is scrutinized. To minimize the half-integer stop band for a bunched beam, and hence increase the space charge limit, lattice corrections are applied: Including space charge in the optimization procedure recovers results equivalent to conventional lattice correction. Therefore, we find that conventional correction tools are well suited to increase the gradient-error-induced space charge limit of synchrotrons.

physics.acc-ph↗

arXiv2022

Simulation Study of the Space Charge Limit in Heavy-ion Synchrotrons

The SIS100 synchrotron as a part of the new FAIR accelerator facility at GSI should be operated at the "space charge limit" for light and heavy ion beams. Beam losses due to space charge induced resonance crossing should not exceed a few percent during a full cycle. The recent advances in the performance of particle tracking tools with self-consistent solvers for the 3D space charge forces now allow us to reliably identify low-loss areas in tune space, considering the full 1s (160'000 turns) accumulation plateau in SIS100. A realistic magnet error model, extracted from precise bench measurements of the SIS100 main dipole and quadrupole magnets, is included in the simulations. Previously such beam dynamics simulations required non-self-consistent space charge models. By comparing to the self-consistent simulations results we are now able to demonstrate that the predictions from such faster space charge models can be used to identify low-loss regions with sufficient accuracy. The findings are applied by identifying a low-loss working point region in SIS100 for the design FAIR beam parameters. The bunch intensity at the space charge limit is determined. Several counter-measures to space charge are proposed to enlarge the low-loss area and to further increase the space charge limit.

physics.acc-ph↗

arXiv2020

Threedimensional Alternating-Phase Focusing for Dielectric-Laser Electron Accelerators

The concept of dielectric-laser acceleration (DLA) provides the highest gradients among breakdown-limited (nonplasma) particle accelerators and thus the potential of miniaturization. The implementation of a fully scalable electron accelerator on a microchip by twodimensional alternating phase focusing (APF), which relies on homogeneous laser fields and external magnetic focusing in the third direction, was recently proposed. In this Letter, we generalize the APF for DLA scheme to 3D, such that stable beam transport and acceleration is attained without any external equipment, while the structures can still be fabricated by entirely twodimensional lithographic techniques. In the new scheme, we obtain signifcantly higher accelerating gradients at given incident laser field by additionally exploiting the new horizontal edge. This enables ultra-low injection energies of about 2.5 keV (beta = 0.1) and bulky high voltage equipment as used in previous DLA experiments can be omitted. DLAs have applications in ultrafast time-resolved electron microscopy and -diffraction. Our fndings are crucial for the miniaturization of the entire setup and pave the way towards integration of DLAs in optical fiber driven endoscopes, e.g., for medical purposes.

physics.acc-ph↗

arXiv2019

Tracking with wakefields in dielectric laser acceleration grating structures

Due to the tiny apertures of dielectric laser acceleration grating structures within the range of the optical wavelength, wakefields limit the bunch charge for relativistic electrons to a few femtocoulomb. In this paper, we present a wakefield upgrade of our six-dimensional tracking scheme DLAtrack6D in order to analyze these limitations. Simulations with CST Studio Suite provide the wake functions to calculate the kicks within each tracking step. Scaling laws and the dependency of the wake on geometrical changes are calculated. The tracking with wakefields is applied to beam and structure parameters following recently performed and planned experiments. We compare the results to analytical models and identify intensity limits due to the transverse beam breakup and strong head-tail instability. Furthermore, we reconstruct phase advance spectrograms and use them to analyze possible stabilization mechanisms.

physics.acc-ph↗

arXiv2018

Silicon dual pillar structure with a distributed Bragg reflector for dielectric laser accelerators: Design and fabrication

Dielectric laser accelerators (DLAs) have proven to be good candidates for miniaturized particle accelerators. They rely on micro-fabricated dielectrics which are able to modulate the kinetic energy of the incoming electron beam under a proper laser illumination. In this paper we demonstrate a dual pillar structure with a distributed Bragg reflector to mimic a double sided illumination to the electron path. The structure is fabricated by an electron beam lithography technique followed by a cryogenic reactive ion etching process. Such a structure can accelerate the injected 28 keV electrons by a gradient of approximately 150 MeV/m which can be further optimized towards the GeV/m regime.

physics.acc-ph↗

arXiv2018

Alternating Phase Focusing for Dielectric Laser Acceleration

The concept of Dielectric Laser Acceleration (DLA) provides highest gradients among non-plasma particle accelerators. However, stable beam transport and staging have not been shown experimentally yet. We present a scheme that confines the beam longitudinally and in one transverse direction. Confinement in the other direction is obtained by a single conventional quadrupole magnet. Within the small aperture of 420 nm we find the matched distributions, which allow an optimized injection into pure transport, bunching, and accelerating structures. The combination of these resembles the photonics analogue of the Radio Frequency Quadrupole (RFQ), but since our setup is entirely twodimensional, it can be manufactured on a microchip by lithographic techniques. This is a crucial step towards relativistic electrons in the MeV range from low-cost, handheld devices.

physics.acc-ph↗

arXiv2017

Cooling rates and intensity limitations for laser-cooled ions at relativistic energies

The ability of laser cooling for relativistic ion beams is investigated. For this purpose, the excitation of relativistic ions with a continuous wave and a pulsed laser is analyzed, utilizing the optical Bloch equations. The laser cooling force is derived in detail and its scaling with the relativistic factor $γ$ is discussed. The cooling processes with a continuous wave and a pulsed laser system are investigated. Optimized cooling scenarios and times are obtained in order to determine the required properties of the laser and the ion beam for the planed experiments. The impact of beam intensity effects, like intrabeam scattering and space charge are analyzed. Predictions from simplified models are compared to particle-in-cell simulations and are found to be in good agreement. Finally two realistic example cases of Carbon ions in the ESR and relativistic Titanium ions in SIS100 are compared in order to discuss prospects for future laser cooling experiments.

physics.acc-ph↗

arXiv2017

Enhancement of space-charge induced damping due to reactive impedances for head-tail modes

Landau damping of head-tail modes in bunches due to spreads in the tune shift can be a deciding factor for beam stability. We demonstrate that the coherent tune shifts due to reactive impedances can enhance the space-charge induced damping and change the stability thresholds (here, a reactive impedance implies the imaginary part of the impedance of both signs). For example, high damping rates at strong space-charge, or damping of the $k=0$ mode, can be possible. It is shown and explained, how the negative reactive impedances (causing negative coherent tune shifts similarly to the effect of space-charge) can enhance the Landau damping, while the positive coherent tune shifts have an opposite effect. It is shown that the damping rate is a function of the coherent mode position in the incoherent spectrum, in accordance with the concept of the interaction of a collective mode with resonant particles. We present an analytical model, which allows for quantitative predictions of damping thresholds for different head-tail modes, for arbitrary space-charge and coherent tune-shift conditions, as it is verified using particle tracking simulations.

physics.acc-ph↗