Computationally efficient methods for modelling laser wakefield acceleration in the blowout regime

Electron self-injection and acceleration until dephasing in the blowout regime is studied for a set of initial conditions typical of recent experiments with 100 terawatt-class lasers. Two different approaches to computationally efficient, fully explicit, three-dimensional particle-in-cell modelling are examined. First, the Cartesian code VORPAL using a perfect-dispersion electromagnetic solver precisely describes the laser pulse and bubble dynamics, taking advantage of coarser resolution in the propagation direction, with a proportionally larger time step. Using third-order splines for macroparticles helps suppress the sampling noise while keeping the usage of computational resources modest. The second way to reduce the simulation load is using reduced-geometry codes. In our case, the quasi-cylindrical code CALDER-CIRC uses decomposition of fields and currents into a set of poloidal modes, while the macroparticles move in the Cartesian 3D space. Cylindrical symmetry of the interaction allows using just two modes, reducing the computational load to roughly that of a planar Cartesian simulation while preserving the 3D nature of the interaction. This significant economy of resources allows using fine resolution in the direction of propagation and a small time step, making numerical dispersion vanishingly small, together with a large number of particles per cell, enabling good particle statistics. Quantitative agreement of the two simulations indicates that they are free of numerical artefacts. Both approaches thus retrieve physically correct evolution of the plasma bubble, recovering the intrinsic connection of electron self-injection to the nonlinear optical evolution of the driver

Ion optics and beam dynamics optimization at the HESR storage ring for the SPARC experiments with highly charged heavy ions

The High-Energy Storage Ring (HESR) is a part of an upcoming International Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt [1]. A key part of a scientific program, along with antiproton physics, will be physics with highly-charged heavy ions. Phase-space cooled beams together with fixed internal target will provide an excellent environment for storage ring experiments at the HESR for the SPARC collaboration [2–4]. Until recently, however, the existing ion optical lattice for the HESR was designed only for the experiments with antiproton beams. The thesis presents a new ion optical mode developed specifically for the operation of the HESR with highly charged heavy ions. The presence of the errors, such as beam momentum spread, magnetic field impurities or magnets misalignments, leads to disruption of beam dynamics: exciting of resonant motion and loss of beam stability. Within the paper, these effects are investigated with the help of numerical codes for particle accelerator design and simulation MAD-X and MIRKO. A number of correction techniques are applied to minimize the nonlinear impact on the beam dynamics and improve the experimental conditions. The application of the analytical and numerical tools is demonstrated in the experiment with uranium U90+ beam at the existing storage ring ESR, GSI

Design of a nonlinear quasi-integrable lattice for resonance suppression at the University of Maryland Electron Ring

Conventional particle accelerators use linear focusing forces for transverse confinement. As a consequence of linearity, accelerating rings are sensitive to myriad resonances and instabilities. At high beam intensity, uncontrolled resonance-driven losses can deteriorate beam quality and cause damage or radio-activation in beam line components and surrounding areas. This is currently a major limitation of achievable current densities in state-of-the-art accelerators. Incorporating nonlinear focusing forces into machine design should provide immunity to resonances through nonlinear detuning of particle orbits from driving terms. A theory of nonlinear integrable beam optics is currently being investigated for use in accelerator rings. Such a system has potential to overcome the limits on achievable beam intensity. This dissertation presents a plan for implementing a proof-of-principle quasi-integrable octupole lattice at the University of Maryland Electron Ring (UMER). UMER is an accelerator platform that supports the study of high-intensity beam dynamics. In this dissertation, two designs are presented that differ in both complexity and strength of predicted effects. A configuration with a single, relatively long octupole magnet is expected to be more stabilizing than an arrangement of many short, distributed octupoles. Preparation for this experiment required the development and characterization of a low-intensity regime previously not operated at UMER. Additionally, required tolerances for the control of first and second order beam moments in the proposed experiments have been determined on the basis of simulated beam dynamics. In order to achieve these tolerances, a new method for improved orbit correction is developed. Finally, a study of resonance-driven losses in the linear UMER lattice is discussed

Particle Physics Reference Library

This third open access volume of the handbook series deals with accelerator physics, design, technology and operations, as well as with beam optics, dynamics and diagnostics. A joint CERN-Springer initiative, the “Particle Physics Reference Library” provides revised and updated contributions based on previously published material in the well-known Landolt-Boernstein series on particle physics, accelerators and detectors (volumes 21A,B1,B2,C), which took stock of the field approximately one decade ago. Central to this new initiative is publication under full open acces

Ion Beam Collimation for Future Hadron Colliders

The application of integrated simulation frameworks, which include particle tracking and physical interactions, to heavy-ion beam collimation in existing and future hadron colliders is presented. The SixTrack-FLUKA coupling and Beam Delivery Simulation (BDSIM) were used and the tools and techniques developed for the simulations are presented. A simulation study of the collimation cleaning inefficiency for heavy-ion beams was performed for the Large Hadron Collider (LHC), using both frameworks, and compared to measurements taken during operation. A detailed energy deposition study of ion beam collimation in a 3D model of the entire LHC ring was performed using BDSIM. The SixTrack-FLUKA coupling was used to study heavy-ion beam collimation in the Future Circular hadron- hadron Collider (FCC-hh). An analysis of the most limiting losses and an evaluation of the collimation system performance were carried out. The performance of the High-Energy Large Hadron Collider (HE-LHC) collimation system with heavy-ion beams was also investigated. The dominant beam loss clusters were identified and possible mitigation strategies are discussed. Support for partially stripped ions (PSI), which retain some of their bound electrons, was added to BDSIM and a physics model that treats charge-changing interactions of PSI with matter was implemented. Using the newly added features in BDSIM, the collimation of PSI beams in the LHC was studied in the context of the Gamma Factory initiative

Investigation of a Compact Accelerator for Radioisotope Production

In this thesis the design and performance of a non-linear non-scaling Fixed Field Alternating Gradient (FFAG) accelerator is described. The imagined application of the design is for radioisotope production and in particular the production of 99mTc and 211At. The performance of the design in combination with an internal target and recycled beam, is also investigated as a potential way to increase isotope yields. The basic design consists of four separate radial sector magnets and two RF cavities. The design differs from a conventional cyclotron in that the edge angles have been optimised with the field gradient to produce a lattice that is isochronous to �0.15% and has stabilised tunes. Simulations conducted using the OPAL code showed that the dynamic apertures are large, peaking at 150 and 41.4 � m mrad in the horizontal and vertical planes respectfully. Acceleration with protons is possible at up the 5th harmonic with 100 kV/turn accelerating gradient and at the 1st harmonic for alpha particles. Space charge simulations suggested strong performance under high current conditions. A proton beam of 20 mA was simulated with 2.3% losses, dropping to 0% losses at 4 mA. Alpha particle beams were simulated with beam currents of up to 800�A with minimal losses. The best harmonic to operate at for handling high currents was found to be either the 2nd or 3rd. Simulations of the internal target demonstrated that ionisation cooling has an effect even with high Z materials. Two aspects were identifed as key to increasing beam survival; the vertical aperture and cooling the beam longitudinally. It was found that increasing the vertical aperture by �1 cm could double the beam survival time. Additionally by using a combination of a wedge shaped target and RF stabilisation to cool the beam longitudinally, a 140% increase in beam survival time was achieved. Finally several iterations of the design were created investigating possible improvements to the design including tune adjustment by introducing a magnet shift, a dual proton alpha particle design and a compact 35 MeV design

Simulations of RF beam manipulations including intensity effects for CERN PSB and SPS upgrades

During Long Shutdown 2 (LS2, 2019-2021) all the injectors of the CERN LHC will undergo several upgrades to fulfill the requests of the LHC Injectors Upgrade (LIU) Project. Among them, an increase in luminosity of the LHC beam by a factor of ten and two respectively for proton and ion beams is expected. The upgrades of the CERN PSB, the first synchrotron in the LHC proton injection chain, will be significant. The injection and extraction beam energies will be increased respectively from 50 MeV to 160 MeV kinetic energy (via the new Linac4) and from 1.4 GeV to 2 GeV (using new magnet power supplies). The required beam intensities will be a factor of two higher for High-Luminosity LHC (HL-LHC) beams, and the currently used narrow-band ferrite RF systems will be replaced by broad-band Finemet® cavities. For ion beams instead, a fundamental upgrade will concern the CERN SPS, the LHC injector, where the Low Lever RF functionalities will be considerably enhanced to allow the interleaving of two batches in longitudinal phase space through momentum slip-stacking, aiming at halving the bunch spacing. In order to predict future longitudinal beam stability and optimize complex RF manipulations both for PSB and SPS, longitudinal macro-particle simulations have been performed. Concerning the PSB, an accurate impedance model and a careful estimation of the space charge effects were included in simulations. Beam and cavity-based feedbacks were also taken into account. Controlled longitudinal emittance blow-up, currently obtained through phase modulation with a dedicated higher harmonic RF system, was achieved in measurements and simulations for the first time injecting RF phase noise in the main harmonic cavity, showing some advantages in using this new method. As for the SPS, the slip-stacking dynamics with collective effects has been studied in details aiming at optimizing the numerous parameters present and satisfying the stringent constraints on losses and bunch length at extraction. Beam quality issues were analyzed together with possible remedies. All simulations have been performed with the macro-particle longitudinal beam dynamics CERN BLonD code, after particular efforts have been spent to implement several algorithms for non ultra-relativistic energy machines (like the PSB) and for slip-stacking dynamics in order to easily optimize the large parameter space available. Benchmarks between BLonD, other codes and analytical formulas have been performed to study different approaches for induced voltage calculation and give some guidelines on the pros and cons of each of them