Search

Determining a model for the time scaling of the dynamic aperture of a circular accelerator is a topic of strong interest and intense research efforts in accelerator physics. The motivation arises in the possibility of finding a method to reliably extrapolate the results of numerical simulations well beyond what is currently possible in terms of CPU time. In earlier work, a proposal for a model based on Nekhoroshev theorem and Kolmogorov--Arnold--Moser theory was made. This model has been studied in detail and proved successful in describing the evolution of the dynamic aperture in numerical simulations, however, a number of shortcomings had been identified and new models are proposed in this paper, which solve the observed issues. The new models have been benchmarked against numerical simulations for a simple system, the 4D H\'enon map, as well as a realistic, non-linear representation of the beam dynamics in the LHC at 6.5 TeV providing in both cases excellent results. Determining a model for the time scaling of the dynamic aperture of a circular accelerator is a topic of strong interest and intense research efforts in accelerator physics. The motivation arises in the possibility of finding a method to reliably extrapolate the results of numerical simulations well beyond what is currently possible in terms of CPU time. In earlier work, a proposal for a model based on Nekhoroshev theorem and Kolmogorov–Arnold–Moser theory was made. This model has been studied in detail and proved successful in describing the evolution of the dynamic aperture in numerical simulations, however a number of shortcomings had been identified and new models are proposed in this paper, which solve the observed issues. The new models have been benchmarked against numerical simulations for a simple system, the 4D Hénon map, as well as a realistic, non-linear representation of the beam dynamics in the LHC at 6.5 TeV providing in both cases excellent results.

In this paper, the experimental results of the recent dynamic aperture at top energy for the CERN Large Hadron Collider are analysed by means of a diffusion model whose novelty consists of deriving the functional form of the diffusion coefficient from Nekhoroshev theorem. This theorem provides an optimal estimate of the remainder of perturbative series for Hamiltonian systems. As a consequence, a three-parameter diffusion model is built that reproduces the experimental results with a high level of accuracy. A detailed discussion of the physical interpretation of the proposed model is also presented. In this paper the experimental results of the recent dynamic aperture at top energy for the CERN Large Hadron Collider are analysed by means of a diffusion model whose novelty consists of deriving the functional form of the diffusion coefficient from Nekhoroshev theorem. This theorem provides an optimal estimate of the remainder of perturbative series for Hamiltonian systems. As a consequence, a three-parameter diffusion model is built that reproduces the experimental results with a high level of accuracy. A detailed discussion of the physical interpretation of the proposed model is also presented.

Longitudinal injection is a promising on-axis injection scheme for diffraction-limited storage rings. In the latest version of the Hefei advanced light source (HALS), both the dynamic aperture and momentum aperture have been optimized. A longitudinal injection scheme was investigated on the HALS using a double-frequency radio frequency system. To evaluate the injection performance, various errors were considered. A series of tracking simulations were conducted, and the injection efficiency was obtained under different error levels.

This paper describes the design and simulation of a proof-of-concept octupole lattice at the University of Maryland Electron Ring (UMER). This experiment tests the feasibility of nonlinear integrable optics, a novel technique that is expected to mitigate resonant beam loss and enable low-loss high-intensity beam transport in rings. Integrable lattices with large amplitude-dependent tune spreads, created by nonlinear focusing elements, are proposed to damp beam response to resonant driving perturbations while maintaining large dynamic aperture. At UMER, a lattice with a single octupole insert is designed to test the predictions of this theory. The planned experiment employs a low-current high-emittance beam with low space charge tune shift ($\ensuremath{\sim}0.005$) to probe the dynamics of a lattice with large externally-induced tune spread. Design studies show that a lattice composed of a 25-cm octupole insert and existing UMER optics can induce a tune spread of $\ensuremath{\sim}0.13$. Stable transport is observed in PIC simulation for many turns at space charge tune spread 0.008. A maximum spread of $\mathrm{\ensuremath{\Delta}}\ensuremath{\nu}=0.11$ (rms 0.015) is observed for modest octupole strength (peak $50\text{ }\text{ }\mathrm{T}/{\mathrm{m}}^{3}$). A simplified model of the system explores beam sensitivity to steering and focusing errors. Results suggest that control of orbit distortion to $l0.2\text{ }\text{ }\mathrm{mm}$ within the insert region is essential. However, we see only weak dependence on deviations of lattice phase advance ($\ensuremath{\le}0.1\text{ }\text{ }\mathrm{rad}$.) from the invariant-conserving condition.

We describe a benchmark study of collective and nonlinear dynamics in the Advanced Photon Source storage ring. A 1-mm long bunch was assumed in the calculation of wakefield and element by element particle tracking with distributed wakefield components along the ring was performed in an elegant simulation. Although the accurate prediction of nonlinear beam dynamics with collective effects is extremely challenging, the simulations agree well with experimental measurements.

Diagnostics of nonlinear beam dynamics has become more important for the LHC as it advances into increasingly challenging regimes of operation, as well as for the High Luminosity LHC where machine nonlinearities will have a significantly larger impact. Limitations of traditional excitation methods at top energy, in particular due to machine protection, have pushed the development of safe alternative methods using ac dipoles to characterize the nonlinear content of the LHC. One of the methods that has been proposed is the dynamic aperture under forced oscillation of ac dipoles. This new observable has the potential to help characterize relative changes in the nonlinear content of the machine, improve the understanding of the nonlinear models by comparing to simulations, validate nonlinear optics corrections, and give a qualitative lower bound estimate on the free dynamic aperture. This paper presents the first experimental demonstration of forced dynamic aperture measurements under forced oscillations performed using the LHC ac dipoles, and discusses the benefits of forced dynamic aperture measurements in circular colliders.

In this text, results of a 0.35 terahertz (THz) dynamic aperture imaging approach are presented. The experiments use an optical modulation approach and a single pixel detector at a stand-off imaging distance of approx 1 meter. The optical modulation creates dynamic apertures of 5cm diameter with approx 2000 individually controllable elements. An optical modulation approach is used here for the first time at a large far-field distance, for the investigation of various test targets in a field-of-view of 8 x 8 cm. The results highlight the versatility of this modulation technique and show that this imaging paradigm is applicable even at large far-field distances. It proves the feasibility of this imaging approach for potential applications like stand-off security imaging or far field THz microscopy., 9 pages, 13 figures

In a lepton storage ring of very high energy (e.g., in the e+e- Higgs factory) synchrotron radiation from quadrupoles constrains transverse dynamic aperture even in the absence of any magnetic nonlinearities. This was observed in tracking for LEP and the Future Circular e+e- Collider (FCC-ee). Here we describe a new mechanism of instability created by modulation of the particle energy at the double betatron frequency by synchrotron radiation in the quadrupoles. Energy modulation varies transverse focusing strength at the same frequency and creates a parametric resonance of the betatron oscillations with unusual properties. It occurs at arbitrary betatron frequency (the resonant detuning is always zero) and the magnitude of the parameter modulation of the betatron oscillation (strength of the resonance driving term) depends on the oscillation amplitude. Equilibrium between the radiation damping and the resonant excitation gives the boundary of the stable motion. Starting from 6d equations of motion we derive and solve the relevant differential equation describing the resonance, and show good agreement between analytical results and numerical simulation.

International audience; NICA (Nuclotron-based Ion Collider fAcility) [1] is a heavy-ion collider for studying the properties of hot and dense baryonic matter to be constructed at JINR (Dubna). A major restricting factor on the NICA’s transverse dynamic aperture is the nonlinear fringe field of final-focus quadrupole lenses. We propose to enhance the NICA dynamic aperture with a set of multipole lenses whose characteristics and configuration are optimized using a genetic algorithm.

An interleaved sextupole scheme using cross-cell betatron phase cancellation technique is adopted as a candidate for the future NSLS-II upgrade lattice. The lattice uses as many NSLS-II installed magnets as possible, including 30 dipoles, to compose a triple bend achromat lattice. A 300 pm.rad horizontal beam emittance is achieved. The emittance can be further reduced to around 200 pm rad with damping wigglers. Various design concepts used in modern 4th-generation light sources, such as adopting longitudinal gradient dipoles and anti-bend scheme, are incorporated into the design as well. The betatron phase-advance between sextupoles is designed to have a cross-cell interleaving cancellation pattern in the transverse planes. The dynamic aperture is big enough for the conventional off-axis top-off injection. At the same time, a large energy acceptance looks promising to ensure a sufficiently long beam lifetime., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

To generate terahertz radiation at HLS-II, a low-alpha lattice scheme is proposed. The new lattice can reduce the bunch length in the storage ring, thus enhancing the coherent synchrotron radiation in the THz region. In this paper, the design and optimization of a low-alpha lattice is reported. The new lattice preserves the symmetry of nominal lattice and reduces the first and second order momentum factor at the cost of increasing maximum beta function and natural emittance. The bunch length is tracked and the result shows that the low-alpha lattice can effectively compress bunches in the storage ring. The performance of this low-alpha lattice can be further studied and improved., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

One of the limiting factors of electron beam lifetime in low emittance storage rings is Head-Tail (HT) insta-bility. Low emittance storage rings typically have a large negative natural chromaticity due to the strong quadru-poles. Above transition large negative natural chroma-ticity leads to large Head-Tail instability which limit the beam lifetime. Since the threshold current of HT insta-bility is directly related to linear chromaticity, increasing the linear chromaticity to slightly positive value is a solution to prevent HT instability. In this paper we in-creased the chromaticity of Iranian Light Source Facility (ILSF) to (+4, +4) and we will investigate the beam dy-namics of ILSF 3GeV storage ring in high chromaticity. For reaching this aim we have used two families of sex-tupoles for chromaticity correction and then optimized them to maximize the dynamic aperture and Touschek lifetime. The beam dynamics of high chromaticity lattice is presented in this paper., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Two groups of 10ns-level superfast kickers are needed in the on-axis swap out injection scheme, adopted by the High Energy Photon Source (HEPS) to cope with the very small dynamic aperture of its baseline 7BA lattice design. In order to fit into the very tight longitudinal space in the injection/extraction region, and to relax the strength requirement of the kickers, five units of 300 mm long strip-line kickers are placed into a single stainless-steel vacuum chamber, to form a very compact 5-cell kicker module. Such a novel 5-cell strip-line kicker module design and its prototype development are presented in this paper. The results of the time-domain reflectometer (TDR) test, the high voltage pulse test and the beam coupling impedance test show that the strip-line kickers can meet the requirements of HEPS.

In the design of multi-bend achromat (MBA) lattices for diffraction-limited storage rings (DLSRs), usually, many magnet parameters need to be adjusted, and the constraints to be satisfied can be stringent. When using an evolutionary algorithm to optimize such a complicated lattice, there can be only few or even none of lattice solutions satisfying the constraints in the early evolution stage of the algorithm, which may significantly affect the optimization result. Therefore, the techniques for constraint handling in an evolutionary algorithm will be important for better optimizing MBA lattices. In this paper, three typical constraint handling methods that are incorporated into a multi-objective particle swarm optimization algorithm are used to optimize a hybrid 7BA lattice for a 2.2 GeV DLSR. In this lattice optimization, the impacts of the population size of the algorithm and the constraint condition on the optimization result are studied for these methods, and comparisons are also made among these methods. It is shown that, in general, the penalty function method is a better constraint handling method for optimizing MBA lattices. From the optimization result obtained by the penalty function method, a lattice with a natural emittance of about 84 pm ⋅ rad is selected, which has large dynamic aperture and momentum aperture.

A fast dynamic aperture (DA) optimization method for storage rings has been developed through the use of reversal integration. Even if dynamical systems have an exact reversal symmetry, a numerical forward integration differs from its reversal. For a chaotic trajectory, cumulative round-off errors are scaled, which results in an exponential growth on the difference. The exponential effect is a generic chaos indicator which represents the sensitivity of the chaotic motion to its initial condition. The chaos indicator of the charged particle motion can be obtained by comparing the forward integrations of particle trajectories with corresponding reversals, a.k.a. “backward integrations.” The indicator is observable even through short-term particle tracking simulations. Therefore, adopting it as an objective function could speed up optimization. The DA of the National Synchrotron Light Source II storage ring, and another test diffraction-limited light source ring, were optimized using this method for the purpose of demonstration.

The Hefei Advanced Light Facility (HALF) is a vacuum ultraviolet (VUV) and X-ray diffraction-limited storage ring light source. Because of its extremely small dynamic aperture, an injection scheme with a nonlinear kicker (NLK) was considered for the HALF. This magnet was designed with ferrite cores to achieve a higher excitation efficiency and a small gap shield in the central area for a flat magnetic field. In this paper, the design parameters, calculations and measurements of the kicker are described, and further optimization of the magnet structure is discussed.

Diffraction-limited storage ring (DLSR) light sources are being developed towards the goal of reaching the diffraction-limited emittances. To reduce the emittances, multi-bend achromat (MBA) lattices with many bend unit cells are used in DLSR designs. The bend unit cell with the combination of longitudinal gradient bend (LGB) and reverse bend (RB) can achieve much lower emittance, which has produced the SLS-2 7BA lattice (Streun et al., 2018). In this paper, a 6BA lattice with LGB/RB unit cells is designed for a DLSR with an energy of 2.2 GeV and 20 periods. An ultra-low natural emittance of 36 pm ⋅ rad is achieved for the designed DLSR, and the beta functions at straight sections are also relatively low so as to enhance the radiation brightness of insertion devices. The optimized dynamic aperture is relatively large, larger than 4 mm in the horizontal direction, and the momentum aperture is also reasonable. Besides, the intra-beam scattering effect is estimated and discussed.

A Machine Learning approach to scientific problems has been in use in Science and Engineering for decades. High-energy physics provided a natural domain of application of Machine Learning, profiting from these powerful tools for the advanced analysis of data from particle colliders. However, Machine Learning has been applied to Accelerator Physics only recently, with several laboratories worldwide deploying intense efforts in this domain. At CERN, Machine Learning techniques have been applied to beam dynamics studies related to the Large Hadron Collider and its luminosity upgrade, in domains including beam measurements and machine performance optimization. In this paper, the recent applications of Machine Learning to the analyses of numerical simulations of nonlinear beam dynamics are presented and discussed in detail. The key concept of dynamic aperture provides a number of topics that have been selected to probe Machine Learning. Indeed, the research presented here aims to devise efficient algorithms to identify outliers and to improve the quality of the fitted models expressing the time evolution of the dynamic aperture., peer-reviewed

Due to recent advances in the physics and technology of relativistic circular colliders, it is now possible to design storage rings whose emittance is close to the diffraction threshold of synchrotron radiation (e ~ 10 pm for the radiation critical wavelength of λ c ~ 1A). Methods for minimizing emittance by optimizing the magnetic structure without reducing the dynamic aperture and the energy acceptance, as well as possible implementations of these methods, are discussed in this paper.

The multi-bend achromat (MBA) lattice, which can provide a small horizontal emittance in the subnanometer range, shows promise for future storage-ring-based light-source facilities. We present the linear and the nonlinear properties of an optical design and the results of its optimization. The MBA lattice is designed as a five-bend achromat, and an emittance of 0.270 nm rad is achieved. The energy and the circumference of the designed ring are 3 GeV and 499.3 m, respectively. We investigated an injection system with a single-pulsed sextupole magnet in the storage ring. We describe the space allocation in the injection section and the particle dynamics of the injected beam. The investigation shows that our design exhibits a very low emittance and a sufficient dynamic aperture, and provides a suitable injection scheme for a 3-GeV light source.

Setting up collisions in high energy circular colliders requires beam acceleration and “beta-squeeze”. The latter produces small beam sizes, and hence, high luminosity by applying strong focusing with quadrupoles near the interaction points. At the Relativistic Heavy Ion Collider (RHIC), these two processes, beam acceleration and beta-squeeze, have been performed simultaneously during recent years. In the past, beam optics correction at RHIC has only taken place at injection and at final energy, with interpolation of corrections partially into the acceleration cycle. Recent measurements of the beam optics during acceleration and squeeze have evidenced significant beta-beats that, if corrected, could minimize undesirable emittance dilutions and maximize the spin polarization of polarized proton beams by avoiding the high-order multipole fields sampled by particles within the bunch. We recently demonstrated beam optics corrections during acceleration at RHIC. As a valuable by-product, these corrections minimized the beta-beat at the profile monitors, so providing more accurate measurements of the evolution of the beam emittances during acceleration.

Nonlinear beam dynamics optimization is essential in a low emittance storage ring design. Multi-objective optimization algorithms are needed in order to simultaneously optimize the dynamic aperture and the momentum aperture. In this study we demonstrate the application of a highly efficient stochastic optimization algorithm, the multi-generation Gaussian process optimizer (MG-GPO), to storage ring nonlinear dynamics optimization by successfully applying the method to the SPEAR3 upgrade lattice. It is shown that the new method, owing to its capability of selecting high rank candidates from a large number of trial solutions, converges significantly faster than the commonly used traditional algorithms, multi-objective genetic algorithms (MOGA) and particle swarm optimization (PSO).

In the tracking of the future circular Higgs factories, significant reduction of dynamic aperture due to the synchrotron radiation has been observed. This paper will analyze the synchrotron radiation effects including the closed orbit and optics distortion, radiation damping and quantum excitation for the lattice of CEPC.

In storage rings, the dynamic aperture is a key concept of nonlinear beam dynamics to evaluate the overall machine performance. Therefore, its optimization becomes very essential, especially during the design stage of a machine. In recent years, with the progress in the field of parallel computing, various multi-objective optimization algorithms have been widely applied to the dynamic aperture optimization of storage ring light sources. In this paper, an alternative algorithm, so-called differential evolution algorithm is introduced to perform dynamic aperture optimization of a very high energy e + e − storage ring collider, e.g. Circular Electron Positron Collider (CEPC). A multi-objective optimization code based on the differential evolution algorithm has been developed for this purpose and proved to be effective in increasing the dynamic aperture. In our code, a method called diffusion map analysis, in which the diffusion may come from quantum fluctuation of synchrotron radiation, beamstrahlung effect and nonlinearity in the lattice, is used to set the constraints in the dynamic aperture optimization, which can also help us find solutions with good beam lifetime.

As the multibend achromats had been applied to the lattice design in latest light sources to achieve ultralow beam emittance, whereas its performance is restricted by the strong sextupoles and concomitant nonlinearities to a certain extent. Contractive dynamic aperture becomes an inevitable but pivotal characteristic of future diffraction-limited storage rings, which lead to the exclusion of the conventional off-axis injection schemes. In this paper we will present a new on-axis injection scheme in allusion to future light sources, which is based on a triple-frequency rf system. By means of delicate superposition of rf voltages with fundamental, 2nd and 3rd hamonic frequencies, a commodious and rational main bucket which can accommodate an injected bunch and a circulating bunch simultaneously is able to be formed. The injected bunch can be captured by the longitudinal acceptance on-axis in a reasonable time offset with respect to the circulating bunch, utilizing the ultrafast pulse kicker, and ultimately merging to the center of the main bucket through synchrotron radiation damping. Detailed construction of the triple-frequency rf system and application of this scheme to the High Energy Photon Source will be discussed in the paper, relevant simulation studies and discussions are also presented.

In this paper, a PIN dioded loaded programmable metasurface element and dynamic apeture has been proposed. The programmable element-a complementary electric LC (cELC) resonator is patterned into the microstrip transmission line. Two PIN diodes are integrated across the capacitive gap of the cELC element, The digital states of each coding element can be controlled in real time by changing the states of PIN diodes. The proposed dynamic aperture has potential applications in dynamic beamforming, electromagnetic imaging, and security check.

Absorbance modulation enables lateral superresolution in optical lithography and transmission microscopy by generating a dynamic aperture within a photochromic absorbance-modulation layer (AML) coated on a substrate or a specimen. The absorbance-modulation is the property of photochromic molecules modulated between two states. The process is therefore solely controlled by far-field radiation at different wavelengths. The applicability of this concept to reflection microscopy has not been addressed so far, although reflection imaging exhibits the important ability to image a wide range of samples, transparent or opaque, dielectric or metallic. We will present a simulation model for absorbance-modulation imaging (AMI) in confocal reflection microscopy and it is shown that imaging well beyond the diffraction limit is feasible. Our model includes the imaging properties of confocal microscopy, reflections at the boundaries, the photochromic process and diffraction due to propagation through a subwavelength aperture. We derive an analytical design equation which estimates the dependence of the achievable resolution on relevant parameters, such as the AML properties and the applied light powers. This equation is very similar to the corresponding equation for STED (Stimulated emission depletion) microscopy and it is helpful for a fast design of the arrangement of optical setup and AML. As rapid scanning is relevant for a short imaging duration, we further derived an estimation for the pixel dwell time. We prove the validity of these equations by comparing the estimations with the complex numerical simulations. In addition, we show that a resolution enhancement down to 1/5 of the diffraction limit is possible.

Betatron phase measured from excited oscillation can be used to correct the beta function and the nonlinear lattice. With an improved algorithm the measurement precision has achieved 1 mrad (rms), or equivalently, 0.3% of beta beat at NSLS-II. The beta beating can be corrected to 1% in less than half an hour. This precise technique can be applied to the nonlinear lattice correction as well. The betatron phase probed by an off-axis beam provides information on the sextupole strength. In comparison with the model the nominal strength can be restored. It was shown that the proposed scheme treated all the leading order resonance driving terms generated by sextupoles, as well as the detuning terms and the nonlinear chromaticity. At NSLS-II a half percent sextupole correction led to a 15% increase of the dynamic aperture.

In recent years, modelling the evolution of beam losses in circular proton machines starting from the concept of dynamic aperture its time evolution has been the focus of intense research. Results from single-particle non-linear beam dynamics have been used to build simple models that proved to be in good agreement with beam measurements. These results have been generalised, thus opening the possibility to describe also the luminosity evolution in a circular hadron collider. In a companion paper (Part I), the derivation of a scaling law for luminosity, which includes both burn off and pseudo-diffusive effects, has been carried out. In this paper, the proposed models are applied to the analysis of the data collected during the CERN Large Hadron Collider (LHC) Run 1. A data set referring to the proton physics runs for the years 2011 and 2012 has been analysed and the results are proposed and discussed in detail in this paper., v2 (after having implemented refereeing comments)

In recent years, modelling the evolution of beam losses in circular proton machines starting from the evolution of the dynamic aperture has been the focus of intense research. Results from single-particle, non-linear beam dynamics have been used to build simple models that proved to be in good agreement with beam measurements. These results have been generalised, thus opening the possibility to describe also the luminosity evolution in a circular hadron collider. In this paper, the focus is on the derivation of scaling laws for luminosity, which include both burn off and additional pseudo-diffusive effects. It is worthwhile stressing that time-dependence of some beam parameters can be taken into account in the proposed framework. The proposed models are applied to the analysis of a subset of the data collected during the CERN Large Hadron Collider (LHC) Run 1 in a companion paper (Giovannozzi and Van der Veken, 2018). In recent years, modelling the evolution of beam losses in circular proton machines starting from the evolution of the dynamic aperture has been the focus of intense research. Results from single-particle, non-linear beam dynamics have been used to build simple models that proved to be in good agreement with beam measurements. These results have been generalised, thus opening the possibility to describe also the luminosity evolution in a circular hadron collider. In this paper, the focus is on the derivation of scaling laws for luminosity, which include both burn off and additional pseudo-diffusive effects. It is worthwhile stressing that time-dependence of some beam parameters can be taken into account in the proposed framework. The proposed models are applied to the analysis of a subset of the data collected during the CERN Large Hadron Collider (LHC) Run~1 in a companion paper (Part II).

Physical review accelerators and beams 21(5), 051601 (2018). doi:10.1103/PhysRevAccelBeams.21.051601, A conceptual design and performance of a round beam lattice for synchrotron light sources based on the phase space exchange principle and the noninterleaved sextupole distribution is presented. Optics design is performed for an approximately 30 pm emittance 6 GeV machine of 2300 m circumference which combines cells with and without straight sections for the insertion devices., Published by American Physical Society, College Park, MD

With the aid of machine learning techniques, the genetic algorithm has been enhanced and applied to the multi-objective optimization problem presented by the dynamic aperture of the NSLS-II Ring. During the evolution employed by the genetic algorithm, the population is classified into different clusters. The clusters with top average fitness are given elite status. Intervention is implemented by repopulating some potentially competitive candidates based on the accumulated data. These candidates replace randomly selected candidates among the original data pool. The average fitness of the population is improved while diversity is not lost. The quality of the population increases and produces more competitive descendants accelerating the evolution process significantly. When identifying the distribution of optimal candidates, they appear to be located in isolated islands within the search space. Some of these optimal candidates have been experimentally confirmed at the NSLS-II storage ring. The machine learning techniques that exploit the genetic algorithm can also be used in other population-based optimization problems such as particle swarm algorithm., Proceedings of the 13th Int. Computational Accelerator Physics Conf., ICAP2018, Key West, FL, USA

Absorbance modulation enables lateral superresolution in optical lithography and transmission microscopy by generating a dynamic aperture within a photochromic absorbance-modulation layer (AML) coated on a substrate or a specimen. The applicability of this concept to reflection microscopy has not been addressed so far, although reflection imaging exhibits the important ability to image a wide range of samples, transparent or opaque, dielectric or metallic. In this paper, a simulation model for absorbance-modulation imaging (AMI) in confocal reflection microscopy is presented and it is shown that imaging well beyond the diffraction limit is feasible. In addition, we derive analytical design equations and estimate the dependence of the achievable resolution and pixel dwell time on relevant parameters, such as the AML properties and the applied light powers. We prove the validity of these equations through a comparison with the simulation results and we show that a resolution enhancement down to 1/5 of the diffraction limit is possible.

We present results from beam commissioning of the MAX IV 3 GeV storage ring as well as a summary of the beam dynamics studies that have so for been carried out. We report on injection and accumulation using a single dipole kicker, top-up injection, slow orbit feedback, restoring the linear optics to design, effects of in-vacuum undulators with closed gaps, and adjusting nonlinear optics to achieve design chromaticity correction as well as dynamic aperture sufficient for high injection efficiency and good Touschek lifetime., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

Generation of magnetic field in units of booster synchrotron for the NICA project is one of the most important conditions for getting the required parameters and qualitative accelerator operation. Research of linear and nonlinear dynamics of ion beam 197Au31+ in the booster have carried out with MADX program. Analytical estimation of magnetic field errors tolerance and numerical computation of dynamic aperture of booster DFO-magnetic lattice are presented. Closed orbit distortion with random errors of magnetic fields and errors in layout of booster units was evaluated.

The High Energy LHC (HE-LHC) is one option for a next generation hadron collider explored in the FCC-hh program. The core concept of the HE-LHC is to install FCC-hh technology magnets in the LHC tunnel. The higher beam rigidity and the increased radiation debris, however, impose severe challenges on the design of the triplet for the low beta insertions. In order to achieve 25 cm β^{*} optics and survive a lifetime integrated luminosity of 10 ab-1 a new longer triplet was designed that provides sufficient shielding and enough beam stay clear. This triplet has been designed using complimentary radiation studies to optimise the shielding that will also be presented. The optics for the rest of the interaction region had to be adjusted in order to host this more rigid beam and longer triplet whilst leaving enough room for crab cavities. Moreover, the effects non-linear errors in this triplet have on the dynamic aperture will be outlined., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

In the past decade, the so-called diffraction-limited storage ring (DLSR) light sources were proposed, promising much better radiation performance than available in the existing third generation light sources. Regarding the very strong focusing and chromatic sextupoles that required for reaching an ultralow emittance, to optimize the nonlinear dynamics and achieve an adequate dynamic aperture is an important topic in a DLSR design. In this paper we will present some tips distilled from the DA optimization experience of the High Energy Photon Source over the past ten years, hoping it could provide some aids to other ultralow-emittance designs., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The dependence of the dynamic aperture in the NICA collider on the number of turns has been calculated by MAD-X tracking code with the two independent algorithms: a program of symplectic tracking PTC (Polymorphic technology Tracking Code) and a program of the thin-lenses tracking method. The results of the numerical integration of particle motion forecast the asymptotic dynamic aperture and the possible losses of particles in the collider.

SimTrack is a compact c++ code of 6-d symplectic element-by-element particle tracking in accelerators originally designed for head-on beam–beam compensation simulation studies in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It provides a 6-d symplectic orbit tracking with the 4th order symplectic integration for magnet elements and the 6-d symplectic synchro-beam map for beam–beam interaction. Since its inception in 2009, SimTrack has been intensively used for dynamic aperture calculations with beam–beam interaction for RHIC. Recently, proton spin tracking and electron energy loss due to synchrotron radiation were added. In this article, I will present the code architecture, physics models, and some selected examples of its applications to RHIC and a future electron-ion collider design eRHIC.

In this paper, we present conceptual design of the Iranian Light Source Facility (ILSF) injection systems. Beam dynamics issue and expected performance of the designed injectors have been described. We introduce layout of the injection systems, give the optimized parameters of the components and discuss the injection and extraction procedures with detail.

Dynamic aperture is one of the deciding parameters of the low emittance electron storage ring performance. Sufficient dynamic aperture is required to reach higher injection efficiency as well as good beam lifetime. In low emittance storage rings, dynamic aperture is limited mainly by the chromaticity correcting sextupoles, which is enhanced by introducing more sextupole magnets in the dispersion free straight section of the ring lattice, known as “harmonic sextupoles”. In Indus-2 storage ring lattice also, there is a plan to accommodate harmonic sextupoles. In this paper we present, how the strength of harmonic sextupoles is optimized for suppressing resonance driving terms up to third order, those are responsible for reducing the dynamic aperture. In such optimization, one of the main difficulties is to choose the optimal weight factor for the different resonance driving terms. We evolved an approach for assigning the relative weight to the various resonances driving terms which is found to be working very well for Indus-2 storage ring. Following this approach, the strength of the harmonic sextupoles is optimized and there is a reasonable enhancement of dynamic aperture with harmonic sextupoles for two different working points of Indus-2.

In the J-PARC 3-GeV Rapid Cycling Synchrotron (RCS), transverse injection painting is utilized to manipulate the transverse beam profile according to the requirements from the downstream facilities as well as to mitigate the space-charge induced beam loss in RCS. Therefore, a flexible control is required for the transverse painting area. But now the available range of transverse painting is limited to small area due to beta function beating caused by the edge focus of injection bump magnets which operate during the beam injection period. This beta function beating additionally excites various random betatron resonances through a distortion of the lattice super-periodicity, causing a shrinkage of the dynamic aperture during the injection period. This decrease of the dynamic aperture leads to extra beam loss at present when applying large transverse painting. For beta function beating caused by the edge focus, we proposed a correction scheme with additional pulse-type quadrupole correctors. In this paper, we will discuss the feasibility and effectiveness of this correction scheme for expanding the transverse injection painting area with no extra beam loss, while considering the beam loss and its mitigation mechanisms, based on numerical simulations.