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Each of the two proton beams in the High-Luminosity Large Hadron Collider (HL-LHC) will carry a total energy of 720 MJ. One concern for machine protection is the energy stored in the transverse beam tails, estimated to potentially reach up to 5% of the total stored energy. Several failure scenarios could drive these tails into the collimators, potentially causing damage and therefore severely affecting operational efficiency. Hollow Electron Lenses (HEL) were integrated in the HL-LHC baseline to mitigate this risk by depleting the tails in a controlled way. A hollow-shaped electron beam runs co-axially to the hadron beam over about 3 m, such that halo particles at large amplitudes become unstable, while core particles ideally remain undisturbed. Residual fields from e-beam asymmetries can, however, induce emittance growth of the beam core. Various options for the pulsing of the HEL are considered and are compared using two figures of merit: halo depletion efficiency and core emittance growth. This contribution presents simulations for these two effects with different HEL pulsing modes using the final HL-LHC optics, that was optimized at the location of the lenses., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Resonance studies have been conducted during the recommissioning of the CERN Proton Synchrotron Booster (PSB) following the implementation of the LHC Injectors Upgrade (LIU) project. In particular, resonance identification through so-called loss maps has been applied on all four rings of the PSB, revealing various resonances up to fourth order. In a second step, compensation schemes for the observed resonances were developed using a combination of analytical methods, experimental data and machine learning tools. These resonance compensation schemes have been deployed in operation to minimize losses for reaching high intensity and high brightness, thereby achieving the target brightness for the LHC-type beams., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

At the end of 2018, an instability with multiple bunches has been consistently observed during high intensity studies at the CERN-SPS. This instability could be a significant limitation to achieve the bunch intensity expected after the LHC Injector Upgrade (LIU). Therefore, a deep understanding of the phenomena is essential to identify the best mitigation strategy. Extensive simulation studies have been performed to explore the consistency of the current SPS model, give a possible interpretation of the instability mechanism and outline some possible cures., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

In the context of the LHC Injectors Upgrade Project (LIU), the Proton Synchrotron Booster (PSB) developed an H⁻ charge exchange injection system. The four short rectangular dipoles of the injection chicane induce focusing errors through edge focusing and Eddy currents. These errors excite the half-integer resonance 2Qy = 9 and cause a dynamically changing beta-beating in the first milliseconds after injection. Using the beta-beating at the positions of two individually powered quadrupoles, measured with k-modulation, correction functions based on a model response matrix have been calculated and applied. Minimizing the beta-beating at injection allows the machine to be operated with betatron tunes closer to the half-integer resonance and therefore with larger space charge tune spreads. In this contribution the results of the beta-beating compensation studies and the impact on the achievable beam brightness limit of the machine are presented., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Control of chromaticity is often critical to mitigate collective instabilities in high energy synchrotrons, yet classical measurement methods are of limited use during high intensity operation. We explore the possibility to extract this information from beam transfer function measurements, with the development of a theoretical background that includes the impact of wakefields and by analysis of multi-particle tracking simulations. The investigations show promising results that could improve the operation of the HL-LHC by increasing stability margins., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

In recent years, transverse beam splitting by crossing a stable resonance has become the operational means to perform MultiTurn Extraction (MTE) from the CERN PS to the SPS. This method delivers the high-intensity proton beams for fixed-target physics at the SPS. More recently, further novel manipulations have been studied, with the goal of devising new techniques to manipulate transverse beam properties. AC magnetic elements can allow beam splitting to be performed in one of the transverse degrees of freedom. Crossing 2D nonlinear resonances can be used to control the sharing of the transverse emittances. Furthermore, cooling the transverse emittance of an annular beam can be achieved through an AC dipole. These techniques will be presented and discussed in detail, considering future lines of research., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Controlled longitudinal emittance blow-up will be required to longitudinally stabilize the beams for the High-Luminosity LHC in the SPS. Bandwidth-limited noise is injected at synchrotron frequency sidebands of the RF voltage of the main accelerating system through the beam phase loop. The setup of the blow-up parameters is complicated by bunch-by-bunch differences in their phase, shape, and intensity, as well as by the interplay with the fourth harmonic Landau RF system and transient beam loading in the main RF system. During previous runs, an optimization of the blow-up had to be repeated manually at every intensity step up, requiring hours of precious machine time. With the higher beam intensity, the difficulties will be exacerbated, with bunch-by-bunch differences becoming even more important. We look at the extent of the impact of intensity effects on the controlled longitudinal blow-up by means of macro-particle tracking, as well as analytical calculations, and we derive criteria for quantifying its effectiveness. These studies are relevant to identify the parameters and observables which become key to the operational setup and exploitation of the blow-up., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Particles in an intense bunch experience longitudinal self-fields due to space~charge. This effect, conveniently described by geometric factors dependent on a particle’s transverse position, beam size, and beam pipe aperture, is usually incorporated into longitudinal particle tracking on a per-turn basis. The influence of transverse betatron motion on longitudinal space~charge forces is, however, usually neglected in pure longitudinal tracking codes. A dedicated tracking code was developed to characterize the CERN PS such that an effective geometric factor of a given particle could be derived from its transverse emittance, betatron phase~advance, and momentum~spread. The effective geometry factor is then estimated per particle by interpolation without the need for full transverse tracking and incorporated into the longitudinal tracker BLonD. The paper evaluates this effect under conditions representative of the PS, where space~charge is dominant at low energy and progressively becomes negligible along the acceleration ramp. The synchrotron frequency distribution is modified and the filamentation rate is moreover increased, which could suggest a stabilizing space~charge phenomenon., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

An ideal accelerator built from linear components will exhibit bounded and stable particle motion. However, in reality, any imperfections in the magnetic field strength or slight misalignments of components can introduce chaotic and unstable particle motion. All accelerators are prone to these non-linearities but the effects are amplified when studying high intensity particle beams with the presence of space charge effects. This work aims to explore the non-linearities which arise in high intensity particle beams using a scaled experiment called IBEX. The IBEX experiment is a linear Paul trap which allows the transverse dynamics of a collection of trapped particles to be studied. It does this by mimicking the propagation through multiple quadrupole lattice periods whilst remaining stationary in the laboratory frame. IBEX is currently undergoing a nonlinear upgrade with the goal of investigating Quasi-Integrable Optics (QIO), a form of Nonlinear Integrable Optics (NIO), in order to improve our understanding and utilisation of high intensity particle beams., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

In the context of the LHC Injectors Upgrade (LIU) project, a series of studies have been performed in order to better understand the beam brightness limitations imposed by resonances and space charge effects. Space charge simulations using the analytic (frozen) space charge solver as implemented in the MAD-X code conducted for the CERN Proton Synchrotron (PS) show that a particle approaching the integer tune of Qx = 6 demonstrates a resonant behavior. The analysis of the single particle transverse motion reveals the excitation of a second order resonance. The interplay of the space charge effect and the optics perturbation in the regime of the integer tune on this excitation was further investigated. The simulations were complemented with the analysis of the resonance driving terms coming from the space charge potential derived in a classical perturbative approach., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

In 2018 as part of a collaboration between CERN and FNAL, the space charge (SC) implementation has been upgraded in a test version of MAD-X. The goal has been to implement the 3D symplectic SC kick together with a number of new features and benchmark it with earlier MADX-SC versions. Emphasis has given to the use of the Sigma Matrix approach that allows to extend MAD-X optics calculations. In the meantime, significant effort has been made to fully debug and optimize the code and in particular to achieve a speed-up of the simulations by a factor of 2. The code has been ported to the latest MAD-X version, the elaborated set-up procedures have been automated and a user manual has been written., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Landau damping is a natural stabilization mechanism to mitigate coherent beam instabilities in the longitudinal phase space plane. In a single RF system, binominal particle distributions with a constant inductive impedance above transition (or capacitive below) would lead to a vanishing threshold for the loss of Landau damping, which can be avoided by introducing an upper cut-off frequency to the impedance. This work aims at expanding the recent loss of Landau damping studies to the common case of double harmonic RF systems. Special attention has been paid to the configuration in the SPS with a higher harmonic RF system at four times the fundamental RF frequency, and with both RF systems in counter-phase (bunch shortening mode). Refined analytical estimates for the synchrotron frequency distribution allowed to extend the analytical expression for the loss of Landau damping threshold. The results are compared with semi-analytical calculations using the MELODY code, as well as with macroparticle simulations in BLonD., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

In the J-PARC MR, according to the beam power upgrade over 100 kW, beam losses due to transverse collective beam instabilities had started to appear. We had introduced "bunch-by-bunch feedback" system in 2010. Continuing beam power upgrade over 250 kW again caused the transverse instabilities. We introduced "intra-bunch feedback" system in 2014. This has been suppressing those instabilities very effectively. But further beam power upgrade over 500 kW (2.6·10⁺¹⁴ ppp, 8 bunches) needs upgrade of "intra-bunch feedback" system. The current understanding of the transverse instabilities in the MR and the effect of the feedback system are presented from the view points of simplified simulation without the space charge effect and measurements. We are upgrading the system in two steps. The first step is "time-interleaved sampling and kicking" with two feedback systems. The second step is getting the sampling rate twice as much as the current rate, ~110 MHz. Details are explained using simulation., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Harmonics of the mains frequency (50 Hz) have been systematically observed in the form of dipolar excitations in the transverse beam spectrum of the Large Hadron Collider (LHC) since the beginning of its operation. The power supply ripple, consisting of both fundamental and higher frequency components, is proven not to be the result of an artifact of the instrumentation systems with which they are observed. Potential sources of the perturbation have been identified through systematic analysis and experimental studies. Single-particle tracking simulations have been performed including a realistic power supply ripple spectrum, as acquired from experimental observations, to demonstrate the impact of such noise effects on beam performance., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Indirect space charge contributes significantly to the impedance of non ultrarelativistic machines such as the LEIR, PSB and PS, at CERN. While general expressions exist in frequency domain for the beam coupling impedance, the time domain wake function is typically obtained numerically, thanks to an inverse Fourier transform. An analytical expression for the indirect space charge wake function, including the time dependence as a function of particle velocity, is nevertheless highly desirable to improve the accuracy of time domain beam dynamics simulations of coherent instabilities. In this work, a general formula for the indirect space charge wake function is derived from the residue theorem. Moreover, simple approximated expressions reproducing the time and velocity dependence are also provided, which can even be corrected to recover an exact formula, thanks to a numerical factor computed once for all. The expressions obtained are successfully benchmarked with a purely numerical approach based on the Fourier transform., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

The Fermilab Booster is an RCS with h=84 and gammaT =5.47 and, during standard operation it accelerates ~4.5E12ppBc from 400 MeV to 8 GeV at 15 Hz. The Booster is being upgraded to handle higher beam intensity >6.7E12ppBc and repetition rate of 20Hz. In the current mode of operation, we perform multi-turn beam injection and capture beam in h=84 system adiabatically. However, we have observed coupled bunch (CB) instabilities in the extracted beam. This issue is expected to worsen at higher beam intensities. In principle, for h=84 one expects 41 modes of oscillations contributing to these CB instabilities. Currently, we have a digital mode damper to mitigate prominent CB modes [1]. We would like to understand at what time in the beam cycle a particular mode is going to originate and how much it contributes at a different time of the cycle. In this regard, we have collected wall current monitor data from injection to extraction and looked for the start of a particular mode of CB instability and its growth for different intensities. This paper presents the results from this study and future plans to mitigate the CB instability in Booster., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

A self-consistent beam maintains linear space charge forces under any linear transport, even with the inclusion of space charge in the dynamics. Simulation indicates that it is possible to approximate certain self-consistent distributions in a ring with the use of phase space painting. We focus on the so-called Danilov distribution, which is a uniform density, rotating, elliptical distribution in the transverse plane and a coasting beam in the longitudinal plane. Painting the beam requires measurement and control of the orbit at the injection point, and measuring the beam requires re- construction of the four-dimensional (4D) transverse phase space. We discuss efforts to meet these requirements in the Spallation Neutron Source (SNS) ring., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Recent advances in the theoretical understanding of beam stability in the presence of strong space charge, has suggested a new class of instabilities known as convective instabilities. A novel approach to excite and study these instabilities will be to install a ‘waker’ system, a dedicated wake-building feedback system. The System was installed in the Fermilab Recycler and commissioned during 2021. The first results are presented., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Landau damping is a very important stabilization mechanism of beams in circular hadron accelerators. In the longitudinal plane, Landau damping is lost when the coherent mode is outside of the incoherent synchrotron frequency spread. In this paper, the threshold for loss of Landau damping (LLD) for constant inductive impedance ImZ/k is derived using the Lebedev matrix equation (1968). The results are confirmed by direct numerical solutions of the Lebedev equation and using the Oide-Yokoya method (1990). For more realistic impedance models of the ring, new definitions of an effective impedance and the corresponding cutoff frequency are introduced which allow using the same analytic expression for the LLD threshold. We also demonstrate that this threshold is significantly overestimated by the Sacherer formalism based on the previous definition of an effective impedance using the eigenfunctions of the coherent modes., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

In the context of the LHC Injector Upgrade (LIU) project, the main longitudinal limitations in the CERN PS are coupled bunch instabilities and uncontrolled emittance blow-up leading to losses at injection into the downstream accelerator, the SPS. To complement beam measurements, particle tracking simulations are an important tool to study these limitations. However, to avoid excessive runtime, simulations are usually targeting only a fraction of the cycle assuming that bunches are initially matched to the RF bucket. This ignores all initial perturbations that could seed an instability. Simulations were therefore performed along the full PS cycle by using the BLonD tracking code optimized with advanced parallelization schemes. They include beam manipulations with several RF harmonics (batch compression, merging, splittings), controlled emittance blow-up, a model of the beam coupling impedance covering a wide frequency range, as well as beam and cavity feedbacks. A large number of macroparticles is required as well as arrays to store beam induced voltage spanning several revolutions to account for long range wakefields., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

The CERN PS Booster (PSB) has gone through major upgrades during the Long Shutdown 2 (LS2) and the recommissioning with beam started in December 2020. Two of the aspects leading to improved operation will be described in this paper: a new tune control implementation; and a full re-alignment campaign. The operation of the PSB requires a large range of working points to be accessible along the acceleration cycle. As part of the LIU project, the PSB main power supply was upgraded to raise the extraction energy from 1.4 GeV to 2 GeV, in order to improve the brightness reach of the downstream machines. A new tune control implementation was necessary to take into account saturation effects of the bending magnets and the reconfiguration of the main circuits, as well as the additional complexity of the new H⁻ charge exchange injection. The first part of the paper describes the implementation of the new tune control and its experimental verification and optimization. The second part describes the results of the PSB alignment campaign after LS2, giving emphasis to the method developed to perform a combined closed orbit correction through quadrupole alignments., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Understanding the 3D collective long-term response of beams exposed to resonances is of theoretical interest and essential for advancing high intensity synchrotrons. This study of a hitherto unexplored beam dynamical regime is based on 2D and 3D self-consistent particle-in-cell simulations and on careful analysis using tune spectra and phase space. It shows that in Gaussian-like beams Landau damping suppresses all coherent parametric resonances, which are of higher than second order (the "envelope instability"). Our 3D results are obtained in an exemplary stopband, which includes the second order coherent parametric resonance and a fourth order structural resonance. They show that slow synchrotron oscillation plays a significant role. Moreover, for the early time evolution of emittance growth the interplay of incoherent and coherent resonance response matters, and differentiation between halo and different core regions is essential. In the long-term behavior we identify a progressive, self-consistent drift of particles toward and across the resonance, which results in effective compression of the initial tune spectrum. However, no visible imprint of the coherent features is left over, which only control the picture during the first one or two synchrotron periods. An intensity limit criterion and an asymptotic formula for long-term rms emittance growth are suggested. Comparison with the commonly used non-self-consistent "frozen space charge" model shows that in 3D this approximation yields a fast and useful orientation, but it is a conservative estimate of the tolerable intensity., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

This study reports on an alternative method to generate transverse Landau damping to suppress coherent instabilities in circular accelerators. The incoherent betatron tune spread can be produced through detuning with longitudinal rather than transverse action. This approach is motivated by the high-brightness, low transverse emittance beams in future colliders where detuning with transverse amplitude will be less effective. Detuning with longitudinal action can be introduced with a radio frequency (rf) quadrupole, or similarly, using second-order chromaticity. The latter was enhanced in the Large Hadron Collider (LHC) at CERN and experimental results on single-bunch stabilization are briefly recapped. The observations are interpreted analytically by extending the Vlasov formalism to include nonlinear chromaticity. Finally, the newly developed theory is benchmarked against circulant matrix and particle tracking models., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

In recent years, models for the time-evolution of the dynamic aperture have been proposed and applied to the analysis of non-linear betatronic motion in circular accelerators. In this paper, these models are used to derive scaling laws for the luminosity evolution and are applied to the analysis of the data collected during the LHC physics runs. An extended set of fills from the LHC proton physics has been analysed and the results presented and discussed in detail. The long-term goal of these studies is to improve the estimate of the performance reach of the HL-LHC., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Booster Ring (BRing) of the new approved High Intensity heavy-ion Accelerator Facility (HIAF) in China is designed to stack 0.3-1.0·10¹¹ number of 238U³⁵⁺ ions by painting injection and deliver over such intensity beam in extraction. However, depressed tune spread caused by space charge effect crosses the low-order resonance stop-bands after bunching the storage beam. To keep a low beam loss during crossing, stop-band compensation scheme is proposed covering the whole process of RF capture and early acceleration., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

In the framework of the LHC Injectors Upgrade (LIU) project, the injection process in the CERN Proton Synchrotron Booster (PSB) will be renovated after the connection with the Linac4. A new H⁻ charge exchange injection system using a stripping foil is foreseen to increase the brightness of the stored beams and to provide high flexibility in terms of emittance tailoring at 160 MeV. Realistic multi-particle simulations of the future injection processes for high brightness beams (i.e. for the LHC) and high intensity beams (i.e. for the ISOLDE experiment) are presented in this paper. The simulations are based on the present performance of Linac4 and include scattering induced by the foil, space charge effects and compensation of the lattice perturbation introduced by the bumpers of the injection chicane., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Longitudinal beam instability in the CERN SPS is a major limitation in the ability to achieve the bunch intensities required for the goals of the High-Luminosity LHC project (HL-LHC). One of the major drivers in limiting the intensity of the machine is the broadband contribution to the beam-coupling impedance due to the kicker magnets. The extraction kickers (MKE) discussed in this paper are known to give a significant contribution to the overall longitudinal beam-coupling impedance. We present the results of bench measurements of the MKE's impedance to determine the accuracy of electromagnetic simulation models from which the impedance modelused for beam dynamics simulationsis constructed. In addition, we discuss the feasibility and implementation of beam measurements that can indicate the contribution of the MKE magnets to the longitudinal beam-coupling impedance of the SPS., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Because of the differences of magnetic saturation and eddy current effects between different magnets, magnetic field tracking errors between different magnets is larger than 2.5 % at the Rapid Cycling Synchrotron (RCS) of Chinese Spallation Neutron Source (CSNS), and the induced tune shift is larger than 0.1. So larger tune shift may lead the beam to pass through the resonance lines. To reduce the magnetic field tracking errors, a method of wave form compensation for magnets of the Rapid Cycling Synchrotron was investigated on the magnets of CSNS/RCS. The wave form compensation was applied to CSNS/RCS commissioning. By performing wave form compensation, the maximum magnetic field tracking error was reduced from 2.5 % to 0.08 %, and the maximum tune shift over the ramping process was reduced from 0.1 to 0.004., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Beam loss due to space charge is a major problem at current and future high intensity particle accelerators. The space charge force can be compensated for proton or ion beams by creating a column of electrons with a charge distribution matched to that of the beam, maintaining electron-proton stability. The column is created by the beam ionizing short sections of high pressure gas. The ionization electrons are then shaped appropriately using electric and magnetic fields. The Integrable Optics Test Accelerator (IOTA) at Fermilab is a test bed for beam loss and instability mitigation techniques. Simulations using the particle-in-cell code, Warp, have been made to track the evolution of both the electron column and the beam over multiple passes. A 2.5 MeV proton beamline is under construction at IOTA, to be used to study the effect of the electron column on a space charge dominated beam., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Beam cooling enables an increase of peak and average luminosities and significantly expands the discovery potential of colliders; therefore it is an indispensable component of any modern design. Optical Stochastic Cooling (OSC) is a high-bandwidth, beam-cooling technique that will advance the present state-of-the-art, stochastic cooling rate by more than three orders of magnitude. It is an enabling technology for next-generation, discovery-science machines at the energy and intensity frontiers including hadron and electron-ion colliders. This paper presents the status of our experimental effort to demonstrate OSC at the Integrable Optics Test Accelerator (IOTA) ring, a testbed for advanced beam-physics concepts and technologies that is currently being commissioned at Fermilab. Our recent efforts are centered on the development of an integrated design that is prepared for final engineering and fabrication. The paper also presents a comparison of theoretical calculations and numerical simulations of the pickup-undulator radiation and its interaction with electrons in the kicker-undulator., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

In the framework of the LHC Injectors Upgrade (LIU), beams with about twice the intensity compared to the present values will have to be accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). Machine studies with intensity higher than the nominal LHC beam have shown that coherent instabilities in both transverse planes may develop at injection energy, potentially becoming a limitation for the future high intensity operation. In particular, a transverse mode coupling instability is encountered in the vertical plane, the threshold of which can be sufficiently increased by changing the machine optics. In addition, a headtail instability of individual bunches is observed in the horizontal plane in multi-bunch operation, which requires stabilization by high chromaticity. The PyHEADTAIL code has been used to check if the present SPS impedance model reproduces the experimental observations. The instability growth rates have been studied for different machine optics configurations and different chromaticity settings. Other stabilizing mechanisms like tune spread from octupoles or the transverse damper have also been investigated., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

In high-current accelerators, interaction of the beam with fundamental impedance of the accelerating cavities can limit machine performance. It can result in a significant variation of bunch-by-bunch parameters (bunch length, synchronous phase, etc.) and lead to longitudinal coupled-bunch instability. In this work, these limitations are analysed together with possible cures for the high-current option (Z machine) of the future circular electron-positron collider (FCC-ee). The time-domain calculations of steady-state beam loading are presented and compared with frequency-domain analysis., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

At injection into the CERN Proton Synchrotron (PS) a significant horizontal emittance blow-up of the present high brightness beams for the LHC is observed. A partial contribution to this effect is suspected to be an important mismatch between the dispersion function in the transfer line from the PS Booster (PSB) and the ring itself. This mismatch will be unacceptable in view of the beam parameters requested by the LHC Injectors Upgrade (LIU) project with high longitudinal emittance and momentum spread. To deliver the requested beam parameters the PSB-to-PS transfer line will be upgraded and the optics in the line changed to improve the matching from all the four PSB rings. A re-matching campaign from the PSB ring 3 has been carried out to evaluate the impact of the present optics mismatch as a source of emittance growth both in simulations and measurements., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

The transverse mode coupling instability occurs in individual bunches when two transverse oscillation modes couple at high intensity. Simulations predict an instability threshold in the LHC at a single bunch intensity of 3*10¹¹ protons. The TMCI threshold can be inferred by measuring the tune shift as a function of intensity. This measurement was performed in the LHC for different machine impedances and bunch intensities. The impedance was changed by varying the primary and secondary collimators gaps to increase their contribution to the resistive wall impedance. The experiment also allowed to assess the validity of the LHC impedance model in the single bunch case., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Intrabeam scattering (IBS) of charged particles in a particle beam results in an exchange of energy between different degrees of freedom. That results in an increase of average energy of particles in the beam frame and an increase of the 3D-emittance. The paper considers calculations of beam emittance growth rates for different options of NICA collider and IBS effects in close vicinity of the transition., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

The efforts of the Fixed Field Accelerators FFA (formerly known as FFAG accelerators) community to address the high intensity challenge are reviewed. Starting from analytic estimates and linear models for space charge computation, the current possibilities of precise 3D models for start to end modeling are discussed., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Complementary to the physics research at the LHC, several fixed target facilities receive beams from the LHC injector complex. In the scope of the fixed target physics program at the Super Proton Synchrotron, high-intensity proton beams from the Proton Synchrotron are extracted using the Multi-Turn Extraction scheme, which is based on particle trapping in stable islands of the horizontal phase space. Considering the number of protons requested by future experimental fixed target facilities, such as the Search for Hidden Particles experiment, the currently operationally delivered beam intensities are insufficient. Therefore, experimental studies have been conducted to optimize the Multi-Turn Extraction technique and to exploit the possible intensity reach. The results of these studies along with the operational performance of high-intensity beams during the 2017 run are presented in this paper. Furthermore, the impact of the hardware changes pursued in the framework of the LHC Injectors Upgrade project on the high-intensity beam properties is briefly mentioned., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

The Microbunched Electron Cooling (MBEC) is a promising cooling technique that can find applications in future hadron and electron-ion colliders. In this paper we give a qualitative derivation of the cooling rate for MBEC and estimate the cooling time for the eRHIC electron-ion collider. We then argue that MBEC with two plasma amplification stages should be sufficient to overcome the emittance growth due to the intra-beam scattering in eRHIC., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

The LHC Injectors Upgrade (LIU) Project at CERN aims at doubling the total intensity of the Pb-ion beam for the High-Luminosity LHC (HL-LHC) project. This goal can be achieved by using momentum slip-stacking (MSS) in the SPS, the LHC injector. This RF gymnastics, originally proposed to increase bunch intensity, will be used on the intermediate energy plateau to interleave two batches, reducing the bunch spacing from 100 to 50 ns. The MSS feasibility can be tested only in 2021, after the beam controls upgrade of the SPS 200 MHz RF system, so beam dynamics simulations are used to design this complicated beam manipulation. Simulations of the MSS were performed using the CERN BLonD code with a full SPS impedance model. Attention has been paid to the choice of the RF and machine parameters (beam energy, time duration, RF frequency and voltage programmes) to reduce losses and the final bunch length which is crucial for the injection into the LHC 400 MHz buckets. The initial beam parameters used in simulations were obtained from beam measurements in the first part of the SPS cycle taking into account bunch-by-bunch losses on flat bottom and development of bunch instabilities., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

A high bandwidth transverse feedback demonstrator system has been devised within the LARP framework in collaboration with SLAC for the LHC Injectors Upgrade (LIU) Project. The initial system targeted the Super Proton Synchrotron (SPS) at CERN to combat TMCI and electron cloud instabilities induced for bunches with bunch lengths at the 100 MHz scale. It features a very fast digital signal processing system running at up to 4~GS/s and high bandwidth kickers with a frequency reach of ultimately beyond 1~GHz. In recent years, the system has gradually been extended and now includes two stripline kickers for a total power of 1~kW delivering correction signals at frequencies of currently more than 700~MHz. This talk will cover recent studies using this demonstrator system to overcome TMCI limitations in the SPS. We will conclude with future plans and also briefly mention potential applications and requirements for larger machines such as the LHC or the HL-LHC., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Long-lasting phase oscillations have been observed at injection into the LHC since its first start-up with beam. These oscillations, however, were not leading to noticeable losses or blow-up in operation, and were therefore not studied in detail. In 2017, dedicated measurements with high-intensity bunches revealed that oscillations can lead to losses even slightly below the baseline intensity for the high-luminosity upgrade of the LHC. For the first time, high-resolution bunch profile acquisitions were triggered directly at injection and the formation of large-amplitude non-rigid dipole oscillations was observed on a turn-by-turn basis. First simulations can reproduce this instability via bunch filamentation that takes place after injection, depending on the mismatch between the bunch and bucket size in momentum at injection., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Large dynamic vacuum pressure rises of orders of magnitude which caused by the lost heavy ions can seriously limit the ion intensity and beam lifetime of the heavy ion accelerator, especially for the machine that operate the intermediate charge state heavy ion. The High Intensity heavy ion Accelerator Facility (HIAF) which will be built by the IMP will accumulate the intermediate charge state ion 238U³⁵⁺ to intensity 2*10¹¹ ppp to different terminals. In order to control the dynamic vacuum effects induced by the lose beams and design the collimation system for the BRing of the HIAF, a newly developed simulation program (ColBeam) and GSI's simulation code StrahlSim are both conducted and the dynamic vacuum simulation result is calculated by the StrahlSim. According to the simulation result, 3*10¹¹ ppp particles is the up limit beam intensity can be extracted for the current BRing vacuum system design. Higher beam intensity can be reach to 5*10¹¹ ppp when the NEG coating technology must be implemented for the dipole and quadrupole chamber., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

A local Crab Cavity (CC) scheme will recover the head-on collisions at the IP of the High Luminosity LHC (HL-LHC), which aims to increase the LHC luminosity by a factor of 3-10. The tight space constraints at the CC location result in axially non-symmetric cavity designs that introduce high order multipole CC components. The impact of these high order components on the long term stability of the beam in the SPS machine, where two prototype crab cavities are presently installed in the CERN SPS to perform tests with beam, is presented. Furthermore, the Dynamic Aperture is studied in the presence of the SPS errors. Future plans are discussed., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

The J-PARC RCS is a high-power rapid cycling synchrotron aiming for a 1-MW output beam power. This talk reports the recent progress of the J-PARC RCS beam commissioning and operation especially focusing on our efforts for beam dynamics issues that we faced during the process of the beam power ramp-up., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

One of the strong limitations for reaching higher beam intensities in the SPS, the injector of the LHC at CERN, are particle losses at flat bottom that increase with beam intensity. In this paper, different sources of these losses are investigated for two available SPS optics, using both measurements and simulations. Part of the losses originate from the PS-to-SPS bunch-to-bucket transfer, because the PS bunches are rotated in longitudinal phase space before injection and do not completely fit into the SPS RF bucket. The injection losses due to different injected bunch distributions were analyzed. Furthermore, at high intensities the transient beam loading in the SPS has a strong impact, which is (partially) compensated by the LLRF system. The effect of the present and future upgraded one-turn delay feedback system and phase loop on flat-bottom losses was studied using the longitudinal tracking code BLonD. Finally, the total particle losses are also affected by limitations in the SPS momentum aperture, visible for higher RF capture voltages in optics with lower transition energy and higher dispersion., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

The Main Injector (MI) at Fermilab currently produces high-intensity beams of protons at energies of 120 GeV for a variety of physics experiments. Acceleration of polarized protons in the MI would provide opportunities for a rich spin physics program at Fermilab. To achieve polarized proton beams in the Fermilab accelerator com-plex, shown in Fig.1.1, detailed spin tracking simulations with realistic parameters based on the existing facility are required. This report presents studies at the MI using a single 4-twist Siberian snake to determine the depolariz-ing spin resonances for the relevant synchrotrons. Results will be presented first for a perfect MI lattice, followed by a lattice that includes the real MI imperfections, such as the measured magnet field errors and quadrupole misa-lignments. The tolerances of each of these factors in maintaining polarization in the Main Injector will be discussed., Proceedings of the 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams, HB2016, Malmö, Sweden

In the CERN PS Booster, wire-scanner profile measurements performed at injection energy are affected by a strong asymmetry. The shape was reproduced with the code pyOrbit, assuming that the effect is due to the beam evolution during the scans, under the influence of space-charge forces and Multiple Coulomb Scattering at the wire itself. Reproducing the transverse profiles during beam evolution allows to use them reliably as input for simulation benchmarking., Proceedings of the 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams, HB2016, Malmö, Sweden

The CERN PS Booster (PSB) is presently running with a space-charge tune spread larger than 0.5 at injection. Since the High Luminosity LHC (HL-LHC) will require beams with twice the intensity and brightness of today, the LHC Injector Upgrade (LIU) Project is putting in place an upgrade program for all the injector chain and, in particular, it relies on the important assumption that the PS Booster can successfully produce these beams after the implementation of the 160 MeV H⁻ injection from Linac4. This contribution describes the studies (measurements and simulations) that have been carried out to confirm that the PSB can indeed perform as needed in terms of beam brightness for the future HL-LHC runs. The importance of the mitigation measures already in place, such as the correction of the half-integer line, and the effects of non-linear resonances on the beam are also discussed., Proceedings of the 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams, HB2016, Malmö, Sweden

Since the first transverse instability observed in 2010, many studies have been performed on both measurement and simulation sides and several lessons have been learned. In a machine like the LHC, not only all the mechanisms have to be understood separately, but the possible interplays between the different phenomena need to be analyzed in detail, including the beam-coupling impedance (with in particular all the necessary collimators to protect the machine but also new equipment such as crab cavities for HL-LHC), linear and nonlinear chromaticity, Landau octupoles (and other intrinsic nonlinearities), transverse damper, space charge, beam-beam (long-range and head-on), electron cloud, linear coupling strength, tune separation between the transverse planes, tune split between the two beams, transverse beam separation between the two beams, etc. This paper reviews all the transverse beam instabilities observed and simulated so far, the mitigation measures which have been put in place, the remaining questions and challenges and some recommendations for the future., Proceedings of the 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams, HB2016, Malmö, Sweden

The beams required for the high luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN call for efficient mechanisms to suppress transverse collective instabilities. In addition to octupole magnets installed for the purpose of Landau damping, we propose to use radio frequency (rf) quadrupole structures to considerably enhance the aforementioned stabilising effect. By means of the PyHEADTAIL macroparticle tracking code, the stabilising mechanism introduced by an rf quadrupole is studied and discussed. As a specific example, the performance of an rf quadrupole system in presence of magnetic octupoles is demonstrated for HL-LHC. Furthermore, potential performance limitations such as the excitation of synchro-betatron resonances are pointed out. Finally, efforts towards possible measurements with the CERN Super Proton Synchrotron (SPS) are discussed aiming at studying the underlying stabilising mechanisms experimentally., Proceedings of the 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams, HB2016, Malmö, Sweden