Status and Recent Developments at the Fermilab Accelerator Complex
J.S. Eldred
Fermilab, Batavia, Illinois, USA
In June 2021, Fermilab achieved an 843 kW power record at the NuMI beamline. The implications and limitations of this high-power running-mode are discussed. We survey the year-round performance plots across the Fermilab HEP proton complex. We present recent machine upgrade and beam study campaigns for the Fermilab Linac, Booster, Recycler and Main Injector. We provide updates on the timeline for the PIP-II SRF Linac and LBNF neutrino beamline. A brief overview of the latest results and upcoming research program at FAST / IOTA complex is presented. We summarize the recent progress at the superconducting RF and magnets technology R&D program at Fermilab Technology Division.
Optical Stochastic Cooling was recently demonstrated at the IOTA ring in Fermilab. The talk discusses major theory developments required for the implementation of optical stochastic cooling at the IOTA and understanding the experimental results. In addition to previously reported developments, the talk discusses how strong x-y coupling affects the redistribution of cooling rates between horizontal and vertical planes and the how the cooling ranges can be obtained from the measurements when OSC is switched to anti-cooling (heating) regime.
Ion Beam Growth Caused by Space-Charge Force of Electron Bunches
S. Seletskiy, A.V. Fedotov, D. Kayran, H. Zhao
BNL, Upton, New York, USA
Presence of electron beam created by either electron coolers or electron lenses in an ion storage ring can cause an unwanted emittance growth (heating) of the ion bunches. This electron-ion heating is a result of the electron bunch space-charge force randomized by various effects. In this paper we report experimental studies of the electron-ion heating in the Low Energy RHIC electron Cooler (LEReC) and compare the obtained data to theoretical predictions of several models.
Development of an Injection-Painted Self-Consistent Beam in the Spallation Neutron Source Ring
7
A.M. Hoover
UTK, Knoxville, Tennessee, USA
N.J. Evans
ORNL RAD, Oak Ridge, Tennessee, USA
T.V. Gorlov, J.A. Holmes
ORNL, Oak Ridge, Tennessee, 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.
Resonance Compensation for High Intensity and High Brightness Beams in the CERN PSB
40
F. Asvesta, S.C.P. Albright, F. Antoniou, H. Bartosik, C. Bracco, G.P. Di Giovanni, E.H. Maclean, B. Mikulec, T. Prebibaj, E. Renner
CERN, Geneva, Switzerland
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.
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Chromaticity Measurement Using Beam Transfer Function in High Energy Synchrotrons
46
X. Buffat, S.V. Furuseth, G. Vicentini
CERN, Geneva, Switzerland
S.V. Furuseth
EPFL, Lausanne, Switzerland
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.
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Recent Progress on Nonlinear Beam Manipulations in Circular Accelerators
52
F. Capoani, M. Giovannozzi
CERN, Geneva, Switzerland
A. Bazzani
Bologna University, Bologna, Italy
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.
P.D. Hermes, R. Bruce, R. De Maria, M. Giovannozzi, A. Mereghetti, D. Mirarchi, S. Redaelli
CERN, Geneva, Switzerland
G. Stancari
Fermilab, Batavia, Illinois, USA
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.
Closed Form Formulas of the Indirect Space Charge Wake Function for Axisymmetric Structures
65
N. Mounet, E. Dadiani, E. Métral, C. Zannini
CERN, Geneva, Switzerland
A. Rahemtulla
EPFL, Lausanne, Switzerland
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.
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Controlled Longitudinal Emittance Blow-Up for High Intensity Beams in the CERN SPS
71
D. Quartullo, H. Damerau, I. Karpov, G. Papotti, E.N. Shaposhnikova, C. Zisou
CERN, Geneva, Switzerland
D. Quartullo
Sapienza University of Rome, Rome, Italy
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.
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Understanding of the CERN-SPS Horizontal Instability with Multiple Bunches
77
C. Zannini, H. Bartosik, M. Carlà, K.S.B. Li, E. Métral, G. Rumolo, B. Salvant
CERN, Geneva, Switzerland
L.R. Carver
ESRF, Grenoble, France
M. Schenk
EPFL, Lausanne, Switzerland
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.
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Influence of Transverse Motion on Longitudinal Space Charge in the CERN PS
83
A.J. Laut, A. Lasheen
CERN, Geneva 23, Switzerland
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.
The PS Booster Alignment Campaign and a New Tune Control Implementation After the LHC Injectors Upgrade at CERN
89
F. Antoniou, F. Asvesta, H. Bartosik, J.F. Comblin, G.P. Di Giovanni, M. Hostettler, A. Huschauer, B. Mikulec, J.-M. Nonglaton, T. Prebibaj
CERN, Meyrin, Switzerland
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.
Threshold for Loss of Longitudinal Landau Damping in Double Harmonic RF Systems
95
L. Intelisano, H. Damerau, I. Karpov
CERN, Meyrin, Switzerland
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.
New Analytical Criteria for Loss of Landau Damping in Longitudinal Plane
100
I. Karpov, T. Argyropoulos, E.N. Shaposhnikova
CERN, Meyrin, Switzerland
S. Nese
University of Bergen, Bergen, Norway
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.
End-to-End Longitudinal Simulations in the CERN PS
106
A. Lasheen, H. Damerau, K. Iliakis
CERN, Meyrin, Switzerland
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.
Injection Chicane Beta-Beating Correction for Enhancing the Brightness of the CERN PSB Beams
112
T. Prebibaj, S.C.P. Albright, F. Antoniou, F. Asvesta, H. Bartosik, C. Bracco, G.P. Di Giovanni, E.H. Maclean, B. Mikulec, E. Renner
CERN, Meyrin, Switzerland
T. Prebibaj
IAP, Frankfurt am Main, Germany
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.
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Optimised Transverse Painting Schemes for the New 160 MeV H⁻ Injection System at CERN
118
E. Renner, S.C.P. Albright, F. Antoniou, F. Asvesta, H. Bartosik, C. Bracco, G.P. Di Giovanni, B. Mikulec, T. Prebibaj, F.M. Velotti
CERN, Meyrin, Switzerland
A major aspect of the LHC Injectors Upgrade (LIU) project at CERN is the Proton Synchrotron Booster (PSB) connection to the newly built Linac4 and the related installation of a new 160 MeV H⁻ charge exchange injection. This contribution presents the first operational experience with the new injection system and its flexibility of applying horizontal phase space painting to tailor different beams to the respective user-defined brightness targets. The presented measurement and multi-particle simulation results focus on the optimisation of the required transverse injection settings to reduce losses when producing high-intensity beams, i.e. for the ISOLDE experiment. In this context, feasibility studies towards applying numerical optimisation algorithms for improving and efficiently adapting the respective injection settings online are presented.
Space Charge Resonance Analysis at the Integer Tune for the CERN PS
124
F. Schmidt, F. Asvesta
CERN, Meyrin, Switzerland
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.
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3D Symplectic Space Charge Implementation in the Latest Mad-X Version
129
F. Schmidt, A. Latina, H. Renshall
CERN, Meyrin, Switzerland
Y.I. Alexahin
Fermilab, Batavia, Illinois, 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.
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A Dedicated Wake-Building Feedback System to Study Single Bunch Instabilities in the Presence of Strong Space Charge
135
R. Ainsworth, A.V. Burov, N. Eddy, A. Semenov
Fermilab, Batavia, Illinois, 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.
Coupled Bunch Instabilities Growth in the Fermilab Booster During Acceleration Cycle
140
C.M. Bhat, N. Eddy
Fermilab, Batavia, Illinois, USA
Funding:This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. 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. [1] Nathan Eddy (private communications, 2020).
Compensation of Ultimate Space Charge with Electron Lenses
E.G. Stern, Y.I. Alexahin, A.V. Burov, V.D. Shiltsev
Fermilab, Batavia, Illinois, USA
Space-charge effects set stringent limits on the performance of frontier high power proton accelerators. They manifest themselves in beam losses and emittance growth. Compensation of the space-charge effects in positively charged proton beams is possible by propagating the beam through negatively charged electron lenses which employ high brightness magnetized and externally controlled electron beams. While the method was previously assessed theoretically and in simplified tracking simulations, it has never been modeled by PIC codes to get reliable quantitative estimates of the efficiency of the compensation. Here we report on the first evidence using the Synergia particle-in-cell simulation code that a suitable number of electron lens type elements can protect the machine from emittance growth caused by space-charge forces in a model beam optics lattice with imperfections. For effective electron lens space-charge compensation, the compensating elements must be placed within not too large betatron phase advance from each other. Electron lens elements could become the basis of new generation of high power proton and ion rapid cycling synchrotrons.
Simulating Magnetized Electron Cooling for EIC with JSPEC
S.J. Coleman, D.T. Abell, D.L. Bruhwiler, B. Nash, I.V. Pogorelov
RadiaSoft LLC, Boulder, Colorado, USA
H. Zhang
JLab, Newport News, Virginia, USA
We present a possible electron cooling configuration for the proposed Electron Ion Collider (EIC) facility, developed using a Nelder-Mead Simplex optimization procedure built into JSPEC, an electron cooling code developed at Jefferson Lab. The time evolution of the emittance of the ion beam in the presence of this cooler is evaluated assuming the ion distribution remains Gaussian. We also show that bi-gaussian distributions emerge in simulations of ion macro-particles, where Gaussian distributions are not enforced. The Sirepo/JSPEC and Sirepo/Jupyter apps will be presented, with instructions enabling the community to reproduce our simulations
Self-Consistent Long-Term Dynamics of Space Charge Driven Resonances in 2D and 3D
160
A. Oeftiger, I. Hofmann
GSI, Darmstadt, Germany
O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
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. HB’21 talk on "Effect of Space Charge on Bunch Stability and Space Charge Compensation Schemes" based on this APS PR-AB published contribution.
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Impact of Power Supply Ripple on the Beam Performance of the Large Hadron Collider and the High-Luminosity LHC
170
S. Kostoglou, H. Bartosik, Y. Papaphilippou, G. Sterbini
CERN, Geneva, Switzerland
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.
N. Biancacci, X. Buffat, N. Mounet, E. Métral, D. Valuch
CERN, Meyrin, Switzerland
A. Oeftiger
GSI, Darmstadt, Germany
Landau damping is an essential mechanism for ensuring collective beam stability in particle accelerators. Precise knowledge of the strength of Landau damping is key to making accurate predictions on beam stability for state-of-the-art high-energy colliders. We demonstrate an experimental procedure that would allow quantifying the strength of Landau damping and the limits of beam stability using an active transverse feedback as a controllable source of beam coupling impedance. In a proof-of-principle test performed at the Large Hadron Collider, stability diagrams for a range of Landau octupole strengths have been measured. In the future, the procedure could become an accurate way of measuring stability diagrams throughout the machine cycle.
High Intensity Beam Dynamics Preparations for FAIR
O. Boine-Frankenheim
GSI, Darmstadt, Germany
The FAIR accelerator complex is designed to deliver heavy ions beams of unprecedented beam intensity and quality. Such beams will enable high yield in-flight production of exotic nuclei and their precise identification at high energies, for example. Intense primary ion beams will be delivered to the new SIS100 synchrotron from the upgraded UNILAC/SIS18 complex. Both, the existing SIS18 and the new SIS100 will be operated at the ’space charge limit’ for light and heavy ion beams. Only due to the recent advances in the performance of particle tracking tools with self-consistent 3D space charge solvers we were able to reliably identify low-loss areas in tune space over the full 1 s accumulation plateau in SIS100. A realistic magnet error model, extracted from bench measurements, is included in the simulations. Different measures are proposed to enlarge the low-loss area and to further increase the space charge limit. A key rf manipulation in SIS100 will be the single bunch generation and compression before extraction to the production targets. Simulation results to prepare for the later operation will be shown.
HL-LHC: Project Status and Beam Dynamics Challenges
S. Redaelli
CERN, Geneva, Switzerland
The Large Hadron Collider (LHC) at CERN has been producing physics data since 2010. It will be upgraded in the years 2025-27 to sustain and further extend its physics discovery potential. The High-luminosity LHC upgrade (HL-LHC) targets at least a factor five increase of peak luminosity, and a ten-fold improvement of integrated luminosity, compared to the LHC design. To achieve this, the HL-LHC beams are two times more intense and more than five times brighter. These ambitious goals pose obvious beam dynamics challenges that will be addressed through several upgrades of the LHC accelerator. The HL-LHC will use high-field superconducting magnets based on Nb₃Sn for the final beam focusing, crab cavities to optimize luminosity conditions, a new generation of collimators that withstand the higher operational beam losses while reducing the beam impedance, hollow electron lenses for active halo control as well as crystal collimators for improved cleaning efficiency for heavy-ion beams. This advances the LHC state-of-the-art accelerator technology in various domains. This contribution reviews the plans and status of the HL-LHC upgrade and the main challenges associated with this project.
Beam Instability Issue and Transverse Feedback System in the MR of J-PARC
208
T. Toyama, A. Kobayashi, T. Nakamura, M. Okada, M. Tobiyama
KEK, Tokai, Ibaraki, Japan
Y. Shobuda
JAEA/J-PARC, Tokai-mura, Japan
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.
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Space-Charge Particle Resonances and Mode Parametric Resonances
D. Jeon, J.-H. Jang
IBS, Daejeon, Republic of Korea
Y.L. Cheon, M. Chung
UNIST, Ulsan, Republic of Korea
As the beam intensity increases in modern high-power accelerators, self-field effects of the beam become significant. There are two distinct families of space-charge halo mechanisms in high-intensity accelerators, and yet they need to be differentiated: resonances (particle resonances or incoherent resonances) and instabilities (parametric resonances or coherent resonances). What we call resonances are resonances of beam particles excited through the space-charge nonlinear multipoles. What we call instabilities are instabilities of the beam modes. Instabilities are also called parametric resonances because they are parametric resonances of the Vlasov-Poisson equations. They would better be called mode parametric resonances to distinguish them from particle parametric resonances. Resonances and instabilities may look alike in the phase space, and yet they have distinct differences. Instabilities (or mode parametric resonances) do not have the resonant frequency component. Various orders of resonances and instabilities are presented along with the beam distributions with which the particular mechanism is observed.
Exploring Quasi-Integrable Optics with the IBEX Paul Trap
214
J.A.D. Flowerdew
University of Oxford, Oxford, United Kingdom
D.J. Kelliher, S. Machida, S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
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.
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