Beam Dynamics in Rings
Paper Title Page
MOPAB05 Global Optics Correction for Low Energy RHIC Run 34
 
  • C. Liu, K.A. Drees, A. Marusic, M.G. Minty, C. Montag
    BNL, Upton, Long Island, New York, USA
  
  Funding: The work was performed under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
There has been increasing interest in low energy run in RHIC to study the QCD phase diagram and search for the critical point. The machine optics is one of the critical pieces for a successful low energy run since it affects the luminosity and its lifetime. Despite the difficulties of taking optics measurement data, progress has been made in recent years to analyze and correct the global optics errors. The analysis technique and specific exception handling, and the results of optics correction for low energy runs will be presented in the report. 		 
 
MOPAB08 Longitudinal Dynamics Simulation at Transition Crossing in RHIC with New Landau Cavity 37
 
  • C. Liu, M. Blaskiewicz, J.M. Brennan, K. Mernick, M.G. Minty, C. Montag, K.S. Smith
    BNL, Upton, Long Island, New York, USA
  
  Funding: The work was performed under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
At RHIC, heavy ion beams cross transition energy during acceleration to energies required by the physics programs. In the past, to battle longitudinal instabilities, a Landau cavity was turned on just after acceleration through transition energy. The Landau cavity with modified frequency will be implemented before beam crosses transition in Run-14. Longitudinal dynamics with this new configuration have been simulated to optimize the phase and amplitude of the Landau cavity. We will present simulation results in the report. 		 
 
MOPAB10 Beam-based Performance of the CERN PS Transverse Feedback 40
 
  • G. Sterbini, A. Blas, S.S. Gilardoni
    CERN, Geneva, Switzerland
  
  The CERN PS transverse damper is a flexible wideband system to damp injection coherent oscillations, inter and intra-bunch transverse instabilities at different energies along the cycle, to perform controlled emittance blow-up and to serve as abort cleaning device. In this paper we summarise some beam-based observations of the CERN PS transverse feedback performance and compare them with the expected results.  
 
MOPAB11 Transverse Decoherence of Ion Bunches with Space Charge and Feedback System 45
 
  • I. Karpov
    TEMF, TU Darmstadt, Darmstadt, Germany
  • O. Boine-Frankenheim, V. Kornilov
    GSI, Darmstadt, Germany
  
  The transverse decoherence of the bunch signal after an initial bunch displacement is an important process in synchrotrons and storage rings. It can be useful, for the diagnostic purposes, or undesirable. Collective bunch oscillations can appear after the bunch-to-bucket transfer between synchrotrons and can lead to the emittance blow-up. In order to preserve the beam quality and to control the emittance blow-up, transverse feedback systems (TFS) are used. But, TFS operation can also lead to emittance blow-up due to imperfections (noise, bandwidth limitation, time delay errors), which also depends on the TFS settings. In heavy ion and proton beams, like in SIS100 synchrotron of the FAIR project, transverse space charge strongly modify decoherence. The resulting transverse bunch decoherence and beam blow-up is due to a combination of the lattice settings (like chromaticity), nonlinearities (residual or imposed by octupole magnets), space-charge, and the TFS. We study these effects using particle tracking simulations with the objective of correct combinations for a controlled beam blow-up.  
 
MOPAB12 Slip-stacking Dynamics and the 20 Hz Booster 50
 
  • J.S. Eldred
    Indiana University, Bloomington, Indiana, USA
  • J.S. Eldred, R.M. Zwaska
    Fermilab, Batavia, Illinois, USA
  
  Slip-stacking is an accumulation technique used at Fermilab since 2004 which nearly doubles the proton intensity. The Proton Improvement Plan II intensity upgrades require a reduction in slip-stacking losses by approximately a factor of 2. We study the single-particle dynamics that determine the stability of slip-stacking particles. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We show the particle loss as a function of time. We calculate the injection efficiency as a function of longitudinal emittance and aspect-ratio. We demonstrate that the losses from RF single particle dynamics can be reduced by a factor of 4-10 (depending on beam parameters) by upgrading the Fermilab Booster from a 15-Hz cycle-rate to a 20-Hz cycle-rate. We recommend a change in injection scheme to eliminate the need for a greater momentum aperture in the Fermilab Recycler.  
 
MOPAB21 A Novel Code with High-order Adaptive Dynamics to Solve the N-body Problem 70
 
  • S. Abeyratne, B. Erdelyi, H.D. Schaumburg
    Northern Illinois University, DeKalb, Illinois, USA
  • B. Erdelyi
    ANL, Argonne, USA
  
  Although there are several publicly available algorithms to model the behavior of natural systems such as the N-body system, limited computing power hinders the attempt to simulate them efficiently. With the improvement of high performance computing, scientists will be able to run simulations at an unprecedented scale in the future. Therefore, it is necessary to develop new algorithms and data structures to harness the power of high performance computing. In this paper we show a newly developed code, particles’ high order adaptive dynamics (PHAD), to serve future computing demands. We use Fast Multipole Method (FMM) to calculate the interactions among charged particles. We use the Strang splitting technique to reduce the number of FMM calls and enhance the efficiency. Picard iterations-based novel integrators are employed to achieve very high accuracies. Electron cooling in the proposed Electron Ion Collider (EIC) has been identified as a potential testing environment for PHAD.  
 
MOPAB23 Resonance Structures in the Impedance of a Ceramic Break and the Measured Results 74
 
  • Y. Shobuda
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • Y.H. Chin, K. Takata
    KEK, Ibaraki, Japan
  • T. Toyama
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  
  Recently, we have developed a new theory to evaluate longitudinal and transverse impedances of any size of ceramic break sandwiched between metal chambers. The theory successfully reproduces the resonance structures in the impedance due to trapped modes inside the ceramic break. The comparisons between the theoretical and the simulation results such as ABCI and CST Studio show excellent agreements, indicating that they can be used as a good benchmark test for accuracy of simulation codes. To demonstrate the existence of such resonances, the transverse impedance of the ceramic break is measured using the wire-method. The measurement results reproduce the simulations well. The theory is particularly useful for the evaluation of the impedance of the ceramic break with titanium nitride coating.  
 
MOPAB24 Identification of Intra-bunch Transverse Dynamics for Feedback Control Purposes at CERN Super Proton Synchrotron 79
 
  • O. Turgut, J.D. Fox, C.H. Rivetta
    SLAC, Menlo Park, California, USA
  • W. Höfle
    CERN, Geneva, Switzerland
  • S.M. Rock
    Stanford University, Stanford, California, USA
  
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
We present methods for parameter estimation of intra-bunch transverse beam dynamics. The dynamics is represented via reduced order linear models. These models are useful in beam monitoring and in the design of feedback controllers to stabilize intra-bunch transverse instabilities. The effort is motivated by the plans to increase currents in the Super Proton Synchrotron as part of the HL-LHC upgrade where feedback methods could control instabilities and allow greater freedom in machine lattice parameters. Identification algorithms use subspace methods to compute a discrete multi-input multi-output (MIMO) representation of the nonlinear dynamics. We use macro particle simulation data (CMAD and HEADTAIL) and SPS machine measurements as the source of dynamics information for the identification of beam dynamics. Reduced models capture the essential dynamics of the beam motion or instability at a particular operating point, and can then be used analytically to design optimal feedback controllers. The robustness of the model parameters against noise and external excitation signals is studied, as is the effect of the MIMO model order on the accuracy of the identification algorithms. 		 
 
MOPAB26 Study of Beam Dynamics in Linear Paul Traps 84
 
  • D.J. Kelliher, S. Machida, C.R. Prior, S.L. Sheehy
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  
  The Hamiltonian governing the dynamics in a Linear Paul Trap (LPT) is identical in form to that of a beam in a focusing channel. This similarity, together with the LPT’s flexibility, compactness and low cost make it a useful tool for the study of a wide range of accelerator physics topics. Existing work has focused on high intensity collective effects as well as, more recently, the study of integer resonance crossing in the low intensity regime. A natural extension of this work is to investigate space charge effects of intense beams in more realistic lattices to directly inform accelerator design and development. For this purpose we propose to construct a modified Paul Trap specifically for these studies. Among other features, it is envisaged that this new LPT should be able to model non-linear elements and a wider range of lattice configurations. This work will be undertaken in collaboration with Hiroshimi University.  
 
MOPAB27 Characterisation of the KURRI 150 MeV FFAG and Plans for High Intensity Experiments 89
 
  • S.L. Sheehy, D.J. Kelliher, S. Machida, C.R. Prior, C.T. Rogers
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  
  Fixed field alternating gradient (FFAG) accelerators hold a lot of promise for high power operation due to their high repetition rate and strong focusing optics. However, to date these machines have not been operated with high intensity beams. Since November 2013 an experimental collaboration has been underway to characterise the 150 MeV proton FFAG at KURRI, Japan. Here we report on the results of characterisation experiments and discuss plans for further experiments in the high intensity regime.  
 
MOPAB38 Simulations of the Head-tail Instability on the ISIS Synchrotron 113
 
  • R.E. Williamson, D.J. Adams, B. Jones, C.M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • V. Kornilov
    GSI, Darmstadt, Germany
  
  ISIS is the pulsed spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. Operation is centred on a loss limited 50 Hz proton synchrotron which accelerates 3·1013 protons per pulse (ppp) from 70 MeV to 800 MeV, delivering a mean beam power of 0.2 MW. Present studies are focussed on key aspects of high intensity beam dynamics with a view to increasing operational intensity, understanding loss mechanisms and identifying possible upgrade routes. Of particular interest is the head-tail instability observed on ISIS, which is currently the main limitation on beam intensity. This paper presents initial simulations using HEADTAIL to compare with experimental data taken on the ISIS synchrotron. The details and assumptions of the impedance model and simulations are discussed. Plans for future head-tail measurements, simulations and analysis are outlined.  
 
MOPAB39 Image Fields in the Rectangular Vacuum Vessels of the ISIS Synchrotron 118
 
  • B.G. Pine, C.M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  ISIS is the pulsed spallation neutron source based at Rutherford Appleton Laboratory in the UK. Operation is based on a 50 Hz, 800 MeV proton synchrotron, accelerating up to 3·1013 protons per pulse, which provides beam to two target stations. Space charge effects contribute significantly to beam loss. Fields from the intense beam interact strongly with their environment. At ISIS the vacuum vessel is rectangular and profiled to follow the shape of the design beam envelope. Past studies have suggested that closed orbit induced image fields may contribute to beam loss under certain conditions. Image fields for parallel plate and rectangular geometries are reviewed, in particular their expansion as power series is determined. A simulation tool has been developed for particle tracking. The code contains both FFT and FEA field solvers, which have been used here to test the power series expansions for centred and off-centred beams. These expansions are then used to determine driving terms for the transverse beam motion. Of particular interest for ISIS is the resonant behaviour of beams with a harmonic closed orbit, which can be compared with the output of beam tracking simulations.  
 
MOPAB40 Studies of Loss Mechanisms Associated with the Half Integer Limit on the ISIS Ring 123
 
  • C.M. Warsop, D.J. Adams, B. Jones, B.G. Pine, H. V. Smith, C.C. Wilcox, R.E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. The facility centres on an 800 MeV rapid cycling proton synchrotron, which provides 0.2 MW of beam power operating at high levels of transverse space charge (peak incoherent tune shift ~ 0.5), but with low loss. Half integer resonance is considered to be a main driver for loss that limits the intensity in high power, medium energy proton rings like ISIS. However, the detailed mechanisms causing loss as the half integer limit is approached are not well understood, particularly in the context of a real machine. In this paper we report progress on experiments on the ISIS synchrotron inducing half integer loss, comparing with detailed simulations and attempts to relate these to simplified theoretical and simulation models. Effects of longitudinal motion on growth mechanisms, e.g. in coasting, “frozen” bunched and rapid cycling bunched beams are discussed, as is how these losses might be minimised and thus the real space charge limit effectively increased.  
 
MOPAB51 Beam Dynamics Study for J-PARC Main Ring by Using the 'Pencil' and Space-charge Dominated Beam: Measurements and Simulations 157
 
  • A.Y. Molodozhentsev, S. Igarashi, Y. Sato, J. Takano
    KEK, Ibaraki, Japan
  
  J-PARC Main Ring (MR) study has been performed during 2013-2014 to optimize the machine performance. As the result of this activity the ‘200 kW’ proton beam has been successfully extracted from MR into the ‘Neutrino’ beamline. Total particle losses, localized at the MR collimation section, have been estimated as 150 W. The 'low-losses' MR operation has been achieved after optimization the injection process, setting the MR RF system, dynamic control of the chromaticity and compensation the linear coupling resonance. In frame of this report we will discuss the obtained experimental results and compare it with simulations, performed extensively for different machine operation scenario, including the 'pencil' low intensity beam and the space-charge dominated beam. The obtained results demonstrate agreement between simulations and measurements for emittance evolution and losses for different cases. The developed MR computational model will be used to optimize the machine performance for the ‘MegaWatt’ MR operation scenario with limited losses. The modeling of the beam dynamics for these cases has been performed by using the ‘PTC-ORBIT’ combined code, installed on the KEK supercomputer.  
 
TUO3LR01 Understanding Beam Losses in High Intensity Proton Accumulator Rings 192
 
  • R.J. Macek, J.S. Kolski
    LANL, Los Alamos, New Mexico, USA
  
  Funding: U.S. Department of Energy under contract DE-AC52-06NA25396
Beam losses and the resulting radio-activation of accelerator components are major considerations governing the operations, development and performance of medium-energy, high-intensity proton accumulator rings such as the Los Alamos Proton Storage Ring (PSR). Several beam loss mechanisms contribute including beam scattering (nuclear and large angle Coulomb scattering) in the injection foil, production of excited states of H0 in the H− injection stripper foil that subsequently field strip in the magnetic fields down stream of the foil, halo growth from space charge effects, beam instabilities and losses from the fast extraction process. This talk will cover progress in the diagnosis, measurement, and modeling of beam losses at PSR with some comparisons to other rings. The roles the computer codes MAD8*, ORBIT**, G4Beamline***, and others used in modeling beam losses will be discussed and the modeling results compared with relevant experimental data. Concepts and prospects for future improvements such as laser striping for injection will be discussed at the end of the presentation.
* F. Christoph Iselin, The MAD Program, 1994, CERN-BE/ABP
** J. A. Holmes, ICFA BD Newsletter, No 30, page100, 2003.
*** Muons, Inc, G4Beamline, http://www.muonsinternal.com/muons3/Computer+Programs 		 
slides icon Slides TUO3LR01 [1.947 MB]  
 
TUO3LR02 BOOSTER UPGRADE FOR 700KW NOVA OPERATIONS 198
 
  • K. Seiya
    Fermilab, Batavia, Illinois, USA
  
  Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The Fermilab Proton Source is in the process of an upgrade referred to as the Proton Improvement Plan (PIP). [1] One PIP goal is to have Booster capable of delivering ~2.3·1017 protons/hour, 130% higher than the present typical flux of ~1017 protons/hour. The increase will be achieved mainly by increasing the Booster beam cycle rate from 9 Hz to 15 Hz. Beam loss due to the increased flux will need to be controlled, so as not to create larger integrated doses. The status of present operations and progress of beam studies will be discussed in this paper. 		 
slides icon Slides TUO3LR02 [3.313 MB]  
 
TUO3LR03 High Intensity Loss Mechanisms on the ISIS Rapid Cycling Synchrotron 203
 
  • C.M. Warsop, D.J. Adams, B. Jones, S.J. Payne, B.G. Pine, H. V. Smith, R.E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • V. Kornilov
    GSI, Darmstadt, Germany
  
  ISIS is the spallation neutron source at the Rutherford Appleton laboratory in the UK. Operation centres on a loss limited, 800 MeV, 50 Hz proton synchrotron which delivers 0.2 MW to two targets. Understanding loss mechanisms on the ISIS ring is important for optimal operation, machine developments and upgrades, as well as improving understanding for future machines. The high space charge levels, combined with the low loss achieved for high power operation, makes the ring an ideal tool for studying the physics of beam loss, particularly in a fast ramping context. The ability to reconfigure the beam in storage ring mode, and ongoing developments of diagnostics and beam measurements, are allowing detailed studies of image effects, resonances, beam stability and activation. We summarise recent work and progress on these topics, comparing with theory and simulation where appropriate.  
slides icon Slides TUO3LR03 [2.534 MB]  
 
WEO1LR01 Instabilities and Space Charge 235
 
  • M. Blaskiewicz, K. Mernick
    BNL, Upton, Long Island, New York, USA
  
  The coherent stability problem for proton and heavy ion beams is reviewed. For all but the highest energies space charge is the dominant coherent force. While space charge alone appears benign, its interaction with other impedances is less clear. The main assumptions used in calculations and their justifications will be reviewed. Transverse beam transfer function data from RHIC will be used to compare theory and experiment and some pitfalls will be discussed.  
slides icon Slides WEO1LR01 [1.251 MB]  
 
WEO1LR02 Thresholds of the Head-Tail Instability in Bunches with Space Charge 240
 
  • V. Kornilov, O. Boine-Frankenheim
    GSI, Darmstadt, Germany
  • D.J. Adams, B. Jones, B.G. Pine, C.M. Warsop, R.E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  Recent experimental studies of the unstable head-tail modes in the ISIS synchrotron (RAL, UK) provided intriguing findings about the intensity thresholds for the instability/stability along the acceleration ramp for different bunch parameters in single-rf and dual-rf operation. We explain the role of space-charge and the related Landau damping using particle tracking simulations and an airbag-bunch theory, and relate the observations to the classical single-rf, no space-charge theories in order to identify the driving impedances.  
slides icon Slides WEO1LR02 [3.203 MB]  
 
WEO3AB01 Measurements of Beam Halo Diffusion and Population Density in the Tevatron and in the Large Hadron Collider 294
 
  • G. Stancari
    Fermilab, Batavia, Illinois, USA
  
  Funding: Fermilab is operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the US DOE. Work partially supported by US LARP and by EU FP7 HiLumi LHC, Grant Agreement 284404.
Halo dynamics influences global accelerator performance: beam lifetimes, emittance growth, dynamic aperture, and collimation efficiency. Halo monitoring and control are also critical for the operation of high-power machines. For instance, in the high-luminosity upgrade of the LHC, the energy stored in the beam tails may reach several megajoules. Fast losses can result in superconducting magnet quenches, magnet damage, or even collimator deformation. The need arises to measure the beam halo and to remove it at controllable rates. In the Tevatron and in the LHC, halo population densities and diffusivities were measured with collimator scans by observing the time evolution of losses following small inward or outward collimator steps, under different experimental conditions: with single beams and in collision, and, in the case of the Tevatron, with a hollow electron lens acting on a subset of bunches. After the LHC resumes operations, it is planned to compare measured diffusivities with the known strength of transverse damper excitations. New proposals for nondestructive halo population density measurements are also briefly discussed. 		 
slides icon Slides WEO3AB01 [7.131 MB]  
 
THO1LR01 Long-term Beam Losses in the CERN Injector Chain 325
 
  • S.S. Gilardoni, G. Arduini, H. Bartosik, E. Benedetto, H. Damerau, V. Forte, M. Giovannozzi, B. Goddard, S. Hancock, K. Hanke, A. Huschauer, M. Kowalska, M. McAteer, M. Meddahi, B. Mikulec, E. Métral, Y. Papaphilippou, G. Rumolo, E.N. Shaposhnikova, G. Sterbini, R. Wasef
    CERN, Geneva, Switzerland
  
  For the production of the LHC type beams, but also for the high intensity ones, the budget allocated to losses in the CERN injector chain is maintained as tight as possible, in particular to keep as low as possible the activation of the different machine elements. Various beam dynamics effects, like for example beam interaction with betatronic resonances, beam instabilities, but also reduced efficiency of the RF capture processes or RF noise, can produce losses even on a very long time scale. The main different mechanisms producing long term losses observed in the CERN injectors, and their cure or mitigation, will be revised.  
slides icon Slides THO1LR01 [5.913 MB]  
 
THO1LR02
 Recent Commissioning of High-Intensity Proton Beams in J-PARC Main Ring  
 
  • Y. Sato, T. Koseki, J. Takano, S. Yamada, N. Yamamoto
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • H. Harada, M.J. Shirakata, F. Tamura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • S. Igarashi
    KEK, Ibaraki, Japan
  
  In the J-PARC, the main ring (MR) provides high power proton beams of 240 kW (1.24·1014 protons per pulse) to the neutrino experiment. The linac energy was upgraded from 181 MeV to 400 MeV in 2013, and its current is going to be from 30 mA to 50 mA in 2014. If the beam losses are minimized and localized in the MR, the MR will have the capability to provide over 300 kW after the upstream upgrades. Based on the upgrades and improvements of the 3-50BT and the MR in 2013 and 2014, following approaches have been tested and commissioned: 2nd harmonic RFs under the faster rise-up time improvement of the injection kickers, to increase bunching factor; intra-bunch feed-back system and chromaticity patterned correction, to suppress instability; intra-bunch feed-back, tail and reflection improvement of the injection kickers, and 6D matching between the 3-50BT and the MR, to reduce injection losses; achromatic tuning at the collimator section of the 3-50BT to cut beam halo effectively; collimator upgrades, aperture enlargement at dispersion peaks, and momentum spread control, to localize beam losses in the collimator section; new operation point survey.  
slides icon Slides THO1LR02 [2.553 MB]  
 
THO1LR03 Recent Development in the Mitigation of Long Term High Intensity Beam Loss 330
 
  • G. Franchetti, S. Aumon, F. Kesting, H. Liebermann, C. Omet, D. Ondreka, R. Singh
    GSI, Darmstadt, Germany
  • S.S. Gilardoni, A. Huschauer, F. Schmidt, R. Wasef
    CERN, Geneva, Switzerland
  
  In this talk it is presented the state of the art studies to mitigate the long term beam loss in the FAIR accelerator. The effect of high intensity is discussed in relation with high intensities. In particular the discussion is made on the interplay of space charge with coupled machine resonance as the 3rd order. A new development in the theory of the 3rd order resonance is used to discuss the periodic crossing of resonances, hence the mitigation of the resonance effects, and experimental investigation (CERN-PS, and GSI) are addressed and interpreted.  
 
THO2AB02 The Kicker Impedance and its Effect on the RCS in J-PARC 369
 
  • Y. Shobuda, P.K. Saha, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • Y.H. Chin, Y. Irie
    KEK, Ibaraki, Japan
  • T. Toyama
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  
  Measurements demonstrate that the kicker impedance dominates along the RCS. Based on a newly developed theory, the impedance is measured by observing the beam-induced voltages at the ends of power cable of the kicker. Toward one mega-watt goal, it is essential to take advantage of tune manipulations and the space charge damping effect. A reduction scheme of the kicker impedance is proposed to pursue the ultimate goal at the RCS.  
slides icon Slides THO2AB02 [9.113 MB]  
 
THO2AB03
 Study on Impedance for the Extraction Kicker in CSNS/RCS  
 
  • L. Huang, Y.D. Liu, S. Wang
    IHEP, Beijing, People's Republic of China
  
  Funding: Supported by National Natural Science Foundation of China (11175193, 11275221) # huangls@ihep.ac.cn
The fast extraction kicker system is the main source of impedance in China Spallation Neutron Source Rapid Cycling Synchrotron. Longitudinal and transverse impedance of a fast kicker has been measured for the design and development of the accelerator. The conventional wire method and the improved wire method are employed in the bench measurement. 		 
slides icon Slides THO2AB03 [2.995 MB]  
 
THO3LR02 Ring Simulation and Beam Dynamics Studies for ISIS Upgrades 0.5 to 10 MW 374
 
  • D.J. Adams, B. Jones, B.G. Pine, H. V. Smith, C.M. Warsop, R.E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • C.R. Prior, G.H. Rees
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  
  Various upgrade routes are under study for the ISIS spallation neutron source at RAL in the UK. Recent work has concentrated on upgrading the injector, increasing injection energy from 70 to 180 MeV, and studying the challenging possibility of reaching powers up to 0.5 MW in the existing 800 MeV RCS. Studies for the longer term are exploring the possibilities of a 5 MW, 3.2 GeV RCS that could form part of a new stand-alone 10+ MW next generation “ISIS II” facility. A central part of these ring studies is the use of computer simulations to guide designs, for example optimising the injection painting configuration and providing an indication of expected loss levels. Here we summarise the computer models used, indicate where benchmarking has been possible, describe optimisations and results from studies, and outline the main uncertainties. Understanding the limitations in high power RCS accelerators is an important part of determining optimal facility designs for the future.  
slides icon Slides THO3LR02 [2.658 MB]  
 
THO3AB01 Performance of Transverse Intra-Bunch Feedback System at J-PAC MR 384
 
  • Y.H. Chin, T. Obina, M. Okada, M. Tobiyama, T. Toyama
    KEK, Ibaraki, Japan
  • K.G. Nakamura
    Kyoto University, Kyoto, Japan
  • Y. Shobuda
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  
  A new broadband (~100 MHz) feedback system has been developed for suppression of intra-bunch oscillations and reduction of particle losses at the J-PARC Main Ring (MR). A new BPM has been designed and fabricated, based on Linnecar’s exponential coupler stripline type, for a flatter and wider frequency response. The design and performance of the new BPM as well as preparation of a newly installed exciter and power amplifier is presented. We also report beam test results of suppression of horizontal intra-bunch oscillations at 3 GeV with the bunch length of 150-200 ns.  
slides icon Slides THO3AB01 [6.245 MB]  
 
THO4LR01 Longitudinal Microwave Instability in a Multi-RF System 404
 
  • T. Argyropoulos
    CERN, Geneva, Switzerland
  
  The longitudinal microwave instability is observed as a fast increase of the bunch length above some threshold intensity. Recently, this type of instability was seen for a single proton bunch at high energies in the CERN SPS and is proven to be one of the limitations for an intensity increase required by the HL-LHC project. In this paper a theoretical approach to the analysis of the microwave instability is verified by particle simulations. The study is applied to the SPS and is based on the current SPS impedance model. Finally, the effect of the 4th harmonic RF system on the microwave instability threshold is investigated as well.  
slides icon Slides THO4LR01 [0.855 MB]  
 
THO4LR02 Synchrotron Frequency Shift as a Probe of the CERN SPS Reactive Impedance 409
 
  • A. Lasheen, T. Argyropoulos, J.V. Campelo, J.F. Esteban Müller, D. Quartullo, E.N. Shaposhnikova, H. Timko
    CERN, Geneva, Switzerland
  
  Longitudinal instability in the CERN SPS is a serious limitation for the future increase of bunch intensity required by HiLumi LHC project. The impedance driving this instability is not known precisely and a lot of effort goes into creating an accurate impedance model. The reactive impedance of the machine can be probed by measuring the bunch length oscillations of a mismatched bunch at injection. The frequency of these oscillations as a function of intensity has a slope that depends on the reactive impedance and the emittance. Measurements were done for three values of longitudinal emittances and then compared with particle simulations based on the impedance model using particle distribution close to the measured one. Comparison of measured and calculated frequency shifts gives an estimation of the missing impedance in the model. In addition, scanning of initial emittance for diverse particle distributions in simulations shows that the frequency shift greatly depends on emittance and initial distribution. Small variations of these parameters can lead to very different results and explain partially the discrepancy between measured and calculated values of frequency shifts.  
slides icon Slides THO4LR02 [1.499 MB]  
 
THO4LR03 Studies on Controlled RF Noise for the LHC 414
 
  • H. Timko, P. Baudrenghien, E.N. Shaposhnikova
    CERN, Geneva, Switzerland
  • T. Mastoridis
    CalPoly, San Luis Obispo, California, USA
  
  RF phase noise is purposely injected into the LHC 400 MHz RF system during the acceleration ramp for controlled longitudinal emittance blow-up, in order to maintain longitudinal beam stability. Although the operational blow-up works reliably, studies of the injected RF noise are desirable not only to allow for a better-controlled, more flexible blow-up, but also for other applications such as the mitigation of machine-component heating through appropriate bunch shaping. Concerning the noise injection, an alternative algorithm was developed and implemented in the hardware, but first tests revealed unexpected modulation of the achieved bunch length along the ring, and subsequently, theoretical studies have been launched. In this paper, we present a summary of ongoing measurement analysis and simulation studies that shall explain previous observations, predict what can be expected in different cases, and thus help to optimise the RF noise in general.  
slides icon Slides THO4LR03 [1.440 MB]  
 
THO4LR04 Fast Transverse Instability and Electron Cloud Measurements in Fermilab Recycler 419
 
  • J.S. Eldred, P. Adamson, D. Capista, N. Eddy, I. Kourbanis, D.K. Morris, J.C.T. Thangaraj, M.-J. Yang, R.M. Zwaska
    Fermilab, Batavia, Illinois, USA
  • J.S. Eldred
    Indiana University, Bloomington, Indiana, USA
  • Y. Ji
    IIT, Chicago, Illinois, USA
  
  A new transverse instability is observed that may limit the proton intensity in the Fermilab Recycler. The instability is fast, leading to a beam-abort loss within two hundred turns. The instability primarily affects the first high-intensity batch from the Fermilab Booster in each Recycler cycle. This paper analyzes the dynamical features of the destabilized beam. The instability excites a horizontal betatron oscillation which couples into the vertical motion and also causes transverse emittance growth. This paper describes the feasibility of electron cloud as the mechanism for this instability and presents the first measurements of the electron cloud in the Fermilab Recycler. Direct measurements of the electron cloud are made using a retarding field analyzer (RFA) newly installed in the Fermilab Recycler. Indirect measurements of the electron cloud are made by propagating a microwave carrier signal through the beampipe and analyzing the phase modulation of the signal. The maximum betatron amplitude growth and the maximum electron cloud signal occur during minimums of the bunch length oscillation.  
slides icon Slides THO4LR04 [1.608 MB]  
 
THO4LR05 Transverse Emittance Preservation Studies for the CERN PS Booster Upgrade 428
 
  • E. Benedetto, C. Bracco, V. Forte, B. Mikulec, V. Raginel, G. Rumolo
    CERN, Geneva, Switzerland
  • V. Forte
    Université Blaise Pascal, Clermont-Ferrand, France
  
  As part of the LHC Injectors Upgrade Project, the CERN PS Booster will undergo an ambitious upgrade program which includes the increase of injection energy from 50 MeV to 160 MeV and the implementation of an H− charge-exchange injection from the new Linac4. Compared to rings characterized by similar space-charge tune spreads (about 0.5 at low energy), the peculiarity of the PSB is the small transverse emittance that needs to be preserved in order to provide high brightness beams to the LHC. We here try to identify what is the minimum emittance that can be achieved for a given intensity, via measurements, scaling estimates and simulation studies. The latest are based on our best knowledge of the optics model and take into account known perturbations such as the one induced by the short and fast ramping chicane injection magnets.  
slides icon Slides THO4LR05 [1.122 MB]