HB2012 - List of Keywords (simulation)

Paper	Title	Other Keywords	Page
MOI1C01	Intense-beam Issues in CSNS and C-ADS Accelerators	linac, cavity, emittance, lattice	25
	S. Fu, S.X. Fang, Z. Li, J. Peng, J.Y. Tang, S. Wang, F. Yan IHEP, Beijing, People's Republic of China
	In 2011 construction of two intense-beam accelerators were launched for China Spallation Neutron Source (CSNS) project and China Accelerator Driven System (C-ADS) project. CSNS uses a pulsed accelerator with an H⁻ linac and a rapid cycling synchrotron, and C-ADS has a CW proton linac with superconducting cavities. In both cases, the beam power is high and beam loss control is a key issue in beam dynamics. Beam emittance growth and beam halo formation must be carefully studied in beam dynamics and well controlled in machine design. This paper will present a brief introduction to the physics design of the two intense-beam accelerators, especially on the issue of beam instability. In their linac design equapartitioning focusing scheme is adopted to avoid coupling instability. Some beam halo formation experimental results due to mismatching will be compared with simulations. Beam halo generation due to the quench of superconducting cavity and magnet is investigated in detail and compensation scheme is also proposed. Beam loss study for the error effects and orbit correction will be presented.
	Slides MOI1C01 [3.747 MB]

MOI1C02	Challenges in Benchmarking of Simulation Codes against Real High Intensity Accelerators	space-charge, resonance, emittance, linac	30
	I. Hofmann GSI, Darmstadt, Germany
	Benchmarking of simulation codes for linear or circular accelerators involves several levels of complexity, which will be revisited and discussed in this talk. As ultimate goal of benchmarking it is hoped that a predictive capacity and a practical control over emittance growth and/or beam loss can be obtained. We first give some examples of how simulation codes can be used to gain as much understanding of the underlying physics mechanisms as possible, which is an almost inevitable first step. With more and more experimental data from running high intensity accelerators having become available in recent years more questions need to be raised: Besides the proper physics, can we feed our codes with an accurate enough model of the real machine? What actually is the required accuracy, and does a specific accelerator have enough diagnostics to enable this accuracy? In the paper we explore these questions by discussing several examples of benchmarking efforts, their achievements as well as the limits and difficulties that have been encountered.
	Slides MOI1C02 [2.838 MB]

MOP203	Bunch-by-Bunch Beam Loss Diagnostics with Diamond Detectors at the LHC	beam-losses, injection, proton, kicker	41
	M. Hempel BTU, Cottbus, Germany T. Baer University of Hamburg, Hamburg, Germany S. Bart Pedersen, B. Dehning, E. Effinger, E. Griesmayer, A. Lechner, R. Schmidt CERN, Geneva, Switzerland W. Lohmann DESY, Hamburg, Germany
	A main challenge in the operation with high intensity beams is managing beam losses that imply the risk of quenching superconducting magnets or even damage equipment. There are various sources of beam losses, such as losses related to injection, to beam instabilities and to UFOs (Unidentified Falling Objects). Mostly surprising in the first years of LHC operation was the observation of UFOs. They are believed to be dust particles with a typical size of 1-100 um, which lead to beam losses with a duration of about ten revolutions when they fall into the beam. 3600 BLMs (Beam Loss Monitors) are installed around the LHC ring, allowing to determinate the accurate location of UFOs. The time resolution of the BLMs is 40 us (half a turn revolution). A measurement of the beam losses with a time resolution better than the bunch spacing of 50 ns is crucial to understand loss mechanisms. Diamond sensors are able to provide such diagnostics and perform particle counting with ns time resolution. In this paper, we present measurements of various types of beam losses with diamond detectors. We also compare measurements of UFO induced beam losses around the LHC ring with results from MadX simulations.

MOP204	A Method to Measure the Incoherent Synchrotron Frequencies in Bunches	space-charge, synchrotron, dipole, injection	46
	O. Chorniy, H. Reeg GSI, Darmstadt, Germany
	The method of measuring the incoherent synchrotron frequencies in a stationary bunch is presented. It can be shown that by measuring the local current at a fixed coordinate in RF bucket the corresponding incoherent synchrotron frequency can be obtained. Test calculations were done using simulation data where longitudinal space charge effects were included. The incoherent frequencies obtained with method are in a good agreement with theory. In real experiment, the incoherent frequencies were determined from bunch profiles recorded in the SIS18 with low intensity beam at injection energy. Bunch profiles were measured with a new Fast Current Transformer which has a relatively broad frequency range. The profiles were recorded using 8 bit resolution oscilloscope. The frequency spectra of local current fluctuation at different longitudinal positions were obtained numerically. The strongest lines in these spectra were at positions of theoretically expected incoherent frequencies. In this paper the method is described in details, the comparison of incoherent frequencies obtained from the simulation and measurement data with theoretical solutions is shown.

MOP207	Planning for Experimental Demonstration of Transverse Emittance Transfer at the GSI UNILAC through Eigen-emittance Shaping	emittance, quadrupole, coupling, scattering	57
	C. Xiao, O.K. Kester IAP, Frankfurt am Main, Germany L. Groening GSI, Darmstadt, Germany
	The minimum transverse emittances achievable in a beam line are determined by the two transverse eigen-emittances of the beam. For vanishing interplane correlations they are equal to the well-know rms-emittances. Eigen-emittances are constants of motion for all symplectic beam line elements, i.e. (even tilted) linear elements. To allow for rms-emittance transfer, the eigen-emittances must be changed by applying a non-symplectic action to the beam, preferably preserving the 4d-rms-emittance. This contribution will introduce the concept for eigen-emittance shaping and rms-emittance transfer at an ion linac. A path towards the experimental demonstration of the concept at the GSI UNILAC is presented.

MOP210	Beam Stacking for High Intensity Pulsed Proton Beam with FFAG	acceleration, extraction, neutron, injection	64
	Y. Mori, Y. Ishi, Y. Kuriyama, J.-B. Lagrange, T. Uesugi Kyoto University, Research Reactor Institute, Osaka, Japan
	Multi-beam stacking scheme to generate an intense short-pulsed proton beam with high repetition proton FFAG is presented.

MOP212	Simulation of Longitudinal Beam Instability caused by HOMs	HOM, linac, cavity, damping	73
	P. Cheng, Z. Li, J.Y. Tang, J.Q. Wang IHEP, Beijing, People's Republic of China
	Superconducting cavities are employed in C-ADS linac to accelerate 10mA CW proton beams from 3.2 MeV to 1.5 GeV. High order modes in superconducting cavities are found by using the simulation tools CST and HFSS, then power dissipation caused by HOMs have been investigated, it is indicated that the Qext should not go beyond 10⁷} in order to limit the additional heat load. Beam instabilities caused by high order modes in elliptical cavity sections are investigated using the code offered by Dr. Jean-Luc Biarrotte (CNRS, IPN Orsay, France). Beam errors, linac errors and high order modes frequency spread are investigated in detail. It shows that the monopole modes do not affect the proton beam critically and need no HOM couplers (Q_ext=10⁵}) if high order modes frequency spread is more than 100 kHz.

MOP216	The Design Study on the Longitudinal Beam Dynamics for CSNS/RCS	injection, acceleration, space-charge, bunching	89
	N. Wang, M.Y. Huang, Y. Li, S. Wang, S.Y. Xu, Y.S. Yuan IHEP, Beijing, People's Republic of China
	Rapid Cycling Synchrotron (RCS) is the key part of China Spallation Neutron Source (CSNS) accelerators. The RCS accumulates and accelerates 80 MeV beam from linac to 1.6 GeV. The particle number is 1.56·10¹³ for each pulse, with repetition rate of 25 Hz. In the RCS, longitudinal beam dynamics plays a crucial role in achieving high intensity beam with low beam loss. Longitudinal parameters are studied and optimized for efficient RF trapping of the beam in the longitudinal phase space. Beam performance is investigated by particle tracking simulations. Beam dynamic issues related to the high order mode induced by the RF generator are studied with a new developed code. Primary study on the adoption of dual harmonic cavity for higher beam power is also addressed.

MOP219	Error Analysis and Correction Scheme in C-ADS Injector-I	emittance, linac, cavity, solenoid	99
	C. Meng, Z. Li, J.Y. Tang IHEP, Beijing, People's Republic of China
	Funding: Supported by the China ADS Project (XDA03020000) C-ADS Injector-I is a 10 mA 10 MeV CW proton linac. It uses a 3.2MeV normal conducting 4-Vane RFQ and 12 superconducting single-Spoke cavities. According to the detailed sensitivity analysis of alignment and RF errors, the error tolerance of both static and dynamic ones for Injector-I are presented. The simulation results show that with the error tolerance there are beam losses, the residual orbit is too large which will produce significant emittance growth, so the correction is necessary for Injector-I. After detailed numerical studies, a correction scheme and monitor distributions are proposed. After correction the RMS residual orbit can be controlled within 0.4mm and RMS emittance growth can be controlled within 10%, but it still has 1.7×10^-6 beam loss, which comes from the RF errors and low longitudinal acceptance. According to detailed analysis and simulations with 10⁸ macro particles, as a consequence, longitudinal emittance control and longitudinal distribution control as well as large longitudinal acceptance are the key to minimizing beam losses in low energy section. To minimize beam loss, a short period Injector-I lattice with larger longitudinal acceptance have been designed and performance very good error tolerance.

MOP221	Physics Design of the C-ADS Main Linac Based on Two Different Injector Design Schemes	linac, emittance, lattice, cavity	107
	F. Yan, Z. Li, C. Meng, J.Y. Tang IHEP, Beijing, People's Republic of China
	Funding: Supported by Advanced Research Project of the Chinese Academy of Science Two design schemes for the main linac of C-ADS (China Accelerator Driven Subcritical system) are presented in this paper. They are corresponding to two different injector schemes. Injector-II scheme makes use of room-temperature RFQ and superconducting HWR cavities with the RF frequency of 162.5 MHz; Injector-I scheme makes use of higher-energy RFQ and superconducting spoke cavities with the RF frequency of 325 MHz. At the first choice, a relatively smaller longitudinal emittance is adopted for the RFQ designs with both the injector schemes to obtain more efficient acceleration. However, compared with the injector-I scheme, with the injector-II scheme, bunch current will be doubled in the main linac due to the half RF frequency in the injector-II. This means stronger space charge effects. Alternate design for the main linac with the injector-II scheme is to increase the longitudinal emittance by 50% so that the space charge effects will be alleviated. However, totally 30 cavities more and 36 m longer in the main linac have to be paid for this design scheme. The design considerations, the lattice designs, the simulation results including halo information are presented.

MOP229	Design of the MEBT1 for C-ADS Injector II	quadrupole, emittance, DTL, rfq	115
	H. Jia, Y. He, S.C. Huang, C.L. Luo, M.T. Song, Y.J. Yuan, X. Zhang IMP, Lanzhou, People's Republic of China
	The MEBT1 of Chinese ADS Injector II is described. It transports a 2.1 MeV, 10 mA CW proton beam through a series of 7 quadruples and two buncher cavities from the RFQ to the superconducting DTL. For emittance preservation, a compact mechanical design is required. Details of the beam dynamics and mechanical design will be given.

MOP231	Study of Non-equi-partitioning Lattice Setting and IBS Effects for J-PARC Linac Upgrade	emittance, lattice, linac, DTL	118
	Y. Liu IMP, Lanzhou, People's Republic of China M. Ikegami JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	For the coming upgrade of J-Parc, the peak power of linac will be greatly increased. This may open many interesting questions. For instance, for efficient acceleration from 19 0MeV to 400 MeV the annular coupled structure (ACS) was applied with frequency jump from 324 MHz to 972 MHz. Upstream part of J-PARC linac from the frequency jump is set with the equi-partitioning (EP) condition, which prevents from the coherent resonances. If EP condition is kept for the downstream part, due to the frequency jump, the transverse focusing should also ‘jump' 3 times with shrink of envelop. The increased beam-density affects the interactions between particles, including the intra-beam stripping (IBS) effect in the H⁻ beam. The temperature ratio between transverse and longitudinal planes is used as a knob for studying the beam behavior for the cases away from equi-partitioning. The IBS effects, as well as strategies for setting downstream non-equi-partitioning lattice due to frequency jump are studied. The matching and beam evolution in the transition section from EP to non-EP (MEBT2) are also studied. The results help to reach an optimum with least risks from resonances and IBS effects and so on.

MOP232	Optimization of the Superconducting Section of Injector Ⅱ for C-ADS	solenoid, emittance, lattice, linac	122
	S.H. Liu, Y. He, Z.J. Wang IMP, Lanzhou, People's Republic of China
	Abstract: The China Accelerator driven System (C-ADS) project which includes a high current SC proton linac is being studied under Chinese Academy of Science. Injector II, one of parallel injectors, is undertaken by Institute of Modern Physics (IMP). The lattice design of Injector II has been done. While in most case, the elements, such as SC cavities and SC solenoids, have different weight to the final beam parameters. What is more, in the real operation process of the machine, the optimized mode is hard to find. In the paper, Latin sampling method specified in DAKOTA code combined with TRACK is adopted to build hundreds of virtual machines to analyse the sensitivity of the SC section and to find optimization operation mode.

MOP233	Error and Tolerance Studies for Injector II of C-ADS	linac, solenoid, alignment, emittance	125
	W.S. Wang, Y. He, Z.J. Wang IMP, Lanzhou, People's Republic of China
	The proposed Chinese Accelerator Driven System (C-ADS) driver linac is being designed by Chinese Academic Science (CAS). Injector II is designed and fabricated in Institute of Modern Physics (IMP). Injector II will accelerate 10 mA proton beams to 10 MeV. Because of the high final beam power (100 kW) specified for the linac operation, beam loss must be limited to 10^-5 level to avoid radiation damage. Misalignment and RF error simulation for cavities and focusing elements after RFQ were performed and the correction schemes developed using the computing code TRACK. Error and tolerance studies for Injector II are presented.

MOP240	High Energy Tests of Advanced Materials for Beam Intercepting Devices at CERN HiRadMat Facility	vacuum, instrumentation, laser, proton	136
	A. Bertarelli, R.W. Aßmann, E. Berthomé, V. Boccone, F. Carra, F. Cerutti, A. Dallocchio, P. Francon, L. Gentini, M. Guinchard, N. Mariani, A. Masi, P. Moyret, S. Redaelli, S.D.M. dos Santos CERN, Geneva, Switzerland L. Peroni, M. Scapin Politecnico di Torino, Torino, Italy
	Predicting by simulations the consequences of LHC particle beams hitting Collimators and other Beam Intercepting Devices (BID) is a fundamental issue for machine protection: this can be done by resorting to highly non-linear numerical tools (Hydrocodes). In order to produce accurate results, these codes require reliable material models that, at the extreme conditions generated by a beam impact, are either imprecise or nonexistent. To validate relevant constitutive models or, when unavailable, derive new ones, a comprehensive experimental test foreseeing intense particle beam impacts on six different materials, either already used for present BID or under development for future applications, is being prepared at CERN HiRadMat facility. Tests will be run at medium and high intensity using the SPS proton beam (440 GeV). Material characterization will be carried out mostly in real time relying on embarked instrumentation (strain gauges, microphones, temperature and pressure sensors) and on remote acquisition devices (Laser Doppler Vibrometer and High-Speed Camera). Detailed post-irradiation analyses are also foreseen after the cool down of the irradiated materials.

MOP241	An Experiment on Hydrodynamic Tunnelling of the SPS High Intensity Proton Beam at the HiRadMat Facility	target, proton, collider, linear-collider	141
	J. Blanco, F. Burkart, N. Charitonidis, I. Efthymiopoulos, D. Grenier, C. Maglioni, R. Schmidt, C. Theis, D. Wollmann CERN, Geneva, Switzerland E. Griesmayer CIVIDEC Instrumentation, Wien, Austria N.A. Tahir GSI, Darmstadt, Germany
	The LHC will collide proton beams with an energy stored in each beam of 362 MJ. To predict damage for a catastrophic failure of the protections systems, simulation studies of the impact of an LHC beam on copper targets were performed. Firstly, the energy deposition of the first bunches in a target with FLUKA is calculated. The effect of the energy deposition on the target is then calculated with a hydrodynamic code, BIG2. The impact of only a few bunches leads to a change of target density. The calculations are done iteratively in several steps and show that such beam can tunnel up to 30-35 m into a target. Similar simulations for the SPS beam also predict hydrodynamic tunnelling. An experiment at the HiRadMat (High Radiation Materials) at CERN using the proton beam from the Super Proton Synchrotron (SPS) is performed to validate the simulations. The particle energy in the SPS beam is 440 GeV and has up to 288 bunches. Significant hydrodynamic tunnelling due to hydrodynamic effects are expected. First experiments are planned for July 2012. Simulation results, the experimental setup and the outcome of the tests will be reported at this workshop.

MOP242	Experimental Verification for a Collimator with In-jaw Beam Position Monitors	alignment, proton, collimation, closed-orbit	146
	D. Wollmann, O. Aberle, R.W. Aßmann, A. Bertarelli, C.B. Boccard, R. Bruce, F. Burkart, M. Cauchi, A. Dallocchio, D. Deboy, M. Gasior, O.R. Jones, V. Kain, L. Lari, A.A. Nosych, S. Redaelli, A. Rossi, G. Valentino CERN, Geneva, Switzerland
	At present the beam based alignment of the LHC collimators is performed by touching the beam halo with the two jaws of each device. This method requires dedicated fills at low intensities that are done infrequently because the procedure is time consuming. This limits the operational flexibility in particular in the case of changes of optics and orbit configuration in the experimental regions. The system performance relies on the machine reproducibility and regular loss maps to validate the settings. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with in-jaw beam position monitors was proposed and successfully tested with a mock-up collimator in the CERN SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper the results of these experiments are discussed. The measured alignment accuracy is compared to the accuracies achieved with the present collimators in the LHC.

MOP243	Experimental Results of Beam Halo at IHEP	rfq, quadrupole, space-charge, beam-transport	151
	H.F. Ouyang, T. Huang, J. Li, J. Peng, T.G. Xu IHEP, Beijing, People's Republic of China
	Space-charge forces acting in mismatched beams have been identified as a major cause of beam halo. In this paper, we describe the beam halo experimental results in a FODO beam line at IHEP. With this beam transport line, experiments are firstly carried out to determine the main beam parameters at the exit of a RFQ with intense beams, and then the measured beam profiles at different positions are compared with the multi-particle simulation profiles to study the formation of beam halo. The maximum measured amplitudes of the matched and mismatched beam profiles agreed well with simulations. Details of the experiment will be presented.

MOP253	Progress with Bunch-shape Measurements at PSI's High-power Cyclotrons and Proton Beam Lines	proton, cyclotron, scattering, background	187
	R. Dölling PSI, Villigen PSI, Switzerland
	As proposed at HB2010, additional bunch-shape monitors have been installed at the last turns of the Injector 2 cyclotron and at several locations in the connecting beam line to the Ring cyclotron (@72 MeV), as well as behind the Ring cyclotron (@590 MeV). Now at each location in the beam lines, longitudinal-transversal 2D-density distributions of the bunched 2.2 mA proton beam can be taken from four angles of view, each separated by 45°. In addition the monitor in Injector 2 has been upgraded to observe the 13 outermost turns (@57 to 72 MeV), some of them from two or three angles of view. The measurement setup, data evaluation and results are outlined.

MOP254	Design of a Photo-detachment Emittance Instrument for FETS	laser, dipole, emittance, diagnostics	192
	C. Gabor STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom G.E. Boorman, A. Bosco Royal Holloway, University of London, Surrey, United Kingdom A.P. Letchford STFC/RAL, Chilton, Didcot, Oxon, United Kingdom P. Savage Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	Photo detachment is a possibility to diagnose non-destructively H⁻ ion beams. For emittance measurements, the produced neutrals are more suitable then the photo-detached electrons. Such a Photo-Detachment Emittance Measurement Instrument (PD-EMI) is planned for the Front End Test Stand (FETS) at Rutherford Appleton Laboratory (RAL/ UK). FETS comprises a Penning ion source of 60 mA beam current with up to 2 ms pulse length at 50pps, a Low Energy Beam Transport (LEBT), a four-vane RFQ with 3 MeV and a Medium Energy Beam Transport (MEBT) with a chopper system. The PD-EMI will be integrated at the end of the MEBT to commission the RFQ which is currently under construction. The introduction gives an overview some results reached so far and explains the conceptual design. Beam simulations show how to implement this to the MEBT being under construction. The remaining paper concentrates then on the hardware which is the dipole magnet, the laser and optics. The design and and engineering of the magnet chamber needs special attention to both satisfy beam transportation and diagnostics purpose. First measurements about the laser and its parameters will be presented.

MOP255	Acceleration in Vertical Orbit Excursion FFAGs with Edge Focussing	space-charge, proton, acceleration, injection	197
	S.J. Brooks STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	FFAGs with vertical orbit excursion (VFFAGs) provide a promising alternative design for rings with fixed-field superconducting magnets. They have a vertical magnetic field component that increases with height in the vertical aperture, yielding a skew quadrupole focussing structure. Edge focussing can provide an alternating gradient within each magnet, thus reducing the ring circumference. Like spiral scaling horizontal FFAGs (but not non-scaling ones) the machine has fixed tunes and no intrinsic limitation on momentum range. Rings to accelerate the 800MeV beam from the ISIS proton synchrotron are investigated, in terms of both magnet field geometry and longitudinal behaviour during acceleration with space charge. The 12GeV ring produces an output power of at least 2.18MW.

MOP257	Space Charge Limits on the ISIS Synchrotron including the Effects of Images	space-charge, synchrotron, resonance, injection	206
	B.G. Pine, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The ISIS synchrotron provides a pulsed, 50 Hz, 800 MeV proton beam for spallation neutron production. Each pulse from the synchrotron contains ~2.8×10¹³ ppp, and at this beam intensity space charge and image forces have a strong effect on transverse beam dynamics. In order to increase intensity in the present machine, and to prepare for possible upgrades running at a higher intensity, studies are under way aimed at understanding the most critical features of such forces and their impact on beam loss. These studies are focused on working point optimisation, including resonances due to space charge and images. A 2D simulation code, Set, has been developed to improve understanding of transverse dynamics at ISIS, using a particle-in-cell algorithm to include space charge and image forces self-consistently. The ISIS synchrotron has profiled vacuum vessels and RF shields which conform to the shape of the beam envelope, and have a distinctive influence on the beam dynamics. Set is specifically designed to include these image forces. A systematic simulation study of possible working points is presented, along with an assessment of the effect on apertures.

MOP258	Simulation of Intense Proton Beams in Novel Isochronous FFAG Designs	space-charge, lattice, cyclotron, extraction	211
	S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom M. Berz, K. Makino MSU, East Lansing, Michigan, USA C. Johnstone Fermilab, Batavia, USA P. Snopok Illinois Institute of Technology, Chicago, Illinois, USA
	Recent developments in the design of non-scaling fixed field alternating gradient (FFAG) accelerators have been focused on achieving isochronous behavior with a small betatron tune excursion. These advances are particularly interesting for applications requiring CW beams, such as Accelerator Driven Systems for energy generation or waste transmutation. The latest advances in lattice design have resulted in a 330 MeV to 1 GeV lattice, isochronous to better than ± 1 percent. This paper reports on simulations of recent lattice designs incorporating 3D space charge effects.

MOP260	Beam Halo Measurements using Adaptive Masking Methods and Proposed Recent Halo Experiment	quadrupole, injection, space-charge, diagnostics	215
	H.D. Zhang, B.L. Beaudoin, S. Bernal, R.B. Fiorito, R.A. Kishek, K. Řežaei, A.G. Shkvarunets UMD, College Park, Maryland, USA
	Beam halo is a common phenomenon in particle beams, especially for modern, advanced accelerators where high beam intensities lead to strong space charge. Halo is generally understood as a population of particles that do, or will, reach large transverse radii relative to a more intense, centralized beam core. It is associated with emittance growth, beam quality degradation and particle loss. The particle-core model [1] is commonly used to describe halo formation as the result of a parametric resonance due to envelope mismatch. Few experiments have been carried out to test this theory [2]. Measurement of beam halo is particularly problematic for faint halos, where light from the intense core obscures the optical image of the halo. In this paper, we present a new diagnostic for high-dynamic range halo measurements based on adaptive masking of the beam core [3]. We also present the design of an experiment to study halo formation from envelope mismatch for beams spanning a wide range of intensities on the University of Maryland Electron Ring (UMER) [4]. [1] R. Gluckstern, Phys. Rev. Lett., vol.73, 1994. [2] C. Allen, Phys. Rev. Lett. Vol 89, 1998 [3] H. Zhang, et al., Proc of PAC11. [4] R.A. Kishek, these proceedings.

MOP262	Observations of Space Charge Effects in the Spallation Neutron Source Accumulator Ring	coupling, space-charge, accumulation, target	223
	R.E. Potts ORNL RAD, Oak Ridge, Tennessee, USA S.M. Cousineau, J.A. Holmes ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The Spallation Neutron Source accumulator ring was designed to allow independent control of the transverse beam distribution in each plane. However, at high beam intensities, nonlinear space charge forces can strongly influence the final beam distribution and compromise our ability to independently control the transverse distributions. In this study we investigate the evolution of the beam at intensities of up to ~8x10¹³ ppp through both simulation and experiment. Specifically, we analyze the evolution of the beam distribution for beams with different transverse aspect ratios and tune splits. We present preliminary results of simulations of our experiments.

TUO1A03	Space Charge Effects in Isochronous FFAGs and Cyclotrons	space-charge, cyclotron, focusing, TRIUMF	231
	T. Planche, R.A. Baartman, Y.-N. Rao TRIUMF, Vancouver, Canada
	Effects of space charge forces on the beam dynamics of isochronous rings will be discussed. Two different kinds of phenomena will be introduced through a brief review of the literature on the topic. The first one is a consequence of the very weak vertical focusing found in the low energy region of most cyclotrons. The space charge tune shift further reduces the vertical focusing, setting an upper limit on instantaneous current. The second one arises from the fact that longitudinal phase space is frozen in isochronous rings. This leads to effects of space charge forces which are very peculiar to isochronous machines. We will finally present the simulation tools being developed at TRIUMF to study these effects.
	Slides TUO1A03 [0.974 MB]

TUO3A01	Dynamical Aspects of Emittance Coupling in Intense Beams	emittance, resonance, linac, coupling	240
	I. Hofmann GSI, Darmstadt, Germany I. Hofmann HIJ, Jena, Germany
	In this paper we study in an idealized lattice model the dynamical behavior of non-equipartitioned beams and of approach to equipartition. It is shown that emittance transfer depends on times scales of tune change, but also the direction of crossing the stopbands of space charge resonances. This provides additional information to support the stability charts suggested previously as design tool for high current linacs.
	Slides TUO3A01 [4.897 MB]

TUO3B05	Beam Dynamics of the 13 MeV/50 mA Proton Linac for the Compact Pulsed Hadron Source at Tsinghua University	rfq, proton, DTL, target	289
	Q.Z. Xing, X. Guan, C. Jiang, C.-X. Tang, X.W. Wang, H.Y. Zhang, S.X. Zheng TUB, Beijing, People's Republic of China J.H. Billen, J. Stovall, L.M. Young TechSource, Santa Fe, New Mexico, USA G.H. Li NUCTECH, Beijing, People's Republic of China
	Funding: Work supported by the Major Research plan of the National Natural Science Foundation of China (Grant No. 91126003) We present the start-to-end simulation result on the high-current proton linac for the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. The CPHS project is a university-based proton accelerator platform (13 MeV, 16 kW, peak current 50 mA, 0.5 ms pulse width at 50 Hz) for multidisciplinary neutron and proton applications. The 13 MeV proton linac contains the ECR ion source, LEBT, RFQ, DTL and HEBT. The function of the whole accelerator system is to produce the proton beam, accelerate it to 13 MeV, and deliver it to the target where one uniform round beam spot is obtained with the diameter of 5 cm.
	Slides TUO3B05 [7.715 MB]

TUO1C01	Recent Developments on High Intensity Beam Diagnostics at SNS	electron, proton, cathode, target	292
	W. Blokland ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The Spallation Neutron Source Ring accumulates 0.6 μs long proton bunches of up to 1.6·10¹⁴ protons with a typical peak current of over 50 A during a 1 ms cycle. To qualify the beam, we perform different transverse profile measurements that can be done at full intensity. The electron beam scanner performs a non-invasive measurement of the transverse and longitudinal profiles of the beam in the ring. Electrons passing over and through the proton beam are deflected and projected on a fluorescent screen. Analysis of the projection yields the transverse profile while multi transverse profiles offset in time yield the longitudinal profile. Progress made with this system will be discussed as well as temperature measurements of the stripping foil and other transverse measurements.
	Slides TUO1C01 [15.498 MB]

TUO1C04	Detection of Unidentified Falling Objects at LHC	emittance, proton, beam-losses, injection	305
	E. Nebot Del Busto, T. Baer, F.V. Day, B. Dehning, E.B. Holzer, A. Lechner, R. Schmidt, J. Wenninger, C. Zamantzas, M. Zerlauth, F. Zimmermann CERN, Geneva, Switzerland M. Hempel BTU, Cottbus, Germany
	About 3600 Ionization Chambers are located around the LHC ring to detect beam losses that could damage the equipment or quench superconducting magnets. The BLMs integrate the losses in 12 different time intervals (from 40 μs to 83.8 s) allowing for different abort thresholds depending on the duration of the loss and the beam energy. The signals are also recorded in a database at 1 Hz for offline analysis. Since the 2010 run, a limiting factor in the machine availability occurred due to unforeseen sudden losses appearing around the ring on the ms time scale. Those were detected exclusively by the BLM system and they are the result of the interaction of macro-particles, of sizes estimated to be 1-100 microns, with the proton beams. In this document we describe the techniques employed to identify such events as well as the mitigations implemented in the BLM system to avoid unnecessary LHC downtime.
	Slides TUO1C04 [6.812 MB]

WEO1A01	Impedance Studies of 2D Azimuthally Symmetric Devices of Finite Length	impedance, coupling, resonance, cavity	344
	N. Biancacci, E. Métral, B. Salvant CERN, Geneva, Switzerland N. Biancacci Rome University La Sapienza, Roma, Italy M. Migliorati, L. Palumbo URLS, Rome, Italy V.G. Vaccaro Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli, Italy
	In circular accelerators, the beam quality can be strongly affected by the self-induced electromagnetic fields excited by the beam in the passage through the elements of the accelerator. The beam coupling impedance quantifies this interaction and allows predicting the stability of the dynamics of high intensity, high brilliance beams. The coupling impedance can be evaluated with finite element methods or using analytical methods, such as Field Matching or Mode Matching. In this paper we present an application of the Mode Matching technique for an azimuthally uniform structure of finite length: a cylindrical cavity loaded with a toroidal slab of lossy dielectric, connected with cylindrical beam pipes. In order to take into account the finite length of the structure, with respect to the infinite length approximation, we decompose the fields in the cavity into a set of orthonormal modes. We obtain a complete set of equations using the magnetic field matching and the non-uniform convergence of the electric field on the cavity boundaries. We present benchmarks done with CST Particle Studio simulations and existing analytical formulas, pointing out the effect of finite length and non-relativistic beta.
	Slides WEO1A01 [6.689 MB]

WEO1A03	Resistive Wall Instability in CSNS/RCS	impedance, extraction, injection, wakefield	354
	L. Huang, Y.D. Liu, S. Wang IHEP, Beijing, People's Republic of China
	Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton accelerator, with average beam power of 100kW. The collective effects caused by the coupling impedance may be the limit to beam power. The impedance estimation for components on beam line shows that the resistive wall impedance and its instability are more serious than any others. Based on the impedance budget, the instability is theoretically estimated. A simple resistive wall wake field model is used to simulate the bunch oscillation and obtain the growth time. In this simulation model, the continuous resistive wall wake field is concentrated to one position in the ring and the long bunch is sliced into many micro-bunches. By tracking the dynamics of the macro-bunches, the transverse growth time are obtained. The simulation results are also confirmed the restriction to instability by natural chromaticity. # Supported by National Natural Science Foundation of China (11175193) *wangs@ihep.ac.cn
	Slides WEO1A03 [1.358 MB]

WEO3A02	Beam Loss and Collimation in the ESS Linac	linac, proton, DTL, collimation	368
	R. Miyamoto, B. Cheymol, H. Danared, M. Eshraqi, A. Ponton, J. Stovall, L. Tchelidze ESS, Lund, Sweden I. Bustinduy ESS Bilbao, Bilbao, Spain A.I.S. Holm, S.P. Møller, H.D. Thomsen ISA, Aarhus, Denmark
	The European Spallation Source (ESS), to be built in Lund, Sweden, is a spallation neutron source based on a 5 MW proton linac. A high power proton linac has a tight tolerance on beam losses to avoid activation of its components and it is ideal to study patterns of the beam loss and prepare beam loss mitigation schemes at the design stage. This paper presents simulations of the beam loss in the ESS linac as well as beam loss mitigation schemes using collimators in beam transport sections.
	Slides WEO3A02 [6.377 MB]

WEO1B04	On Scaling Properties of Third-order Resonance Crossing in Particle Accelerators	resonance, emittance, betatron, booster	394
	S.-Y. Lee Indiana University, Bloomington, Indiana, USA K.Y. Ng Fermilab, Batavia, USA
	Funding: Work supported by the US DOE under contract DEFG02-92ER40747, DE-AC02-07CH11359, and the NSF under contract PHY-0852368 with NSF. The effects of resonances on high power hadron accelerators are explored. These resonances include systematic space-charge resonances, third-order resonance, and other weak random resonances that are often present in FFAG and other RCS accelerators. The distortion of invariant torus during resonance crossing is used to set limit on emittance growth or fraction of particle trapped. The critical resonance strength in the ring lattice is determined from a simple scaling law derived as a function of the tune-ramp rate and initial emittance. Such scaling law can be useful in the evaluation of the performance in high power accelerators.
	Slides WEO1B04 [1.074 MB]

WEO1C01	Effect of Self-consistency on Periodic Resonance Crossing	resonance, space-charge, ion, synchrotron	429
	G. Franchetti GSI, Darmstadt, Germany
	In high intensity bunched beams resonance crossing gives rise to emittance growth and beam loss. Both these effects build up after many synchrotron oscillations. Up to now long term modeling have relied on frozen models neglecting the physics of self-consistency. We address here this issue and present the state of the art of simulations also applied to the SIS100.
	Slides WEO1C01 [3.657 MB]

WEO1C02	Simulation and Measurement of Half Integer Resonance in Coasting Beams in the ISIS Ring	resonance, injection, synchrotron, space-charge	434
	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
	ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a high intensity proton synchrotron, accelerating 3·10¹³ ppp from 70-800 MeV, at a repetition rate of 50 Hz. Present studies are looking at key aspects of high intensity behaviour with a view to increasing operational intensity, identifying optimal upgrade routes and understanding loss mechanisms. Of particular interest is the space charge limit imposed by half integer resonance: we present results from coasting beam experiments with the ISIS ring in storage ring mode, along with detailed 3D (ORBIT) simulations to help interpret observations. The methods for experimentally approaching resonance, and the implications on beam behaviour, measurement and interpretation are discussed. In addition, results from simpler 2D simulations and analytical models are used to help interpret expected beam loss and halo evolution. Plans and challenges for the measurement and understanding of this important beam loss mechanism are summarised, as are some closely related areas of high intensity work on ISIS.
	Slides WEO1C02 [2.224 MB]

WEO1C03	Longitudinal Beam Loss Studies of the CERN PS-to-SPS Transfer	cavity, emittance, injection, impedance	439
	H. Timko, T. Argyropoulos, T. Bohl, H. Damerau, J. Esteban Müller, S. Hancock, E.N. Shaposhnikova CERN, Geneva, Switzerland
	Bunch-to-bucket transfer between the Proton Synchrotron (PS) and the Super Proton Synchrotron (SPS) is required before beams can enter the Large Hadron Collider. The overall beam loss at this transfer is currently around 5-10 %, and is increased for higher intensities or larger longitudinal emittances. Previous attempts to reduce the losses with additional RF voltage from spare cavities in the PS were unsuccessful. In this paper, we modelled the complete PS flat-top bunch splitting and rotation manipulations, PS-to-SPS transfer, SPS flat bottom and acceleration ramp using end-to-end simulations. Starting from the measured bunch distributions, the simulations provide an accurate insight into the problem and allow direct benchmarking with experiments. As a result, it was understood and confirmed by measurements that shorter bunches do not necessarily lead to better transmission. The particle distribution in longitudinal phase space at PS extraction should be optimised instead. A significant loss reduction of up to 50 % is expected from simulations; experimental studies are on-going to verify these theoretical findings.
	Slides WEO1C03 [3.903 MB]

WEO1C06	Measurement and Simulation of Luminosity Leveling in LHC via Beam Separation	luminosity, emittance, beam-beam-effects, target	451
	S. Paret, J. Qiang LBNL, Berkeley, California, USA R. Alemany-Fernandez, R. Calaga, R. Giachino, W. Herr, D. Jacquet, G. Papotti, T. Pieloni, L. Ponce, M. Schaumann CERN, Geneva, Switzerland R. Miyamoto ESS, Lund, Sweden
	Funding: This work supported by the US LHC Accelerator Research Program and the National Energy Research Scientific Computing Center of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Leveling of the luminosity in LHC by means of separating the beams colliding at an interaction point is examined. An experiment in which the separation of the beams was stepwise increased to up to 2.5 times the beam width is presented. The luminosity at all IPs and emittance of the beams were measured to detect possible side effects of the collision with an offset. Strong-strong simulations that closely follow the experimental setup are discussed and compared with the measurements. Finally, potential alternatives for luminosity leveling are briefly described.
	Slides WEO1C06 [1.031 MB]

WEO3C01	Injection and Stripping Foil Studies for a 180 MeV Injection Upgrade at ISIS	injection, synchrotron, dipole, electron	456
	B. Jones, D.J. Adams, M.C. Hughes, S.J.S. Jago, B.G. Pine, H. V. Smith, C.M. Warsop, R.E. Williamson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The Rutherford Appleton Laboratory (RAL) is home to ISIS, the world's most productive spallation neutron source. ISIS has two neutron producing target stations (TS-1 and TS-2), operated at 40 Hz and 10 Hz respectively with a 50 Hz, 800 MeV proton beam from a rapid cycling synchrotron (RCS), which is fed by a 70 MeV H− drift tube linac. The multi-turn charge-exchange injection process used on ISIS has been the subject of a programme of detailed studies in recent years including benchmarked simulations and experiments. More recently, these studies have been expanded as plans for upgrading ISIS have focussed on replacement of the 70 MeV linac with a new, higher energy injector and a new synchrotron injection straight. Whilst much of these studies have been reported elsewhere, this paper presents a summary of the programme with some further details.
	Slides WEO3C01 [4.895 MB]

THO1A01	Beam-beam Effects in RHIC	proton, electron, resonance, emittance	479
	Y. Luo, M. Bai, W. Fischer, C. Montag, S.M. White BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In this article we will review the beam-beam effects in the Relativistic Heavy Ion Collider (RHIC). We will cover the experimental observations, beam-beam simulation techniques and results, and head-on beam-beam compensation with electron lenses. The next luminosity goal in the RHIC polarized proton operation is to double the luminosity with a higher proton bunch intensity. After the upgrade, the beam-beam parameter will reach 0.03. Head-on beam-beam compensation is aimed to reduce the beam-beam tune spread and non-linear beam-beam resonance driving terms.
	Slides THO1A01 [1.355 MB]

THO1A02	Effects of Magnetic Field Tracking Errors and Space Charge on Beam Dynamics at CSNS/RCS	space-charge, quadrupole, resonance, lattice	484
	S.Y. Xu, N. Wang, S. Wang IHEP, Beijing, People's Republic of China
	The China Spallation Neutron Source (CSNS) is an accelerator-based facility. It operates at 25 Hz repetition rate with an design beam power of 100 kW. CSNS consists of a 1.6-GeV Rapid Cycling Synchrotron (RCS) and a 80-MeV linac. The lattice of the CSNS/RCS is triplet based four-fold structure. The preferred working points of CSNS/RCS are (4.86, 4.78) which can avoid the major low-order structure resonances. But because of the chromatic tune shift, space-charge incoherent tune shift and the tune shift caused by magnetic field tracking errors between the quadrupoles and the dipoles, some structure resonances are unavoidable. The chromaticity, space charge effects and magnetic field tracking errors can also induce beta function distortion, and influence the transverse acceptance and the collimation efficiency of the collimation system. In this paper we show results of space-charge simulations introducing magnetic field tracking errors and discuss the combined effects of chromaticity, magnetic field tracking errors and space charge on the beam dynamics for CSNS/RCS.
	Slides THO1A02 [1.613 MB]

THO1A03	Dual-harmonic Acceleration Studies at CSNS RCS	injection, acceleration, bunching, cavity	487
	J.F. Chen, J.Y. Tang, X. Zhang IHEP, Beijing, People's Republic of China
	Dual harmonic acceleration is proposed to alleviate the space charge effects in the RCS (Rapid Cycling Synchrotron) at the upgrading stages of the CSNS (China Spallation Neutron Source). Different dual harmonic acceleration schemes have been studied by using a self-made parameter calculation code - RAMADH and the simulation code - ORBIT. Both complete and partial coverage of the dual harmonic RF system along the acceleration have been considered. The injection by combining beam chopping and off-momentum is used in the macro-particle tracking simulations by ORBIT. In addition, a new idea that unlocks the RF frequency and the magnetic field in the injection period is found very useful in obtaining a good longitudinal painting.
	Slides THO1A03 [1.343 MB]

THO1A04	High Intensity Longitudinal Dynamics Studies for an ISIS Injection Upgrade	injection, synchrotron, bunching, space-charge	492
	R.E. Williamson, D.J. Adams, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the world's most productive pulsed 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 from 70 MeV to 800 MeV, delivering a mean beam power of 0.2 MW. Recent upgrade studies at ISIS have centred on a new 180 MeV linac for injection into the existing ring offering the possibility of beam powers in the 0.5 MW regime through reduction in space charge and optimized injection. A central and critical aspect of such an upgrade is the longitudinal dynamics including beam stability, associated RF parameters, space charge levels and stringent requirements on beam loss. This paper outlines possible longitudinal injection schemes for the injection upgrade meeting key design requirements such as minimising halo, bunching factor and satisfying the Keil-Schnell-Boussard (KSB) stability criterion throughout acceleration. Details of simulation models including calculation of KSB are given together with associated assumptions. Latest results from studies to understand and confirm stability limits on ISIS via simulation and experiment are presented.
	Slides THO1A04 [2.641 MB]

THO3A01	High Intensity Aspects of J-PARC Linac Including Re-commissioning after Earthquake	linac, multipactoring, DTL, rfq	497
	M. Ikegami, K. Futatsukawa, T. Miyao KEK, Ibaraki, Japan Y. Liu KEK/JAEA, Ibaraki-Ken, Japan T. Maruta, A. Miura, J. Tamura JAEA/J-PARC, Tokai-mura, Japan
	We had a massive earthquake in March 2011, which forced us to shutdown J-PARC accelerators for nearly nine months due to its resultant damages. After significant restoration effort, we resumed the beam operation of J-PARC linac in December 2011 and user operation in January 2012. Subsequently, we restored the same beam power as just before the earthquake in March 2012. In the course of the beam commissioning after the earthquake, we have experienced beam losses which were not observed before the earthquake. We discuss the experimentally observed beam losses and its comparison with particle simulations.
	Slides THO3A01 [5.249 MB]

THO3A03	Simulations and Measurements in High Intensity LEBT with Space Charge Compensation	emittance, injection, space-charge, rfq	507
	N. Chauvin CEA/IRFU, Gif-sur-Yvette, France O. Delferrière, R. Gobin, P.A.P. Nghiem, D. Uriot CEA/DSM/IRFU, France R.D. Duperrier ESS, Lund, Sweden
	Over the last years, the interest of the international scientific community for high power accelerators in the megawatt range has been increasing. One of the major challenges is to extract and transport the beam while minimizing the emittance growth in the Low Energy Beam Transport line (LEBT). Consequently, it is crucial to perform precise simulations and cautious design of LEBT. In particular, the beam dynamics calculations have to take into account not only the space charge effects but also the space charge compensation of the beam induced by ionization of the residual gas. The code SOLMAXP has been developed in CEA-Saclay to perform self-consistent calculations taking into account space charge compensation. Extensive beam dynamics simulations have been done with this code to design the IFMIF LEBT (Deuteron beam of 125 mA at 100 keV, cw). The commissioning of the IFMIF injector started a few months ago and emmittance measurements of H⁺ and D⁺ beams have been done. The first experimental results will be presented and compared to simulation.
	Slides THO3A03 [3.165 MB]

THO3B01	Proton Beam Inter-Bunch Extinction and Extinction Monitoring for the Mu2e Experiment	proton, dipole, target, collimation	532
	E. Prebys Fermilab, Batavia, USA
	Funding: U.S. Department of Energy The goal of the Mu2e experiment at Fermilab will be the search for the conversion of a muon into an electron in the field of a nucleus, with a precision roughly four orders of magnitude better than the current limit. The experiment requires a beam consisting of short (~200 ns FW) bunches of protons are separated by roughly 1.5 microseconds. Because the most significant backgrounds are prompt with respect to the arrival of the protons, out of time beam must be suppressed at a level of at least 10^-10 relative to in time beam. The removal of out of time beam is known as "extinction". This talk will discuss the likely sources of out of time beam and the steps we plan to take to remove it. In addition, the plan for monitoring the extinction level will be presented.
	Slides THO3B01 [6.380 MB]

THO3B04	Beam Dynamics Studies of H⁻ Beam Chopping in a LEBT for Project X	ion, emittance, solenoid, ion-source	546
	Q. Ji, D.P. Grote, A.R. Lambert, D. Li, T. Schenkel, J.W. Staples LBNL, Berkeley, California, USA
	Funding: This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231. Project X is proposed as a high intensity proton facility at Fermilab to support a world-leading program in neutrino and flavor physics over the next several decades. The front-end consists of an H⁻ ion source, low-energy beam transport (LEBT), and 162.5 MHz CW Radio-Frequency-Quadrupole (RFQ) accelerator. The LEBT design, currently under study at LBNL, would comprise two solenoids, a dipole magnet and a chopper. The LEBT chopper is designed to achieve 1 MHz beam chopping of a partially neutralized 30 keV, 5 mA H⁻ beam. Preliminary simulation studies show that chopping the beam before the second solenoid is more efficient in terms of chopper bias voltages. However, the space charge neutralization will be lost along the beam after the chopper and through the second solenoid. A beam dynamics study, using WARP 3D (a Particle-in-cell simulation code), has been carried out to investigate both the time-dependence of the partial neutralization in the segment after the chopper, as well as the beam stability and emittance growth. Benchmark experiments are ongoing and simulation and experimental results will be presented in this Workshop.
	Slides THO3B04 [1.868 MB]

FRO1A01	Summary of Working Group A: Beam Dynamics in High-Intensity Circular Machines	space-charge, luminosity, ion, resonance	606
	E. Métral CERN, Geneva, Switzerland G. Franchetti GSI, Darmstadt, Germany J.A. Holmes ORNL, Oak Ridge, Tennessee, USA
	In this proceeding we summarize the presentations of the HB2012 Workshop session on 'Beam Dynamics in High-Intensity Circular Machines' as well as the outcome of the discussion session. This working group hosted 29 presentations in dedicated sessions plus 5 presentations in a joint session with the working C.
	Slides FRO1A01 [7.420 MB]

FRO1A03	Accelerator System Design, Injection, Extraction and Beam-Material Interaction: Working Group C Summary Report	collimation, injection, ion, proton	615
	N.V. Mokhov Fermilab, Batavia, USA D. Li LBNL, Berkeley, California, USA
	Working Group C summary:The performance of high beam power accelerators is strongly dependent on appropriate injection, acceleration and extraction system designs as well as on the way interactions of the beam with machine components are handled. The experience of the previous ICFA High-Brightness Beam workshops has proven that it is quite beneficial to combine analyses and discussion of these issues in one group, WG-C at this Workshop. A broad range of topics was presented and discussed in twenty talks at four WG-C sessions as well as at two joint WGA/C and WG-B/C sessions. Highlights from these talks, outstanding issues along with plans and proposals for future work are briefly described.
	Slides FRO1A03 [4.907 MB]

FRO1B01	Summary of the Working Group on Commissioning and Operation	beam-losses, linac, injection, proton	620
	R. Schmidt CERN, Geneva, Switzerland M.A. Plum ORNL, Oak Ridge, Tennessee, USA Y. Sato J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	The Working Group D summary report focussed on answering the following issues: observation of beam losses (e.g. time structure, other parameters,…), reducing beam losses with operational parameters away from the design set points, reducing beam losses (or concentrating beam losses at a few locations) using collimators, minimizing beam losses due to beam transfer from one accelerator to the following accelerator - what parameters are important? The issue of reducing beam losses with operational parameters away from the design set points is especially valuable as it is rarely discussed.
	Slides FRO1B01 [0.426 MB]

Paper

Title

Other Keywords

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MOI1C01

Intense-beam Issues in CSNS and C-ADS Accelerators

linac, cavity, emittance, lattice

25

S. Fu, S.X. Fang, Z. Li, J. Peng, J.Y. Tang, S. Wang, F. Yan
IHEP, Beijing, People's Republic of China

In 2011 construction of two intense-beam accelerators were launched for China Spallation Neutron Source (CSNS) project and China Accelerator Driven System (C-ADS) project. CSNS uses a pulsed accelerator with an H⁻ linac and a rapid cycling synchrotron, and C-ADS has a CW proton linac with superconducting cavities. In both cases, the beam power is high and beam loss control is a key issue in beam dynamics. Beam emittance growth and beam halo formation must be carefully studied in beam dynamics and well controlled in machine design. This paper will present a brief introduction to the physics design of the two intense-beam accelerators, especially on the issue of beam instability. In their linac design equapartitioning focusing scheme is adopted to avoid coupling instability. Some beam halo formation experimental results due to mismatching will be compared with simulations. Beam halo generation due to the quench of superconducting cavity and magnet is investigated in detail and compensation scheme is also proposed. Beam loss study for the error effects and orbit correction will be presented.

Slides MOI1C01 [3.747 MB]

MOI1C02

Challenges in Benchmarking of Simulation Codes against Real High Intensity Accelerators

space-charge, resonance, emittance, linac

30

I. Hofmann
GSI, Darmstadt, Germany

Benchmarking of simulation codes for linear or circular accelerators involves several levels of complexity, which will be revisited and discussed in this talk. As ultimate goal of benchmarking it is hoped that a predictive capacity and a practical control over emittance growth and/or beam loss can be obtained. We first give some examples of how simulation codes can be used to gain as much understanding of the underlying physics mechanisms as possible, which is an almost inevitable first step. With more and more experimental data from running high intensity accelerators having become available in recent years more questions need to be raised: Besides the proper physics, can we feed our codes with an accurate enough model of the real machine? What actually is the required accuracy, and does a specific accelerator have enough diagnostics to enable this accuracy? In the paper we explore these questions by discussing several examples of benchmarking efforts, their achievements as well as the limits and difficulties that have been encountered.

Slides MOI1C02 [2.838 MB]

MOP203

Bunch-by-Bunch Beam Loss Diagnostics with Diamond Detectors at the LHC

beam-losses, injection, proton, kicker

41

M. Hempel
BTU, Cottbus, Germany
T. Baer
University of Hamburg, Hamburg, Germany
S. Bart Pedersen, B. Dehning, E. Effinger, E. Griesmayer, A. Lechner, R. Schmidt
CERN, Geneva, Switzerland
W. Lohmann
DESY, Hamburg, Germany

A main challenge in the operation with high intensity beams is managing beam losses that imply the risk of quenching superconducting magnets or even damage equipment. There are various sources of beam losses, such as losses related to injection, to beam instabilities and to UFOs (Unidentified Falling Objects). Mostly surprising in the first years of LHC operation was the observation of UFOs. They are believed to be dust particles with a typical size of 1-100 um, which lead to beam losses with a duration of about ten revolutions when they fall into the beam. 3600 BLMs (Beam Loss Monitors) are installed around the LHC ring, allowing to determinate the accurate location of UFOs. The time resolution of the BLMs is 40 us (half a turn revolution). A measurement of the beam losses with a time resolution better than the bunch spacing of 50 ns is crucial to understand loss mechanisms. Diamond sensors are able to provide such diagnostics and perform particle counting with ns time resolution. In this paper, we present measurements of various types of beam losses with diamond detectors. We also compare measurements of UFO induced beam losses around the LHC ring with results from MadX simulations.

MOP204

A Method to Measure the Incoherent Synchrotron Frequencies in Bunches

space-charge, synchrotron, dipole, injection

46

O. Chorniy, H. Reeg
GSI, Darmstadt, Germany

The method of measuring the incoherent synchrotron frequencies in a stationary bunch is presented. It can be shown that by measuring the local current at a fixed coordinate in RF bucket the corresponding incoherent synchrotron frequency can be obtained. Test calculations were done using simulation data where longitudinal space charge effects were included. The incoherent frequencies obtained with method are in a good agreement with theory. In real experiment, the incoherent frequencies were determined from bunch profiles recorded in the SIS18 with low intensity beam at injection energy. Bunch profiles were measured with a new Fast Current Transformer which has a relatively broad frequency range. The profiles were recorded using 8 bit resolution oscilloscope. The frequency spectra of local current fluctuation at different longitudinal positions were obtained numerically. The strongest lines in these spectra were at positions of theoretically expected incoherent frequencies. In this paper the method is described in details, the comparison of incoherent frequencies obtained from the simulation and measurement data with theoretical solutions is shown.

MOP207

Planning for Experimental Demonstration of Transverse Emittance Transfer at the GSI UNILAC through Eigen-emittance Shaping

emittance, quadrupole, coupling, scattering

57

C. Xiao, O.K. Kester
IAP, Frankfurt am Main, Germany
L. Groening
GSI, Darmstadt, Germany

The minimum transverse emittances achievable in a beam line are determined by the two transverse eigen-emittances of the beam. For vanishing interplane correlations they are equal to the well-know rms-emittances. Eigen-emittances are constants of motion for all symplectic beam line elements, i.e. (even tilted) linear elements. To allow for rms-emittance transfer, the eigen-emittances must be changed by applying a non-symplectic action to the beam, preferably preserving the 4d-rms-emittance. This contribution will introduce the concept for eigen-emittance shaping and rms-emittance transfer at an ion linac. A path towards the experimental demonstration of the concept at the GSI UNILAC is presented.

MOP210

Beam Stacking for High Intensity Pulsed Proton Beam with FFAG

acceleration, extraction, neutron, injection

64

Y. Mori, Y. Ishi, Y. Kuriyama, J.-B. Lagrange, T. Uesugi
Kyoto University, Research Reactor Institute, Osaka, Japan

Multi-beam stacking scheme to generate an intense short-pulsed proton beam with high repetition proton FFAG is presented.

MOP212

Simulation of Longitudinal Beam Instability caused by HOMs

HOM, linac, cavity, damping

73

P. Cheng, Z. Li, J.Y. Tang, J.Q. Wang
IHEP, Beijing, People's Republic of China

Superconducting cavities are employed in C-ADS linac to accelerate 10mA CW proton beams from 3.2 MeV to 1.5 GeV. High order modes in superconducting cavities are found by using the simulation tools CST and HFSS, then power dissipation caused by HOMs have been investigated, it is indicated that the Qext should not go beyond 10⁷} in order to limit the additional heat load. Beam instabilities caused by high order modes in elliptical cavity sections are investigated using the code offered by Dr. Jean-Luc Biarrotte (CNRS, IPN Orsay, France). Beam errors, linac errors and high order modes frequency spread are investigated in detail. It shows that the monopole modes do not affect the proton beam critically and need no HOM couplers (Q_ext=10⁵}) if high order modes frequency spread is more than 100 kHz.

MOP216

The Design Study on the Longitudinal Beam Dynamics for CSNS/RCS

injection, acceleration, space-charge, bunching

89

N. Wang, M.Y. Huang, Y. Li, S. Wang, S.Y. Xu, Y.S. Yuan
IHEP, Beijing, People's Republic of China

Rapid Cycling Synchrotron (RCS) is the key part of China Spallation Neutron Source (CSNS) accelerators. The RCS accumulates and accelerates 80 MeV beam from linac to 1.6 GeV. The particle number is 1.56·10¹³ for each pulse, with repetition rate of 25 Hz. In the RCS, longitudinal beam dynamics plays a crucial role in achieving high intensity beam with low beam loss. Longitudinal parameters are studied and optimized for efficient RF trapping of the beam in the longitudinal phase space. Beam performance is investigated by particle tracking simulations. Beam dynamic issues related to the high order mode induced by the RF generator are studied with a new developed code. Primary study on the adoption of dual harmonic cavity for higher beam power is also addressed.

MOP219

Error Analysis and Correction Scheme in C-ADS Injector-I

emittance, linac, cavity, solenoid

99

C. Meng, Z. Li, J.Y. Tang
IHEP, Beijing, People's Republic of China

Funding: Supported by the China ADS Project (XDA03020000)
C-ADS Injector-I is a 10 mA 10 MeV CW proton linac. It uses a 3.2MeV normal conducting 4-Vane RFQ and 12 superconducting single-Spoke cavities. According to the detailed sensitivity analysis of alignment and RF errors, the error tolerance of both static and dynamic ones for Injector-I are presented. The simulation results show that with the error tolerance there are beam losses, the residual orbit is too large which will produce significant emittance growth, so the correction is necessary for Injector-I. After detailed numerical studies, a correction scheme and monitor distributions are proposed. After correction the RMS residual orbit can be controlled within 0.4mm and RMS emittance growth can be controlled within 10%, but it still has 1.7×10^-6 beam loss, which comes from the RF errors and low longitudinal acceptance. According to detailed analysis and simulations with 10⁸ macro particles, as a consequence, longitudinal emittance control and longitudinal distribution control as well as large longitudinal acceptance are the key to minimizing beam losses in low energy section. To minimize beam loss, a short period Injector-I lattice with larger longitudinal acceptance have been designed and performance very good error tolerance.

MOP221

Physics Design of the C-ADS Main Linac Based on Two Different Injector Design Schemes

linac, emittance, lattice, cavity

107

F. Yan, Z. Li, C. Meng, J.Y. Tang
IHEP, Beijing, People's Republic of China

Funding: Supported by Advanced Research Project of the Chinese Academy of Science
Two design schemes for the main linac of C-ADS (China Accelerator Driven Subcritical system) are presented in this paper. They are corresponding to two different injector schemes. Injector-II scheme makes use of room-temperature RFQ and superconducting HWR cavities with the RF frequency of 162.5 MHz; Injector-I scheme makes use of higher-energy RFQ and superconducting spoke cavities with the RF frequency of 325 MHz. At the first choice, a relatively smaller longitudinal emittance is adopted for the RFQ designs with both the injector schemes to obtain more efficient acceleration. However, compared with the injector-I scheme, with the injector-II scheme, bunch current will be doubled in the main linac due to the half RF frequency in the injector-II. This means stronger space charge effects. Alternate design for the main linac with the injector-II scheme is to increase the longitudinal emittance by 50% so that the space charge effects will be alleviated. However, totally 30 cavities more and 36 m longer in the main linac have to be paid for this design scheme. The design considerations, the lattice designs, the simulation results including halo information are presented.

MOP229

Design of the MEBT1 for C-ADS Injector II

quadrupole, emittance, DTL, rfq

115

H. Jia, Y. He, S.C. Huang, C.L. Luo, M.T. Song, Y.J. Yuan, X. Zhang
IMP, Lanzhou, People's Republic of China

The MEBT1 of Chinese ADS Injector II is described. It transports a 2.1 MeV, 10 mA CW proton beam through a series of 7 quadruples and two buncher cavities from the RFQ to the superconducting DTL. For emittance preservation, a compact mechanical design is required. Details of the beam dynamics and mechanical design will be given.

MOP231

Study of Non-equi-partitioning Lattice Setting and IBS Effects for J-PARC Linac Upgrade

emittance, lattice, linac, DTL

118

Y. Liu
IMP, Lanzhou, People's Republic of China
M. Ikegami
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

For the coming upgrade of J-Parc, the peak power of linac will be greatly increased. This may open many interesting questions. For instance, for efficient acceleration from 19 0MeV to 400 MeV the annular coupled structure (ACS) was applied with frequency jump from 324 MHz to 972 MHz. Upstream part of J-PARC linac from the frequency jump is set with the equi-partitioning (EP) condition, which prevents from the coherent resonances. If EP condition is kept for the downstream part, due to the frequency jump, the transverse focusing should also ‘jump' 3 times with shrink of envelop. The increased beam-density affects the interactions between particles, including the intra-beam stripping (IBS) effect in the H⁻ beam. The temperature ratio between transverse and longitudinal planes is used as a knob for studying the beam behavior for the cases away from equi-partitioning. The IBS effects, as well as strategies for setting downstream non-equi-partitioning lattice due to frequency jump are studied. The matching and beam evolution in the transition section from EP to non-EP (MEBT2) are also studied. The results help to reach an optimum with least risks from resonances and IBS effects and so on.

MOP232

Optimization of the Superconducting Section of Injector Ⅱ for C-ADS

solenoid, emittance, lattice, linac

122

S.H. Liu, Y. He, Z.J. Wang
IMP, Lanzhou, People's Republic of China

Abstract: The China Accelerator driven System (C-ADS) project which includes a high current SC proton linac is being studied under Chinese Academy of Science. Injector II, one of parallel injectors, is undertaken by Institute of Modern Physics (IMP). The lattice design of Injector II has been done. While in most case, the elements, such as SC cavities and SC solenoids, have different weight to the final beam parameters. What is more, in the real operation process of the machine, the optimized mode is hard to find. In the paper, Latin sampling method specified in DAKOTA code combined with TRACK is adopted to build hundreds of virtual machines to analyse the sensitivity of the SC section and to find optimization operation mode.

MOP233

Error and Tolerance Studies for Injector II of C-ADS

linac, solenoid, alignment, emittance

125

W.S. Wang, Y. He, Z.J. Wang
IMP, Lanzhou, People's Republic of China

The proposed Chinese Accelerator Driven System (C-ADS) driver linac is being designed by Chinese Academic Science (CAS). Injector II is designed and fabricated in Institute of Modern Physics (IMP). Injector II will accelerate 10 mA proton beams to 10 MeV. Because of the high final beam power (100 kW) specified for the linac operation, beam loss must be limited to 10^-5 level to avoid radiation damage. Misalignment and RF error simulation for cavities and focusing elements after RFQ were performed and the correction schemes developed using the computing code TRACK. Error and tolerance studies for Injector II are presented.

MOP240

High Energy Tests of Advanced Materials for Beam Intercepting Devices at CERN HiRadMat Facility

vacuum, instrumentation, laser, proton

136

A. Bertarelli, R.W. Aßmann, E. Berthomé, V. Boccone, F. Carra, F. Cerutti, A. Dallocchio, P. Francon, L. Gentini, M. Guinchard, N. Mariani, A. Masi, P. Moyret, S. Redaelli, S.D.M. dos Santos
CERN, Geneva, Switzerland
L. Peroni, M. Scapin
Politecnico di Torino, Torino, Italy

Predicting by simulations the consequences of LHC particle beams hitting Collimators and other Beam Intercepting Devices (BID) is a fundamental issue for machine protection: this can be done by resorting to highly non-linear numerical tools (Hydrocodes). In order to produce accurate results, these codes require reliable material models that, at the extreme conditions generated by a beam impact, are either imprecise or nonexistent. To validate relevant constitutive models or, when unavailable, derive new ones, a comprehensive experimental test foreseeing intense particle beam impacts on six different materials, either already used for present BID or under development for future applications, is being prepared at CERN HiRadMat facility. Tests will be run at medium and high intensity using the SPS proton beam (440 GeV). Material characterization will be carried out mostly in real time relying on embarked instrumentation (strain gauges, microphones, temperature and pressure sensors) and on remote acquisition devices (Laser Doppler Vibrometer and High-Speed Camera). Detailed post-irradiation analyses are also foreseen after the cool down of the irradiated materials.

MOP241

An Experiment on Hydrodynamic Tunnelling of the SPS High Intensity Proton Beam at the HiRadMat Facility

target, proton, collider, linear-collider

141

J. Blanco, F. Burkart, N. Charitonidis, I. Efthymiopoulos, D. Grenier, C. Maglioni, R. Schmidt, C. Theis, D. Wollmann
CERN, Geneva, Switzerland
E. Griesmayer
CIVIDEC Instrumentation, Wien, Austria
N.A. Tahir
GSI, Darmstadt, Germany

The LHC will collide proton beams with an energy stored in each beam of 362 MJ. To predict damage for a catastrophic failure of the protections systems, simulation studies of the impact of an LHC beam on copper targets were performed. Firstly, the energy deposition of the first bunches in a target with FLUKA is calculated. The effect of the energy deposition on the target is then calculated with a hydrodynamic code, BIG2. The impact of only a few bunches leads to a change of target density. The calculations are done iteratively in several steps and show that such beam can tunnel up to 30-35 m into a target. Similar simulations for the SPS beam also predict hydrodynamic tunnelling. An experiment at the HiRadMat (High Radiation Materials) at CERN using the proton beam from the Super Proton Synchrotron (SPS) is performed to validate the simulations. The particle energy in the SPS beam is 440 GeV and has up to 288 bunches. Significant hydrodynamic tunnelling due to hydrodynamic effects are expected. First experiments are planned for July 2012. Simulation results, the experimental setup and the outcome of the tests will be reported at this workshop.

MOP242

Experimental Verification for a Collimator with In-jaw Beam Position Monitors

alignment, proton, collimation, closed-orbit

146

D. Wollmann, O. Aberle, R.W. Aßmann, A. Bertarelli, C.B. Boccard, R. Bruce, F. Burkart, M. Cauchi, A. Dallocchio, D. Deboy, M. Gasior, O.R. Jones, V. Kain, L. Lari, A.A. Nosych, S. Redaelli, A. Rossi, G. Valentino
CERN, Geneva, Switzerland

At present the beam based alignment of the LHC collimators is performed by touching the beam halo with the two jaws of each device. This method requires dedicated fills at low intensities that are done infrequently because the procedure is time consuming. This limits the operational flexibility in particular in the case of changes of optics and orbit configuration in the experimental regions. The system performance relies on the machine reproducibility and regular loss maps to validate the settings. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with in-jaw beam position monitors was proposed and successfully tested with a mock-up collimator in the CERN SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper the results of these experiments are discussed. The measured alignment accuracy is compared to the accuracies achieved with the present collimators in the LHC.

MOP243

Experimental Results of Beam Halo at IHEP

rfq, quadrupole, space-charge, beam-transport

151

H.F. Ouyang, T. Huang, J. Li, J. Peng, T.G. Xu
IHEP, Beijing, People's Republic of China

Space-charge forces acting in mismatched beams have been identified as a major cause of beam halo. In this paper, we describe the beam halo experimental results in a FODO beam line at IHEP. With this beam transport line, experiments are firstly carried out to determine the main beam parameters at the exit of a RFQ with intense beams, and then the measured beam profiles at different positions are compared with the multi-particle simulation profiles to study the formation of beam halo. The maximum measured amplitudes of the matched and mismatched beam profiles agreed well with simulations. Details of the experiment will be presented.

MOP253

Progress with Bunch-shape Measurements at PSI's High-power Cyclotrons and Proton Beam Lines

proton, cyclotron, scattering, background

187

R. Dölling
PSI, Villigen PSI, Switzerland

As proposed at HB2010, additional bunch-shape monitors have been installed at the last turns of the Injector 2 cyclotron and at several locations in the connecting beam line to the Ring cyclotron (@72 MeV), as well as behind the Ring cyclotron (@590 MeV). Now at each location in the beam lines, longitudinal-transversal 2D-density distributions of the bunched 2.2 mA proton beam can be taken from four angles of view, each separated by 45°. In addition the monitor in Injector 2 has been upgraded to observe the 13 outermost turns (@57 to 72 MeV), some of them from two or three angles of view. The measurement setup, data evaluation and results are outlined.

MOP254

Design of a Photo-detachment Emittance Instrument for FETS

laser, dipole, emittance, diagnostics

192

C. Gabor
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
G.E. Boorman, A. Bosco
Royal Holloway, University of London, Surrey, United Kingdom
A.P. Letchford
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
P. Savage
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

Photo detachment is a possibility to diagnose non-destructively H⁻ ion beams. For emittance measurements, the produced neutrals are more suitable then the photo-detached electrons. Such a Photo-Detachment Emittance Measurement Instrument (PD-EMI) is planned for the Front End Test Stand (FETS) at Rutherford Appleton Laboratory (RAL/ UK). FETS comprises a Penning ion source of 60 mA beam current with up to 2 ms pulse length at 50pps, a Low Energy Beam Transport (LEBT), a four-vane RFQ with 3 MeV and a Medium Energy Beam Transport (MEBT) with a chopper system. The PD-EMI will be integrated at the end of the MEBT to commission the RFQ which is currently under construction. The introduction gives an overview some results reached so far and explains the conceptual design. Beam simulations show how to implement this to the MEBT being under construction. The remaining paper concentrates then on the hardware which is the dipole magnet, the laser and optics. The design and and engineering of the magnet chamber needs special attention to both satisfy beam transportation and diagnostics purpose. First measurements about the laser and its parameters will be presented.

MOP255

Acceleration in Vertical Orbit Excursion FFAGs with Edge Focussing

space-charge, proton, acceleration, injection

197

S.J. Brooks
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

FFAGs with vertical orbit excursion (VFFAGs) provide a promising alternative design for rings with fixed-field superconducting magnets. They have a vertical magnetic field component that increases with height in the vertical aperture, yielding a skew quadrupole focussing structure. Edge focussing can provide an alternating gradient within each magnet, thus reducing the ring circumference. Like spiral scaling horizontal FFAGs (but not non-scaling ones) the machine has fixed tunes and no intrinsic limitation on momentum range. Rings to accelerate the 800MeV beam from the ISIS proton synchrotron are investigated, in terms of both magnet field geometry and longitudinal behaviour during acceleration with space charge. The 12GeV ring produces an output power of at least 2.18MW.

MOP257

Space Charge Limits on the ISIS Synchrotron including the Effects of Images

space-charge, synchrotron, resonance, injection

206

B.G. Pine, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The ISIS synchrotron provides a pulsed, 50 Hz, 800 MeV proton beam for spallation neutron production. Each pulse from the synchrotron contains ~2.8×10¹³ ppp, and at this beam intensity space charge and image forces have a strong effect on transverse beam dynamics. In order to increase intensity in the present machine, and to prepare for possible upgrades running at a higher intensity, studies are under way aimed at understanding the most critical features of such forces and their impact on beam loss. These studies are focused on working point optimisation, including resonances due to space charge and images. A 2D simulation code, Set, has been developed to improve understanding of transverse dynamics at ISIS, using a particle-in-cell algorithm to include space charge and image forces self-consistently. The ISIS synchrotron has profiled vacuum vessels and RF shields which conform to the shape of the beam envelope, and have a distinctive influence on the beam dynamics. Set is specifically designed to include these image forces. A systematic simulation study of possible working points is presented, along with an assessment of the effect on apertures.

MOP258

Simulation of Intense Proton Beams in Novel Isochronous FFAG Designs

space-charge, lattice, cyclotron, extraction

211

S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
M. Berz, K. Makino
MSU, East Lansing, Michigan, USA
C. Johnstone
Fermilab, Batavia, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Recent developments in the design of non-scaling fixed field alternating gradient (FFAG) accelerators have been focused on achieving isochronous behavior with a small betatron tune excursion. These advances are particularly interesting for applications requiring CW beams, such as Accelerator Driven Systems for energy generation or waste transmutation. The latest advances in lattice design have resulted in a 330 MeV to 1 GeV lattice, isochronous to better than ± 1 percent. This paper reports on simulations of recent lattice designs incorporating 3D space charge effects.

MOP260

Beam Halo Measurements using Adaptive Masking Methods and Proposed Recent Halo Experiment

quadrupole, injection, space-charge, diagnostics

215

H.D. Zhang, B.L. Beaudoin, S. Bernal, R.B. Fiorito, R.A. Kishek, K. Řežaei, A.G. Shkvarunets
UMD, College Park, Maryland, USA

Beam halo is a common phenomenon in particle beams, especially for modern, advanced accelerators where high beam intensities lead to strong space charge. Halo is generally understood as a population of particles that do, or will, reach large transverse radii relative to a more intense, centralized beam core. It is associated with emittance growth, beam quality degradation and particle loss. The particle-core model [1] is commonly used to describe halo formation as the result of a parametric resonance due to envelope mismatch. Few experiments have been carried out to test this theory [2]. Measurement of beam halo is particularly problematic for faint halos, where light from the intense core obscures the optical image of the halo. In this paper, we present a new diagnostic for high-dynamic range halo measurements based on adaptive masking of the beam core [3]. We also present the design of an experiment to study halo formation from envelope mismatch for beams spanning a wide range of intensities on the University of Maryland Electron Ring (UMER) [4].
[1] R. Gluckstern, Phys. Rev. Lett., vol.73, 1994.
[2] C. Allen, Phys. Rev. Lett. Vol 89, 1998
[3] H. Zhang, et al., Proc of PAC11.
[4] R.A. Kishek, these proceedings.

MOP262

Observations of Space Charge Effects in the Spallation Neutron Source Accumulator Ring

coupling, space-charge, accumulation, target

223

R.E. Potts
ORNL RAD, Oak Ridge, Tennessee, USA
S.M. Cousineau, J.A. Holmes
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
The Spallation Neutron Source accumulator ring was designed to allow independent control of the transverse beam distribution in each plane. However, at high beam intensities, nonlinear space charge forces can strongly influence the final beam distribution and compromise our ability to independently control the transverse distributions. In this study we investigate the evolution of the beam at intensities of up to ~8x10¹³ ppp through both simulation and experiment. Specifically, we analyze the evolution of the beam distribution for beams with different transverse aspect ratios and tune splits. We present preliminary results of simulations of our experiments.

TUO1A03

Space Charge Effects in Isochronous FFAGs and Cyclotrons

space-charge, cyclotron, focusing, TRIUMF

231

T. Planche, R.A. Baartman, Y.-N. Rao
TRIUMF, Vancouver, Canada

Effects of space charge forces on the beam dynamics of isochronous rings will be discussed. Two different kinds of phenomena will be introduced through a brief review of the literature on the topic. The first one is a consequence of the very weak vertical focusing found in the low energy region of most cyclotrons. The space charge tune shift further reduces the vertical focusing, setting an upper limit on instantaneous current. The second one arises from the fact that longitudinal phase space is frozen in isochronous rings. This leads to effects of space charge forces which are very peculiar to isochronous machines. We will finally present the simulation tools being developed at TRIUMF to study these effects.

Slides TUO1A03 [0.974 MB]

TUO3A01

Dynamical Aspects of Emittance Coupling in Intense Beams

emittance, resonance, linac, coupling

240

I. Hofmann
GSI, Darmstadt, Germany
I. Hofmann
HIJ, Jena, Germany

In this paper we study in an idealized lattice model the dynamical behavior of non-equipartitioned beams and of approach to equipartition. It is shown that emittance transfer depends on times scales of tune change, but also the direction of crossing the stopbands of space charge resonances. This provides additional information to support the stability charts suggested previously as design tool for high current linacs.

Slides TUO3A01 [4.897 MB]

TUO3B05

Beam Dynamics of the 13 MeV/50 mA Proton Linac for the Compact Pulsed Hadron Source at Tsinghua University

rfq, proton, DTL, target

289

Q.Z. Xing, X. Guan, C. Jiang, C.-X. Tang, X.W. Wang, H.Y. Zhang, S.X. Zheng
TUB, Beijing, People's Republic of China
J.H. Billen, J. Stovall, L.M. Young
TechSource, Santa Fe, New Mexico, USA
G.H. Li
NUCTECH, Beijing, People's Republic of China

Funding: Work supported by the Major Research plan of the National Natural Science Foundation of China (Grant No. 91126003)
We present the start-to-end simulation result on the high-current proton linac for the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. The CPHS project is a university-based proton accelerator platform (13 MeV, 16 kW, peak current 50 mA, 0.5 ms pulse width at 50 Hz) for multidisciplinary neutron and proton applications. The 13 MeV proton linac contains the ECR ion source, LEBT, RFQ, DTL and HEBT. The function of the whole accelerator system is to produce the proton beam, accelerate it to 13 MeV, and deliver it to the target where one uniform round beam spot is obtained with the diameter of 5 cm.

Slides TUO3B05 [7.715 MB]

TUO1C01

Recent Developments on High Intensity Beam Diagnostics at SNS

electron, proton, cathode, target

292

W. Blokland
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
The Spallation Neutron Source Ring accumulates 0.6 μs long proton bunches of up to 1.6·10¹⁴ protons with a typical peak current of over 50 A during a 1 ms cycle. To qualify the beam, we perform different transverse profile measurements that can be done at full intensity. The electron beam scanner performs a non-invasive measurement of the transverse and longitudinal profiles of the beam in the ring. Electrons passing over and through the proton beam are deflected and projected on a fluorescent screen. Analysis of the projection yields the transverse profile while multi transverse profiles offset in time yield the longitudinal profile. Progress made with this system will be discussed as well as temperature measurements of the stripping foil and other transverse measurements.

Slides TUO1C01 [15.498 MB]

TUO1C04

Detection of Unidentified Falling Objects at LHC

emittance, proton, beam-losses, injection

305

E. Nebot Del Busto, T. Baer, F.V. Day, B. Dehning, E.B. Holzer, A. Lechner, R. Schmidt, J. Wenninger, C. Zamantzas, M. Zerlauth, F. Zimmermann
CERN, Geneva, Switzerland
M. Hempel
BTU, Cottbus, Germany

About 3600 Ionization Chambers are located around the LHC ring to detect beam losses that could damage the equipment or quench superconducting magnets. The BLMs integrate the losses in 12 different time intervals (from 40 μs to 83.8 s) allowing for different abort thresholds depending on the duration of the loss and the beam energy. The signals are also recorded in a database at 1 Hz for offline analysis. Since the 2010 run, a limiting factor in the machine availability occurred due to unforeseen sudden losses appearing around the ring on the ms time scale. Those were detected exclusively by the BLM system and they are the result of the interaction of macro-particles, of sizes estimated to be 1-100 microns, with the proton beams. In this document we describe the techniques employed to identify such events as well as the mitigations implemented in the BLM system to avoid unnecessary LHC downtime.

Slides TUO1C04 [6.812 MB]

WEO1A01

Impedance Studies of 2D Azimuthally Symmetric Devices of Finite Length

impedance, coupling, resonance, cavity

344

N. Biancacci, E. Métral, B. Salvant
CERN, Geneva, Switzerland
N. Biancacci
Rome University La Sapienza, Roma, Italy
M. Migliorati, L. Palumbo
URLS, Rome, Italy
V.G. Vaccaro
Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli, Italy

In circular accelerators, the beam quality can be strongly affected by the self-induced electromagnetic fields excited by the beam in the passage through the elements of the accelerator. The beam coupling impedance quantifies this interaction and allows predicting the stability of the dynamics of high intensity, high brilliance beams. The coupling impedance can be evaluated with finite element methods or using analytical methods, such as Field Matching or Mode Matching. In this paper we present an application of the Mode Matching technique for an azimuthally uniform structure of finite length: a cylindrical cavity loaded with a toroidal slab of lossy dielectric, connected with cylindrical beam pipes. In order to take into account the finite length of the structure, with respect to the infinite length approximation, we decompose the fields in the cavity into a set of orthonormal modes. We obtain a complete set of equations using the magnetic field matching and the non-uniform convergence of the electric field on the cavity boundaries. We present benchmarks done with CST Particle Studio simulations and existing analytical formulas, pointing out the effect of finite length and non-relativistic beta.

Slides WEO1A01 [6.689 MB]

WEO1A03

Resistive Wall Instability in CSNS/RCS

impedance, extraction, injection, wakefield

354

L. Huang, Y.D. Liu, S. Wang
IHEP, Beijing, People's Republic of China

Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton accelerator, with average beam power of 100kW. The collective effects caused by the coupling impedance may be the limit to beam power. The impedance estimation for components on beam line shows that the resistive wall impedance and its instability are more serious than any others. Based on the impedance budget, the instability is theoretically estimated. A simple resistive wall wake field model is used to simulate the bunch oscillation and obtain the growth time. In this simulation model, the continuous resistive wall wake field is concentrated to one position in the ring and the long bunch is sliced into many micro-bunches. By tracking the dynamics of the macro-bunches, the transverse growth time are obtained. The simulation results are also confirmed the restriction to instability by natural chromaticity.
# Supported by National Natural Science Foundation of China (11175193)
*wangs@ihep.ac.cn

Slides WEO1A03 [1.358 MB]

WEO3A02

Beam Loss and Collimation in the ESS Linac

linac, proton, DTL, collimation

368

R. Miyamoto, B. Cheymol, H. Danared, M. Eshraqi, A. Ponton, J. Stovall, L. Tchelidze
ESS, Lund, Sweden
I. Bustinduy
ESS Bilbao, Bilbao, Spain
A.I.S. Holm, S.P. Møller, H.D. Thomsen
ISA, Aarhus, Denmark

The European Spallation Source (ESS), to be built in Lund, Sweden, is a spallation neutron source based on a 5 MW proton linac. A high power proton linac has a tight tolerance on beam losses to avoid activation of its components and it is ideal to study patterns of the beam loss and prepare beam loss mitigation schemes at the design stage. This paper presents simulations of the beam loss in the ESS linac as well as beam loss mitigation schemes using collimators in beam transport sections.

Slides WEO3A02 [6.377 MB]

WEO1B04

On Scaling Properties of Third-order Resonance Crossing in Particle Accelerators

resonance, emittance, betatron, booster

394

S.-Y. Lee
Indiana University, Bloomington, Indiana, USA
K.Y. Ng
Fermilab, Batavia, USA

Funding: Work supported by the US DOE under contract DEFG02-92ER40747, DE-AC02-07CH11359, and the NSF under contract PHY-0852368 with NSF.
The effects of resonances on high power hadron accelerators are explored. These resonances include systematic space-charge resonances, third-order resonance, and other weak random resonances that are often present in FFAG and other RCS accelerators. The distortion of invariant torus during resonance crossing is used to set limit on emittance growth or fraction of particle trapped. The critical resonance strength in the ring lattice is determined from a simple scaling law derived as a function of the tune-ramp rate and initial emittance. Such scaling law can be useful in the evaluation of the performance in high power accelerators.

Slides WEO1B04 [1.074 MB]

WEO1C01

Effect of Self-consistency on Periodic Resonance Crossing

resonance, space-charge, ion, synchrotron

429

G. Franchetti
GSI, Darmstadt, Germany

In high intensity bunched beams resonance crossing gives rise to emittance growth and beam loss. Both these effects build up after many synchrotron oscillations. Up to now long term modeling have relied on frozen models neglecting the physics of self-consistency. We address here this issue and present the state of the art of simulations also applied to the SIS100.

Slides WEO1C01 [3.657 MB]

WEO1C02

Simulation and Measurement of Half Integer Resonance in Coasting Beams in the ISIS Ring

resonance, injection, synchrotron, space-charge

434

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

ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a high intensity proton synchrotron, accelerating 3·10¹³ ppp from 70-800 MeV, at a repetition rate of 50 Hz. Present studies are looking at key aspects of high intensity behaviour with a view to increasing operational intensity, identifying optimal upgrade routes and understanding loss mechanisms. Of particular interest is the space charge limit imposed by half integer resonance: we present results from coasting beam experiments with the ISIS ring in storage ring mode, along with detailed 3D (ORBIT) simulations to help interpret observations. The methods for experimentally approaching resonance, and the implications on beam behaviour, measurement and interpretation are discussed. In addition, results from simpler 2D simulations and analytical models are used to help interpret expected beam loss and halo evolution. Plans and challenges for the measurement and understanding of this important beam loss mechanism are summarised, as are some closely related areas of high intensity work on ISIS.

Slides WEO1C02 [2.224 MB]

WEO1C03

Longitudinal Beam Loss Studies of the CERN PS-to-SPS Transfer

cavity, emittance, injection, impedance

439

H. Timko, T. Argyropoulos, T. Bohl, H. Damerau, J. Esteban Müller, S. Hancock, E.N. Shaposhnikova
CERN, Geneva, Switzerland

Bunch-to-bucket transfer between the Proton Synchrotron (PS) and the Super Proton Synchrotron (SPS) is required before beams can enter the Large Hadron Collider. The overall beam loss at this transfer is currently around 5-10 %, and is increased for higher intensities or larger longitudinal emittances. Previous attempts to reduce the losses with additional RF voltage from spare cavities in the PS were unsuccessful. In this paper, we modelled the complete PS flat-top bunch splitting and rotation manipulations, PS-to-SPS transfer, SPS flat bottom and acceleration ramp using end-to-end simulations. Starting from the measured bunch distributions, the simulations provide an accurate insight into the problem and allow direct benchmarking with experiments. As a result, it was understood and confirmed by measurements that shorter bunches do not necessarily lead to better transmission. The particle distribution in longitudinal phase space at PS extraction should be optimised instead. A significant loss reduction of up to 50 % is expected from simulations; experimental studies are on-going to verify these theoretical findings.

Slides WEO1C03 [3.903 MB]

WEO1C06

Measurement and Simulation of Luminosity Leveling in LHC via Beam Separation

luminosity, emittance, beam-beam-effects, target

451

S. Paret, J. Qiang
LBNL, Berkeley, California, USA
R. Alemany-Fernandez, R. Calaga, R. Giachino, W. Herr, D. Jacquet, G. Papotti, T. Pieloni, L. Ponce, M. Schaumann
CERN, Geneva, Switzerland
R. Miyamoto
ESS, Lund, Sweden

Funding: This work supported by the US LHC Accelerator Research Program and the National Energy Research Scientific Computing Center of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Leveling of the luminosity in LHC by means of separating the beams colliding at an interaction point is examined. An experiment in which the separation of the beams was stepwise increased to up to 2.5 times the beam width is presented. The luminosity at all IPs and emittance of the beams were measured to detect possible side effects of the collision with an offset. Strong-strong simulations that closely follow the experimental setup are discussed and compared with the measurements. Finally, potential alternatives for luminosity leveling are briefly described.

Slides WEO1C06 [1.031 MB]

WEO3C01

Injection and Stripping Foil Studies for a 180 MeV Injection Upgrade at ISIS

injection, synchrotron, dipole, electron

456

B. Jones, D.J. Adams, M.C. Hughes, S.J.S. Jago, B.G. Pine, H. V. Smith, C.M. Warsop, R.E. Williamson
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The Rutherford Appleton Laboratory (RAL) is home to ISIS, the world's most productive spallation neutron source. ISIS has two neutron producing target stations (TS-1 and TS-2), operated at 40 Hz and 10 Hz respectively with a 50 Hz, 800 MeV proton beam from a rapid cycling synchrotron (RCS), which is fed by a 70 MeV H− drift tube linac. The multi-turn charge-exchange injection process used on ISIS has been the subject of a programme of detailed studies in recent years including benchmarked simulations and experiments. More recently, these studies have been expanded as plans for upgrading ISIS have focussed on replacement of the 70 MeV linac with a new, higher energy injector and a new synchrotron injection straight. Whilst much of these studies have been reported elsewhere, this paper presents a summary of the programme with some further details.

Slides WEO3C01 [4.895 MB]

THO1A01

Beam-beam Effects in RHIC

proton, electron, resonance, emittance

479

Y. Luo, M. Bai, W. Fischer, C. Montag, S.M. White
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In this article we will review the beam-beam effects in the Relativistic Heavy Ion Collider (RHIC). We will cover the experimental observations, beam-beam simulation techniques and results, and head-on beam-beam compensation with electron lenses. The next luminosity goal in the RHIC polarized proton operation is to double the luminosity with a higher proton bunch intensity. After the upgrade, the beam-beam parameter will reach 0.03. Head-on beam-beam compensation is aimed to reduce the beam-beam tune spread and non-linear beam-beam resonance driving terms.

Slides THO1A01 [1.355 MB]

THO1A02

Effects of Magnetic Field Tracking Errors and Space Charge on Beam Dynamics at CSNS/RCS

space-charge, quadrupole, resonance, lattice

484

S.Y. Xu, N. Wang, S. Wang
IHEP, Beijing, People's Republic of China

The China Spallation Neutron Source (CSNS) is an accelerator-based facility. It operates at 25 Hz repetition rate with an design beam power of 100 kW. CSNS consists of a 1.6-GeV Rapid Cycling Synchrotron (RCS) and a 80-MeV linac. The lattice of the CSNS/RCS is triplet based four-fold structure. The preferred working points of CSNS/RCS are (4.86, 4.78) which can avoid the major low-order structure resonances. But because of the chromatic tune shift, space-charge incoherent tune shift and the tune shift caused by magnetic field tracking errors between the quadrupoles and the dipoles, some structure resonances are unavoidable. The chromaticity, space charge effects and magnetic field tracking errors can also induce beta function distortion, and influence the transverse acceptance and the collimation efficiency of the collimation system. In this paper we show results of space-charge simulations introducing magnetic field tracking errors and discuss the combined effects of chromaticity, magnetic field tracking errors and space charge on the beam dynamics for CSNS/RCS.

Slides THO1A02 [1.613 MB]

THO1A03

Dual-harmonic Acceleration Studies at CSNS RCS

injection, acceleration, bunching, cavity

487

J.F. Chen, J.Y. Tang, X. Zhang
IHEP, Beijing, People's Republic of China

Dual harmonic acceleration is proposed to alleviate the space charge effects in the RCS (Rapid Cycling Synchrotron) at the upgrading stages of the CSNS (China Spallation Neutron Source). Different dual harmonic acceleration schemes have been studied by using a self-made parameter calculation code - RAMADH and the simulation code - ORBIT. Both complete and partial coverage of the dual harmonic RF system along the acceleration have been considered. The injection by combining beam chopping and off-momentum is used in the macro-particle tracking simulations by ORBIT. In addition, a new idea that unlocks the RF frequency and the magnetic field in the injection period is found very useful in obtaining a good longitudinal painting.

Slides THO1A03 [1.343 MB]

THO1A04

High Intensity Longitudinal Dynamics Studies for an ISIS Injection Upgrade

injection, synchrotron, bunching, space-charge

492

R.E. Williamson, D.J. Adams, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the world's most productive pulsed 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 from 70 MeV to 800 MeV, delivering a mean beam power of 0.2 MW. Recent upgrade studies at ISIS have centred on a new 180 MeV linac for injection into the existing ring offering the possibility of beam powers in the 0.5 MW regime through reduction in space charge and optimized injection. A central and critical aspect of such an upgrade is the longitudinal dynamics including beam stability, associated RF parameters, space charge levels and stringent requirements on beam loss. This paper outlines possible longitudinal injection schemes for the injection upgrade meeting key design requirements such as minimising halo, bunching factor and satisfying the Keil-Schnell-Boussard (KSB) stability criterion throughout acceleration. Details of simulation models including calculation of KSB are given together with associated assumptions. Latest results from studies to understand and confirm stability limits on ISIS via simulation and experiment are presented.

Slides THO1A04 [2.641 MB]

THO3A01

High Intensity Aspects of J-PARC Linac Including Re-commissioning after Earthquake

linac, multipactoring, DTL, rfq

497

M. Ikegami, K. Futatsukawa, T. Miyao
KEK, Ibaraki, Japan
Y. Liu
KEK/JAEA, Ibaraki-Ken, Japan
T. Maruta, A. Miura, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan

We had a massive earthquake in March 2011, which forced us to shutdown J-PARC accelerators for nearly nine months due to its resultant damages. After significant restoration effort, we resumed the beam operation of J-PARC linac in December 2011 and user operation in January 2012. Subsequently, we restored the same beam power as just before the earthquake in March 2012. In the course of the beam commissioning after the earthquake, we have experienced beam losses which were not observed before the earthquake. We discuss the experimentally observed beam losses and its comparison with particle simulations.

Slides THO3A01 [5.249 MB]

THO3A03

Simulations and Measurements in High Intensity LEBT with Space Charge Compensation

emittance, injection, space-charge, rfq

507

N. Chauvin
CEA/IRFU, Gif-sur-Yvette, France
O. Delferrière, R. Gobin, P.A.P. Nghiem, D. Uriot
CEA/DSM/IRFU, France
R.D. Duperrier
ESS, Lund, Sweden

Over the last years, the interest of the international scientific community for high power accelerators in the megawatt range has been increasing. One of the major challenges is to extract and transport the beam while minimizing the emittance growth in the Low Energy Beam Transport line (LEBT). Consequently, it is crucial to perform precise simulations and cautious design of LEBT. In particular, the beam dynamics calculations have to take into account not only the space charge effects but also the space charge compensation of the beam induced by ionization of the residual gas. The code SOLMAXP has been developed in CEA-Saclay to perform self-consistent calculations taking into account space charge compensation. Extensive beam dynamics simulations have been done with this code to design the IFMIF LEBT (Deuteron beam of 125 mA at 100 keV, cw). The commissioning of the IFMIF injector started a few months ago and emmittance measurements of H⁺ and D⁺ beams have been done. The first experimental results will be presented and compared to simulation.

Slides THO3A03 [3.165 MB]

THO3B01

Proton Beam Inter-Bunch Extinction and Extinction Monitoring for the Mu2e Experiment

proton, dipole, target, collimation

532

E. Prebys
Fermilab, Batavia, USA

Funding: U.S. Department of Energy
The goal of the Mu2e experiment at Fermilab will be the search for the conversion of a muon into an electron in the field of a nucleus, with a precision roughly four orders of magnitude better than the current limit. The experiment requires a beam consisting of short (~200 ns FW) bunches of protons are separated by roughly 1.5 microseconds. Because the most significant backgrounds are prompt with respect to the arrival of the protons, out of time beam must be suppressed at a level of at least 10^-10 relative to in time beam. The removal of out of time beam is known as "extinction". This talk will discuss the likely sources of out of time beam and the steps we plan to take to remove it. In addition, the plan for monitoring the extinction level will be presented.

Slides THO3B01 [6.380 MB]

THO3B04

Beam Dynamics Studies of H⁻ Beam Chopping in a LEBT for Project X

ion, emittance, solenoid, ion-source

546

Q. Ji, D.P. Grote, A.R. Lambert, D. Li, T. Schenkel, J.W. Staples
LBNL, Berkeley, California, USA

Funding: This work is supported by the Office of Science, United States Department of Energy under DOE contract DE-AC02-05CH11231.
Project X is proposed as a high intensity proton facility at Fermilab to support a world-leading program in neutrino and flavor physics over the next several decades. The front-end consists of an H⁻ ion source, low-energy beam transport (LEBT), and 162.5 MHz CW Radio-Frequency-Quadrupole (RFQ) accelerator. The LEBT design, currently under study at LBNL, would comprise two solenoids, a dipole magnet and a chopper. The LEBT chopper is designed to achieve 1 MHz beam chopping of a partially neutralized 30 keV, 5 mA H⁻ beam. Preliminary simulation studies show that chopping the beam before the second solenoid is more efficient in terms of chopper bias voltages. However, the space charge neutralization will be lost along the beam after the chopper and through the second solenoid. A beam dynamics study, using WARP 3D (a Particle-in-cell simulation code), has been carried out to investigate both the time-dependence of the partial neutralization in the segment after the chopper, as well as the beam stability and emittance growth. Benchmark experiments are ongoing and simulation and experimental results will be presented in this Workshop.

Slides THO3B04 [1.868 MB]

FRO1A01

Summary of Working Group A: Beam Dynamics in High-Intensity Circular Machines

space-charge, luminosity, ion, resonance

606

E. Métral
CERN, Geneva, Switzerland
G. Franchetti
GSI, Darmstadt, Germany
J.A. Holmes
ORNL, Oak Ridge, Tennessee, USA

In this proceeding we summarize the presentations of the HB2012 Workshop session on 'Beam Dynamics in High-Intensity Circular Machines' as well as the outcome of the discussion session. This working group hosted 29 presentations in dedicated sessions plus 5 presentations in a joint session with the working C.

Slides FRO1A01 [7.420 MB]

FRO1A03

Accelerator System Design, Injection, Extraction and Beam-Material Interaction: Working Group C Summary Report

collimation, injection, ion, proton

615

N.V. Mokhov
Fermilab, Batavia, USA
D. Li
LBNL, Berkeley, California, USA

Working Group C summary:The performance of high beam power accelerators is strongly dependent on appropriate injection, acceleration and extraction system designs as well as on the way interactions of the beam with machine components are handled. The experience of the previous ICFA High-Brightness Beam workshops has proven that it is quite beneficial to combine analyses and discussion of these issues in one group, WG-C at this Workshop. A broad range of topics was presented and discussed in twenty talks at four WG-C sessions as well as at two joint WGA/C and WG-B/C sessions. Highlights from these talks, outstanding issues along with plans and proposals for future work are briefly described.

Slides FRO1A03 [4.907 MB]

FRO1B01

Summary of the Working Group on Commissioning and Operation

beam-losses, linac, injection, proton

620

R. Schmidt
CERN, Geneva, Switzerland
M.A. Plum
ORNL, Oak Ridge, Tennessee, USA
Y. Sato
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

The Working Group D summary report focussed on answering the following issues:

observation of beam losses (e.g. time structure, other parameters,…),
reducing beam losses with operational parameters away from the design set points,
reducing beam losses (or concentrating beam losses at a few locations) using collimators,
minimizing beam losses due to beam transfer from one accelerator to the following accelerator - what parameters are important?

The issue of reducing beam losses with operational parameters away from the design set points is especially valuable as it is rarely discussed.

Slides FRO1B01 [0.426 MB]