2011 Particle Accelerator Conference - List of Keywords (space-charge)

Paper	Title	Other Keywords	Page
MOOBS2	Status of High Intensity Effects in the Spallation Neutron Source Accumulator Ring	coupling, injection, resonance, collective-effects	17
	S.M. Cousineau ORNL, Oak Ridge, Tennessee, USA
	Funding: This research is supported by UT-Battelle, LLC for the U. S. Department of Energy under contract No. DE-AC05-00OR22725 The 248-meter Spallation Neutron Source (SNS) accumulator ring has accumulated up to 1.55·10¹⁴, 1 GeV protons. At this intensity, space charge effects contribute significantly to the beam dynamics. Here we present observations of space charge effects in the SNS ring, with emphasis on space charge effects and e-p instabilities.
	Slides MOOBS2 [3.704 MB]

MOOBS3	Bunch-End Interpenetration During Evolution to Longitudinal Uniformity in a Space-Charge-Dominated Storage Ring	simulation, electron, diagnostics, longitudinal-dynamics	22
	T.W. Koeth, B.L. Beaudoin, S. Bernal, I. Haber, R.A. Kishek, P.G. O'Shea UMD, College Park, Maryland, USA
	The University of Maryland Electron Ring is a facility for study of the novel physics that occurs as intense space-charge-dominated beams that are transported over long distances. An example presented here is the role of space-charge longitudinal expansion and bunch-end interpenetration in the relaxation of a coasting bunch towards uniformly filling the ring. By comparing experiment to simplified longitudinal simulations the relaxation process is shown to be largely independent of details of the transverse dynamics. However, to get detailed agreement it was found necessary to include the consequences of transverse current loss. Since the AC coupled diagnostics lose information on any DC current loss, a novel beam knockout technique was developed to recover this information.
	Slides MOOBS3 [2.501 MB]

MOOCS5	Space-charge Effects in H⁻ Low-energy Beam Transport of LANSCE	emittance, beam-transport, simulation, vacuum	64
	Y.K. Batygin, C. Pillai, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	The 750-keV low-energy beam transport of the Los Alamos Neutron Science Center (LANSCE) linac consists of two independent beam lines for simultaneous injection of H⁺ and H⁻ beams into the linear accelerator. While transport of the H⁺ beam is seriously affected by uncompensated space charge forces, the same effect for H⁻ is hidden by presence of multiple beam collimators and beam chopping. Recent results from beam development experiments indicate a significant influence of space charge on H⁻ beam dynamics in the low-energy beam transport. Measurements of beam emittance along beam transport show the formation of S-shaped filamentation in the particle distribution phase space, typical with the presence of non-linear space charge forces. Results are supported by particle tracking simulations with the PARMILA, BEAMPATH, and TRACE codes.
	Slides MOOCS5 [6.304 MB]

MOODS1	Space-Charge Effects in Bunched and Debunched Beams	focusing, electron, linac, emittance	85
	B.L. Beaudoin, S. Bernal, K. Fiuza, I. Haber, R.A. Kishek, T.W. Koeth, P.G. O'Shea, M. Reiser, D.F. Sutter UMD, College Park, Maryland, USA
	Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office The University of Maryland Electron Ring (UMER) is a machine designed to study high-intensity beam physics. With the application of axial fields to the bunch ends, we are able to keep a beam with an injected tune shift of 1.0, bunched over multiple turns. This is feasible with the application of tailored fields to optimally match the space-charge self-fields while minimizing the excitation of longitudinal space-charge waves. With this scheme, we have been able to extend the number of turns at the University of Maryland Electron Ring (UMER) by a factor of ten. Without the use of longitudinal focusing, head and tail effects begin to dominate, especially with the higher current beams. Time resolved measurements of the peak correlated energy spread have shown in some cases a change in the overall spread of 1.8% for the 0.6 mA beam, from the injected beam energy.
	Slides MOODS1 [2.834 MB]

MOP152	G4beamline Particle Tracking in Matter Dominated Beam Lines	simulation, collider, electron, wakefield	373
	T.J. Roberts, K.B. Beard Muons, Inc, Batavia, USA S. Ahmed JLAB, Newport News, Virginia, USA D. Huang, D.M. Kaplan Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86281 The G4beamline program is a useful and steadily improving tool to quickly and easily model beam lines and experimental equipment without user programming. It has both graphical and command-line user interfaces. Unlike most accelerator physics codes, it easily handles a wide range of materials and fields, being particularly well suited for the study of muon and neutrino facilities. As it is based on the Geant4 toolkit, G4beamline includes most of what is known about the interactions of particles with matter. We are continuing the development of G4beamline to facilitate its use by a larger set of beam line and accelerator developers. A major new feature is the calculation of space-charge effects. G4beamline is open source and freely available.

MOP243	Design of a Compact, High-Resolution Analyzer for Longitudinal Energy Studies in the University of Maryland Electron Ring	focusing, simulation, electron, high-voltage	571
	E.C. Voorhies, S. Bernal, I. Haber, R.A. Kishek, T.W. Koeth, P.G. O'Shea UMD, College Park, Maryland, USA
	Funding: Work supported by US Dept. of Energy Offices of High Energy Physics and Fusion Energy Sciences, the Dept. of Defense Office of Naval Research, and the Joint Technology Office. Retarding-potential energy analyzers have long been used for energy spread measurements in low-energy beams. In addition to energy spread and energy profile measurements, a high-resolution analyzer can be used to reconstruct the longitudinal phase space. This is useful for our experimental studies of longitudinal physics topics, such as dispersion, space charge waves, and longitudinal focusing. A previous energy analyzer designed at the University of Maryland demonstrated high-resolution measurements of a 5 keV electron beam.* Motivated by the need to characterize the 10 keV electron beam of the University of Maryland Electron Ring, we have improved on the design of the earlier analyzer, increasing its high voltage breakdown threshold and vacuum performance. Results of high-voltage testing and particle optics simulations of the new design are presented. *Y. Cui, Y. Zou, et al., "Design and Operation of a Retarding Field Energy Analyzer with Variable Focusing for Space-Charge Dominated Electron Beams," Review of Scientific Instruments 75(8), 2736 (2004).

TUP011	Multipactor Dynamics in Dielectric-loaded Accelerator Structures	electron, multipactoring, simulation, plasma	829
	O.V. Sinitsyn, T.M. Antonsen, G.S. Nusinovich UMD, College Park, Maryland, USA
	Funding: This work has been supported by the Office of High Energy Physics of the U.S. Department of Energy. In this paper the authors present results of threedimensional analysis of multipactor in dielectric-loaded accelerator structures. The studies are aimed at checking some assumptions that were used in previous two-dimensional theory. In particular, it is demonstrated that the spatial distribution of charged particles can be azimuthally non-uniform which suggests using a more complex space charge model in some cases. Also, it is shown that the particle axial velocity components can be making a substantial contribution to particle energy and should not be ignored in future studies.

WEP092	Space Charge Effect of the High Intensity Proton Beam during the Resonance Extraction for the MU2E Experiment at Fermilab	extraction, septum, sextupole, resonance	1645
	C.S. Park, J.F. Amundson, J.A. Johnstone, V.P. Nagaslaev, S.J. Werkema Fermilab, Batavia, USA
	The proposed Mu2e experiment to search for direct μ to e conversion at Fermilab plans slow, resonant extraction of a beam with 3× 10¹² protons from the Debuncher ring. Space charge of this high intensity beam is a critical factor, since it induces significant betatron tune spread and consequently affects resonance extraction processes, such as spill uniformity and beam losses. This study shows the multi-particle simulation results in the early stages of resonance extraction and spill uniformity in the presence of 2D and 3D space charge effects.

WEP094	Space Charge Measurements with a High Intensity Bunch at the Fermilab Main Injector	proton, simulation, emittance, injection	1648
	K. Seiya, B. Chase, J.E. Dey, P.W. Joireman, I. Kourbanis Fermilab, Batavia, USA A. Yagodnitsyna NSU, Novosibirsk, Russia
	Fermilab Main Injector will be required to operate with 3 times higher bunch intensity than today for Project X. The plan to study the space charge effects at the injection energy with intense bunches will be discussed.

WEP096	Simulations of Space Charge in the Fermilab Main Injector	emittance, simulation, proton, lattice	1654
	E.G. Stern, J.F. Amundson, P. Spentzouris Fermilab, Batavia, USA J. Qiang, R.D. Ryne LBNL, Berkeley, California, USA
	The Fermilab Project X plan for future high intensity running relies on the Main Injector as the engine for delivering protons in the 60-120 GeV energy range. Project X plans call for increasing the number of protons per Main Injector bunch from the current value of 1.0× 10¹¹ to 3.0× 10¹¹. Space charge effects at the injection energy of 8 GeV have the potential to seriously disrupt operations. We report on ongoing simulations with Synergia, our multi-physics process accelerator modeling framework, to model space charge effects in the Main Injector combined with the effects of magnet fringe fields and apertures.

WEP098	Formation of High Charge State Heavy Ion Beams with Intense Space Charge	ion, target, electron, heavy-ion	1657
	P.A. Seidl, J.-L. Vay LBNL, Berkeley, California, USA
	Funding: This work was performed under the auspices of the U.S Department of Energy by LBNL under contract DE-AC02-05CH11231. High charge-state heavy-ion beams are of interest and used for a number of accelerator applications. Some accelerators produce the beams downstream of the ion source by stripping bound electrons from the ions as they pass through a foil or gas. In other accelerator systems, ions of charge state >1 are produced directly in the ion source. Heavy-ion inertial fusion (HIF) would benefit from low-emittance, high current ion beams with charge state >1. For these accelerators, the desired dimensionless perveance upon extraction from the emitter is ~0.001, and the electrical current of the beam pulse is ~ 1 A. For accelerator applications where high charge state and very high current are desired, space charge effects might present unique challenges. For example, in a stripper, the separation of charge states might create significant nonlinear space-charge forces which would impact the beam brightness. We will report on the particle-in-cell simulation of the formation of such beams for HIF, and review the possible technical approaches.

WEP099	Numerical Solution for the Potential and Density Profile of a Thermal Equilibrium Sheet Beam	focusing, plasma, ion, controls	1659
	S.M. Lund LLNL, Livermore, California, USA G. Bazouin LBNL, Berkeley, California, USA
	Funding: This research was performed under the auspices of the US DOE at the Lawrence Livermore and Lawrence Berkeley National Laboratories under contract numbers DE-AC52-07NA27344 and DE-AC02-05CH11231. A one-dimensional Vlasov-Poisson model for sheet beams is presented to provide a simple framework for analysis of space-charge effects. Centroid and rms envelope equations including image charge effects are derived and reasonable parameter equivalences with commonly employed 2D transverse models of unbunched beams are established. This sheet beam model is applied to analyze several problems of fundamental interest. First, a sheet beam thermal equilibrium distribution in a continuous focusing channel is constructed and shown to have analogous properties to two- and three-dimensional thermal equilibrium models in terms of the equilibrium structure and Deybe screening properties. Second, the simpler formulation for sheet beams is exploited to explicitly calculate the distribution of particle oscillation frequencies within a thermal equilibrium beam. It is shown that as space-charge intensity increases, the frequency distribution becomes broad which suggesting robust stability properties for beams with strong space-charge.

WEP101	Smooth Approximation of Dispersion with Strong Space Charge	emittance, beam-transport, heavy-ion, focusing	1665
	S. Bernal, B.L. Beaudoin, T.W. Koeth, P.G. O'Shea UMD, College Park, Maryland, USA
	Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office. We apply the Venturini-Reiser envelope-dispersion equations* to a continuous beam in a uniform focusing/bending lattice to study the combined effects of linear dispersion and space charge. Within this simple model we investigate the scaling of average dispersion and the effects on beam dimensions; we also introduce a generalization of the space-charge intensity parameter and apply it to the University of Maryland Electron Ring (UMER) and other machines. In addition, we present results of calculations to test the smooth approximation by solving the Venturini-Reiser original equations and also through simulations with the code ELEGANT. *M. Venturini and M. Reiser, Phys. Rev. Lett. 81, 1, p. 96, 6 July 1998

WEP102	Current Dependent Tune Shifts in the University of Maryland Electron Ring UMER	vacuum, electron, storage-ring, focusing	1668
	D.F. Sutter, B.L. Beaudoin, S. Bernal, M. Cornacchia, R.A. Kishek, T.W. Koeth, P.G. O'Shea UMD, College Park, Maryland, USA
	Funding: Work supported by the U.S. DOE Offices of High Energy Physics and Fusion Energy Sciences and by the U.S. DOD Office of Naval Research and Joint Technology Office. The shift in betatron tunes as a function of space charge has been studied in many accelerators and storage rings. Because of its low operating energy (10 keV, γ = 1.02) and wide range of beam currents (0.6 to 100 mA, corresponding respectively to predicted incoherent tune shifts of 1.2 to 5.2), the University of Maryland electron ring (UMER) provides a unique opportunity to study space charge driven tune shifts over a wide parameter space. Comparisons of predictions and measurements are presented, including a discussion of special factors such as the magnetic penetration of the vacuum chamber walls.

WEP131	A New Approach to Calculate the Transport Matrix in RF cavities	cavity, acceleration, linac, focusing	1725
	Y.I. Eidelman BINP SB RAS, Novosibirsk, Russia N.V. Mokhov, S. Nagaitsev, N. Solyak Fermilab, Batavia, USA
	Funding: Work supported by USDoE A realistic approach to calculate the transport matrix in RF cavities is developed. It is based on joint solution of equations of longitudinal and transverse motion of a charged particle in an electromagnetic field of the linac. This field is a given by distribution (measured or calculated) of the component of the longitudinal electric field on the axis of the linac. New approach is compared with other matrix methods to solve the same problem. The comparison with code ASTRA has been carried out. Complete agreement for tracking results for a TESLA-type cavity is achieved. A corresponding algorithm has been implemented into the MARS15 code.

WEP133	Adaptive Space-charge Meshing in the General Particle Tracer Code	electron, simulation, brightness, injection	1728
	S.B. van der Geer Pulsar Physics, Eindhoven, The Netherlands O.J. Luiten, M.J. de Loos TUE, Eindhoven, The Netherlands G. Pöplau, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
	Efficient and accurate space-charge calculations are essential for the design of high-brightness charged particle sources. Space-charge calculations in the General Particle Tracer (GPT) code make use of an efficient multigrid Poisson solver developed for non-equidistant meshes at Rostock University. GPT uses aggressive mesh-adaptation with highly non-equidistant spacing to speed up calcula- tion time, where the mesh line positions are based upon the projected charge density. Here we present a new meshing scheme where the solution of an intermediate step in the multigrid algorithm is used to define optimal mesh line positions. An analytical test case and comparison with a molecular dynamics calculation of an ultrafast electron diffraction experiment demonstrate the capabilities of this new algorithm in the GPT code.

WEP136	Modelling of the EMMA ns-FFAG Ring Using GPT	injection, quadrupole, emittance, electron	1734
	R.T.P. D'Arcy UCL, London, United Kingdom J.K. Jones, B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	EMMA (Electron Machine with Many Applications) is a prototype non-scaling Fixed-Field Alternating Gradient (ns-FFAG) accelerator whose construction at Daresbury Laboratory, UK, was completed in Aug 2010. The energy recovery linac ALICE will serve as an injector for EMMA, within an energy range of 10^-20 MeV. The injection line consists of a dogleg to extract the beam from ALICE, a matching section, and tomography section for transverse emittance measurements. This is followed by a transport section to the injection point of the EMMA ring. The ring is composed of forty two cells, each containing one focusing and one defocusing quadrupole. Commissioning of the EMMA ring started in late 2010. A number of different injection energy and bunch charge regimes are planned; for some of the regimes the effects of space charge may be significant. It is therefore necessary to model the electron beam transport in the injection line and the ring using a code capable of both calculating the effect of and compensating for space charge. Therefore the General Particle Tracer (GPT) code has been used. A range of injection beam parameters have been modelled for comparison with experimental results.

WEP157	An Implementation of the Fast Multipole Method for High Accuracy Particle Tracking of Intense Beams	multipole, simulation, hadron, brightness	1782
	E.W. Nissen, B. Erdelyi Northern Illinois University, DeKalb, Illinois, USA
	We implement a single level version of the fast multipole method in the software package COSY Infinity. This algorithm has been used in other physics fields to determine high accuracy electrostatic potentials, and is implemented here for charged particle beams. The method scales like NlogN with the particle number and has a priori error estimates, which can be reduced to essentially machine precision if multipole expansions of high enough order are employed, resulting in a highly accurate algorithm for simulation of intense beams without averaging such as encountered in PIC methods. In order to further speed up the algorithm we use COSY Infinity’s innate differential algebraic methods to help with the expansions inherent in this system. Differential algebras allow for fast and exact numerical differentiation of functions that carries through any mathematical transformations performed, and can be used to quickly create the expansions used in the fast multipole method. This can then be combined with moment method techniques to extract transfer maps which include space charge within distributions that are difficult to approximate.

WEP160	Inclusion of Surface Roughness Effects in Emission Modeling With the MICHELLE Code	cathode, electron, brightness, emittance	1788
	J.F. DeFord STAAR/AWR Corporation, Mequon, USA N.J. Dionne, S.G. Ovtchinnikov, J.J. Petillo SAIC, Burlington, Massachusetts, USA
	High-brightness electron beams are needed in millimeter-wave tubes and other high-power RF applications. Cathode surface roughness at the micron scale, commonly due to machining or other effects, can lead to broadening of the velocity distribution of electrons downstream, increasing emittance and lowering beam brightness. In this paper we investigate methods of including surface roughness effects in the MICHELLE code. Modeling of typical surface imperfections over an entire cathode is not feasible, since it requires representation of features that are 3 to 5 orders of magnitude smaller than the cathode. Moreover, the actual surface imperfections for a given cathode are unknown without a prohibitive microscopic investigation of the surface, and these details vary between cathodes with the same machining history. To avoid these problems we investigated modifications to emission models that can account for these effects in an average sense, allowing the use of a smooth emission surface in a model while retaining the essential effects of the rough surface on the beam. We present the results of this investigation, along with representative solutions for sample structures. John Petillo, et al., “Recent Developments in the MICHELLE 2D/3D Electron Gun and Collector Modeling Code”, IEEE Trans. Electron Devices Sci., vol. 52, no. 5, May 2005, pp. 742-748.

WEP164	Accelerating Beam Dynamics Simulations with GPUs	quadrupole, simulation, collective-effects, acceleration	1800
	I.V. Pogorelov, K. Amyx, P. Messmer Tech-X, Boulder, Colorado, USA
	Funding: This work is funded by the DOE/BES Grant No. DE-SC0004585, and by Tech-X Corp. We present recent results of prototyping general-purpose particle tracking on GPUs, discussing our CUDA implementation of transfer maps for single-particle dynamics and collective effects. Our goal being incorporation of the GPU-accelerated tracking into ANL's accelerator code ELEGANT, we used the code's quadrupole and drift-with-LSC elements as test cases. We discuss the use of data-parallel and hardware-assisted approaches (segmented scan and atomic updates) for resolving memory contention issues at the charge deposition stage of algorithms for modeling collective effects.

WEP270	A High Current Density Li+ Alumino-silicate Ion Source for Target Heating Experiments	ion, extraction, ion-source, target	1981
	P.K. Roy, W.G. Greenway, J.W. Kwan, P.A. Seidl, W.L. Waldron LBNL, Berkeley, California, USA
	Funding: This work was performed under the auspices of the U.S Department of Energy by LLNL under contract DE AC52 07NA27344, and by LBNL under contract DE-AC02-05CH11231. The NDCX-II accelerator has been designed for target heating experiments in the warm dense matter regime. It will use a large diameter (≈ 10.9 cm) Li+ doped alumino-silicate source with a pulse duration of 0.5 μs, and beam current of ≈ 93 mA. Characterization of a prototype lithium alumino-silicate sources is presented. Using 6.35 mm diameter prototype emitters (coated and sintered on a ≈ 75% porous tungsten substrate), at a temperature of ≈1275° C, a space-charge limited Li+ beam current density of ≈ 1 mA/cm² was measured. At higher extraction voltage, the source is emission limited at around ≈ 1.5 mA/cm², weakly dependent on the applied voltage. The lifetime of the ion source is ≈ 50 hours while pulsing the extraction voltage at 2 to 3 times per minute. Measurements under these conditions show that the lifetime of the ion source does not depend only on beam current extraction, and lithium loss may be dominated by neutral loss or by evaporation. The thickness of the coating does not affect the emission density. It is inferred that pulsed heating, synchronized with the beam pulse rate may increase the life time of a source.

WEP280	Development of an Ultra-Low-Emittance RF PhotoInjector for a Future X-Ray FEL Oscillator	emittance, laser, cavity, gun	2005
	X.W. Dong, K.-J. Kim, N. Sereno, C.-X. Wang, A. Zholents ANL, Argonne, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DEAC02-06CH11357. The proposed x-ray free-electron laser oscillator* requires continuous electron bunches with ultra-low normalized transverse emittance of less than 0.1 micrometer, a bunch charge of 40 pC, an rms uncorrelated energy spread of less than 1.4 MeV, produced at a rate between 1 MHz to 10 MHz. The bunches are to be compressed to an rms length of ~1 ps and accelerated to the final energy of 7 GeV. In this paper, we discuss a design for an ultra-low-emittance injector based on a 325-MHz room-temperature rf cavity and a Cs2Te photocathode. The results of initial optimizations of the beam dynamics with a focus on extracting and preserving ultra-low emittance will be presented. * K.-J. Kim et al., Phys. Rev. Lett. 100, 244802 (2008).

THP081	Beam Lifetime and Limitations during Low-Energy RHIC Operation	emittance, ion, collider, luminosity	2285
	A.V. Fedotov, M. Bai, M. Blaskiewicz, W. Fischer, D. Kayran, C. Montag, T. Satogata, S. Tepikian, G. Wang BNL, Upton, Long Island, New York, USA
	Funding: Work performed under contract No. DE-AC02-98CH10886 with the auspices of the DoE of United States. The low-energy physics program at the Relativistic Heavy Ion Collider (RHIC), motivated by a search for the QCD phase transition critical point, requires operation at low energies. At these energies, large nonlinear magnetic field errors and large beam sizes produce low beam lifetimes. A variety of beam dynamics effects such as Intrabeam Scattering (IBS), space charge and beam-beam forces also contribute. All these effects are important to understand beam lifetime limitations in RHIC at low energies. During the low-energy RHIC physics run in May-June 2010 at beam γ=6.1 and γ=4.1, gold beam lifetimes were measured for various values of space-charge tune shifts, transverse acceptance limitation by collimators, synchrotron tunes and RF voltage. This paper summarizes our observations and initial findings.

THP200	Photoinjector Beam Dynamics for a Next Generation X-Ray FEL	emittance, FEL, bunching, laser	2495
	C. F. Papadopoulos, J.N. Corlett, D. Filippetto, G. Penn, J. Qiang, F. Sannibale, J.W. Staples, M. Venturini, R.P. Wells, M.S. Zolotorev LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231. In this paper, we will present the status of the beam dynamics simulations for a Next Generation Light Source (NGLS) injector, based on a high repetition rate (1 MHz), high brightness design. A multi-stage beam compression scheme is proposed, based on the concepts of velocity bunching and emittance compensation. For the optimization of the design parameters we use a genetic algorithm approach, and we focus on a mode providing charges of 300 pC, with normalized transverse emittance less than 0.6 microns, suitable to operate a next generation light source based on an X-ray FEL. In addition, we discuss the effects of bunch compression and linearity of the transverse and longitudinal phase space of the beam.

Paper

Title

Other Keywords

Page

MOOBS2

Status of High Intensity Effects in the Spallation Neutron Source Accumulator Ring

coupling, injection, resonance, collective-effects

17

S.M. Cousineau
ORNL, Oak Ridge, Tennessee, USA

Funding: This research is supported by UT-Battelle, LLC for the U. S. Department of Energy under contract No. DE-AC05-00OR22725
The 248-meter Spallation Neutron Source (SNS) accumulator ring has accumulated up to 1.55·10¹⁴, 1 GeV protons. At this intensity, space charge effects contribute significantly to the beam dynamics. Here we present observations of space charge effects in the SNS ring, with emphasis on space charge effects and e-p instabilities.

Slides MOOBS2 [3.704 MB]

MOOBS3

Bunch-End Interpenetration During Evolution to Longitudinal Uniformity in a Space-Charge-Dominated Storage Ring

simulation, electron, diagnostics, longitudinal-dynamics

22

T.W. Koeth, B.L. Beaudoin, S. Bernal, I. Haber, R.A. Kishek, P.G. O'Shea
UMD, College Park, Maryland, USA

The University of Maryland Electron Ring is a facility for study of the novel physics that occurs as intense space-charge-dominated beams that are transported over long distances. An example presented here is the role of space-charge longitudinal expansion and bunch-end interpenetration in the relaxation of a coasting bunch towards uniformly filling the ring. By comparing experiment to simplified longitudinal simulations the relaxation process is shown to be largely independent of details of the transverse dynamics. However, to get detailed agreement it was found necessary to include the consequences of transverse current loss. Since the AC coupled diagnostics lose information on any DC current loss, a novel beam knockout technique was developed to recover this information.

Slides MOOBS3 [2.501 MB]

MOOCS5

Space-charge Effects in H⁻ Low-energy Beam Transport of LANSCE

emittance, beam-transport, simulation, vacuum

64

Y.K. Batygin, C. Pillai, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

The 750-keV low-energy beam transport of the Los Alamos Neutron Science Center (LANSCE) linac consists of two independent beam lines for simultaneous injection of H⁺ and H⁻ beams into the linear accelerator. While transport of the H⁺ beam is seriously affected by uncompensated space charge forces, the same effect for H⁻ is hidden by presence of multiple beam collimators and beam chopping. Recent results from beam development experiments indicate a significant influence of space charge on H⁻ beam dynamics in the low-energy beam transport. Measurements of beam emittance along beam transport show the formation of S-shaped filamentation in the particle distribution phase space, typical with the presence of non-linear space charge forces. Results are supported by particle tracking simulations with the PARMILA, BEAMPATH, and TRACE codes.

Slides MOOCS5 [6.304 MB]

MOODS1

Space-Charge Effects in Bunched and Debunched Beams

focusing, electron, linac, emittance

85

B.L. Beaudoin, S. Bernal, K. Fiuza, I. Haber, R.A. Kishek, T.W. Koeth, P.G. O'Shea, M. Reiser, D.F. Sutter
UMD, College Park, Maryland, USA

Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office
The University of Maryland Electron Ring (UMER) is a machine designed to study high-intensity beam physics. With the application of axial fields to the bunch ends, we are able to keep a beam with an injected tune shift of 1.0, bunched over multiple turns. This is feasible with the application of tailored fields to optimally match the space-charge self-fields while minimizing the excitation of longitudinal space-charge waves. With this scheme, we have been able to extend the number of turns at the University of Maryland Electron Ring (UMER) by a factor of ten. Without the use of longitudinal focusing, head and tail effects begin to dominate, especially with the higher current beams. Time resolved measurements of the peak correlated energy spread have shown in some cases a change in the overall spread of 1.8% for the 0.6 mA beam, from the injected beam energy.

Slides MOODS1 [2.834 MB]

MOP152

G4beamline Particle Tracking in Matter Dominated Beam Lines

simulation, collider, electron, wakefield

373

T.J. Roberts, K.B. Beard
Muons, Inc, Batavia, USA
S. Ahmed
JLAB, Newport News, Virginia, USA
D. Huang, D.M. Kaplan
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86281
The G4beamline program is a useful and steadily improving tool to quickly and easily model beam lines and experimental equipment without user programming. It has both graphical and command-line user interfaces. Unlike most accelerator physics codes, it easily handles a wide range of materials and fields, being particularly well suited for the study of muon and neutrino facilities. As it is based on the Geant4 toolkit, G4beamline includes most of what is known about the interactions of particles with matter. We are continuing the development of G4beamline to facilitate its use by a larger set of beam line and accelerator developers. A major new feature is the calculation of space-charge effects. G4beamline is open source and freely available.

MOP243

Design of a Compact, High-Resolution Analyzer for Longitudinal Energy Studies in the University of Maryland Electron Ring

focusing, simulation, electron, high-voltage

571

E.C. Voorhies, S. Bernal, I. Haber, R.A. Kishek, T.W. Koeth, P.G. O'Shea
UMD, College Park, Maryland, USA

Funding: Work supported by US Dept. of Energy Offices of High Energy Physics and Fusion Energy Sciences, the Dept. of Defense Office of Naval Research, and the Joint Technology Office.
Retarding-potential energy analyzers have long been used for energy spread measurements in low-energy beams. In addition to energy spread and energy profile measurements, a high-resolution analyzer can be used to reconstruct the longitudinal phase space. This is useful for our experimental studies of longitudinal physics topics, such as dispersion, space charge waves, and longitudinal focusing. A previous energy analyzer designed at the University of Maryland demonstrated high-resolution measurements of a 5 keV electron beam.* Motivated by the need to characterize the 10 keV electron beam of the University of Maryland Electron Ring, we have improved on the design of the earlier analyzer, increasing its high voltage breakdown threshold and vacuum performance. Results of high-voltage testing and particle optics simulations of the new design are presented.
*Y. Cui, Y. Zou, et al., "Design and Operation of a Retarding Field Energy Analyzer with Variable Focusing for Space-Charge Dominated Electron Beams," Review of Scientific Instruments 75(8), 2736 (2004).

TUP011

Multipactor Dynamics in Dielectric-loaded Accelerator Structures

electron, multipactoring, simulation, plasma

829

O.V. Sinitsyn, T.M. Antonsen, G.S. Nusinovich
UMD, College Park, Maryland, USA

Funding: This work has been supported by the Office of High Energy Physics of the U.S. Department of Energy.
In this paper the authors present results of threedimensional analysis of multipactor in dielectric-loaded accelerator structures. The studies are aimed at checking some assumptions that were used in previous two-dimensional theory. In particular, it is demonstrated that the spatial distribution of charged particles can be azimuthally non-uniform which suggests using a more complex space charge model in some cases. Also, it is shown that the particle axial velocity components can be making a substantial contribution to particle energy and should not be ignored in future studies.

WEP092

Space Charge Effect of the High Intensity Proton Beam during the Resonance Extraction for the MU2E Experiment at Fermilab

extraction, septum, sextupole, resonance

1645

C.S. Park, J.F. Amundson, J.A. Johnstone, V.P. Nagaslaev, S.J. Werkema
Fermilab, Batavia, USA

The proposed Mu2e experiment to search for direct μ to e conversion at Fermilab plans slow, resonant extraction of a beam with 3× 10¹² protons from the Debuncher ring. Space charge of this high intensity beam is a critical factor, since it induces significant betatron tune spread and consequently affects resonance extraction processes, such as spill uniformity and beam losses. This study shows the multi-particle simulation results in the early stages of resonance extraction and spill uniformity in the presence of 2D and 3D space charge effects.

WEP094

Space Charge Measurements with a High Intensity Bunch at the Fermilab Main Injector

proton, simulation, emittance, injection

1648

K. Seiya, B. Chase, J.E. Dey, P.W. Joireman, I. Kourbanis
Fermilab, Batavia, USA
A. Yagodnitsyna
NSU, Novosibirsk, Russia

Fermilab Main Injector will be required to operate with 3 times higher bunch intensity than today for Project X. The plan to study the space charge effects at the injection energy with intense bunches will be discussed.

WEP096

Simulations of Space Charge in the Fermilab Main Injector

emittance, simulation, proton, lattice

1654

E.G. Stern, J.F. Amundson, P. Spentzouris
Fermilab, Batavia, USA
J. Qiang, R.D. Ryne
LBNL, Berkeley, California, USA

The Fermilab Project X plan for future high intensity running relies on the Main Injector as the engine for delivering protons in the 60-120 GeV energy range. Project X plans call for increasing the number of protons per Main Injector bunch from the current value of 1.0× 10¹¹ to 3.0× 10¹¹. Space charge effects at the injection energy of 8 GeV have the potential to seriously disrupt operations. We report on ongoing simulations with Synergia, our multi-physics process accelerator modeling framework, to model space charge effects in the Main Injector combined with the effects of magnet fringe fields and apertures.

WEP098

Formation of High Charge State Heavy Ion Beams with Intense Space Charge

ion, target, electron, heavy-ion

1657

P.A. Seidl, J.-L. Vay
LBNL, Berkeley, California, USA

Funding: This work was performed under the auspices of the U.S Department of Energy by LBNL under contract DE-AC02-05CH11231.
High charge-state heavy-ion beams are of interest and used for a number of accelerator applications. Some accelerators produce the beams downstream of the ion source by stripping bound electrons from the ions as they pass through a foil or gas. In other accelerator systems, ions of charge state >1 are produced directly in the ion source. Heavy-ion inertial fusion (HIF) would benefit from low-emittance, high current ion beams with charge state >1. For these accelerators, the desired dimensionless perveance upon extraction from the emitter is ~0.001, and the electrical current of the beam pulse is ~ 1 A. For accelerator applications where high charge state and very high current are desired, space charge effects might present unique challenges. For example, in a stripper, the separation of charge states might create significant nonlinear space-charge forces which would impact the beam brightness. We will report on the particle-in-cell simulation of the formation of such beams for HIF, and review the possible technical approaches.

WEP099

Numerical Solution for the Potential and Density Profile of a Thermal Equilibrium Sheet Beam

focusing, plasma, ion, controls

1659

S.M. Lund
LLNL, Livermore, California, USA
G. Bazouin
LBNL, Berkeley, California, USA

Funding: This research was performed under the auspices of the US DOE at the Lawrence Livermore and Lawrence Berkeley National Laboratories under contract numbers DE-AC52-07NA27344 and DE-AC02-05CH11231.
A one-dimensional Vlasov-Poisson model for sheet beams is presented to provide a simple framework for analysis of space-charge effects. Centroid and rms envelope equations including image charge effects are derived and reasonable parameter equivalences with commonly employed 2D transverse models of unbunched beams are established. This sheet beam model is applied to analyze several problems of fundamental interest. First, a sheet beam thermal equilibrium distribution in a continuous focusing channel is constructed and shown to have analogous properties to two- and three-dimensional thermal equilibrium models in terms of the equilibrium structure and Deybe screening properties. Second, the simpler formulation for sheet beams is exploited to explicitly calculate the distribution of particle oscillation frequencies within a thermal equilibrium beam. It is shown that as space-charge intensity increases, the frequency distribution becomes broad which suggesting robust stability properties for beams with strong space-charge.

WEP101

Smooth Approximation of Dispersion with Strong Space Charge

emittance, beam-transport, heavy-ion, focusing

1665

S. Bernal, B.L. Beaudoin, T.W. Koeth, P.G. O'Shea
UMD, College Park, Maryland, USA

Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office.
We apply the Venturini-Reiser envelope-dispersion equations* to a continuous beam in a uniform focusing/bending lattice to study the combined effects of linear dispersion and space charge. Within this simple model we investigate the scaling of average dispersion and the effects on beam dimensions; we also introduce a generalization of the space-charge intensity parameter and apply it to the University of Maryland Electron Ring (UMER) and other machines. In addition, we present results of calculations to test the smooth approximation by solving the Venturini-Reiser original equations and also through simulations with the code ELEGANT.
*M. Venturini and M. Reiser, Phys. Rev. Lett. 81, 1, p. 96, 6 July 1998

WEP102

Current Dependent Tune Shifts in the University of Maryland Electron Ring UMER

vacuum, electron, storage-ring, focusing

1668

D.F. Sutter, B.L. Beaudoin, S. Bernal, M. Cornacchia, R.A. Kishek, T.W. Koeth, P.G. O'Shea
UMD, College Park, Maryland, USA

Funding: Work supported by the U.S. DOE Offices of High Energy Physics and Fusion Energy Sciences and by the U.S. DOD Office of Naval Research and Joint Technology Office.
The shift in betatron tunes as a function of space charge has been studied in many accelerators and storage rings. Because of its low operating energy (10 keV, γ = 1.02) and wide range of beam currents (0.6 to 100 mA, corresponding respectively to predicted incoherent tune shifts of 1.2 to 5.2), the University of Maryland electron ring (UMER) provides a unique opportunity to study space charge driven tune shifts over a wide parameter space. Comparisons of predictions and measurements are presented, including a discussion of special factors such as the magnetic penetration of the vacuum chamber walls.

WEP131

A New Approach to Calculate the Transport Matrix in RF cavities

cavity, acceleration, linac, focusing

1725

Y.I. Eidelman
BINP SB RAS, Novosibirsk, Russia
N.V. Mokhov, S. Nagaitsev, N. Solyak
Fermilab, Batavia, USA

Funding: Work supported by USDoE
A realistic approach to calculate the transport matrix in RF cavities is developed. It is based on joint solution of equations of longitudinal and transverse motion of a charged particle in an electromagnetic field of the linac. This field is a given by distribution (measured or calculated) of the component of the longitudinal electric field on the axis of the linac. New approach is compared with other matrix methods to solve the same problem. The comparison with code ASTRA has been carried out. Complete agreement for tracking results for a TESLA-type cavity is achieved. A corresponding algorithm has been implemented into the MARS15 code.

WEP133

Adaptive Space-charge Meshing in the General Particle Tracer Code

electron, simulation, brightness, injection

1728

S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands
O.J. Luiten, M.J. de Loos
TUE, Eindhoven, The Netherlands
G. Pöplau, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany

Efficient and accurate space-charge calculations are essential for the design of high-brightness charged particle sources. Space-charge calculations in the General Particle Tracer (GPT) code make use of an efficient multigrid Poisson solver developed for non-equidistant meshes at Rostock University. GPT uses aggressive mesh-adaptation with highly non-equidistant spacing to speed up calcula- tion time, where the mesh line positions are based upon the projected charge density. Here we present a new meshing scheme where the solution of an intermediate step in the multigrid algorithm is used to define optimal mesh line positions. An analytical test case and comparison with a molecular dynamics calculation of an ultrafast electron diffraction experiment demonstrate the capabilities of this new algorithm in the GPT code.

WEP136

Modelling of the EMMA ns-FFAG Ring Using GPT

injection, quadrupole, emittance, electron

1734

R.T.P. D'Arcy
UCL, London, United Kingdom
J.K. Jones, B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

EMMA (Electron Machine with Many Applications) is a prototype non-scaling Fixed-Field Alternating Gradient (ns-FFAG) accelerator whose construction at Daresbury Laboratory, UK, was completed in Aug 2010. The energy recovery linac ALICE will serve as an injector for EMMA, within an energy range of 10^-20 MeV. The injection line consists of a dogleg to extract the beam from ALICE, a matching section, and tomography section for transverse emittance measurements. This is followed by a transport section to the injection point of the EMMA ring. The ring is composed of forty two cells, each containing one focusing and one defocusing quadrupole. Commissioning of the EMMA ring started in late 2010. A number of different injection energy and bunch charge regimes are planned; for some of the regimes the effects of space charge may be significant. It is therefore necessary to model the electron beam transport in the injection line and the ring using a code capable of both calculating the effect of and compensating for space charge. Therefore the General Particle Tracer (GPT) code has been used. A range of injection beam parameters have been modelled for comparison with experimental results.

WEP157

An Implementation of the Fast Multipole Method for High Accuracy Particle Tracking of Intense Beams

multipole, simulation, hadron, brightness

1782

E.W. Nissen, B. Erdelyi
Northern Illinois University, DeKalb, Illinois, USA

We implement a single level version of the fast multipole method in the software package COSY Infinity. This algorithm has been used in other physics fields to determine high accuracy electrostatic potentials, and is implemented here for charged particle beams. The method scales like NlogN with the particle number and has a priori error estimates, which can be reduced to essentially machine precision if multipole expansions of high enough order are employed, resulting in a highly accurate algorithm for simulation of intense beams without averaging such as encountered in PIC methods. In order to further speed up the algorithm we use COSY Infinity’s innate differential algebraic methods to help with the expansions inherent in this system. Differential algebras allow for fast and exact numerical differentiation of functions that carries through any mathematical transformations performed, and can be used to quickly create the expansions used in the fast multipole method. This can then be combined with moment method techniques to extract transfer maps which include space charge within distributions that are difficult to approximate.

WEP160

Inclusion of Surface Roughness Effects in Emission Modeling With the MICHELLE Code

cathode, electron, brightness, emittance

1788

J.F. DeFord
STAAR/AWR Corporation, Mequon, USA
N.J. Dionne, S.G. Ovtchinnikov, J.J. Petillo
SAIC, Burlington, Massachusetts, USA

High-brightness electron beams are needed in millimeter-wave tubes and other high-power RF applications. Cathode surface roughness at the micron scale, commonly due to machining or other effects, can lead to broadening of the velocity distribution of electrons downstream, increasing emittance and lowering beam brightness. In this paper we investigate methods of including surface roughness effects in the MICHELLE code*. Modeling of typical surface imperfections over an entire cathode is not feasible, since it requires representation of features that are 3 to 5 orders of magnitude smaller than the cathode. Moreover, the actual surface imperfections for a given cathode are unknown without a prohibitive microscopic investigation of the surface, and these details vary between cathodes with the same machining history. To avoid these problems we investigated modifications to emission models that can account for these effects in an average sense, allowing the use of a smooth emission surface in a model while retaining the essential effects of the rough surface on the beam. We present the results of this investigation, along with representative solutions for sample structures.
*John Petillo, et al., “Recent Developments in the MICHELLE 2D/3D Electron Gun and Collector Modeling Code”, IEEE Trans. Electron Devices Sci., vol. 52, no. 5, May 2005, pp. 742-748.

WEP164

Accelerating Beam Dynamics Simulations with GPUs

quadrupole, simulation, collective-effects, acceleration

1800

I.V. Pogorelov, K. Amyx, P. Messmer
Tech-X, Boulder, Colorado, USA

Funding: This work is funded by the DOE/BES Grant No. DE-SC0004585, and by Tech-X Corp.
We present recent results of prototyping general-purpose particle tracking on GPUs, discussing our CUDA implementation of transfer maps for single-particle dynamics and collective effects. Our goal being incorporation of the GPU-accelerated tracking into ANL's accelerator code ELEGANT, we used the code's quadrupole and drift-with-LSC elements as test cases. We discuss the use of data-parallel and hardware-assisted approaches (segmented scan and atomic updates) for resolving memory contention issues at the charge deposition stage of algorithms for modeling collective effects.

WEP270

A High Current Density Li+ Alumino-silicate Ion Source for Target Heating Experiments

ion, extraction, ion-source, target

1981

P.K. Roy, W.G. Greenway, J.W. Kwan, P.A. Seidl, W.L. Waldron
LBNL, Berkeley, California, USA

Funding: This work was performed under the auspices of the U.S Department of Energy by LLNL under contract DE AC52 07NA27344, and by LBNL under contract DE-AC02-05CH11231.
The NDCX-II accelerator has been designed for target heating experiments in the warm dense matter regime. It will use a large diameter (≈ 10.9 cm) Li+ doped alumino-silicate source with a pulse duration of 0.5 μs, and beam current of ≈ 93 mA. Characterization of a prototype lithium alumino-silicate sources is presented. Using 6.35 mm diameter prototype emitters (coated and sintered on a ≈ 75% porous tungsten substrate), at a temperature of ≈1275° C, a space-charge limited Li+ beam current density of ≈ 1 mA/cm² was measured. At higher extraction voltage, the source is emission limited at around ≈ 1.5 mA/cm², weakly dependent on the applied voltage. The lifetime of the ion source is ≈ 50 hours while pulsing the extraction voltage at 2 to 3 times per minute. Measurements under these conditions show that the lifetime of the ion source does not depend only on beam current extraction, and lithium loss may be dominated by neutral loss or by evaporation. The thickness of the coating does not affect the emission density. It is inferred that pulsed heating, synchronized with the beam pulse rate may increase the life time of a source.

WEP280

Development of an Ultra-Low-Emittance RF PhotoInjector for a Future X-Ray FEL Oscillator

emittance, laser, cavity, gun

2005

X.W. Dong, K.-J. Kim, N. Sereno, C.-X. Wang, A. Zholents
ANL, Argonne, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DEAC02-06CH11357.
The proposed x-ray free-electron laser oscillator* requires continuous electron bunches with ultra-low normalized transverse emittance of less than 0.1 micrometer, a bunch charge of 40 pC, an rms uncorrelated energy spread of less than 1.4 MeV, produced at a rate between 1 MHz to 10 MHz. The bunches are to be compressed to an rms length of ~1 ps and accelerated to the final energy of 7 GeV. In this paper, we discuss a design for an ultra-low-emittance injector based on a 325-MHz room-temperature rf cavity and a Cs2Te photocathode. The results of initial optimizations of the beam dynamics with a focus on extracting and preserving ultra-low emittance will be presented.
* K.-J. Kim et al., Phys. Rev. Lett. 100, 244802 (2008).

THP081

Beam Lifetime and Limitations during Low-Energy RHIC Operation

emittance, ion, collider, luminosity

2285

A.V. Fedotov, M. Bai, M. Blaskiewicz, W. Fischer, D. Kayran, C. Montag, T. Satogata, S. Tepikian, G. Wang
BNL, Upton, Long Island, New York, USA

Funding: Work performed under contract No. DE-AC02-98CH10886 with the auspices of the DoE of United States.
The low-energy physics program at the Relativistic Heavy Ion Collider (RHIC), motivated by a search for the QCD phase transition critical point, requires operation at low energies. At these energies, large nonlinear magnetic field errors and large beam sizes produce low beam lifetimes. A variety of beam dynamics effects such as Intrabeam Scattering (IBS), space charge and beam-beam forces also contribute. All these effects are important to understand beam lifetime limitations in RHIC at low energies. During the low-energy RHIC physics run in May-June 2010 at beam γ=6.1 and γ=4.1, gold beam lifetimes were measured for various values of space-charge tune shifts, transverse acceptance limitation by collimators, synchrotron tunes and RF voltage. This paper summarizes our observations and initial findings.

THP200

Photoinjector Beam Dynamics for a Next Generation X-Ray FEL

emittance, FEL, bunching, laser

2495

C. F. Papadopoulos, J.N. Corlett, D. Filippetto, G. Penn, J. Qiang, F. Sannibale, J.W. Staples, M. Venturini, R.P. Wells, M.S. Zolotorev
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
In this paper, we will present the status of the beam dynamics simulations for a Next Generation Light Source (NGLS) injector, based on a high repetition rate (1 MHz), high brightness design. A multi-stage beam compression scheme is proposed, based on the concepts of velocity bunching and emittance compensation. For the optimization of the design parameters we use a genetic algorithm approach, and we focus on a mode providing charges of 300 pC, with normalized transverse emittance less than 0.6 microns, suitable to operate a next generation light source based on an X-ray FEL. In addition, we discuss the effects of bunch compression and linearity of the transverse and longitudinal phase space of the beam.