Keyword: simulation
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MOOBS3 Bunch-End Interpenetration During Evolution to Longitudinal Uniformity in a Space-Charge-Dominated Storage Ring space-charge, 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 icon Slides MOOBS3 [2.501 MB]  
 
MOOBS4 Electron Cloud Experiments at Fermilab: Formation and Mitigation electron, proton, vacuum, instrumentation 27
 
  • R.M. Zwaska
    Fermilab, Batavia, USA
 
  We have performed a series at Fermilab to explore the Electron Cloud phenomenon. The Main Injector will have its beam intensity increased four-fold in the Project X upgrade, and would be subject to instabilities from the Electron Cloud. We present measurements of the Cloud formation in the Main Injector and experiments with materials for the mitigation of the Cloud. An experimental installation of Titanium-Nitride (TiN) coated beam pipes has been under study in the Main Injector since 2009; this material was directly compared to an adjacent stainless chamber through Electron Cloud measurement with Retarding Field Analyzers (RFAs). Over the long period of running we were able to observe the secondary electron yield (SEY) change and correlate it with electron fluence, establishing a conditioning history. Additionally, the installation has allowed measurement of the electron energy spectrum, comparison of instrumentation techniques, and energy-dependent behavior of the Electron Cloud. Finally, a new installation, developed in conjunction with Cornell and SLAC, will allow direct SEY measurement of material samples irradiated in the accelerator.  
slides icon Slides MOOBS4 [2.975 MB]  
 
MOOCS2 Numerical Verification of the Power Transfer and Wakefield Coupling in the CLIC Two-beam Accelerator wakefield, dipole, coupling, damping 51
 
  • A.E. Candel, K. Ko, Z. Li, C.-K. Ng, V. Rawat, G.L. Schussman
    SLAC, Menlo Park, California, USA
  • A. Grudiev, I. Syratchev, W. Wuensch
    CERN, Geneva, Switzerland
 
  The Compact Linear Collider (CLIC) provides a path to a multi-TeV accelerator to explore the energy frontier of High Energy Physics. Its two-beam accelerator concept envisions large complex 3D structures, which must be modeled to high accuracy so that simulation results can be directly used to prepare CAD drawings for machining. The required simulations include not only the fundamental mode properties of the accelerating structures but also the Power Extraction and Transfer Structure (PETS), as well as the coupling between the two systems. Time-domain simulations will be performed to understand pulse formation, wakefield damping, fundamental power transfer and wakefield coupling in these structures. Applying SLAC's parallel finite element code suite, these large-scale problems will be solved on some of the largest supercomputers available. The results will help to identify potential issues and provide new insights on the design, leading to further improvements on the novel two-beam accelerator scheme.  
slides icon Slides MOOCS2 [286.042 MB]  
 
MOOCS3 Numerical and Analytical Studies of Matched Kinetic Quasi-Equilibrium Solutions for an Intense Charged Particle Beam Propagating Through a Periodic Focusing Quadrupole Lattice focusing, lattice, quadrupole, plasma 56
 
  • E. Startsev, R.C. Davidson, M. Dorf
    PPPL, Princeton, New Jersey, USA
 
  Funding: Research supported by the U. S. Department of Energy.
A recently developed novel perturbative Hamiltonian transformation method which allows the determination of approximate matched kinetic quasi-equilibrium solutions for an intense charged particle beam propagating through a periodic focusing quadrupole lattice is presented.* Using this method we have identified numerically the class of self-consistent periodic kinetic 'equilibria' for intense beam propagation in alternating-gradient focusing systems, and extended the nonlinear perturbative particle simulation method to intense beam propagation in such systems. The new method has been implemented in the nonlinear perturbative particle-in-cell code BEST which is used to study properties of the newly constructed beam 'equilibria'. The results of these studies are presented and analyzed in detail.
* E.A. Startsev, R.C. Davidson and M. Dorf, Phys. Rev. ST Accel. Beams 13, 064402 (2010).
 
slides icon Slides MOOCS3 [0.508 MB]  
 
MOOCS5 Space-charge Effects in H Low-energy Beam Transport of LANSCE emittance, space-charge, beam-transport, 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 icon Slides MOOCS5 [6.304 MB]  
 
MOODN1 Results of Head-on Beam-beam Compensation Studies at the Tevatron antiproton, electron, proton, emittance 67
 
  • A. Valishev, G. Stancari
    Fermilab, Batavia, USA
 
  Funding: Work supported by the Fermi Research Alliance, LLC under Contract DE-AC02-07CH11359 with the United States Department of Energy, and by the DOE through the US LHC Accelerator Research Program (LARP).
At the Tevatron collider, we studied the feasibility of suppressing the antiproton head-on beam-beam tune spread using a magnetically confined 5-keV electron beam with Gaussian transverse profile overlapping with the circulating beam. When electron cooling of antiprotons is applied in regular Tevatron operations, the head-on beam-beam effect on antiprotons is small. Therefore, we first focused on the operational aspects, such as beam alignment and stability, and on fundamental observations of tune shifts, tune spreads, lifetimes, and emittances. We also attempted two special collider stores with only 3 proton bunches colliding with 3 antiproton bunches, to suppress long-range forces and enhance head-on effects. We present here the results of this study and a comparison between numerical simulations and observations, in view of the planned application of this compensation concept to RHIC.
 
slides icon Slides MOODN1 [2.680 MB]  
 
MOODN2 Optimizing the Electron Beam Parameters for Head-on Beam-beam Compensation in RHIC proton, electron, dynamic-aperture, gun 70
 
  • Y. Luo, W. Fischer, X. Gu, A.I. Pikin
    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.
Head-on beam-beam compensation is adopted to compensate the large beam-beam tune spread from the proton-proton interactions at IP6 and IP8 in the Relativistic Heavy Ion Collider (RHIC). Two e-lenses are being built and to be in stalled near IP10 in the end of 2011. In this article we perform numeric simulation to investigate the effect of the electron beam parameters on the proton dynamics. The electron beam parameters include its transverse profile, size, current, offset and random errors in them.
 
slides icon Slides MOODN2 [0.601 MB]  
 
MOODN3 Advanced Bent Crystal Collimation Studies at the Tevatron (T-980) collimation, collider, controls, beam-losses 73
 
  • V.V. Zvoda, J. Annala, R.A. Carrigan, A.I. Drozhdin, T.R. Johnson, S. Kwan, N.V. Mokhov, A. Prosser, R.E. Reilly, R. Rivera, V.D. Shiltsev, D.A. Still, L. Uplegger, J.R. Zagel
    Fermilab, Batavia, USA
  • E. Bagli, V. Guidi, A. Mazzolari
    INFN-Ferrara, Ferrara, Italy
  • Y.A. Chesnokov, I.A. Yazynin
    IHEP Protvino, Protvino, Moscow Region, Russia
  • Yu.M. Ivanov
    PNPI, Gatchina, Leningrad District, Russia
 
  Funding: * Work is supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy through the US LHC Accelerator Research Program (LARP).
The T-980 bent crystal collimation experiment at the Tevatron has recently acquired substantial enhancements. First, two new crystals - a 16-strip one manufactured and characterized by the INFN Ferrara group and a quasi-mosaic crystal manufactured and characterized by the PNPI group. Second, a two plane telescope with 3 high-resolution pixel detectors per plane along with corresponding mechanics, electronics, control and software has been manufactured, tested and installed in the E0 crystal region. The purpose of the pixel telescope is to measure and image channeled (CH), volume-reflected (VR) and multiple volume-reflected (MVR) beam profiles produced by bent crystals. Third, an ORIGIN-based system has been developed for thorough analysis of experimental and simulation data. Results of analysis are presented for different types of crystals used from 2005 to present for channeling and volume reflection including pioneering tests of two-plane crystal collimation at the collider, all in comparison with detailed simulations.
 
slides icon Slides MOODN3 [1.052 MB]  
 
MOODN4 Beam Losses Due to Abrupt Crab Cavity Failures in the LHC cavity, collimation, luminosity, lattice 76
 
  • R. Calaga
    BNL, Upton, Long Island, New York, USA
  • T. Baer, J. Barranco, R. Tomás, J. Wenninger, F. Zimmermann
    CERN, Geneva, Switzerland
  • B. Yee-Rendon
    CINVESTAV, Mérida, Mexico
 
  Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
A major concern for the implementation of crab crossing in a future high-luminosity LHC (HL-LHC) is machine protection in an event of a fast crab-cavity failure. Certain types of abrupt crab-cavity phase and amplitude changes are simulated to characterize the effect of failures on the beam and the resulting particle-loss signatures. The time-dependent beam loss distributions around the ring and particle trajectories obtained from the simulations allow for a first assessment of the resulting beam impact on LHC collimators and on sensitive components around the ring. The simulation results are used to derive tolerances on the maximum rate of change in crab-cavity phase and amplitude which can be allowed with regard to machine safety.
 
slides icon Slides MOODN4 [1.620 MB]  
 
MOODS5 3D Electromagnetic Design and Beam Dynamics Simulations of a Radio-Frequency Quadrupole rfq, cavity, target, linac 97
 
  • B. Mustapha, A. Kolomiets, P.N. Ostroumov
    ANL, Argonne, USA
 
  Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
During the design of the 60.635 MHz RFQ for the ATLAS efficiency and intensity upgrade*, we have established a new full 3D approach for the electromagnetic and beam dynamics simulations of a RFQ. A Detailed full 3D model (four meter long) including vane modulation was built and simulated using CST Microwave Studio, which is made possible by the ever advancing computing capabilities. The approach was validated using experimental measurements on a prototype 57.5 MHz RFQ**. The effects of the radial matchers, vane modulation and tuners on the resonant frequency and field flatness have been carefully studied. The full 3D field distribution was used for beam dynamics simulations using both CST Particle Studio and the beam dynamics code TRACK***. In the final design we have used trapezoidal modulation instead of the standard sinusoidal in the accelerating section of the RFQ to achieve more energy gain for the same length, following the leading work of the Protvino group****. In our case, the output energy increased from 260 keV/u to 295 keV/u with minimal change in the beam dynamics.
* P.N. Ostroumov et al, Proceedings of LINAC-2010
** P.N. Ostroumov et al, Proceedings of LINAC-2006
*** TRACK @ http://www.phy.anl.gov/atlas/TRACK
**** O.K. Belyaev et al, Proceedings of LINAC-2000
 
slides icon Slides MOODS5 [2.531 MB]  
 
MOODS6 Beam Dynamics Simulations on the ESS Bilbao RFQ rfq, emittance, cavity, acceleration 100
 
  • D. de Cos, I. Bustinduy, O. Gonzalez, J.L. Munoz, A. Velez
    ESS Bilbao, Bilbao, Spain
  • F.J. Bermejo
    Bilbao, Faculty of Science and Technology, Bilbao, Spain
  • V. Etxebarria, J. Portilla
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
  • J. Feuchtwanger
    ESS-Bilbao, Zamudio, Spain
  • S. Jolly, P. Savage
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  • A.P. Letchford
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
 
  Funding: European Spallation Source - Bilbao
The Bilbao Accelerator RFQ is aimed to accelerate a 75 mA proton beam from 75 keV to 3 MeV, while keeping the beam both transversely and longitudinally focused, and presenting a minimum emittance growth. We report on the current status of the project, mainly focusing on the Beam Dynamics aspects of the design. Several particle simulations are carried out with RFQSIM, GPT and TRACK codes, in order to study the particle transmission of the RFQ under several circumstances, such as different current levels, vane geometry changes due to thermal stress, and different input beam characteristics obtained by changing the LEBT operation settings.
 
slides icon Slides MOODS6 [3.264 MB]  
 
MOP001 Charge Separation for Muon Collider Cooling emittance, solenoid, collider, acceleration 103
 
  • R. B. Palmer, R.C. Fernow
    BNL, Upton, Long Island, New York, USA
 
  Most schemes for six dimensional muon ionization cooling work for only one sign. It is then necessary to have charge separation prior to that cooling. Schemes of charge separation using bent solenoids are described, and their simulated performances reported. It is found that for efficient separation, it should take place at somewhat higher momenta than commonly used for the cooling.  
 
MOP002 Tapered Six-Dimensional Cooling Channel for a Muon Collider emittance, collider, solenoid, lattice 106
 
  • R. B. Palmer, R.C. Fernow
    BNL, Upton, Long Island, New York, USA
 
  A high-luminosity muon collider requires a reduction of the six-dimensional emittance of the captured muon beam by a factor of approximately 106. Most of this cooling takes place in a dispersive channel that simultaneously reduces all six phase space dimensions. We describe a tapered 6D cooling channel that should meet the requirements of a muon collider. The parameters of the channel are given and preliminary simulations are shown of the expected performance.  
 
MOP003 Six-Dimensional Bunch Merging for Muon Collider Cooling emittance, wiggler, kicker, collider 109
 
  • R. B. Palmer, R.C. Fernow
    BNL, Upton, Long Island, New York, USA
 
  A muon collider requires single, intense, muon bunches with small emittances in all six dimensions. It is most efficient to initally phase-rotate the muons into many separate bunches, cool these bunches in six dimensions (6D), and, when cool enough, merge them into single bunches (one of each sign). Previous studies only merged in longitudinal phase space (2D). In this paper we describe merging in all six dimensions (6D). The scheme uses rf for longitudinal merging, and kickers and transports with differing lengths (trombones) for transverse merging. Preliminary simulations, including incorporation in 6D cooling, is described.  
 
MOP010 Resonance, Particle Stability, and Acceleration in the Micro-Accelerator Platform electron, resonance, laser, acceleration 121
 
  • J.C. McNeur, J.B. Rosenzweig, G. Travish, J. Zhou
    UCLA, Los Angeles, USA
  • R.B. Yoder
    Manhattanville College, Purchase, New York, USA
 
  Funding: US Defense Threat Reduction Agency
A micron-scale dielectric-based slab-symmetric accelerator is currently being designed and fabricated at UCLA. This Micro-Accelerator Platform (MAP) accelerates electrons in a 800nm wide vacuum gap via a resonant accelerating mode excited by a side-coupled optical-wavelength laser. Detailed results of particle dynamics and field simulations are presented. In particular, we examine various methods of achieving net acceleration and particle stability. Additionally, structural designs that produce accelerating fields synchronous with both relativistic and sub-relativistic electrons are discussed.
 
 
MOP011 Standing Wakefield Accelerator Based on Periodic Dielectric Structures wakefield, electron, radiation, vacuum 124
 
  • X. Wei, G. Andonian, J.B. Rosenzweig, D. Stratakis
    UCLA, Los Angeles, USA
 
  In recent years dielectric wakefield accelerators (DWA) have attracted significant attention for applications in high energy physics and THz radiation sources. However, one needs sufficiently short driving bunches in order to take advantage of the DWA's scaling characteristics to achieve high gradient and high frequency accelerating fields. Since a single large charge Q driving bunch is difficult to be compressed to the needed rms bunch length, a driving bunch train with smaller Q and small emittance, should be used instead for the DWA. In view of this senario, the group velocity of the excited wakefields needs to be decreased to nearly zero, so the electromagnetic energy does not vacate the structure during the bunch train. In this paper we propose a standing wakefield accelerator based on periodic dielectric structures, and address the difference between the proposed structure and the conventional DWA.  
 
MOP012 Ultra-High Gradient Compact S-Band Accelerating Structure klystron, coupling, linac, vacuum 127
 
  • L. Faillace, R.B. Agustsson, P. Frigola, A.Y. Murokh
    RadiaBeam, Santa Monica, USA
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • V. Yakimenko
    BNL, Upton, Long Island, New York, USA
 
  Funding: Dept. of Energy DE-SC0000866
In this paper, we present the radio-frequency design of the DECA (Doubled Energy Compact Accelerator) S-band accelerating structure operating in the pi-mode at 2.856 GHz, where RF power sources are commonly available. The development of the DECA structure will offer an ultra-compact drop-in replacement for a conventional S-band linac in research and industrial applications such as drivers for compact light sources, medical and security systems. The electromagnetic design has been performed with the codes SuperFish and HFSS. The choice of the single cell shape derives from an optimization process aiming to maximize RF efficiency and minimize surface fields at very high accelerating gradients, i.e. 50 MV/m and above. Such gradients can be achieved utilizing shape-optimized elliptical irises, dual-feed couplers with the "fat-lip" coupling slot geometry, and specialized fabrication procedures developed for high gradient structures. The thermal-stress analysis of the DECA structure is also presented.
* V. Dolgashev, "Status of X-band Standing Wave Structure Studies at SLAC", SLAC-PUB-10124, (2003).
** C. Limborg et al., "RF Design of LCLS Gun", LCLS-TN-05-03 (2005).
 
 
MOP016 Preliminary Simulations of Plasma Wakefield Accelerator Experiments at FACET plasma, electron, wakefield, emittance 136
 
  • W. An, C. Joshi, W. Lu, W.B. Mori
    UCLA, Los Angeles, California, USA
  • M.J. Hogan
    SLAC, Menlo Park, California, USA
  • C. Huang
    LANL, Los Alamos, New Mexico, USA
 
  Funding: This work is supported by USDoE under DE-FC02-07ER41500, DE-FG02-92ER40727 and NSF under NSF PHY-0904039, PHY-0936266.
Recent experiments on former facility FFTB at SLAC has demonstrated that a single electron beam driven Plasma Wakefield Accelerator (PWFA) can be produced with an accelerating gradient of 52 GeV/m over a meter-long scale*. If another electron bunch is properly loaded into such a wakefield, it will obtain a high energy gain in a short distance as well as a small energy spread. Such PWFA experiment with two bunches will be performed in FACET, which is a new facility at SLAC**. Simulation results show that with possible beam parameters in FACET the first electron bunch (with less current than that in the FFTB experiment) can still produce a meter-long plasma column with a density of 5x1016 cm-3 via field ionization when we use a gas with a lower ionization energy. The second electron bunch can have a 10 GeV energy gain with a very narrow energy spread. If a pre-ionized plasma is used instead of the neutral gas, the energy gain of the second bunch can be enhanced to 30 GeV.
* I. Blumenfeld et al., Nature 445, 741 (2007).
** M. J.Hogan, et al.,NewJ. Phys.12, 055030(2010).
 
 
MOP017 A Sphere Cooler Scheme for Muon Cooling collider, solenoid, factory, high-voltage 139
 
  • Y. Bao
    MPI, Muenchen, Germany
  • A. Caldwell, D. Greenwald
    MPI-P, München, Germany
 
  Muon cooling is the greatest obstacle for producing an intensive muon beam. The frictional cooling method holds promise for delivering low-energy muon beams with narrow energy spreads. We outline a sphere cooler scheme based on frictional cooling to effectively produce such a “cold” muon beam. As an example source, we take the parameters of a surface muon source available at the Paul Scherrer Institute. Simulation results show that the sphere cooler has an efficiency of 50% to produce a “cold” muon beam with an energy spread of 0.9 keV. The high quality beam can potentially meet the requirements of a neutrino factory or a muon collider.  
 
MOP019 Performance of the Bucked Coils Muon Cooling Lattice for the Neutrino Factory lattice, emittance, factory, cavity 145
 
  • A. Alekou
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  • J. Pasternak
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  • C.T. Rogers
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
 
  Ionization cooling is essential to the Neutrino Factory in order to decrease the large emittance of the tertiary muon beam. Strong focusing and a large RF gradient in the cooling channel are required for efficient cooling; however, the presence of a strong magnetic field inside the RF cavities limits their performance by lowering the breakdown limit. In order to mitigate this problem a new lattice configuration, the Bucked Coils, is proposed: two solenoidal coils of different radius and opposite polarities are placed along the channel at the same z-positions. The Bucked Coils lower the magnetic field in the RF cavities while also providing strong focusing. This paper presents the results of the beam dynamics simulations in the new lattice, using the G4MICE code. The comparison of the achieved cooling performance and transmission between the currently proposed Neutrino Factory baseline lattice (FSIIA) and the new configuration is provided in detail.  
 
MOP036 Epicyclic Twin-Helix Ionization Cooling Simulations resonance, optics, quadrupole, betatron 163
 
  • A. Afanasev
    Hampton University, Hampton, Virginia, USA
  • Y.S. Derbenev, V.S. Morozov
    JLAB, Newport News, Virginia, USA
  • V. Ivanov, R.P. Johnson
    Muons, Inc, Batavia, USA
 
  Funding: Supported in part by DOE SBIR grant DE-SC0005589
Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. For the implementation of PIC, we earlier developed an epicyclic twin-helix channel with correlated behavior of the horizontal and vertical betatron motions and dispersion. We now insert absorber plates with short energy-recovering units located next to them at the appropriate locations in the twin-helix channel. We first demonstrate conventional ionization cooling in such a system with the optics uncorrelated. We then adjust the correlated optics state and induce a parametric resonance to study ionization cooling under the resonant condition.
 
 
MOP038 Non-Magnetic Momentum Spectrometer Based on Fast Time-of-Flight System electron, factory, scattering, cathode 169
 
  • R.J. Abrams, C.M. Ankenbrandt, G. Flanagan, S.A. Kahn, M. Notani, T.J. Roberts
    Muons, Inc, Batavia, USA
  • H.J. Frisch
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
 
  Funding: Supported in part by SBIR Grant DE-SC0005445
A new generation of large-area, low cost time-of-flight detectors with time resolutions ≤ 10 ps and space resolutions ≤ 1 mm is being developed for use in nuclear and particle physics experiments, as well as for medical and industrial applications. Such detectors can serve as the basis for measuring momenta without requiring measurement of curvature in magnetic fields. Factors affecting measurement accuracy and simulation results are presented.
 
 
MOP040 Fast Time-of-Flight System for Muon Cooling Experiments cathode, scattering, emittance, collider 172
 
  • R.J. Abrams, C.M. Ankenbrandt, G. Flanagan, S.A. Kahn, M. Notani, T.J. Roberts
    Muons, Inc, Batavia, USA
  • H.J. Frisch
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
 
  Funding: Supported in part by SBIR Grant DE-SC0005445.
A new generation of large-area, low cost time-of-flight detectors with time resolutions ≤ 10 ps and space resolutions ≤ 1 mm is being developed for use in nuclear and particle physics experiments, as well as for medical and industrial applications. Such detectors are being considered for use in muon cooling channel tests. Designs and fabrication of prototype planes and associated readout electronics are described. Results of simulations of time and space resolutions are presented.
 
 
MOP041 17 GHz Overmoded Dielectric Photonic Bandgap Accelerator Cavity cavity, lattice, HOM, vacuum 175
 
  • A.M. Cook, B.J. Munroe, M.A. Shapiro, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
 
  Funding: This research is supported by the U.S. Department of Energy, Office of High Energy Physics.
We present the design of an overmoded photonic band gap (PBG) accelerator cavity, made from a 2D lattice of sapphire rods supported between copper plates, that operates in a TM02-like mode at 17 GHz. The cavity does not support the lower-frequency TM01-like mode. Higher-order modes are damped effectively by removing rods from the lattice so that only the operating mode is supported with a high quality factor. The TM02 cavity mitigates the high pulsed heating of the copper surface seen in some metal-rod TM01 PBG cavities, which may be an advantage for high-gradient operation. We discuss plans for testing a 17 GHz TM02 standing-wave cavity at gradients above 100 MV/m.
 
 
MOP043 Simulations of a Muon Linac for a Neutrino Factory linac, acceleration, synchrotron, factory 181
 
  • K.B. Beard
    Muons, Inc, Batavia, USA
  • S.A. Bogacz, V.S. Morozov, Y. Roblin
    JLAB, Newport News, Virginia, USA
 
  Funding: Supported in part by DOE grant DE-FG-08ER86351
The Neutrino Factory baseline design involves a complex chain of accelerators including a single-pass linac, two recirculating linacs and an FFAG. The first linac follows the capture and bunching section and accelerates the muons from about 244 to 900 MeV. It must accept a high emittance beam about 30 cm wide with a 10% energy spread. This linac uses counterwound, shielded superconducting solenoids and 201 MHz superconducting cavities. Simulations have been carried out using several codes including Zgoubi, OptiM, GPT, and G4beamline, both to determine the optics and to estimate the radiation loads on the elements due to beam loss and muon decay.
 
 
MOP046 RF Breakdown Studies Using Pressurized Cavities cavity, vacuum, pick-up, plasma 184
 
  • R. Sah, A. Dudas, R.P. Johnson, M.L. Neubauer
    Muons, Inc, Batavia, USA
  • M. BastaniNejad, A.A. Elmustafa
    Old Dominion University, Norfolk, Virginia, USA
  • J.M. Byrd, D. Li
    LBNL, Berkeley, California, USA
  • M.E. Conde, W. Gai
    ANL, Argonne, USA
  • A. Moretti, M. Popovic, K. Yonehara
    Fermilab, Batavia, USA
  • D. Rose
    Voss Scientific, Albuquerque, New Mexico, USA
 
  Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and FRA DOE Contract DE-AC02-07CH11359
Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved, and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual gas and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of radiofrequency and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) has been built, and a series of detailed experiments is planned at the Argonne Wakefield Accelerator. These experiments will be followed by additional experiments using a second test cell operating at 402.5 MHz.
 
 
MOP047 Helical Channels with Variable Slip Factor for Neutrino Factories and Muon Colliders solenoid, collider, longitudinal-dynamics, target 187
 
  • C. Y. Yoshikawa, C.M. Ankenbrandt
    Muons, Inc, Batavia, USA
  • D.V. Neuffer, K. Yonehara
    Fermilab, Batavia, USA
 
  Funding: Supported in part by DOE SBIR grant DE-SC0002739.
In order to realize a muon collider or a neutrino factory based on a muon storage ring, the muons must be captured and cooled efficiently. For a muon collider, the resulting train of bunches should be coalesced into a single bunch. Design concepts for a system to capture, cool, and coalesce a muon beam are described here. In particular, variants of a helical channel are used, taking advantage of the ability to vary the slip factor and other parameters of such a channel. The cooling application has been described before; this paper reports recent studies of a system that includes two novel concepts to accomplish capture and coalescing via a slip-controlled helical channel.
 
 
MOP051 End-to-End Simulation of an Inverse Cyclotron for Muon Cooling cyclotron, emittance, injection, collider 193
 
  • K. Paul, E. Cormier-Michel
    Tech-X, Boulder, Colorado, USA
  • T. Hart, D.J. Summers
    UMiss, University, Mississippi, USA
 
  Funding: DOE Office of High-Energy Physics, SBIR DE-FG02-08ER85044
Neutrino factories and muon colliders require significant cooling of the muon beam. Most muon cooling channels are long and expensive single-pass structures, due to the difficulty injecting very large emittance beams into a circular device. Inverse cyclotrons can potentially solve the injection problems associated with other circular cooling channels, and they can potentially provide substantial initial cooling of the beam. We present the first end-to-end (injection to extraction) simulations of an inverse cyclotron for muon cooling, performed with the particle-in-cell code VORPAL. We study the cooling capability of the device as well as potential limitations due to space charge effects and material interactions with the beam.
 
 
MOP054 Racetrack Muon Ring Cooler Using Dipoles and Solenoids for a Muon Collider dipole, lattice, solenoid, collider 202
 
  • X.P. Ding, D.B. Cline
    UCLA, Los Angeles, California, USA
  • J.S. Berg, H.G. Kirk
    BNL, Upton, Long Island, New York, USA
  • A.A. Garren
    Particle Beam Lasers, Inc., Northridge, California, USA
 
  Funding: DOE Grant No. DE-FG02-92ER40695
A racetrack muon ring cooler for a muon collider is considered. The achromatic cooler uses both dipoles and solenoids. We describe the ring lattice and show the results of beam dynamic simulation that demonstrates a large aperture for acceptance. We also examine the 6D cooling of the muon beam in the cooler and discuss the prospects for the future.
 
 
MOP057 A SLAB Dielectric Structure as a Source of Wakefield Acceleration and THz Cherenkov Radiation Generation wakefield, radiation, acceleration, electron 211
 
  • D. Stratakis, G. Andonian, J.B. Rosenzweig, X. Wei
    UCLA, Los Angeles, California, USA
 
  Funding: Work is funded by US Dept. of Energy grant numbers DE-FG03-92ER40693.
Acceleration of electrons in wakefields set up by a series of drive bunches in a dielectric structure has been proposed as a possible component of next-generation accelerators. Here, we discuss future experimental work with a slab sub-millimeter dielectric loaded accelerator structure that in contrast to conventional dielectric tubes should diminish the effects of transverse wakes and will permit higher total charge to be accelerated. The proposed experiment will allow the generation of unprecedented peak power at THz frequencies. In addition, it can generate ~50-150 MV/m drive fields and thus will allow the testing of acceleration using witness and drive beams. We examine details of the geometry and composition of the structures to be used in the experiment.
 
 
MOP059 Simulations of the Tapered Guggenheim 6d Cooling Channel for the Muon Collider emittance, lattice, collider, extraction 217
 
  • P. Snopok
    IIT, Chicago, Illinois, USA
  • G.G. Hanson
    UCR, Riverside, California, USA
  • R. B. Palmer
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work is supported by the U.S. Department of Energy.
Recent progress in six-dimensional (6D) cooling simulations for the Muon Collider based on the RFOFO ring layout is presented. In order to improve the performance of the cooling channel a tapering scheme is studied that implies changing the parameters such as cell length, magnetic field strength, RF frequency, and the amount of the absorbing material along the cooling channel. This approach allows us to keep the cooling rates high throughout the process. The results of the simulations carried out in G4beamline are presented.
 
 
MOP060 Wedge Absorber Design and Simulation for MICE Step IV emittance, lattice, controls, scattering 220
 
  • C.T. Rogers
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • L. Coney, G.G. Hanson
    UCR, Riverside, California, USA
  • P. Snopok
    IIT, Chicago, Illinois, USA
 
  Funding: Work is supported by the Science and Technology Facilities Council, the U.S. Department of Energy and the U.S. National Science Foundation.
In the Muon Ionization Cooling Experiment (MICE), muons are cooled by passing through material, then through RF cavities to compensate for the energy loss; which reduces the transverse emittance. It is planned to demonstrate longitudinal emittance reduction via emittance exchange in MICE by using a solid wedge absorber in Step IV. Based on the outcome of previous studies, the shape and material of the wedge were chosen. We address here further simulation efforts for the absorber of choice as well as engineering considerations in connection with the absorber support design.
 
 
MOP062 Usage of Li-rods for Ionization Cooling of Muons emittance, plasma, collider, focusing 226
 
  • A.N. Skrinsky
    BINP SB RAS, Novosibirsk, Russia
  • T.V. Zolkin
    University of Chicago, Chicago, Illinois, USA
 
  Four different schemes of final ionization cooling are discussed. The first scheme is the straight channel based on lithium rods, which can provide only 4D cooling, but which can be modified to obtain 6D cooling. The helical orbit scheme with decrement redistribution is one such modification. Two other modifications use emittance redistribution and emittance exchange procedures, respectively, to transfer phase-space volume from longitudinal to transverse degrees of freedom (where the transverse degrees of freedom alternate for each successive exchange or redistribution). By emittance redistribution is meant a arbitrary redistribution of phase-space volume from one degree of freedom to another and by emittance exchange is meant a symplectic operation of emittance swap. Estimates of the final emittance, calculations of the technical parameters and simulations of beam movement are presented for each scheme. The study focused on the scheme with emittance exchange because it looks the most promising and simple, both conceptually and in terms of implementation, and it can also extend the cooling process to handle a larger initial emittance relative to the basic straight channel scheme.  
 
MOP064 Asymmetric Laser Radiant Cooling in Storage Rings electron, laser, photon, damping 229
 
  • E.V. Bulyak
    NSC/KIPT, Kharkov, Ukraine
  • J. Urakawa
    KEK, Ibaraki, Japan
  • F. Zimmermann
    CERN, Geneva, Switzerland
 
  Laser pulses with small spatial and temporal dimensions can interact with a fraction of the electron bunches circulating in Compton storage rings. We studied synchrotron dynamics of such bunches when laser photons scatter off from the electrons with energy higher than the synchronous energy. In this case of ‘asymmetric cooling', as shown theoretically, the stationary energy spread is much smaller than under conditions of regular scattering; the oscillations are damped faster. Coherent oscillations of large amplitude may be damped in one synchrotron period, which makes this method feasible for injection the bunches into a ring in the longitudinal phase space. The theoretical results are validated with simulations.  
 
MOP067 Vlasov and PIC Simulations of a Modulator Section for Coherent Electron Cooling ion, electron, plasma, shielding 235
 
  • G.I. Bell, D.L. Bruhwiler, I.V. Pogorelov, B.T. Schwartz
    Tech-X, Boulder, Colorado, USA
  • Y. Hao, V. Litvinenko, G. Wang
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work is supported by the US DOE Office of Science, Office of Nuclear Physics, grant numbers DE-SC0000835 and DE-FC02-07ER41499. Resources of NERSC were used under contract No. DE-AC02-05CH11231.
Next generation ion colliders will require effective cooling of high-energy hadron beams. Coherent electron cooling (CEC) can in principle cool relativistic hadron beams on orders-of-magnitude shorter time scales than other techniques. We present Vlasov-Poisson and delta-f particle-in-cell (PIC) simulations of a CEC modulator section. These simulations correctly capture the subtle time and space evolution of the density and velocity wake imprinted on the electron distribution via anisotropic Debye shielding of a drifting ion. We consider 1D and 2D reduced versions of the problem, and compare the exact solutions of Wang and Blaskiewicz with Vlasov-Poisson and delta-f PIC simulations. We also consider interactions under non-ideal conditions where there is a density gradient in the electron distribution, and present simulations of the ion wake.
* V.N. Litvinenko and Y.S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).
 
 
MOP072 Design of On-Chip Power Transport and Coupling Components for a Silicon Woodpile Accelerator coupling, laser, electron, optics 241
 
  • Z. Wu, E.R. Colby, C. McGuinness, C.-K. Ng
    SLAC, Menlo Park, California, USA
 
  Three-dimensional woodpile photonic bandgap (PBG) waveguide enables high-gradient and efficient laser driven acceleration, while various accelerator components, including laser couplers, power transmission lines, woodpile accelerating and focusing waveguides, and energy recycling resonators, can be potentially integrated on a single monolithic structure via lithographic fabrications. This paper will present designs of this on-chip accelerator based on silicon-on-insulator (SOI) waveguide. Laser power is coupled from free-space or fiber into SOI waveguide by grating structures on the silicon surface, split into multiple channels to excite individual accelerator cells, and eventually gets merged into the power recycle pathway. Design and simulation results will be presented regarding various coupling components involved in this network.  
 
MOP081 Proton Acceleration by Trapping in a Relativistic Laser Driven Uphill Plasma Snowplow laser, plasma, proton, electron 247
 
  • A. Sahai, T.C. Katsouleas
    Duke ECE, Durham, North Carolina, USA
  • W.B. Mori, A. Tableman, J. Tonge, F.S. Tsung
    UCLA, Los Angeles, California, USA
 
  We explore a novel regime of proton and ion acceleration off of overdense Plasma created by a Laser pulse. In Coulomb explosion, Target Normal Sheath, Acoustic shock acceleration regimes the protons are neither high-energy nor monoenergetic enough for applications such as hadron radiation therapy, fast ignition fusion research and particle physics. This calls out for exploration of effective regimes of acceleration. The proposed Snowplow regime of acceleration uses a Snowplow of charge created by a relativistic Laser pulse at the critical density on a uphill Plasma density gradient. The relativistically moving Snowplow's space charge drags the protons and its velocity can be controlled to effectively trap the protons using laser pulse shape and the uphill density profile. We describe the principles behind this mechanism. We derive analytical expressions for the Snowplow velocity and its dependence on the parameter space. We primarily explore the density gradient and laser pulse shape to optimally accelerate protons from rest to the desired velocities. Preliminary, 1-D simulation results are presented and analyzed.  
 
MOP082 Modeling a 10 GeV Laser-Plasma Accelerator with INF&RNO plasma, laser, injection, electron 250
 
  • C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The numerical modeling code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde, pronounced "inferno") is an efficient 2D cylindrical code to model the interaction of a short laser pulse with an underdense plasma. The code is based on an envelope model for the laser while either a particle-in-cell (PIC) or a fluid description can be used for the plasma. The effect of the laser pulse on the plasma is modeled with the time-averaged ponderomotive force. These and other features allow for a significant speedup compared to standard full PIC simulations while still retaining physical fidelity. A boosted Lorentz frame (BLF) modeling capability has been introduced within the fluid framework enhancing the performance of the code. An example of a 10 GeV laser-plasma accelerator modeled using INF&RNO in the BLF is presented.
 
 
MOP086 Fabrication of a Prototype Micro-Accelerator Platform laser, electron, vacuum, coupling 259
 
  • J. Zhou, J.C. McNeur, G. Travish
    UCLA, Los Angeles, USA
  • R.B. Yoder
    Manhattanville College, Purchase, New York, USA
 
  Funding: Work supported by U.S. Defense Threat Reduction Agency, Grant no. HDTRA1-09-1-0043.
The Micro-Accelerator Platform is a laser powered particle acceleration device made from dielectric materials. Its main building blocks, distributed Bragg reflectors and nanoscale coupling slots are fabricated using cutting-edge nanofabrication techniques. In this report, a prototype device will be presented, and technical details with fabrication will be discussed. Optical property of the DBR films is measured by ellipsometry, and film surface roughness is measured using profilometer. In addition, a few remaining challenges with manufacture of this device will be discussed.
 
 
MOP088 A High Transformer Ratio Plasma Wakefield Accelerator Scheme for FACET plasma, optics, wakefield, electron 265
 
  • R.J. England, J.T. Frederico, M.J. Hogan
    SLAC, Menlo Park, California, USA
  • W. An, C. Joshi, W. Lu, W.B. Mori
    UCLA, Los Angeles, California, USA
  • P. Muggli
    USC, Los Angeles, California, USA
 
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515
The ideal drive beam current profile for the plasma wakefield accelerator (PWFA) has been predicted by 1D and 2D simulations to be characterized by a triangular ramp that rises linearly from head to tail, followed by a sharp drop. A technique for generating such bunches experimentally was recently demonstrated. We present here an adaptation of this scheme to generate ramped bunches using the 23 GeV electron beam produced in the first two-thirds of the SLAC linac, and discuss plans to implement this scheme for high transformer ratio demonstration experiments at the FACET plasma wakefield accelerator facility.
 
 
MOP096 Fabrication and Measurement of Dual Layer Silica Grating Structures for Direct Laser Acceleration laser, acceleration, alignment, vacuum 280
 
  • E.A. Peralta, R.L. Byer
    Stanford University, Stanford, California, USA
  • E.R. Colby, R.J. England, C. McGuinness, K. Soong
    SLAC, Menlo Park, California, USA
 
  Funding: Department of Energy: DE-AC02-76SF00515(SLAC),DE-FG06-97ER41276
We present our progress in the fabrication and measurement of a transmission-based dielectric double-grating accelerator structure. The structure lends itself to simpler coupling to the accelerating mode in the waveguide with negligible group velocity dispersion effects, allowing for operation with ultra-short (fs) laser pulses. This document describes work being done at the Stanford Nanofabrication Facility to create a monolithic guided-wave structure with 800 nm period gratings separated by a fixed sub-wavelength gap using standard optical lithographic techniques on a fused silica substrate. An SEM and other characterization tools were used to measure the fabrication deviations of the grating geometry and simulations were carried out in MATLAB and HFSS to study the effects of such deviations on the resulting accelerating gradient.
 
 
MOP097 Modeling of Quasi-Phase Matching for Laser Electron Acceleration laser, plasma, electron, acceleration 283
 
  • M.W. Lin
    The Pennsylvania State University, University Park, Pennsylvania, USA
  • I. Jovanovic
    Penn State University, University Park, Pennsylvania, USA
 
  Funding: This work is supported by the Defense Threat Reduction Agency through contract HDTRA1-10-1-0034.
Sensing of shielded fissile materials at long range is critically dependent on the development of compact particle accelerators. Direct laser acceleration (DLA) of electrons has the potential to meet this requirement. In DLA, the axial component of the electric field of a focused radially polarized laser pulse accelerates particles. The acceleration gradient could be estimated as 77 MeV/mm for 800 nm laser with power of 0.5 TW and 8.5 μm guided mode radius. The implementation of long guided propagation of laser pulses and the phase matching between electrons and laser pulses may limit the DLA in reality. A preformed corrugated plasma waveguide could be applied to extend the laser beam propagation distance and for quasi-phase matching between laser and electron pulses for net acceleration. We perform numerical calculations to estimate the phase matching conditions for a radially polarized laser pulse propagating in a corrugated plasma waveguide. Further, the electric field distribution of a radially polarized laser pulse propagating in this waveguide is also analyzed via particle-in-cell simulations, and will be used to guide future experiments.
* P. Serafim, et al., IEEE Trans. Plasma Sci. 28, 1155 (2000).
** A.G. York, et al., Phys. Rev. Lett. 100, 195001 (2008).
 
 
MOP101 Numerical Study of Self and Controlled Injection in 3-Dimensional Laser-Driven Wakefields plasma, laser, electron, injection 286
 
  • A.W. Davidson, R. Fenseca, C. Joshi, W. Lu, J.L. Martins, W.B. Mori, L.O. Silva
    UCLA, Los Angeles, California, USA
 
  Funding: DOE and NSF
In plasma based accelerators (LWFA and PWFA), the methods of injecting high quality electron bunches into the accelerating wakefield is of utmost importance for various applications. Understanding how injection occurs in both self and controlled scenarios is therefore important. To simplify this understanding, we start from single particle motion in an arbitrary traveling wave wakefields, an electromagnetic structure with a fixed phase velocity(e.g., wakefields driven by non-evolving drivers), and obtain the general conditions for trapping to occur. We then compare this condition with high fidelity 3D PIC simulations through advanced particle and field tracking diagnostics. Numerous numerical convergence tests were performed to ensure the correctness of the simulations. The agreement between theory and simulations helps to clarify the role played by driver evolution on injection, and a physical picture of injection first proposed in * is confirmed through simulations. Several ideas, including ionization assisted injection, for achieving high quality controlled injection were also explored and some simulation results relevant to current and future experiments will be presented.
*W. Lu et al., PRSTAB 10, 061301, 2007
 
 
MOP102 High-Gradient High-Energy-Gain Inverse Free Electron Laser Experiment using a Helical Undulator laser, undulator, electron, radiation 289
 
  • J.P. Duris, R.K. Li, P. Musumeci, E.W. Threlkeld, M.T. Westfall
    UCLA, Los Angeles, California, USA
 
  Funding: UC Lab fee award 09-LR-04-117055-MUSP DOE-HEP grant DE-FG02-92ER40693 Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10-1-0073
Preparations for a high energy gain inverse free electron laser (IFEL) experiment using an undulator and Brookhaven National Lab’s (BNL) Accelerator Test Facility’s (ATF) terawatt CO2 laser are underway. 3D simulations suggest that the experiment will likely accelerate a 50 MeV beam to 117 MeV in 54 cm while maintaining a low energy spread. The helical undulator is currently under construction at UCLA’s Particle Beam Physics Laboratory.
 
 
MOP104 Simulation Studies of the Dielectric Grating as an Accelerating and Focusing Structure focusing, laser, multipole, alignment 292
 
  • K. Soong, E.R. Colby
    SLAC, Menlo Park, California, USA
  • R.L. Byer, E.A. Peralta
    Stanford University, Stanford, California, USA
 
  Funding: Work funded by DOE contract DE‐AC02‐76SF00515 (SLAC)
A grating-based design is a promising candidate for a laser-driven dielectric accelerator. Through simulations, we show the merits of a readily fabricated grating structure as an accelerating component. Additionally, we show that with a small design perturbation, the accelerating component can be converted into a focusing structure. The understanding of these two components is critical in the successful development of any complete accelerator.
 
 
MOP108 Simulation Study of Proton-Driven PWFA Based on CERN SPS Beam plasma, wakefield, proton, acceleration 301
 
  • G.X. Xia, A. Caldwell
    MPI-P, München, Germany
  • C. Huang
    LANL, Los Alamos, New Mexico, USA
  • W.B. Mori
    UCLA, Los Angeles, California, USA
 
  We have proposed an experimental study of the proton-driven plasma wakefield acceleration by using proton beam from the CERN SPS. In this paper, the particle-in-cell (PIC) simulation of the SPS beam-driven plasma wakefield acceleration is introduced. By varying the beam parameters and plasma parameters, simulation shows that electric fields in excess of 1 GeV/m can be achieved.  
 
MOP112 Study of Enhanced Transformer Ratio in a Coaxial Dielectric Wakefield Accelerator using a Profiled Drive Bunch Train wakefield, accelerating-gradient, acceleration, collider 304
 
  • G.V. Sotnikov
    NSC/KIPT, Kharkov, Ukraine
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT, USA
  • T.C. Marshall, G.V. Sotnikov
    Omega-P, Inc., New Haven, Connecticut, USA
 
  Funding: The research was supported by US Department of Energy, Office of High Energy Physics, Advanced Accelerator R & D.
A key parameter of wakefield acceleration is the transformer ratio T. For a dielectric wakefield accelerator, it has been suggested to use a ramped drive bunch train (RBT), or a multizone dielectric structure to enhance T. Here we show the possibility of greatly improving the RBT technique by the use of a numerical algorithm. We study a two-channel 28 GHz structure with two nested Alumina cylindrical shells (CDWA) which is to be excited by a train of four annular bunches having energy 14 MeV and axial RMS size 1mm; the total charge of bunches is 200 nC. For bunch charge and spacing chosen for optimum acceleration gradient, or for optimizing T using the standard method, we obtain T~3.6. We found that if the charge ratios are 1.0:2.4:3.5:5.0 and the spaces between the bunches are 2.5, 2.5, and 4.5 wakefield periods, then T~17. The RBT also can be used successfully in a high gradient THz CDWA structure.
* C.Jing et.al., Phys. Rev. Lett. 98 144801, (2007)
** C. Wang, et.al. Proc. PAC 2005. IEEE, 2005, p.1333.
*** G. Sotnikov et.al. PRST-AB, 061302 (2009).
 
 
MOP115 Progress on Multipactor Studies in Dielectric-Loaded Accelerating Structures multipactoring, electron, impedance, vacuum 310
 
  • S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • D.S. Doran, W. Gai, J.G. Power
    ANL, Argonne, USA
  • B. Feng
    IIT, Chicago, Illinois, USA
 
  Funding: DOE SBIR
Significant progress has been made in the development of high gradient rf driven dielectric accelerating structures (DLA). One principal effect limiting further advances in this technology is the problem of multipactor. The fraction of the power absorbed at saturation in DLA experiments was found to increase with the incident power, with more than 30% of the incident power per unit length being absorbed. We studied a possibility of multipactor mitigation by introduction of surface grooves (transverse and longitudinal) to interrupt the resonant trajectories of electrons in the multipactor discharge. Four DLA structures based on quartz tubes with transverse and longitudinal grooves of various dimensions were designed. In this paper we report simulation results and plans for high-power tests of these structures.
 
 
MOP116 Development of an X-Band Dielectric-Based Wakefield Power Extractor for Potential CLIC Applications wakefield, insertion, impedance, electron 313
 
  • C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, W. Gai, J.G. Power
    ANL, Argonne, USA
  • I. Syratchev
    CERN, Geneva, Switzerland
 
  Funding: Work is funded by DoE SBIR PhaseI.
In the past decade, tremendous efforts have been put into the development of the CLIC Power Extraction and Transfer Structure (PETS), and significant progress has been made. However, one concern remains the manufacturing cost of the PETS, particularly considering the quantities needed for a TeV machine. A dielectric-based wakefield power extractor in principle is much cheaper to build. A low surface electric field to gradient ratio is another big advantage of the dielectric-loaded accelerating/decelerating structure. We are currently investigating the possibility of using a cost-effective dielectric-based wakefield power extractor as an alternative to the CLIC PETS. We designed a 12 GHz dielectric-based power extractor which has a similar performance to CLIC PETS with parameters 23 mm beam channel, 240 ns pulse duration, 135 MW output per structure using the CLIC drive beam. In order to study potential rf breakdown issues, as a first step we are building a 11.424 GHz dielectric-based power extractor scaled from the 12 GHz version, and plan to perform a high power rf test using the SLAC 11.424 GHz high power rf source.
 
 
MOP119 The Dielectric Wakefield Accelerating Structure wakefield, plasma, electron, controls 319
 
  • A. Kanareykin, S.P. Antipov, J.B. Butler, C.-J. Jing, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • W. Gai
    ANL, Argonne, USA
 
  Funding: US Department of Energy
We report here on the development of THz diamond wakefield structures produced using Chemical Vapor Deposition (CVD) technology*. The diamond structures would be used in a THz generation experiment at the new FACET facility at SLAC. We consider a dielectric based accelerating structure to study of the physical limitations encountered driving >GV/m wakefields in the cylindrical and planar geometries of a dielectric wakefield accelerator (DWA). In a DWA, an ultrashort drive bunch traverses the evacuated central region of the structure, creating Cherenkov wakefields in the dielectric to accelerate a witness bunch. A diamond-based DWA structure will allow a sustained accelerating gradient exceeding breakdown threshold demonstrated with the FFTB experiments**. The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric rf structures: high breakdown voltage, extremely low dielectric losses and the highest thermoconductive coefficient available for removing waste heat from the device.
*R. J. Barker et al., Modern Microwave and Millimeter-Wave Power Electronics, IEEE Press/Wiley-Interscience, Piscataway NJ 2005, Chapter 7
**M.C. Thompson et al. Phys. Rev.Lett.100:214801, 2008.
 
 
MOP127 The LLNL/UCLA High Gradient Inverse Free Electron Laser Accelerator laser, electron, undulator, acceleration 331
 
  • S.G. Anderson, G.G. Anderson, M. Betts, S.E. Fisher, D.J. Gibson, S.S.Q. Wu
    LLNL, Livermore, California, USA
  • J.T. Moody, P. Musumeci, A.M. Tremaine
    UCLA, Los Angeles, California, USA
 
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
We describe the Inverse Free Electron Laser (IFEL) accelerator currently under construction at LLNL in collaboration with UCLA. This project combines a strongly tapered undulator with a 10 Hz repetition rate, Ti:Sapphire laser to produce > 200 MeV/m average accelerating gradient over the 50 cm long undulator. The project goal is to demonstrate IFEL accelerator technology that preserves the input beam quality and is well suited for future light source applications. We discuss the accelerator design focusing on issues associated with the use of 800 nm, 100 fs laser pulses. Three-dimensional simulations of the IFEL interaction are presented which guide the choice of laser and electron beam parameters. Finally, experimental plans and potential future developments are discussed.
 
 
MOP128 An Optimized X-band Photoinjector Design for the LLNL MEGa-Ray Project emittance, gun, laser, electron 334
 
  • S.G. Anderson, F. Albert, C.P.J. Barty, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck, R.A. Marsh
    LLNL, Livermore, California, USA
  • C. Adolphsen, A.E. Candel, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou
    SLAC, Menlo Park, California, USA
 
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
We present an optimized 5 + ½ cell, X-band photoinjector designed to produce 7 MeV, 250 pC, sub-micron emittance electron bunches for the LLNL Mono-Energetic Gamma-Ray (MEGa-Ray) light source. This LLNL/SLAC collaboration modifies a design previously demonstrated to sustain 200 MV/m on-axis accelerating fields*. We discuss the photoinjector operating point, optimized by scaling beam dynamics from S-band photo-guns and by evaluation of the MEGa-Ray source requirements. The RF structure design is presented along with the current status of the photoinjector construction and testing.
*A.E. Vlieks, et al., High Energy Density and High Power RF: 6th Workshop, AIP, CP691, p. 358 (2003).
 
 
MOP132 Wakefield Generation in Compact Rectangular Dielectric-Loaded Structures Using Flat Beams wakefield, electron, focusing, emittance 340
 
  • D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • B.M. Cowan, P. Stoltz
    Tech-X, Boulder, Colorado, USA
 
  Funding: This work was supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10-1-0051, to Northern Illinois University
Wakefields with amplitude in the 10's MV/m range can be routinely generated by passing electron beams through dielectric-loaded structures. The main obstacle in obtaining high field amplitude (in the GV/m range) is the ability to focus the high-peak-current electron beam in the transverse plane to micron level, and to maintain the focusing all the way along the dielectric structure. In this paper we explore the use of a flat, high-peak current, electron beams to be produced at the Fermilab's NML facility to drive dielectric loaded structures. Based on beam dynamics simulation we anticipate that we can obtain flat beams with very small vertical size (under 100 microns) and peak current is in excess of 1 kA. We present simulations of the wakefield generation based on theoretical models and PIC simulations with VORPAL.
 
 
MOP133 Fabrication and Measurements of a Silicon Woodpile Accelerator Structure laser, lattice, impedance, electron 343
 
  • C. McGuinness, E.R. Colby, R.J. England, R. Laouar, R.J. Noble, K. Soong, J.E. Spencer, Z. Wu, D. Xu
    SLAC, Menlo Park, California, USA
  • R.L. Byer, E.A. Peralta
    Stanford University, Stanford, California, USA
 
  Funding: DOE grants: DE-AC02-76SF00515 and DE-FG03-97ER41043-II
We present results for the fabrication of a silicon woodpile accelerator structure. The structure was designed to have an accelerating mode at 3.95 μm, with a high characteristic impedance and an accelerating gradient of 530 MeV/m. The fabrication process uses standard nanofabrication techniques in a layer-by-layer process to produce a three-dimensional photonic crystal with 400 nm features. Reflection spectroscopy measurements reveal a peak spanning from three to five microns, and are show good agreement with simulations.
* Sears, PRST-AB, 11, 101301, (2008).
** Cowan, PRST-AB, 11, 011301, (2008).
*** McGuinness, J. Mod. Opt., vol. 56, is. 18, pp. 2142, (2009).
**** Lin, Nature, 394, pp. 251 (1998).
 
 
MOP136 Coupler Studies for PBG Fiber Accelerators coupling, laser, radiation, lattice 346
 
  • J.E. Spencer, R.J. England, C.-K. Ng, R.J. Noble, Z. Wu, D. Xu
    SLAC, Menlo Park, California, USA
 
  Funding: U.S. Dept. of Energy contract DE-AC02-76SF00515
Photonic band gap (PBG) fibers with hollow core defects are being designed and fabricated for use as laser driven accelerators because they appear capable of providing gradients of several GeV/m at picosecond pulse lengths. While we expect to have fiber down to 1.5-2.0 micron wavelengths we still lack a viable means for efficient coupling of laser power into these structures. The reasons for this include the very different character of these TM-like modes from those familiar in the telecom field and the fact that the defect must function as both a longitudinal waveguide for the accelerating field and a transport channel for the particles. We discuss the status of our coupling work in terms of what has been done and the options we are pursuing for both end and side coupling. In both basic coupler types, the symmetry of the PBG crystal leads to significant differences between this and the telecom field. We show that side coupling provides more possibilities and is preferred. Our motivation is to test new fiber for gradient, mode content and throughput on the NLCTA at SLAC.
 
 
MOP137 Predictive Design and Interpretation of Colliding Pulse Injected Laser Wakefield Experiments laser, plasma, electron, emittance 349
 
  • E. Cormier-Michel, D.L. Bruhwiler, B.M. Cowan, V.H. Ranjibar
    Tech-X, Boulder, Colorado, USA
  • M. Chen, E. Esarey, C.G.R. Geddes, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by DOE, NA-22, and Office of Science, HEP via the SciDAC-2 project ComPASS, grant No DE-FC02-07ER41499. Resources of NERSC were used (DOE contract No DE-AC02-05CH11231).
The use of colliding laser pulses to control the injection of plasma electrons into the plasma wake of a laser-plasma accelerator is a promising approach to obtain reproducible and tunable electron bunches with low energy spread and emittance. We present recent particle-in-cell simulations of colliding pulse injection for parameters relevant to ongoing experiments at LBNL. We perform parameter scans in order to determine the best conditions for the production of high quality electron bunches, and compare the results with experimental data. We also evaluate the effect of laser focusing in the plasma channel and of higher order laser mode components on the bunch properties.
 
 
MOP141 Design, Fabrication and Characterization of a Micron-scale Electron Source Based on Field Enhanced Pyroelectric Crystals electron, laser, diagnostics, polarization 352
 
  • H. Badakov, J.M. Allen, N.S. Carranza, G. Travish, J. Zhou
    UCLA, Los Angeles, California, USA
  • E.R. Arab
    PBPL, Los Angeles, USA
  • R.B. Yoder
    Manhattanville College, Purchase, New York, USA
 
  As a part of the Micro-Accelerator Platform (MAP) project, an electron source with a sub-micron size emitter is required. It is also desired that the source produces electrons with energies above the structure's minimum capture energy (about 25 keV) without the use of an external power supply. Field enhanced emission backed by field generation in pyroelectric crystals has been explored for this application. Here we present experimental progress towards characterization of electron, and x-ray emission. Purpose built diagnostics and specialized test assembly for optimized heat transmission are discussed.  
 
MOP145 Physics Design of the Project X CW Linac linac, lattice, cryomodule, focusing 364
 
  • N. Solyak, J.-P. Carneiro, J.S. Kerby, V.A. Lebedev, S. Nagaitsev, J.-F. Ostiguy, A. Saini, A. Vostrikov, V.P. Yakovlev
    Fermilab, Batavia, USA
 
  The general design of the 3 GeV superconducting CW linac of the Project X is presented. Different physical and technical issues and limitations that determine the linac concept are discussed. The results of the RF system optimization are presented as well as the lattice design and beam dynamics analysis.  
 
MOP152 G4beamline Particle Tracking in Matter Dominated Beam Lines space-charge, 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.
 
 
MOP153 High Efficiency Laser Ion Acceleration in Low Density Plasmas proton, acceleration, plasma, laser 376
 
  • E. d'Humières, V. Tikhonchuk
    CELIA, Talence, France
 
  Laser driven sources of high energy ions commonly use thin solid foils. A gaseous target can also produce ion beams with characteristics comparable to those obtained with solid targets. Using Particle-In-Cell simulations, we have studied in detail ion acceleration with high intensity laser pulses interacting with low density plasmas. A two-step acceleration process can be triggered: first, ions are accelerated in volume by electric fields generated by hot electrons, second, the ion energy is boosted in a strong electrostatic shock. 2D and 3D simulations show the potential of this regime. It is possible to model separately these two steps. In the first step a hot electron population and a descending density profile are necessary, and the second step develops if a fast proton wave enters in a low density plasma.  
 
MOP158 Numerical Study of Plasma Wakefields Excited by a Train of Electron Bunches plasma, wakefield, electron, emittance 391
 
  • Y. Fang, P. Muggli
    USC, Los Angeles, California, USA
  • C. Huang
    LANL, Los Alamos, New Mexico, USA
  • W.B. Mori
    UCLA, Los Angeles, California, USA
 
  Funding: Work supported by the US department of Energy
We study numerically the excitation of plasma wakefields by a train of electron bunches using the UCLA particle-in-cell code Quickpic*. We aim to find an optimal regime that combines both the advantages of linear and non-linear plasma wakefield accelerator. On one hand, the longitudinal electric field excited by individual bunches add as in the linear region, and the transformer ratio can be maximized (i.e. much larger than 2) by adjusting the number of particles in the bunches as well as their distance. On the other hand, the bunches create large wakefield independent of transverse sizes evolution while propagating through the plasma as in the non-linear region. In principle, such a scheme can multiply the energy of the witness bunch following the drive bunch train in a single plasma wakefield accelerating stage. The parameters for electron bunches are chosen based on the current experiment at the Brookhaven National Laboratory Accelerator Test Facility (ATF), where this scheme can be tested. Detailed simulation results will be presented.
* C. Huang, J. Comp. Phys.
 
 
MOP159 Ionization-Induced Trapping in Laser-Plasma Accelerators and Synchrotron Radiation from the Betatron Oscillation electron, laser, radiation, injection 394
 
  • M. Chen, E. Esarey, C.G.R. Geddes, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, California, USA
  • D.L. Bruhwiler, E. Cormier-Michel
    Tech-X, Boulder, Colorado, USA
 
  Funding: This work is supported by the U.S. DOE Office of High Energy Physics under Contract No. DE-AC02-05CH11231, and NNSA, NA-22, and used the computational resources of NERSC.
Ionization injection into a laser wakefield accelerator is studied by multi-dimensional particle-in-cell (PIC) simulations. To obtain low energy spread beams we use a short region of gas mixture (H+N) near the start of the stage to trap electrons, while the remainder of the stage uses pure H and is injection-free. Effects of gas mix parameters, including concentration and length of the mixture region, on the final electron injection number and beam quality are studied. Two dimensional PIC simulations show the injected electron beam has filament structures in the plane perpendicular to the laser polarization direction in early time and this structure disappears later due to the betatron oscillation of the electrons in the wakefield. Synchrotron radiation from the accelerated electrons is calculated by a post processing code - Virtual Detector for Synchrotron Radiation (VDSR).
 
 
MOP202 Simulations of the LHC High Luminosity Monitors at Beam Energies 3.5 TeV to 7.0 TeV luminosity, monitoring, instrumentation, interaction-region 471
 
  • H.S. Matis, P. Humphreys, A. Ratti, W.C. Turner
    LBNL, Berkeley, California, USA
  • R. Miyamoto
    BNL, Upton, Long Island, New York, USA
  • J. Stiller
    Heidelberg University, Heidelberg, Germany
 
  Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
We have constructed two pairs of fast ionization chambers (BRAN) for measurement and optimization of luminosity at IR1 and IR5 of the LHC. These devices are capable of monitoring the performance of the LHC at low luminosity 1028 cm-2s−1 during beam commissioning all the way up to the expected full luminosity of 1034 cm-2s−1 at 7.0 TeV. The ionization chambers measure the intensity of hadronic/electromagnetic showers produced by the forward neutral particles of LHC collisions. To predict and improve the understanding of the BRAN performance, we created a detailed FLUKA model of the detector and its surroundings. In this paper, we describe the model and the results of our simulations including the detector’s estimated response to pp collisions at beam energies of 3.5, 5.0, and 7.0 TeV per beam. In addition, these simulations show the sensitivity of the BRAN to the crossing angle of the two LHC beams. It is shown that the BRAN sensitivity to crossing angle is proportional to the measurement of crossing angle by the LHC beam position monitors.
 
 
MOP214 Methods for Quantitative Interpretation of Retarding Field Analyzer Data electron, photon, pick-up, positron 501
 
  • J.R. Calvey, J.A. Crittenden, G. Dugan, M.A. Palmer
    CLASSE, Ithaca, New York, USA
  • M.A. Furman
    LBNL, Berkeley, California, USA
  • K.C. Harkay
    ANL, Argonne, USA
 
  Funding: US Department of Energy grant DE-FC02-08ER41538 US National Science Foundation grant PHY-0734867
Over the course of the CesrTA program at Cornell, over 30 Retarding Field Analyzers (RFAs) have been installed in the CESR storage ring, and a great deal of data has been taken with them. These devices measure the local electron cloud density and energy distribution, and can be used to evaluate the efficacy of different cloud mitigation techniques. Obtaining a quantitative understanding of RFA data requires use of cloud simulation programs, as well as a detailed model of the detector itself. In a drift region, the RFA can be modeled by postprocessing the output of a simulation code, and one can obtain best fit values for important simulation parameters with a chi-square minimization method.
 
 
MOP220 The Feasibility of Near-Field ODR Beam-Size Monitoring at 23 GeV at FACET polarization, monitoring, radiation, booster 513
 
  • A.H. Lumpkin
    Fermilab, Batavia, USA
  • M.J. Hogan
    SLAC, Menlo Park, California, USA
  • P. Muggli
    USC, Los Angeles, California, USA
  • C. Yao
    ANL, Argonne, USA
 
  Funding: Work partially supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Extension of near-field optical diffraction radiation (ODR) imaging to the 23 GeV beams at the proposed FACET facility at SLAC has been evaluated. The beam- size sensitivity at the 10- to 20- μm σ level based on a simple model will be reported. Polarization effects are also seen to be important and will be discussed. The comparisons to previous experimental results and the modeling results indicate sufficient feasibility for planning of the experiments in the coming year.
 
 
MOP243 Design of a Compact, High-Resolution Analyzer for Longitudinal Energy Studies in the University of Maryland Electron Ring focusing, space-charge, 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).
 
 
MOP265 The FONT5 Prototype ILC Intra-train Feedback System at ATF2 feedback, kicker, linear-collider, extraction 600
 
  • P. Burrows, R. Apsimon, D.R. Bett, G.B. Christian, B. Constance, C. Perry, J. Resta-López
    JAI, Oxford, United Kingdom
 
  We present the design and beam test results of a prototype beam-based digital feedback system for the Interaction Point of the International Linear Collider. A custom analogue front-end signal processor, FPGA-based digital signal processing boards, and kicker drive amplifier have been designed, built, deployed and tested with beam in the extraction line of the KEK Accelerator Test Facility (ATF2). The system was used to provide orbit correction in y and y' to the train of bunches extracted from the ATF damping ring. We describe the feedback performance in both single and coupled-loop modes and the optimisation of the loop gains.  
 
MOP273 Calibration and Simulation of the LCLS Undulator Beam Loss Monitors using APS Accelerators radiation, electron, undulator, photon 618
 
  • J.C. Dooling, W. Berg, A.R. Brill, L. Erwin, B.X. Yang
    ANL, Argonne, USA
  • A.S. Fisher, H.-D. Nuhn, M. Santana-Leitner
    SLAC, Menlo Park, California, USA
 
  Funding: U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357
Electrons scattered by alumina ceramic transverse beam profile monitors inserted in the Advanced Photon Source (APS) booster-to-storage ring (BTS) transfer line are used to generate C ̆erenkov light for calibration of beam loss monitors (BLMs) installed in the Linac Coherent Light Source (LCLS) undulator beamline. In addition, gas bremsstrahlung (GB) photons generated by 7-GeV electrons in the APS sector 35 storage ring straight section are used to create pair-production electrons for measurement and calibration purposes. Both cases are modeled with the particle-matter interaction program MARS. The realized tuning fork geometry of the BLM exhibits regions of greater sensitivity in the radiator. Transverse GB beam scans have provided uniformity and sensitivity data throughout the volume of the radiator. Comparisons between predicted and measured signal strengths and thermoluminescent dosimeter readings are given and shown to be in reasonable agreement.
 
 
MOP276 Applying Cascaded Parameter Scan to Study Top-off Safety in NSLS-II Storage Ring injection, photon, interlocks, storage-ring 627
 
  • Y. Li, S.V. Badea, W.R. Casey, G. Ganetis, R. Heese, H.-C. Hseuh, P.K. Job, S. Krinsky, B. Parker, T.V. Shaftan, S.K. Sharma, L. Yang
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by U.S. DOE, Contract No. DE-AC02-98CH10886
In this paper we introduce a new algorithm, the cascaded parameter scan method, to efficiently carry out the scan over magnet parameters in the safety analysis for the NSLS-II top-off injection. In top-off safety analysis, one must track particles populating phase space through a beamline containing magnets and apertures and clearly demonstrate that for all possible magnet settings and errors, all particles are lost on scrapers within the properly shielded region. In the usual approach, the number of tracking runs increases exponentially with the number of magnet settings. In the cascaded parameter scan method, the number of tracking runs only increases linearly. This reduction of exponential to linear dependence on the number of setpoints, greatly reduces the required computation time and allows one to more densely populate phase space and to increase the number of setpoints scanned for each magnet. An example of applying this approach to analyze an NSLS-II beamline, the damping wiggler beamline, is also given.
 
 
TUOBN1 Laser Wakefield Acceleration Beyond 1 GeV using Ionization Induced Injection laser, electron, injection, plasma 707
 
  • K.A. Marsh, C.E. Clayton, C. Joshi, N. Lemos, W. Lu, W.B. Mori, A.E. Pak
    UCLA, Los Angeles, California, USA
  • F. Albert, T. Doeppner, C. Filip, D.H. Froula, S.H. Glenzer, B.B. Pollock, D. Price, J.E. Ralph
    LLNL, Livermore, California, USA
  • R.A. Fonseca, S.F. Martins
    Instituto Superior Tecnico, Lisbon, Portugal
  • L.O. Silva
    IPFN, Lisbon, Portugal
 
  Funding: Supported by DOE Grants No. DE-AC52-07NA27344, DE-FG03-92ER40727, DE-FG02-92ER40727, DE-FC02-07ER41500, DE-FG52-09NA29552, NSF Grants No. PHY-0936266, PHY-0904039 and FCT, Por., No. SFRH/BD/35749/2007
A series of laser wakefield accelerator experiments leading to electron energy exceeding 1 GeV are described. Theoretical concepts and experimental methods developed while conducting experiments using the 10 TW Ti:Sapphire laser at UCLA were implemented and transferred successfully to the 100 TW Calisto Laser System at the Jupiter Laser Facility at LLNL. To reach electron energies greater than 1 GeV with current laser systems, it is necessary to inject and trap electrons into the wake and to guide the laser for more than 1 cm of plasma. Using the 10 TW laser, the physics of self-guiding and the limitations in regards to pump depletion over cm-scale plasmas were demonstrated. Furthermore, a novel injection mechanism was explored which allows injection by ionization at conditions necessary for generating electron energies greater than a GeV. The 10 TW results were followed by self-guiding at the 100 TW scale over cm plasma lengths. The energy of the self-injected electrons, at 3x1018 cm-3 plasma density, was limited by dephasing to 720 MeV. Implementation of ionization injection allowed extending the acceleration well beyond a centimeter and 1.4 GeV electrons were measured.
 
slides icon Slides TUOBN1 [2.488 MB]  
 
TUODN2 Exploration of Parallel Optimization Techniques for Accelerator Design target, quadrupole, coupling, controls 787
 
  • Y. Wang, M. Borland, V. Sajaev
    ANL, Argonne, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Optimization through simulation is a time-consuming task in accelerator design, especially for high dimensional problems. We explored several parallel optimization techniques, including Parallel Genetic Algorithm (PGA), Hybrid Parallel Simplex (HPS), and Parallel Particle Swarm Optimization (PPSO), to solve some real world problems. The serial simplex method in elegant was used as a benchmark for newly-developed parallel optimization algorithms in Pelegant. PGA and HPS are not faster than the serial simplex method, but they more reliably find the global optimum. PPSO is well suited for parallel computing, allowing significantly faster turn-around given sufficient computing resources. Parallel optimization implementations in Pelegant thus promise to not only make optimization results more reliable, but also open the possibility of fast, "real time" optimization of complex problems for accelerator operation.
 
slides icon Slides TUODN2 [0.218 MB]  
 
TUODN3 Beam Dynamics Studies of Parallel-Bar Deflecting Cavities cavity, emittance, electron, extraction 790
 
  • S. Ahmed, J.R. Delayen, A.S. Hofler, G.A. Krafft, M. Spata, M.G. Tiefenback
    JLAB, Newport News, Virginia, USA
  • K.B. Beard
    Muons, Inc, Batavia, USA
  • K.A. Deitrick
    RPI, Troy, New York, USA
  • S.D. Silva
    ODU, Norfolk, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We have performed three-dimensional simulations of beam dynamics for parallel-bar transverse electromagnetic mode (TEM) type RF separators: normal- and superconducting. The compact size of these cavities as compared to conventional TM110 type structures is more attractive particularly at low frequency. Highly concentrated electromagnetic fields between the parallel bars provide strong electrical stability to the beam for any mechanical disturbance. An array of eight 2-cell normal conducting cavities or a one- or two-cell superconducting structure are enough to produce the required vertical displacement at the Lambertson magnet. Both the normal and superconducting structures show very small emittance dilution due to the vertical kick of the beam.
 
slides icon Slides TUODN3 [1.558 MB]  
 
TUODN6 Action and Phase Jump Analysis for LHC Orbits lattice, interaction-region, quadrupole, dipole 796
 
  • O.R. Blanco, J.F. Cardona
    UNAL, Bogota D.C, Colombia
 
  Funding: COLCIENCIAS, Programa Jovenes Investigadores e Innovadores "Virginia Gutierrez de Pineda" 2009 Direccion de Investigacion Sede Bogota, Universidad Nacional de Colombia (DIB, UNAL)
Action and phase orbit correction method is implemented to detect magnetic errors in LHC orbits of late 2009 run. The last achievements in the theory of action and phase jump analysis have been included to reduce action and phase plots noise and to increase precision on the calculation of linear errors. The validation of the implementation is performed by MAD-X simulations of the LHC lattice V6.5, where dipole and quadrupole errors are included and recovered within 0.02%. Then, the implementation is applied to experimental orbits, taken from the 2009 run during November and December, where several interaction regions are analyzed.
orblancog@bt.unal.edu.co, Universidad Nacional de Colombia
jfcardona@unal.edu.co, Professor, Universidad Nacional de Colombia
 
slides icon Slides TUODN6 [1.867 MB]  
 
TUODS6 Optimizing RF Gun Cavity Geometry within an Automated Injector Design System cavity, gun, resonance, SRF 805
 
  • A.S. Hofler, P. Evtushenko
    JLAB, Newport News, Virginia, USA
 
  Funding: Authored by JSA, LLC under U.S. DOE Contract DE-AC05-06OR23177. The U.S. Govt. retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this for U.S. Govt. purposes.
RF guns play an integral role in the success of several light sources around the world, and properly designed and optimized cw superconducting RF (SRF) guns can provide a path to higher average brightness. As the need for these guns grows, it is important to have automated optimization software tools that vary the geometry of the gun cavity as part of the injector design process. This will allow designers to improve existing designs for present installations, extend the utility of these guns to other applications, and develop new designs. An evolutionary algorithm (EA) based system can provide this capability because EAs can search in parallel a large parameter space (often non-linear) and in a relatively short time identify promising regions of the space for more careful consideration. The injector designer can then evaluate more cavity design parameters during the injector optimization process against the beam performance requirements of the injector. This paper will describe an extension to the APISA software that allows the cavity geometry to be modified as part of the injector optimization and provide examples of its application to existing RF and SRF gun designs.
 
slides icon Slides TUODS6 [0.556 MB]  
 
TUP002 Study of Robinson Instabilities with a Higher-Harmonic Cavity for HLS Phase II Project cavity, quadrupole, dipole, coupling 808
 
  • Y. Zhao, W. Li, L. Wang, C.-F. Wu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  In the phase II project of Hefei Light Source, a fourth-harmonic “Landau” cavity will be operated in order to suppress coupled-bunch instabilities and increase the beam lifetime of Hefei Storage Ring. Instabilities limit the utility of the higher-harmonic cavity when the storage ring is operated with a small momentum compaction. Analytical modeling and simulations show that the instabilities result from Robinson mode coupling. In the analytic modeling, we operate an algorithm to consider Robinson instabilities. To study the evolution of unstable behavior, simulations have been performed in which macroparticles are distributed among the buckets. Both the analytic modeling and simulations agree for passive operation of the harmonic cavity.  
 
TUP003 Beam Stop of Spiral2 Facility: Activation and Residual Dose Rate Calculations neutron, photon, factory, shielding 811
 
  • A. Mayoral, M. García, D. López, F. Ogando, J. Sanz, P. Sauvan
    UNED, Madrid, Spain
 
  Funding: *SPIRAL 2 Preparatory Phase. European Strategy Forum on Research Infrastructures. Seventh Framework Programme Ref 212692 **The Spanish Ministery of Science and Innovation. Project ENE2009-07572
SPIRAL2 facility is expected to produce 5mA of deuterons at 40 MeV. A beam dump device (BD) has been designed to stop the beam. In this paper we assess the residual dose rates (RDR) in the BD room during beam-off phases. MCNPX was used to deal with deuterons transport and production and transport of secondary neutrons. Deuteron and neutron induced activation were computed using ACAB* and EAF2007. Decay gammas were transported using MCNPX to compute RDR. Dose rates at cooling times up to one year are presented, showing that it is mainly due to BD copper induced activation. The uncertainties in the results can be attributed to: i) the reliability of the d-Cu activation cross sections reactions, ii) the computational approach used to assess the neutron source. The troublesome radioisotopes from d-Cu and their formation reactions were identified. EAF2007 cross sections for these reactions were compared with the available experimental data. Regarding the computational approach to determine the neutron source from d-Cu interactions two options were used: i) built-in nuclear models of MCNPX, ii) TENDL** and MCUNED***. The available experimental data were used for benchmarking.
* J. Sanz et al. ACAB. User’s manual NEA-1839 (2009)
** A.J. Koning et al. TENDL2008 http://www.talys.eu/tendl-2008/
*** P.Sauvan et al. Nucl. Instr.and Meth. A 614 (2010)3 323-330.
 
 
TUP004 GEANT4 Modelling of Heat Deposition into the ISIS Muon Target target, proton, neutron, ion 814
 
  • A. Bungau, R. Cywinski
    University of Huddersfield, Huddersfield, United Kingdom
  • R.J. Barlow
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • C. Bungau
    Manchester University, Manchester, United Kingdom
  • P.J.C. King, J.S. Lord
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
 
  The energy deposition on the ISIS muon target and the temperature profiles are analysed in this paper. The thermal modelling is performed using the GEANT4 Monte Carlo code. Heat deposition patterns are also simulated for alternative target geometries. Energy deposition in the collimators is also discussed.  
 
TUP005 Comparison of Back-scattering Properties of Electron Emission Materials electron, scattering, target, feedback 817
 
  • Z. Insepov, V. Ivanov, S.J. Jokela, M. Wetstein
    ANL, Argonne, USA
 
  We use “microscopic” Monte Carlo (MC) simulations, empirical theories, and comparison with experiments to identify the influence of back-scattered electrons and the saturation effect on the emissive properties of materials and to study the gain and transit times for various microchannel plates (MCPs). We have applied this method to Al2O3 and MgO emissive materials of various thickness and surface quality. The experimental secondary emission yield (SEY) data were obtained at normal electron impacts and were used as the reference data for adjusting our MC simulations. The SEY data were calculated at oblique angles of the primary electrons in the interval of 0-80 degrees. The energy dependence of backscattered electron coefficients (BSCs) for various primary electron incidence angles was calculated by MC for both materials, and the results were compared with experimental “average” values obtained in the literature. Both SEY and BSC data were used as input files to our “macroscopic” trajectory simulation, which models MCP amplifiers as whole devices and is capable of gain and transit time calculations.  
 
TUP008 Update on Multipactor in Coaxial Waveguides using CST Particle Studio multipactoring, electron, plasma, electromagnetic-fields 820
 
  • G.V. Romanov
    Fermilab, Batavia, USA
 
  CST Particle Studio combines electromagnetic field simulation, multiparticle tracking, adequate post-processing and advanced probabilistic emission model, which is the most important new capability in multipactor simulation. The emission model includes in simulation the stochastic properties of emission and adds primary electron elastic and inelastic reflection from the surfaces. The simulation of multipactor in coaxial waveguides have been performed to study the effects of the innovations on the multipactor threshold and the range over which multipactor can occur. The results compared with available previous experiments and simualtions as well as the technique of MP simulation with CST PS are presented and discussed.  
 
TUP009 A Computational Model for Muons Passing Gas and Plasma Targets: Beam Emittance. target, scattering, emittance, collective-effects 823
 
  • A. Samolov, A.L. Godunov
    ODU, Norfolk, Virginia, USA
 
  A good understanding of interaction of muon beams with gas targets is crucial for attaining high acceleration gradients in gas pressured RF cavities. This physics includes a number of challenging problems. Our objective has been to develop a computational model for studying the most important effects within the same level of accuracy. The computational model simulates scattering of a bunch of charged particles on multiple atomic, molecular and ionic centers. The interaction potentials have been calculated using Hartree-Fock method for atomic targets, and Molecular Orbital method for molecular targets. Target particles are populated randomly to simulate either a gas in a pressured RF cavity with a particular material density, or liquid hydrogen. In the present work the following effects on beam emittance have been studied: effect of multiple scattering (comparing to single particle tracking models), effect of various degree of target ionization (beam-plasma interaction), space charge screening in plasma, effect of strong magnetic fields. Our preliminary results demonstrate that the degree of plasma ionization has a strong effect of the beam emittance.  
 
TUP010 Code TESLA for Modeling and Design of High-Power, High-Efficiency Klystrons klystron, cavity, electron, gun 826
 
  • I.A. Chernyavskiy
    SAIC, McLean, USA
  • T.M. Antonsen
    UMD, College Park, Maryland, USA
  • S.J. Cooke, B. Levush, A.N. Vlasov
    NRL, Washington, DC, USA
 
  Funding: This work was supported by the U.S. Office of Naval Research (ONR).
This work gives an overview of the main features of the 2.5D large-signal code TESLA and its capabilities for the modelling single-beam and multiple-beam klystrons as high-power RF sources. These sources are widely used or proposed to be used in accelerators in the future. Comparison of TESLA modelling results with experimental data for a few multiple-beam klystrons are shown.
 
 
TUP011 Multipactor Dynamics in Dielectric-loaded Accelerator Structures electron, space-charge, multipactoring, 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.
 
 
TUP012 Computer Simulations of Waveguide Window and Coupler Iris for Precision Matching DTL, coupling, linac, cavity 832
 
  • S.W. Lee
    ORNL RAD, Oak Ridge, Tennessee, USA
  • Y.W. Kang, K.R. Shin, A.V. Vassioutchenko
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
A tapered ridge waveguide iris input coupler and a waveguide ceramic disk windows are used on each of six drift tube linac (DTL) cavities in the Spallation Neutron Source (SNS). The coupler design employs rapidly tapered double ridge waveguide to reduce the cross section down to a smaller low impedance transmission line section that can couple to the DTL tank easily. The impedance matching is done by adjusting the dimensions of the thin slit aperture between the ridges that is the coupling element responsible for the power delivery to the cavity. Since the coupling is sensitive to the dimensional changes of the aperture, it requires careful tuning for precise matching. Accurate RF simulation using latest 3-D EM code is desirable to help the tuning for maintenance and spare manufacturing. Simulations are done for the complete system with the ceramic window and the coupling iris on the cavity to see mutual interaction between the components as a whole.
 
 
TUP018 Design of a S-Band 4,5 Cells RF Gun gun, emittance, electron, booster 850
 
  • R. Roux, C. Bruni, H. Monard
    LAL, Orsay, France
 
  Most of radio-frequency (RF) photo-injectors operating in the world are made of 1,5 or 2,5 cells. Although excellent qualities of electron beam have been obtained there are few cases where the extension of the number of cells could be interesting. For instance, the small accelerators with energy in the range of 10-20 MeV which are mostly based on the operation of a RF gun with a booster. One single RF gun fulfilling both functions would simplify the construction and the cost of such machines. The inherent simplicity would also ensure a better reliability. We will present 2D and 3D RF simulations of this 4,5 cells RF photo-injector. In addition we will compare through beam dynamics simulations, with the PARMELA and ASTRA codes, the performances of this gun with respect of classical design based on the couple RF gun plus booster.  
 
TUP020 A New Continuous Muon Beam Line Using a Highly Efficient Pion Capture System at RCNP solenoid, target, proton, dipole 856
 
  • H. Sakamoto, Y. Kuno, A. Sato
    Osaka University, Osaka, Japan
  • S. Cook, R.T.P. D'Arcy
    UCL, London, United Kingdom
  • M. Fukuda, K. Hatanaka
    RCNP, Osaka, Japan
  • T. Ogitsu, A. Yamamoto, M.Y. Yoshida
    KEK, Ibaraki, Japan
 
  A new muon source with continuous time structure is under construction at Research Center of Nuclear Physics (RCNP), Osaka University. The ring cyclotron of RCNP can provide 400W 400MeV proton beam. Using this proton beam, the MuSIC produces a high intense muon beam. The target muon intensity is 108 muons/second, which is achieved by a pion capture with great efficiency to collect pions and muons using a solenoidal magnetic field. A pion production target system is located in a 3.5 Tesla solenoidal magnetic field generated by a super-conducting solenoid magnet. The proton beam hits the target, and backward pions and muons are captured by the field. Then they are transported by a curved solenoid beam line to experimental apparatus. The construction has been started in 2010, and would be finished in 5 years. We plan to carry out not only an experiment to search the lepton flavor violating process but also other experiments for muon science and their applications using the intense muon beam.  
 
TUP023 X-Band RF Photoinjector Research and Development at LLNL emittance, electron, cathode, coupling 859
 
  • R.A. Marsh, S.G. Anderson, C.P.J. Barty, G.K. Beer, R.R. Cross, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck
    LLNL, Livermore, California, USA
  • C. Adolphsen, A.E. Candel, T.S. Chu, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou
    SLAC, Menlo Park, California, USA
 
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and funded by DHS Domestic Nuclear Detection Office
In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test station is being developed to investigate accelerator optimization for future upgrades. This test station will enable work to explore the science and technology paths required to boost the current mono-energetic gamma-ray (MEGa-Ray) technology a higher effective repetition rate, potentially increasing the average gamma-ray brightness by two orders of magnitude. The test station will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. Beam quality must be exceedingly high in order to produce narrow-bandwidth gamma-rays, requiring a robust state of the art photoinjector. The photoinjector will be a high gradient (200 MV/m cathode field) standing wave structure, featuring a dual feed racetrack coupler, elliptical irises, and an optimized first cell length. Detailed design of the rf photoinjector for this test station is complete, and will be presented with modeling simulations, and layout plans.
 
 
TUP029 Low-Beta Superconducting RF Cavity Tune Options cavity, resonance, superconducting-RF, insertion 865
 
  • E.N. Zaplatin
    FZJ, Jülich, Germany
 
  The main method of the superconducting RF cavity frequency tuning is a resonator wall deformation. Since the highest frequency sensitivity on the geometry change is an accelerating gap variation, the "standard" place of deformation tuning force application in different cavity types are the cavity beam ports. A series of low-beta cavities (QWR, HWR, spoke-type) with different options of tuning have been investigated. Every option is compared with beam port displacement. The problem of resonator frequency shift self-compensation caused by external pressure fluctuations is discussed.  
 
TUP031 Project X Elliptical Cavity Structural Analyses cavity, vacuum, linac, cryomodule 868
 
  • E.N. Zaplatin
    FZJ, Jülich, Germany
 
  Project X is proposed at Fermi National Accelerator Laboratory high-intensity proton accelerator complex that could provide beam for a variety of physics projects. Superconducting resonators will be used for beam acceleration. Here we report a structural design of elliptical cavities with resonance frequency 650 MHz and β=0.91 and 0.61. Since there is a concern that the pressure in the helium plumbing will not be stable when the cryomodules are connected to the liquid helium supply and helium gas returns it is necessary to provide the cavity stiffening with requirements of 15 Hz amplitude frequency shift. The cavity RF and mechanical properties are investigated. The calculations of the cavity frequency shift with pressure for different schemes of cavity stiffening were provided. The criterion for the optimization was the minimization of a resonant frequency dependence on an external pressure. Based on the results of these simulations several options on cavity stiffening have been proposed. Additionally, the cavity stiffening structural scheme for self-compensation of resonator detuning caused by external pressure fluctuation have been investigated.  
 
TUP041 Quench Dynamics in SRF Cavities: Can We Locate the Quench Origin with 2nd Sound? cavity, SRF, radio-frequency, instrumentation 883
 
  • Y.B. Maximenko
    MIPT, Dolgoprudniy, Moscow Region, Russia
  • D.A. Sergatskov
    Fermilab, Batavia, USA
 
  A newly developed method of locating quench in SRF cavities by detecting second-sound waves has been gaining popularity in SRF laboratories. The technique is based on measurements of time delays between the quench, as determined by the RF system, and arrival of the 2nd sound wave to the multiple detectors placed around the cavity in superfluid helium. Unlike multi-channel temperature mapping, this approach requires only few sensors and simple readout electronics; it can be used with SRF cavities of almost arbitrary shape. One of its drawbacks is that being an indirect method it requires one to solve an inverse problem to find a location of a quench. We tried to solve this inverse problem by using a parametric forward model. By analyzing the data we found that a simple model where 2nd-sound emitter is a near-singular source does not describe the physical system well enough. A time-dependent analysis of a quench process can help us to put forward a more adequate model. We present here our current algorithm to solve the inverse problem and discuss the experimental results.  
 
TUP042 RF Measurements and Numerical Simulations for the Model of the Bilbao Linac Double Spoke Cavity cavity, HOM, ion, controls 886
 
  • J.L. Munoz, I. Bustinduy, N. Garmendia, V. Toyos
    ESS Bilbao, Bilbao, Spain
  • E. Asua
    UPV-EHU, Leioa, Spain
  • F.J. Bermejo
    Bilbao, Faculty of Science and Technology, Bilbao, Spain
  • V. Etxebarria, J. Portilla
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
  • J. Feuchtwanger
    ESS-Bilbao, Zamudio, Spain
  • J. Lucas
    Elytt Energy, Madrid, Spain
 
  A model of a double spoke resonant cavity (operating frequency 352.2 MHz, βg=0.39) has been designed and fabricated in aluminium. The RF characteristics of the cavity have been measured in our laboratory. Experimental measurements have involved the determination of the main cavity parameters, and the characterization of the accelerating electric field profile along the cavity axis by means of a fully automated bead-pullmethod. Additionally, numerical simulations using COMSOL code have been used to fully characterize the cavity. Electromagnetic numerical simulations of the cavity have been also performed to determine its main figures of merit and to identify the most suitable position for opening a port to install a power coupler. In this paper we report the cavity cold model description, the experimental setup and corresponding techniques, together with the numerical methods. The obtained results are described and discussed in detail.  
 
TUP044 A Comparison of Superconducting RF Structures Optimized for β = 0.285 cryomodule, cavity, ion, SRF 889
 
  • Z.A. Conway, R.L. Fischer, M.P. Kelly, A. Kolomiets, B. Mustapha, P.N. Ostroumov
    ANL, Argonne, USA
 
  Recent advances in low-beta superconducting RF technology have enabled the proposal and construction of ever-increasing-intensity ion accelerators, e.g. The Facility for Rare Isotope Beams (FRIB) at Michigan State University and Project-X at Fermilab. Superconducting TEM-class structures are required for these accelerators and beam quality preservation and cost efficiency are of the highest importance. This paper presents a comparison of the superconducting TEM-class cavities available for the acceleration of ions in the energy range of 16 to 55 MeV/u in order to guide their selection in future ion accelerator projects.  
 
TUP052 HOM Damping Properties of Fundamental Power Couplers in the Superconducting Electron Gun of the Energy Recovery LINAC at Brookhaven National Laboratory cavity, HOM, damping, gun 901
 
  • L.R. Hammons, H. Hahn
    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.
Among the accelerator projects under construction at the Relativistic Heavy Ion Collider (RHIC) is an R&D energy recovery LINAC (ERL) test facility. The ERL includes both a five-cell superconducting cavity as well as a superconducting, photoinjector electron gun. Because of the high-charge and high-current demands, effective higher-order mode (HOM) damping is essential, and several strategies are being pursued. Among these is the use of the fundamental power couplers as a means for damping some HOMs. Simulation studies have shown that the power couplers can play a substantial role in damping certain HOMs, and this presentation will discuss these studies along with measurements.
 
 
TUP056 BNL 703 MHz Superconducting RF Cavity Testing cavity, resonance, cryogenics, LLRF 913
 
  • B. Sheehy, Z. Altinbas, I. Ben-Zvi, D.M. Gassner, H. Hahn, L.R. Hammons, J.P. Jamilkowski, D. Kayran, J. Kewisch, N. Laloudakis, D.L. Lederle, V. Litvinenko, G.T. McIntyre, D. Pate, D. Phillips, C. Schultheiss, T. Seda, R. Than, W. Xu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • A. Burrill
    JLAB, Newport News, Virginia, USA
  • T. Schultheiss
    AES, Medford, NY, USA
 
  Funding: This work received support from Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Brookhaven National Laboratory (BNL) 5-cell, 703 MHz superconducting RF accelerating cavity has been installed in the high-current energy recovery linac (ERL) experiment. This experiment will function as a proving ground for the development of high-current machines in general and is particularly targeted at beam development for an electron-ion collider (eRHIC). The cavity performed well in vertical tests, demonstrating gradients of 20 MV/m and a Q0 of 1010. Here we will present its performance in the horizontal tests, and discuss technical issues involved in its implementation in the ERL.
 
 
TUP057 The Fundamental Power Coupler and Pick-up of the 56 MHz Cavity for RHIC cavity, coupling, feedback, SRF 916
 
  • Q. Wu, S. Bellavia, I. Ben-Zvi, C. Pai
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A fundamental power coupler (FPC) is designed to obtain the ability of fast tuning the 56MHz SRF cavity in RHIC. The FPC will be inserted from one of the chemical cleaning ports at the rear end of the cavity with magnetic coupling to the RF field. The size and the location of the FPC are decided based on the required operational external Q of the cavity. The FPC is designed with variable coupling that would cover a range of power levels, and it is thermally isolated from the base temperature of the cavity, which is 4.2K. A 1kW power amplifier will also be used to close an amplitude control feedback loop. In this paper, we discuss the coupling factor of the FPC with the carefully chosen design, as well as the thermal issues.
 
 
TUP058 Fundamental Damper Power Calculation of the 56MHz SRF Cavity for RHIC cavity, extraction, SRF, insertion 919
 
  • Q. Wu, S. Bellavia, I. Ben-Zvi, M.C. Grau, G. Miglionico, C. Pai
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
At each injection and extraction period of RHIC operation, the beam frequency will be sweeping across a wide range, and some of the harmonics will cross the frequency of the 56MHz SRF cavity. To avoid cavity excitation during these periods, a fundamental damper was designed for the quarter-wave resonator to heavily detune the cavity. The power extracted by the fundamental damper should be compliant with the cooling ability of the system at all stages. In this paper, we discussed the power output from the fundamental damper when it is fully extracted, inserted, and during its movement.
 
 
TUP059 Multipacting in a Grooved Choke Joint at SRF Gun for BNL ERL Prototype cathode, cavity, gun, linac 922
 
  • W. Xu, S.A. Belomestnykh, I. Ben-Zvi, A. Burrill, D. Kayran, G.T. McIntyre, B. Sheehy
    BNL, Upton, Long Island, New York, USA
  • D. Holmes
    AES, Medford, NY, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 703 MHz superconducting gun for BNL ERL prototype was tested at JLab with and without choke-joint and cathode stalk. Without choke-joint and cathode stalk, the gradient reached 25MV/m with Q0~6·109. The gun cathode insertion port is equipped with a choke joint with triangular grooves for multipacting suppression. We carried out tests with choke-joint and cathode stalk. The test results show that there are at least two barriers at about 5MV/m and 3.5 MV/m. We considered several possibilities and finally found that the limitation was because the triangular grooves were rounded after BCP, which caused strong multipacting in the choke-joint. This paper presents the primary test result of test results of the gun and discusses the multipacting analysis in the choke-joint. It also suggests possible solutions for the gun and multipacting suppressing for a similar structure.
 
 
TUP062 Design of Coupler for the NSLS-II Storage Ring Superconducting RF Cavity cavity, coupling, synchrotron, vacuum 931
 
  • M. Yeddulla, J. Rose
    BNL, Upton, Long Island, New York, USA
 
  NSLS-II requires four superconducting cavities working at 499.68 MHz. These cavities should support a 500 mA beam current. To operate the cavities in over-damped coupling condition, an External Quality Factor (Qext) of ~ 65000 is required. We have modified the existing coupler for the CESR-B cavity which has a Qext of ~ 200,000 to meet the requirements of NSLS-II. CESR-B cavity has an aperture coupler with a coupler "tongue" connecting the cavity to the waveguide. We have optimized the length, width and thickness of the "tongue" as well as the width of the aperture to increase the coupling using the three dimensional electromagnetic field solver, HFSS. Several possible designs will be presented.  
 
TUP063 HOM Measurements with Beam at the Cornell Injector Cryomodule HOM, laser, cryomodule, pick-up 934
 
  • S. Posen, M. Liepe
    CLASSE, Ithaca, New York, USA
 
  Funding: NSF
The Cornell ERL injector prototype is undergoing commissioning and testing for running unprecedented currents in an electron cw injector. This paper discusses preliminary measurements of HOMs in the injector prototype’s superconducting RF cryomodule. These include HOM spectra up to 30 GHz measured via small antennae located at the HOM beam line absorbers between the SRF cavities. The spectra are compared at different beam currents and repetition rates. The shape of the spectra are compared to ABCI simulations of the loss factor spectrum of the cryomodule beam line. The total HOM power dissipated in the HOM loads was also measured with beam on, which allowed for an estimate of the loss factor. This measurement was accomplished via temperature sensors on the loads, calibrated to input power by heaters on the loads.
 
 
TUP069 Status of the Mechanical Design of the 650 MHz Cavities for Project X cavity, HOM, linac, status 943
 
  • S. Barbanotti, M.S. Champion, M.H. Foley, C.M. Ginsburg, I.G. Gonin, C.J. Grimm, T.J. Peterson, L. Ristori, V.P. Yakovlev
    Fermilab, Batavia, USA
 
  In the high-energy section of the Project X Linac, acceleration of H- ions takes place in superconducting cavities operating at 650 MHz. Two families of five-cell elliptical cavities are planned: β = 0.61 and β = 0.9. A specific feature of the Project X Linac is low beam loading, and thus, low bandwidth and higher sensitivity to microphonics. Efforts to optimize the mechanical design of the cavities to improve their mechanical stability in response to the helium bath pressure fluctuations will be presented. These efforts take into account constraints such as cost and ease of fabrication. Also discussed will be the overall design status of the cavities and their helium jackets.  
 
TUP073 Development of an L-band Ferroelectric Phase Shifter insertion, controls, linac, high-voltage 955
 
  • S. Kazakov, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT, USA
  • A. Kanareykin, E. Nenasheva
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S.V. Shchelkunov
    Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
 
  Effective operation of the RF cavities in the superconducting accelerators demands fast, high-power RF vector modulators. Recent progress in development of the new materials, ferroelectrics, having tunable dielectric constant and acceptable losses [*] gives the possibility development of such devises. In previous papers [**-***] the authors described different L-band ferroelectric phase shifter designs . At low RF level high operation speed of 2 degree/nsec was demonstrated in waveguide phase shifter. However, the experiments show that a special technology is to be developed that provides a good electric contact between ceramics and the metallic wall. In present paper a new design of the fast high–power ferroelectric phase shifter is described based on the simple ferroelectric elements.
* A. Kanareykin, et al, IPAC 2010, p. 3987
** S. Kazakov, et al, “Fast Ferroelectric Phase Shifter Design For ERLs,” 45th ICFA Beam Dynamics Workshop, 2009
*** S. Kazakov, et al, PAC2007, p. 599.
 
 
TUP075 Cavity Loss Factors of Non-relativistic Beams for Project X cavity, linac, factory, cryomodule 961
 
  • A. Lunin, S. Kazakov, V.P. Yakovlev
    Fermilab, Batavia, USA
 
  Cavity loss factor calculation is an important part of total cryolosses estimation for the super conductive (SC) accelerating structures. There are two approaches how to calculate cavity loss factors, the integration of a wake potential over the bunch profile and the combining of loss factors for individual cavity modes. We applied both methods in order to get reliable results for non-relativistic beam. The time domain CST solver was used for a wake potential calculation and the frequency domain HFSS code was used for the cavity eigenmodes spectrum findings. Finally we present the results of cavity loss factors simulations for a non-relativistic part of the ProjectX and analyze it for various beam parameters.  
 
TUP090 Design of a β = 0.29 Half-wave Resonator for the FRIB Driver Linac cavity, linac, cryomodule, ion 997
 
  • J.P. Holzbauer, W. Hartung, J. Popielarski
    NSCL, East Lansing, Michigan, USA
 
  The driver linac for the Facility for Rare Isotope Beams will produce primary beams of ions at 200 MeV per nucleon for nuclear physics research. The driver linac will require 344 superconducting cavities, consisting of two types of Quarter-Wave Resonators (QWRs, β = 0.041 and 0.085) and two types of Half-Wave Resonators (HWRs, β = 0.29 and 0.53). A first-generation β = 0.29 HWR has been designed, prototyped, and tested. Second-generation versions of the other cavities are being developed, with one or more prototype having been tested. A second-generation β = 0.29 HWR design has been developed, making use of the experience with the first-generation β = 0.29 HWR and second-generation β = 0.53 HWR. In the second-generation design, the inner conductor is tapered to reduce the peak surface magnetic field. The outer conductor is a straight tube to increase the mechanical stiffness and reduce the sensitivity of the resonant frequency to bath pressure fluctuations. Optimization was employed to minimize the peak surface electric field. The second-generation β = 0.29 HWR design will be presented, including the RF design and mechanical analysis.  
 
TUP096 Beam Pipe HOM Absorber for SRF Cavities HOM, insertion, cavity, SRF 1012
 
  • R. Sah, A. Dudas, M.L. Neubauer
    Muons, Inc, Batavia, USA
  • G.H. Hoffstaetter, M. Liepe, H. Padamsee, V.D. Shemelin
    CLASSE, Ithaca, New York, USA
  • K. Ko, C.-K. Ng, L. Xiao
    SLAC, Menlo Park, California, USA
 
  Funding: Supported in part by DOE SBIR grant DE-SC0002733 and USDOE Contract No. DE-AC05-84-ER-40150.
Superconducting RF (SRF) systems typically contain resonances at unwanted frequencies, or higher order modes (HOM). For storage ring and linac applications, these higher modes must be damped by absorbing them in ferrite and other lossy ceramic materials. Typically, these absorbers are brazed to substrates that are often located in the drift tubes adjacent to the SRF cavity. These HOM absorbers must have broadband microwave loss characteristics and must be thermally and mechanically robust, but the ferrites and their attachments are weak under tensile and thermal stresses and tend to crack. Based on prior work on HOM loads for high current storage rings and for an ERL injector cryomodule, a HOM absorber with improved materials and design is being developed for high-gradient SRF systems. This work will use novel construction techniques (without brazing) to maintain the ferrite in mechanical compression. Attachment techniques to the metal substrates will include process techniques for fully-compressed ferrite rings. Prototype structures will be fabricated and tested for mechanical strength under thermal cycling conditions.
 
 
TUP098 Multipacting Analysis of the Superconducting Parallel-bar Cavity cavity, electron, resonance, electromagnetic-fields 1018
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
 
  The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. Multipacting can be a limiting factor to the performance of in any superconducting structure. In the parallel-bar cavity the main contribution to the deflection is due to the transverse deflecting voltage, between the parallel bars, making the design potentially prone to multipacting. This paper presents the results of analytical calculations and numerical simulations of multipacting in the parallel-bar cavity with resonant voltage, impact energies and corresponding particle trajectories.  
 
TUP107 RF-thermal Combined Simulations of a Superconducting HOM Coaxial Coupler HOM, cavity, cryomodule, SRF 1041
 
  • G. Cheng, H. Wang
    JLAB, Newport News, Virginia, USA
  • D.N. Smithe
    Tech-X, Boulder, Colorado, USA
 
  Funding: This work is supported by Jefferson LAB and Tech-X CRADA #2009S005 on “Simulations of Electromagnetic and Thermal Characteristics of SRF Structures”.
To benchmark a multi-physics code VORPAL developed by Tech-X, the High Order Mode (HOM) coaxial coupler design implemented in Jefferson Lab’s 12GeV upgrade cryomodules is analyzed by use of commercial codes, such as ANSYS, HFSS and Microwave Studio. Testing data from a Horizontal Test Bed (HTB) experiment on a dual-cavity prototype are also utilized in the verification of simulation results. The work includes two stages: first, the HOM feedthrough that has a high RRR niobium probe and sapphire insulator is analyzed for the RF-thermal response when there is traveling wave passing through; second, the HTB testing condition is simulated and results from simulation are compared to thermal measurements from HTB tests. The analyses are of coupled-field nature and involve highly nonlinear temperature dependent thermal conductivities and electric resistivities for the eight types of materials used in the design. Accuracy and efficiency are the main factors in evaluation of the performance of the codes.
 
 
TUP111 Multipactoring Observation, Simulation and Suppression on a Superconducting TE011 Cavity cavity, electron, ion, vacuum 1050
 
  • H. Wang, G. Ciovati
    JLAB, Newport News, Virginia, USA
  • L. Ge, Z. Li
    SLAC, Menlo Park, California, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and COMPASS of SciDAC No.
A superconducting cavity of the same shape as used for the development of superconducting photo injectors has been built for the studies of high magnetic field induced Q slope due to the local heating. The multipactoring problem has been observed on the TE011 mode, 3.3GHz with magnetic field barriers. To understand and overcome this problem, 3D multipactoring simulations by Omega3P and Track3P have been done and found these to be one-point multipactors pulled out from the flat bottom surface by finite normal component of electric field. Asymmetric coupling ports on the side of the beam tube could have caused the distortion of the TE011 mode. The thermometry measurement later confirmed the predicted impact locations. A structure modification has been adopted based on the simulation prediction. More experimental results with the new geometry will allow further comparison with the 3D multipactoring simulations.
 
 
TUP123 Performance of the 352-MHz 4-kW CW Solid State RF Power Amplifier System using 1-kW Push-pull Devices klystron, controls, cavity, storage-ring 1059
 
  • D. Horan, G.J. Waldschmidt
    ANL, Argonne, USA
 
  Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Development and testing of a prototype 352-MHz, 4-kW cw solid state rf power amplifier system is underway at the Advanced Photon Source to study and evaluate the performance advantages of an upgrade to solid state rf power technology at the APS. General performance measurement data on the assembled amplifier system is discussed, with emphasis on efficiency improvements possible through the use of dynamic drain voltage control.
 
 
TUP126 Development of a 10 kW CW, S-Band, PPM Focused Klystron klystron, electron, cavity, gun 1068
 
  • P. Ferguson, R.L. Ives, D. Marsden, M.E. Read
    CCR, San Mateo, California, USA
 
  Funding: US Department of Energy SBIR Contract DE-SC0004558
Calabazas Creek Research Inc. (CCR) is developing a 100 kW CW, 2.815 GHz klystron for use in the Advanced Photon Source upgrade light source at Argonne National Laboratory. Periodic permanent magnet (PPM) focusing is used to avoid loss in efficiency due to the power normally required for a solenoid. The PPM structure elements consist of 4 disk (pill box) magnets with a clover-leaf shaped iron pole piece. The gaps between the magnets permit the introduction of liquid cooling into the RF circuit. Design tools include the large signal codes KLSC and TESLA for the efficiency calculations, MAXWELL 3D for the magnetic fields, and the CCR 3D code BOA for the beam trajectories. From initial simulations with seven cavities, the efficiency will be over 62% with a beam voltage of 47 kV. The saturated gain is 44 dB. The design emphasizes high reliability, with simple construction, robust cooling and low thermal loading through high efficiency. The paper will include the details of the design, including results of the simulations of the RF and magnetic structures, beam trajectories, and thermo-mechanical analyses.
 
 
TUP128 Development of a 402.5 MHz 140 kW Inductive Output Tube (IOT) gun, electron, cavity, klystron 1070
 
  • M.E. Read, T. Bui, R.L. Ives, R.H. Jackson
    CCR, San Mateo, California, USA
  • I.A. Chernyavskiy, H. Freund
    SAIC, McLean, USA
 
  Funding: US Department of Energy under SBIR contract DE-SC0004566
Calabazas Creek Research Inc. (CCR) is developing a pulsed 140 kW, 402.5 MHz Inductive Output Tube (IOT) for use in proton accelerators. Unlike other high power multiple-beam IOT's currently under development, this device will use a single electron beam, and will be less expensive and have a higher reliability. The program includes the use of new design tools, including NEMESIS and a version of CCR's 3D Beam Optics Analysis (BOA) code modified to include time dependent modeling. The design will include the electron gun, collector, input and output cavities, input and output couplers and the RF output window. An emphasis will be placed on the electron gun, which will as usual include a grid for the high frequency modulation, and the input cavity. The new version of BOA is expected to be particularly useful in modeling the formation of the bunched beam and will replace the relatively slow 3D PIC code MAGIC as the primary design tool. HFSS and NEMESIS will be used for design of the input cavity. The paper will include details of the design.
 
 
TUP129 Simulation Results of RF Coupler Controllable by Dielectric Fluid coupling, cavity, vacuum, impedance 1073
 
  • P. Chen, D. Yu
    DULY Research Inc., Rancho Palos Verdes, California, USA
 
  Funding: Work supported by DOE SBIR Phase I grant No. DE-FG02-09ER85334.
Tunable couplers for adjusting radiofrequency (RF) power coupling into accelerator cavities are useful devices for achieving optimal operation efficiency. Standard mechanical tuners currently used in large accelerator facilities are bulky and complicated. A novel tuner, based on the introduction of dielectric tubes or fluid-filled volumes adjacent to, but separated by window(s) from the coupler, is described. Simulations have shown that the tuner has a fairly large adjustment range and also demonstrated the viability of the tuning concept using fluid circuit.
 
 
TUP130 Experiments on Voltage Droop Compensation for High Power Marx Modulators controls, high-voltage, factory, linac 1076
 
  • P. Chen, M. Lundquist, D. Yu
    DULY Research Inc., Rancho Palos Verdes, California, USA
 
  Funding: Work supported by DOE SBIR Phase II grant DE-FG02-08ER85052
Marx modulators, promising higher efficiency, longer lifetime and reduced cost compared with existing hard tube modulator options, are under intensive research. In this article, we describe the progress of work on our voltage droop compensation scheme for a Marx modulator. Experimental results on a compensation circuit at moderate voltage are presented.
 
 
TUP141 RF Solid State Driver for Argonne Light Source klystron, booster, storage-ring, background 1097
 
  • B. Popovic
    University of Iowa, Iowa City, Iowa, USA
  • G.J. Waldschmidt
    ANL, Argonne, USA
 
  Funding: 2010 Lee Teng Summer Student Program at Argonne National Laboratory
Currently, power to the APS storage ring and Booster cavities is provided from klystrons with a eventual goal to move to a solid state RF system. A modular design centered around a 1 kW amplifier has been decided on. The driver amplifier was created for this module system using Agilent’s ADS circuit simulation software and then built and tested.
 
 
TUP152 Dipole Corrector Magnets for the LBNE Beam Line dipole, quadrupole, target, synchrotron 1115
 
  • M. Yu, D.J. Harding, G. Velev
    Fermilab, Batavia, USA
 
  The conceptual design of a new dipole corrector magnet has been thoroughly studied. The planned Long-Baseline Neutrino Experiment (LBNE) beam line will require correctors capable of greater range and linearity than existing correctors, so a new design is proposed based on the horizontal trim dipole correctors built for the Main Injector synchrotron at Fermilab. The gap, pole shape, length, and number of conductor turns remain the same. To allow operation over a wider range of excitations without overheating, the conductor size is increased, and to maintain better linearity, the back leg thickness is increased. The magnetic simulation was done using ANSYS to optimize the shape and the size of the yoke. The thermal performance was also modeled and analyzed.  
 
TUP173 Progress on the Modeling and Modification of the MICE Superconducting Spectrometer Solenoids solenoid, radiation, emittance, focusing 1151
 
  • S.P. Virostek, M.A. Green, T.O. Niinikoski, S. Prestemon, M.S. Zisman
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231.
The Muon Ionization Cooling Experiment (MICE) is an international effort sited at Rutherford Appleton Laboratory (RAL) in the UK that will demonstrate ionization cooling in a section of realistic cooling channel using a muon beam. The spectrometer solenoids are an identical pair of five-coil superconducting magnets that will provide a 4-tesla uniform field region at each end of the cooling channel. Scintillating fiber trackers within each of the 400-mm diameter magnet bore tubes will measure the emittance of the beam as it enters and exits the cooling channel. Each of the 3-meter long magnets incorporates a three-coil spectrometer magnet section and a two-coil section that matches the solenoid uniform field into the MICE cooling channel. The cold mass, radiation shield and leads are kept cold by means of a series of two-stage cryocoolers and one single-stage cryocooler. Various thermal, electrical and magnetic analyses are being carried out in order to develop design improvements related to magnet cooling and reliability. The key features of the spectrometer solenoid magnets are presented along with some of the details of the analyses.
 
 
TUP179 Energy Deposition within Superconducting Coils of a 4 MW Target Station target, shielding, neutron, factory 1166
 
  • X.P. Ding
    UCLA, Los Angeles, California, USA
  • J.J. Back
    University of Warwick, Coventry, United Kingdom
  • R.C. Fernow, H.G. Kirk, N. Souchlas
    BNL, Upton, Long Island, New York, USA
  • K.T. McDonald
    PU, Princeton, New Jersey, USA
  • R.J. Weggel
    Particle Beam Lasers, Inc., Northridge, California, USA
 
  Funding: Work Supported by the United States Department of Energy, Contract No. DE-AC02-98CH10886.
A study of energy deposition within superconducting coils of a 4 MW target station for a neutrino factory or muon collider is presented. Using the MARS code, we simulate the energy deposition within the environment surrounding the target. The radiation is produced by interactions of intense proton beams with a free liquid mercury jet. We study the influence of different shielding materials and shielding configurations on the energy deposition in the superconducting coils of the target/capture system. We also examine energy depositions for alternative configurations that allow more space for shielding, thus providing more protection for the superconducting coils.
 
 
TUP191 Booster Main Magnet Power Supply, Present Operation and Potential Future Upgrades power-supply, controls, booster, feedback 1184
 
  • E.M. Bajon, M. Bannon, G. Danowski, I. Marneris, J. Sandberg, S. Savatteri
    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
The Brookhaven Booster Main Magnet Power Supply (MMPS) is a 24 pulse thyristor control supply, rated at 5500 Amps, ±2000 Volts, or 3000 Amps, ±6000 Volts. The power supply is fed directly from the power utility and the peak magnet power is 18 MWatts. This peak power is seen directly at the incoming ac line. This power supply has been in operation for the last 18 years. This paper will describe the present topology and operation of the power supply, the feedback control system and the different modes of operation of the power supply. Since the power supply has been in operation for the last 18 years, upgrading this power supply is essential. A new power supply topology has been studied where energy is stored in capacitor banks. DC to DC converters are used to convert the dc voltage stored in the capacitor banks to pulsed DC voltage into the magnet load. This enables the average incoming power from the ac line to be constant while the peak magnet power is pulsed to ± 18 MWatts. Simulations and waveforms of this power supply will be presented.
 
 
TUP196 SLAC P2 MARX Control System and Regulation Scheme controls, power-supply, interlocks, status 1193
 
  • D.J. MacNair, M.A. Kemp, K.J.P. Macken, M.N. Nguyen, J.J. Olsen
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515
The SLAC P2 MARX P2 Modulator consists of 32 cells charged in parallel by a -4000V supply and discharged in series to provide a -120 KV 140 amp 1.6 millisecond pulse. Each cell has a 350uF main storage capacitor. The voltage on the capacitor will droop approximately 640 volts during each pulse. Each cell will have a boost supply that can add up to 700V to the cell output. This allows the output voltage of the cell to remain constant within 0.1% during the pulse. The modulator output voltage control is determined by the -4KV charging voltage. A voltage divider will measure the modulator voltage on each pulse. The charging voltage will be adjusted by the data from previous pulses to provide the desired output. The boost supply in each cell consists of a 700V buck regulator in series with the main capacitor. The supply uses a lookup table for PWM control. The lookup table is calculated from previous pulse data to provide a constant cell output. The paper will describe the modulator and cell regulation used by the MARX modulator. Measured data from a single cell and three cell string will be included.
 
 
TUP221 Helium Pressures in RHIC Vacuum Cryostats and Relief Valve Requirements from Magnet Cooling Line Failure vacuum, dipole, injection, quadrupole 1229
 
  • C.J. Liaw, R. Than, J.E. Tuozzolo
    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.
A catastrophic failure of the RHIC magnet cooling lines, similar to the LHC superconducting bus failure incident, would pressurize the insulating vacuum in the magnet and transfer line cryostats. Insufficient relief valves on the cryostats could cause a structural failure. A SINDA/FLUINT® model, which simulated the 4.5K/ 4 atm helium flowing through the magnet cooling system distribution lines, then through a line break into the vacuum cryostat and discharging via the reliefs into the RHIC tunnel, had been developed to calculate the helium pressure inside the cryostat. Arc flash energy deposition and heat load from the ambient temperature cryostat surfaces were included in the simulations. Three typical areas: the sextant arc, the Triplet/DX/D0 magnets, and the injection area, had been analyzed. Existing relief valve sizes were reviewed to make sure that the maximum stresses, caused by the calculated maximum pressures inside the cryostats, did not exceed the allowable stresses, based on the ASME Code B31.3 and ANSYS results.
 
 
TUP222 Helium Release Rates and ODH Calculations from RHIC Magnet Line Cooling Line Failure vacuum, injection, controls, collider 1232
 
  • C.J. Liaw, R. Than, J.E. Tuozzolo
    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.
A catastrophic failure of the magnet cooling lines, similar to the LHC superconducting bus failure incident, could discharge cold helium into the RHIC tunnel and cause an Oxygen Deficiency Hazard (ODH) problem. A SINDA/FLUINT® model, which simulated the 4.5K/ 4 atm helium flowing through the magnet cooling system distribution lines, then through a line break into the insulating vacuum volumes and discharging via the reliefs into the RHIC tunnel, had been developed. Arc flash energy deposition and heat load from the ambient temperature cryostat surfaces are included in the simulations. Three typical areas: the sextant arc, the Triplet/DX/D0 magnets, and the injection area, had been analyzed. Results, including helium discharge rates, helium inventory loss, and the resulting oxygen concentration in the RHIC tunnel area, are reported. Good agreement had been achieved when comparing the simulation results, a RHIC sector depressurization test measurement, and some simple analytical calculations.
 
 
TUP232 Super-Conducting Wigglers and the Effect on Injection Efficiency injection, wiggler, storage-ring, betatron 1259
 
  • M.J. Sigrist, L.O. Dallin, W.A. Wurtz
    CLS, Saskatoon, Saskatchewan, Canada
 
  The Canadian Light Source has two superconducting wigglers (SCW) operating at 2.1T and 4.3T peak fields. Injection efficiency into the storage ring is reduced by either device operating at high fields. Currently the CLS operates with a Fill and Decay mode, injecting with both wigglers at reduced field to avoid low injection efficiencies. Future implementation of a Top-up mode will require both wigglers to be operating at full field and better injection efficiencies will be required. Simulations and experiments have shown that the poor injection efficiency is related to operating a high vertical chromaticity. Much improved efficiencies are observed at when the chromaticity is lowered. As well, small improvements to the injection efficiency have been achieved through local correction of the beta-beats and tune shifts caused by the wigglers and optimisation of the injection co-ordinates of the injected beam. Measurements of the injection efficiencies at various chromaticities will be presented along with the betatron oscillations before and after correction.  
 
TUP237 Development of Accurate and Precise In-Vacuum Undulator System vacuum, undulator, coupling, radiation 1268
 
  • A. Deyhim, J.D. Kulesza
    Advanced Design Consulting, Inc, Lansing, New York, USA
  • K.I. Blomqvist
    MAX-lab, Lund, Sweden
 
  Typical in-vacuum undulators, especially long ones, have several associated engineering challenges to be accurate and precise; magnetic centerline stability, inner girder hangers, and magnet period to name a few. The following describes these issues in more detail and ADC’s methods solved these critical issues for long in vacuum undulators. ADC has designed, built and delivered Insertion Devices and Magnetic Measurement Systems to such facilities as; MAXLab (EPU, Planar-2, and Measurement System), ALBA and Australian Synchrotron Project (Wiggler), BNL (Cryo In-Vacuum), SSRF (In-Vacuum – 2, and Measurement System), PAL (In-Vacuum and Measurement System), NSRRC (In-Vacuum), and SRC (Planar and EPU). The information presented here uses data from a recent IVU we delivered to PAL. This IVU will be installed at Pohang Accelerator Laboratory (PAL) for U-SAXS (Ultra Small Angle X-ray Scattering) beamline in 2011. The IVU generates undulator radiation up to ~14 keV using higher harmonic (up to 9th) undulator radiation with 2.5 GeV PLS electron beam  
 
TUP241 End-Field Analysis and Implementation of Correction Coils for a Short-Period NbTi Superconducting Undulator undulator, photon, alignment, emittance 1280
 
  • C.L. Doose, M. Kasa, S.H. Kim
    ANL, Argonne, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A short period superconducting undulator (SCU) is being developed at the Advanced Photon Source (APS). The on-axis field of the prototype 1.6-cm period 42-pole SCU0 was measured with a cryogenic Hall probe system. Typical permanent magnet undulators provide end-field correction by decreasing the strength of the magnets on both ends of each jaw. In the case of the SCU0, a set of correction coils was wound on the two end grooves of each of the steel cores along with the main coils to provide the required end fields. These correction coils were connected in series and energized with one power supply to provide simple and symmetrical operation. The measured phase errors of the SCU0 were below 2 degrees rms without any local magnetic tuning of the device.
 
 
TUP244 Magnetic Simulation of an Electromagnetic Variably Polarizing Undulator * undulator, sextupole, polarization, photon 1289
 
  • M.S. Jaski, R.J. Dejus, E.R. Moog
    ANL, Argonne, USA
 
  Development of an all-electromagnetic variable polarizing undulator is underway at the Advanced Photon Source (APS). This device has a set of Bx poles and coils and a set of By poles and coils. The Bx coils are powered separately from the By coils. Modifying the geometry of the Bx coils or poles changes not only the Bx field but changes the By field as well and vice-versa. Magnetic modeling with OPERA 3-D software was used to optimize the coil and pole geometries. Results of the magnetic field simulation and optimization are presented in this paper.
* Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC02-06CH11357.
 
 
TUP253 AGS Tune Jump Power Supply Design and Test power-supply, controls, high-voltage, resonance 1298
 
  • J.-L. Mi, J.W. Glenn, H. Huang, I. Marneris, P.J. Rosas, J. Sandberg, Y. Tan, W. Zhang
    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.
A horizontal tune jump system has been installed to overcome the horizontal intrinsic spin resonances, which requires jumping the horizontal tune 0.04 units 82 times, 41 up and 41 down. Two quadruple magnets have been installed in AGS ring to do this. The pulsed magnet currents range from about 140 amps near injection to about 1400 amps late. Current pulse rise and fall times are around 100 micro-sec and flat tops time are around 4mS. These quadruples have separate supplies. This tune jump pulse power supply employees all semiconductor parts as the main switches. During dummy load and magnet testing, the test result showed that the power supply could meet the specification. This article will describe some detail of power supply simulation, design and testing. Some test waveform and pictures are presented in this paper.
 
 
TUP276 Measurement of Thermal Dependencies of PBG Fiber Properties laser, acceleration, controls, alignment 1343
 
  • R. Laouar, E.R. Colby, R.J. England, R.J. Noble
    SLAC, Menlo Park, California, USA
 
  Funding: Department Of Energy
Photonic crystal fibers (PCFs) represent a class of optical fibers which have a wide spectrum of applications in the telecom and sensing industries. Currently, the Advanced Accelerator Research Department at SLAC is developing photonic bandgap particle accelerators, which are photonic crystal structures with a central defect used to accelerate electrons and achieve high longitudinal electric fields. Extremely compact and less costly than the traditional accelerators, these structures can support higher accelerating gradients and will open a new era in high energy physics as well as other fields of science. Based on direct laser acceleration in dielectric materials, the so called photonic band gap accelerators will benefit from mature laser and semiconductor industries.
 
 
TUP277 RF Design of the Power Coupler for the Spiral2 Single Bunch Selector vacuum, ion, kicker, impedance 1346
 
  • F. Consoli, A.C. Caruso, G. Gallo, D. Rifuggiato, E. Zappalà
    INFN/LNS, Catania, Italy
  • M. Di Giacomo
    GANIL, Caen, France
 
  Funding: Work supported by the European Community FP7 – Capacities – SPIRAL2 Preparatory Phase n° 212692.
The single bunch selector of the Spiral2 driver uses high impedance travelling wave electrodes driven by fast pulse generators. The characteristic impedance of 100 Ω has been chosen to reduce the total power, but this non standard value requires the development of custom feed-through and transitions to connect the pulse generators and the matching load to the electrodes. The paper reviews the design of these devices.
 
 
TUP279 A CW RFQ Prototype rfq, dipole, linac, vacuum 1352
 
  • U. Bartz, A. Schempp
    IAP, Frankfurt am Main, Germany
 
  A short RFQ prototype was built for tests of high power RFQ structures. We will study thermal effects and determine critical points of the design. HF-simulations with CST Microwave Studio and measurements were done. The RF-tests with continues power of 20 kW/m and simulations of thermal effects with ALGOR were finished successfully. Optimization of some details of the facility are on focus now. First results and the status of the project will be presented.  
 
WEOBS1 The Berkeley Lab Laser Accelerator (BELLA): A 10 GeV Laser Plasma Accelerator laser, plasma, electron, diagnostics 1416
 
  • W. Leemans, R.M. Duarte, E. Esarey, D.S. Fournier, C.G.R. Geddes, D. Lockhart, C.B. Schroeder, C. Tóth, J.-L. Vay, S. Zimmermann
    LBNL, Berkeley, California, USA
 
  An overview is presented of the design of a 10 GeV laser plasma accelerator (LPA) that will be driven by a PW-class laser system and of the BELLA Project, under which the required Ti:sapphire laser system for the acceleration experiments is being installed. The basic design of the 10 GeV stage aims at operation in the quasi-linear regime, where the laser excited wakes are largely sinusoidal and allow acceleration of electrons and positrons. Simulations show that a 10 GeV electron beam can be generated in a meter scale plasma channel guided LPA operating at a density of about 1017 cm-3 and powered by laser pulses containing 30-40 J of energy in a 50-200 fs duration pulse, focused to a spotsize of 50-100 micron. The lay-out of the facility and laser system will be presented as well as the progress on building the facility.  
 
WEOCN3 Operational Results from the LHC Luminosity Monitors luminosity, proton, ion, target 1443
 
  • R. Miyamoto
    BNL, Upton, Long Island, New York, USA
  • E. Bravin
    CERN, Geneva, Switzerland
  • H.S. Matis, A. Ratti, W.C. Turner, H. Yaver, T. stezelberger
    LBNL, Berkeley, California, USA
 
  Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
The Luminosity Monitors for the high luminosity regions in the LHC have been operating to monitor and optimize the luminosity since the beginning of the 2009 run. The device is a gas ionization chamber, which has the ability to resolve bunch-by-bunch luminosity as well as survive the extreme levels of radiation at nominal high intensity LHC operations. The chambers are installed at the zero degree collision angle inside the neutral absorbers 140 m from the interaction point and monitor showers produced by high energy neutral particles from the collisions. A second device, a photo-multiplier based system (PMT) located directly behind the gas ionization chamber, has been also used at low luminosities. We will present operational results for the ionization chambers for both pp and Pb-Pb collisions. These measurements include signal, noise and background studies, and correlation between the gas ionization detector and the PMT. Also, comparison with ongoing modeling efforts will be included.
 
slides icon Slides WEOCN3 [2.609 MB]  
 
WEOCN6 Femtosecond Resolved Determination of Electron Beam and XUV Seed Pulse Temporal Overlap in sFLASH electron, laser, radiation, undulator 1452
 
  • R. Tarkeshian, A. Azima, J. Bödewadt, F. Curbis, M. Drescher, Th. Maltezopoulos, V. Miltchev, M. Mittenzwey, J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • H. Delsim-Hashemi, K. Honkavaara, H. Schlarb, S. Schreiber
    DESY, Hamburg, Germany
  • R. Ischebeck
    PSI, Villigen, Switzerland
 
  sFLASH is a seeded experiment at the Free-Electron Laser FLASH in Hamburg. It uses a 38nm High-Harmonic-Generation (HHG) scheme to seed the FEL-process in a 10 m long variable-gap undulator. The temporal overlap between the electron and HHG pulses is critical to the seeding process. The use of a 3rd harmonic accelerating module provides a high current electron beam with ~400 fs bunch duration. The duration of the HHG laser pulse is ∼20 fs. The desired overlap is achieved in two steps. Firstly, the HHG drive laser is synchronized to the incoherent spontaneous radiation from an upstream undulator with picosecond resolution. Next, the coherent radiation from an undulator is used to determine the exact overlap of the electron beam in a modulator-radiator set-up.  
slides icon Slides WEOCN6 [1.758 MB]  
 
WEOCS4 Integrated EM & Thermal Simulations with Upgraded VORPAL Software HOM, cryogenics, plasma, niobium 1463
 
  • D.N. Smithe, D. Karipides, P. Stoltz
    Tech-X, Boulder, Colorado, USA
  • G. Cheng, H. Wang
    JLAB, Newport News, Virginia, USA
 
  Funding: This work supported by a DOE Phase II SBIR.
Nuclear physics accelerators are powered by microwaves which must travel in waveguides between room-temperature sources and the cryogenic accelerator structures. The ohmic heat load from the microwaves is affected by the temperature-dependent surface resistance and in turn affects the cryogenic thermal conduction problem. Integrated EM & thermal analysis of this difficult non-linear problem is now possible with the VORPAL finite-difference time-domain simulation tool. We highlight thermal benchmarking work with a complex HOM feed-through geometry, done in collaboration with researchers at the Thomas Jefferson National Accelerator Laboratory, and discuss upcoming design studies with this emerging tool. This work is part of an effort to generalize the VORPAL framework to include generalized PDE capabilities, for wider multi-physics capabilities in the accelerator, vacuum electronics, plasma processing and fusion R&D fields, and we will also discuss user interface and algorithmic upgrades which facilitate this emerging multiphysics capability.
 
slides icon Slides WEOCS4 [0.996 MB]  
 
WEODS2 High-Power Targets: Experience and R&D for 2 MW target, radiation, proton, neutron 1496
 
  • P. Hurh
    Fermilab, Batavia, USA
  • O. Caretta, T.R. Davenne, C.J. Densham, P. Loveridge
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  • N. Simos
    BNL, Upton, Long Island, New York, USA
 
  High-power particle production targets are crucial elements of future neutrino and other rare particle beams. Fermilab plans to produce a beam of neutrinos (LBNE) with a 2.3 MW proton beam (Project X). Any solid target is unlikely to survive for an extended period in such an environment - many materials would not survive a single beam pulse. We are using our experience with previous neutrino and antiproton production targets, along with a new series of R&D tests, to design a target that has adequate survivability for this beamline. The issues considered are thermal shock (stress waves), heat removal, radiation damage, radiation accelerated corrosion effects, physics/geometry optimization and residual radiation.  
 
WEP011 Low Energy Beam Transport Developments for the Bilbao Accelerator ion, rfq, ion-source, dipole 1522
 
  • I. Bustinduy, D. de Cos
    ESS Bilbao, Bilbao, Spain
  • F.J. Bermejo
    Bilbao, Faculty of Science and Technology, Bilbao, Spain
  • V. Etxebarria, J. Portilla
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
  • J. Feuchtwanger, Z. Izaola, J.L. Munoz, I. Rodríguez
    ESS-Bilbao, Zamudio, Spain
 
  Funding: European Spallation Source - Bilbao
In this work we present a future upgrade of the ESS-Bilbao multi-source Low Energy Transport System (LEBT). It consists of a set of solenoids and steering dipoles used to match the characteristics of both ion source beams i.e., the Electron Cyclotron Resonance (ECR) H+/D+ source and the H− Penning source, to the input specifications of the RFQ. Different configurations of the geometry and magnetic fields are studied in order to minimize the emittance growth along the LEBT, while providing the beam specifications required by the RFQ.
 
 
WEP015 Initial Simulations of Electron and Ion Beam Optics for the ANL EBIS Electron Collector electron, ion, injection, cathode 1525
 
  • C. Dickerson, S.A. Kondrashev, P.N. Ostroumov
    ANL, Argonne, USA
  • A.I. Pikin
    BNL, Upton, Long Island, New York, USA
 
  Funding: U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357
An Electron Beam Ion Source (EBIS) being developed at the Argonne National Laboratory (ANL) will be used to charge breed rare isotopes from a 1 Ci 252Cf source, the Californium Rare Isotope Breeder Upgrade (CARIBU). Simulations have been performed using commercially available software, TriComp, to ensure the electron collector is properly designed to dissipate the electron beam power and provide adequate acceptance for the injected ion beam.
 
 
WEP021 The Effect of Initial Energy Spread on Longitudinal Beam Modulations in an Electron Gun electron, gun, cathode, radiation 1537
 
  • C.P. Neuman
    CUNY, Bayside, New York, USA
  • P.G. O'Shea
    UMD, College Park, Maryland, USA
 
  Computer simulations are used to investigate the evolution of longitudinal density and energy modulations of an electron beam in a linear accelerator system. This study examines the effect of initial energy spread on the modulations as the beam is accelerated in the electron gun.  
 
WEP022 Status of Low Emittance Tuning at CesrTA emittance, coupling, betatron, quadrupole 1540
 
  • J.P. Shanks, M.G. Billing, R.E. Meller, M.A. Palmer, M.C. Rendina, N.T. Rider, D. L. Rubin, D. Sagan, C.R. Strohman, Y. Yanay
    CLASSE, Ithaca, New York, USA
 
  Funding: Work supported by the National Science Foundation and by the US Department of Energy under contract numbers PHY-0734867 and DE-FC02-08ER41538.
We report on the status of emittance tuning techniques at the CESR Test Accelerator CesrTA. The CesrTA experimental program requires the capability to operate in a variety of machine lattices with the smallest possible emittance. We have attempted to minimize the turn-around time of our low emittance tuning procedure. We utilize high bandwidth BPM electronics for fast, precision measurements of orbit, betatron phase, transverse coupling, and dispersion. Turn by turn data is used to measure BPM button electrode gains to a under a percent. Gain-corrected coupling data is utilized to determine BPM tilts to 10mrad, allowing for measurement of vertical dispersion at the level of 10mm. Measurement and analysis of the data for characterizing BPM response takes 5 minutes. Beam based measurement of machine functions, data analysis, and implementing corrections in the machine takes another 5 minutes. An x-ray beam size monitor provides a real time check on the effectiveness of the procedure. A typical correction results in an emittance less than 20pm at 2.1GeV in 1-2 iterations. Sub 15pm has been achieved with adjustment of closed coupling/vertical dispersion bumps and betatron tunes.
 
 
WEP030 Direct Focusing Error Correction with Ring-wide TBT Beam Position Data quadrupole, lattice, sextupole, focusing 1546
 
  • M.-J. Yang
    Fermilab, Batavia, USA
 
  Turn-By-Turn (TBT) betatron oscillation data is a very powerful tool in studying machine optics. Hundreds and thousands of turns of data are taken in just few tens of milliseconds. With beam in free oscillation and covering all positions and angles at every location focusing error diagnosis can be made almost instantly. This paper describes a new approach that observes focusing error collectively over all available TBT data to find the optimized quadrupole strength, one location at a time. Example will be shown and other issues will be discussed.  
 
WEP033 Using an Emittance Exchanger as a Bunch Compressor emittance, cavity, optics, coupling 1555
 
  • B.E. Carlsten, K. Bishofberger, L.D. Duffy, Q.R. Marksteiner, S.J. Russell, N.A. Yampolsky
    LANL, Los Alamos, New Mexico, USA
 
  Funding: This work is supported by the U.S. Department of Energy through the LANL/LDRD program.
An Emittance EXchanger (EEX), like a chicane, can be used for bunch compression. However, it offers a unique characteristic: the R56 term in an EEX vanishes, which decouples the final longitudinal position from the particles’ energies, thereby suppressing the microbunch instability. Also, it can provide simultaneous compression in both the longitudinal and one transverse dimensions, where, for example, the final longitudinal size is smaller than the initial horizontal size and the final horizontal size is smaller than the initial longitudinal size. In this scheme, there is no dependence on an energy slew needed for compressing the beam, simplifying the rf requirements. A bunch-compression scheme using two EEXs is presented, including CSR calculations.
 
 
WEP035 Intense Sheet Electron Beam Transport in a Periodically Cusped Magnetic Field focusing, electron, gun, optics 1558
 
  • P.B. Larsen, B. Levush, J.A. Pasour
    NRL, Washington, DC, USA
  • T.M. Antonsen
    UMD, College Park, Maryland, USA
  • A.T. Burke, J.J. Petillo
    SAIC, Billerica, Massachusetts, USA
  • K.T. Nguyen
    Beam-Wave Research, Inc., Union City, USA
 
  Funding: Acknowledgements: We gratefully acknowledge funding by the Office of Naval Research.
We explore periodically cusped magnetic (PCM) fields in the regime of a Ka-Band coupled-cavity travelling wave tube (beam current = 3.5A, voltage = 19.5kV, 10:1 beam aspect ratio). We use finite-element beam optics code MICHELLE to simulate the 3-dimensional beam optics for the beam transport within a PCM field. Realistic 3-dimensional magnetic fields have been considered to determine the practicality of these designs. We present the methodology used to focus and transport a thermal beam from a shielded-cathode, high aspect-ratio electron gun.
 
 
WEP036 Start-to-End Beam Dynamics Simulations for the SRF Accelerator Test Facility at Fermilab quadrupole, cavity, emittance, focusing 1561
 
  • C.R. Prokop, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • M.D. Church, Y.-E. Sun
    Fermilab, Batavia, USA
 
  Funding: LANL Laboratory Directed Research and Development program 20110067DR. U.S. DoE contract No. DE-FG02-08ER41532 Northern Illinois University. Fermi Research Alliance, LLC Contract No. DE-AC02-07CH11359.
Fermilab is currently building a superconducting RF (SCRF) linear-accelerator test facility. In addition to testing ILC-spec SCRF accelerating modules for ILC and Project-X, the facility will be capable of supporting a variety of advanced accelerator R&D experiments. The accelerator facility includes a 40-MeV photoinjector capable of producing bunches with variable parameters. In this paper, we present start-to-end simulations of the accelerator beamline.
 
 
WEP038 Physics Design of a Prototype 2-Solenoid LEBT for the SNS Injector solenoid, rfq, ion, beam-transport 1564
 
  • B. Han, D.J. Newland
    ORNL RAD, Oak Ridge, Tennessee, USA
  • T. Hunter, M.P. Stockli
    ORNL, Oak Ridge, Tennessee, USA
 
  To mitigate the operational risks associated with the SNS electrostatic LEBT, an R&D effort is underway to develop a 2-solenoid magnetic LEBT, which should improve the reliability while matching or exceeding the beam dynamic capabilities of the present electrostatic LEBT. This paper discusses the physics design of a prototype 2-solenoid magnetic LEBT.  
 
WEP039 Tracking Stripped Proton Particles in SNS Ring Injection Momentum Dump Line dipole, proton, collimation, injection 1567
 
  • J. G. Wang
    ORNL, Oak Ridge, Tennessee, USA
 
  3D computer simulations are performed to study magnetic field distributions and particle trajectories along the SNS ring injection momentum dump line. Optical properties and transfer maps along the dump line are calculated. The stripped proton particle distributions on the dump window are analyzed. The study has provided useful information for the redesign of the SNS ring injection beam dump.  
 
WEP041 Weak Resonances Induced by Nonlinear Multipoles in a Quadrupole Doublet Lattice linac, octupole, quadrupole, lattice 1570
 
  • Y. Zhang, J. G. Wang
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This submission was sponsored by a contractor of the United States Government under contract DE-AC05-00OR22725 with the United States Department of Energy.
In this paper we report the effects on beam dynamics from two intrinsic multipole components of a quadrupole magnet – dodecapole and psedu-octupole, in a quadrupole doublet lattice. Weak resonances at transverse phase advances 60°; and 90°; per cell, which may contribute to halo formation and beam loss in a linac, are shown from multi-particle tracking simulations. Although the net effect of the psedu-octupole component alone is very small due to substantial cancellations within the same magnet, its existence may significantly enhance the weak resonances which are induced by the dodecapole component of quadrupole magnets. The combined contributions of these two magnetic field components may not be simply linear-scaled because of the extreme nonlinear nature.
 
 
WEP042 FACET Emittance Growth emittance, plasma, wakefield, acceleration 1573
 
  • J.T. Frederico, M.J. Hogan, M.D. Litos, Y. Nosochkov, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration. The FACET beamline consists of a chicane and final focus system to compress the 23 GeV, 3 nC electron bunches to ~20μm long and ~10μm wide. Simulations of the FACET beamline indicate the short-duration and large, 1.5% rms energy spread beams may suffer a factor of four emittance growth from a combination of chromaticity, incoherent synchrotron radiation (ISR), and coherent synchrotron radiation (CSR). Emittance growth is directly correlated to head erosion in plasma wakefield acceleration and is a limiting factor in single stage performance. Studies of the geometric, CSR, and ISR components are presented. Numerical calculation of the rms emittance can be overwhelmed by long tails in the simulated phase space distributions; more useful definitions of emittance are given. A complete simulation of the beamline is presented as well, which agrees with design specifications.
 
 
WEP048 Comparison of RF Cavity Transport Models for BBU Simulations linac, cavity, focusing, optics 1582
 
  • I. Shin
    University of Connecticut, Storrs, Connecticut, USA
  • S. Ahmed, T. Satogata, B.C. Yunn
    JLAB, Newport News, Virginia, USA
 
  The transverse focusing effect in RF cavities plays a considerable role in beam dynamics for low-energy beamline sections and can contribute to beam breakup (BBU) instability. The purpose of this analysis is to examine RF cavity models in simulation codes which will be used for BBU experiments at Jefferson Lab and improve BBU simulation results. We review two RF cavity models in the simulation codes elegant and TDBBU (a BBU simulation code developed at Jefferson Lab). elegant can include the Rosenzweig-Serafini (R-S) model for the RF focusing effect. Whereas TDBBU uses a model from the code TRANSPORT which considers the adiabatic damping effect, but not the RF focusing effect. Quantitative comparisons are discussed for the CEBAF beamline. We also compare the R-S model with the results from numerical simulations for a CEBAF-type 5-cell superconducting cavity to validate the use of the R-S model as an improved low-energy RF cavity transport model in TDBBU. We have implemented the R-S model in TDBBU. It will cause BBU simulation results to be better matched with analytic calculations and experimental results.  
 
WEP050 Advances in Modeling the University of Maryland Electron Ring dipole, focusing, quadrupole, lattice 1585
 
  • R.A. Kishek, B.L. Beaudoin, S. Bernal, M. Cornacchia, K. Fiuza, I. Haber, T.W. Koeth, P.G. O'Shea, D.F. Sutter, H.D. Zhang
    UMD, College Park, Maryland, USA
 
  Funding: Work funded by the US Dept. of Energy Offices of Fusion Energy Sciences and High Energy Physics, and by the Dept. of Defense Office of Naval Research and the Joint Technology Office.
The University of Maryland Electron Ring (UMER) is a research accelerator designed to operate with extreme space charge. The existence of high-precision experimental measurements of tune, dispersion, chromaticity, response matrix elements, and other parameters*, **, *** has prompted a revision of the models used to describe the machine. Due to the low energy (10 keV) of the electrons, the dipole and quadrupole magnets used are air-core printed-circuit coils whose fields we calculate using a Biot-Savart solver. Different levels of approximations for the magnetic fields have been developed. We present simulation results from the particle-in-cell code WARP, and from the accelerator code, ELEGANT. These are compared both against simpler models as well as experimental results. The improved modeling has significantly reduced the discrepancies between simulation and experiment.
* D.F. Sutter, et al., Proc. PAC 2009
** C. Wu, et al., Proc. PAC 2009
*** S. Bernal, et al., Proc. AAC 2010
 
 
WEP064 Beam Dynamics Study of the Intermediate Energy X-Ray Wiggler for the Advanced Photon Source wiggler, undulator, magnet-design, electron 1594
 
  • A. Xiao, M. Borland, L. Emery, M.S. Jaski, V. Sajaev
    ANL, Argonne, USA
 
  Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An intermediate-energy x-ray (IEX) helical wiggler is planned for the APS storage ring. Because of its high field and rapid field roll-off, the disturbance to the beam dynamics is large and needs to be well understood before the installation. We present a new method of fitting the magnetic field to an analytical wiggler model, which simplifies the usual nonlinear fitting problem and guarantees the best fit. The fitting method was validated by comparison to an analytical method.
 
 
WEP066 Tracking Code Developement for Beam Dynamics Optimization lattice, damping, wiggler, dynamic-aperture 1600
 
  • L. Yang
    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.
Dynamic aperture (DA) optimization with direct particle tracking is a straight forward approach when the computing power is permitted. It can have various realistic errors included and is more close than theoretical estimations. In this approach, a fast and parallel tracking code could be very helpful. In this presentation, we describe an implementation of storage ring particle tracking code TESLA for beam dynamics optimization. It supports MPI based parallel computing and is robust as DA calculation engine. This code has been used in the NSLS-II dynamics optimizations and obtained promising performance.
 
 
WEP067 Cornell ERL Tolerance Simulations lattice, undulator, emittance, quadrupole 1603
 
  • C.E. Mayes
    CLASSE, Ithaca, New York, USA
 
  Funding: Supported by NSF award DMR-0807731
Cornell University is planning to build an Energy Recovery Linac (ERL) hard x-ray lightsource operating at 5 GeV. Simulations of its approximately 3 km of electron beamline that incorporate a host of reasonable alignment and field errors, and their compensation by an orbit correction scheme, are presented. These simulations start with realistic particle distributions just after injection and track them through acceleration, the production of undulator radiation, deceleration (energy recovery), and finally transport to the beam stop. To this realistic model, single error sources are further added with increasing magnitudes in order to establish alignment and field tolerance estimates.
 
 
WEP074 Correcting Aberrations in Complex Magnet Systems for Muon Cooling Channels collider, dipole, resonance, quadrupole 1615
 
  • J.A. Maloney, B. Erdelyi
    Northern Illinois University, DeKalb, Illinois, USA
  • A. Afanasev, R.P. Johnson
    Muons, Inc, Batavia, USA
  • Y.S. Derbenev
    JLAB, Newport News, Virginia, USA
  • V.S. Morozov
    ODU, Norfolk, Virginia, USA
 
  Funding: Supported in part by DOE SBIR grant DE-SC0005589
Designing and simulating complex magnet systems needed for cooling channels in both neutrino factories and muon colliders requires innovative techniques to correct for both chromatic and spherical aberrations. Optimizing complex systems, such as helical magnets for example, is also difficult but essential. By using COSY INFINITY, a differential algebra based code, the transfer and aberration maps can be examined to discover what critical terms have the greatest influence on these aberrations.
 
 
WEP079 Mathematical Models of Feedback Systems for Control of Intra-Bunch Instabilities Driven by E-Clouds and TMCI feedback, electron, controls, proton 1621
 
  • C.H. Rivetta, J.D. Fox, T. Mastoridis, M.T.F. Pivi, O. Turgut
    SLAC, Menlo Park, California, USA
  • W. Höfle
    CERN, Geneva, Switzerland
  • R. Secondo, J.-L. Vay
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the U.S. Department of Energy under contract # DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
The feedback control of intrabunch instabilities driven by E-Clouds or strong head-tail coupling (TMCI) requires sufficient bandwidth to sense the vertical position and drive multiple sections of a nanosecond scale bunch. These requirements impose challenges and limits in the design and implementation of the feedback system. This paper presents models for the feedback subsystems: receiver, processing channel, amplifier and kicker, that take into account their frequency response and limits. These models are included in multiparticle simulation codes (WARP/CMAD/Head-Tail) and reduced mathematical models of the bunch dynamics to evaluate the impact of subsystem limitations in the bunch stabilization and emittance improvement. With this realistic model of the hardware, it is possible to analyze and design the feedback system. This research is crucial to evaluate the performance boundary of the feedback control system due to cost and technological limitations. These models define the impact of spurious perturbations, noise and parameter variations or mismatching in the performance of the feedback system. The models are validated with simulation codes and measurements of lab prototypes.
 
 
WEP085 Beam Breakup Studies for New Cryo-Unit HOM, cavity, damping, linac 1633
 
  • S. Ahmed, F.E. Hannon, A.S. Hofler, R. Kazimi, G.A. Krafft, F. Marhauser, B.C. Yunn
    JLAB, Newport News, Virginia, USA
  • I. Shin
    University of Connecticut, Storrs, Connecticut, USA
 
  In this paper, we report the numerical simulations of cumulative beam breakup studies for a new cryo-unit for injector design at Jefferson lab. The system consists of two 1-cell and one 7-cell superconducting RF cavities. The study has been performed using a 2-dimensional time-domain code TDBBU developed in-house. The stability has been confirmed for the present setup of beamline elements with different initial offsets and currents ranging 1 mA - 100 mA.  
 
WEP090 Simulation Study of Intrabeam Scattering in Low Emittance Ring scattering, emittance, lattice, storage-ring 1639
 
  • W. Fan, G. Feng, D.H. He, W. Li, L. Wang, S.C. Zhang, T. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  HALS(Hefei Advanced Light Source) is under designing dedicated to good coherence and high brightness at 1.5GeV. Low emittance is required to reach the design request. Due to the low energy and emittance with relative high bunch charge, intrabeam scattering effect will be very strong. It is worth accurately calculating to check if the design goal can be reached. Theoretic calculation based on Gaussian beam distribution doesn't warrant in strong IBS regime. In this paper we present the results of particle simulation study of intrabeam scattering effect on a temporary design lattice of HALS ring.  
 
WEP091 Implementation of H Intrabeam Stripping into TRACK linac, ion, beam-losses, proton 1642
 
  • J.-P. Carneiro
    Fermilab, Batavia, USA
  • B. Mustapha, P.N. Ostroumov
    ANL, Argonne, USA
 
  H intrabeam stripping has been presented* as potentially harmful to MW scale H linacs. If not taken properly into account, intrabeam stripping of the H beam could lead to losses in excess of the 1 W/m limit and result in non-tolerable beamline elements activation. This paper describes the implementation of the H intrabeam stripping effect into the beam dynamics code TRACK**. Simulations results and numerical applications will be presented for the SNS linac and the FNAL ProjectX.
* V. Lebedev, "Intrabeam Stripping in H Linacs", LINAC2010
** P. Ostroumov, "TRACK, The Beam Dynamics Code", PAC2005
 
 
WEP094 Space Charge Measurements with a High Intensity Bunch at the Fermilab Main Injector proton, emittance, space-charge, 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.  
 
WEP095 Analysis of the Beam Loss Mechanism in the Project-X Linac linac, solenoid, quadrupole, beam-losses 1651
 
  • N. Solyak, J.-P. Carneiro, V.A. Lebedev, S. Nagaitsev, J.-F. Ostiguy
    Fermilab, Batavia, USA
 
  Minimization of the beam losses in a multi-MW H-minus linac of the Project X to the level below 1W/m is a challenging task. Analysis of different mechanisms of beam stripping, including stripping in electric and magnetic fields, residual gas, black-body radiation and intra-beam stripping, is analyzed. Other sources of beam losses are misalignment of beamline elements and errors in RF fields and phase. We presented the requirements for dynamics errors and correction schemes to keep beam losses under control  
 
WEP096 Simulations of Space Charge in the Fermilab Main Injector space-charge, emittance, 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.  
 
WEP100 Energy Spread Compensation for Multi-Bunch Linac Operation Mode electron, linac, wakefield, cavity 1662
 
  • D. Mihalcea
    Northern Illinois University, DeKalb, Illinois, USA
  • W. Gai, J.G. Power
    ANL, Argonne, USA
 
  Funding: This work was supported under the U.S. Department of Energy contract number: DE-AC02-06CH11357 with Argonne National Laboratory.
Higher wakefield gradients can be achieved by increasing the total beam charge which is passed through a dielectric-loaded structure and by reducing the transverse size of the beam. Currently, the Argonne AWA photoinjector operates with electron bunches of up to 100 nC and the goal is to raise the total beam charge to about 1000 nC and to improve the beam focusing to a few 100's microns transverse spot size. The increase of the beam charge can be done by superimposing electron bunches that fill up several consecutive RF buckets. Although the energy stored in a single 7-cell linac is by design large the multi-bunch operation with short bunch trains (~10 ns) is still plagued by large energy spread due to significant beam loading effects. In this paper we present a technique intended to reduce the energy spread for a high charge bunch train by properly choosing the time delay between consecutive bunches. The simulations show that the energy spread can be lowered to about 2.8% from about 6.0% for a 10-bunch train of total charge 1000 nC and kinetic energy of about 70 MeV.
 
 
WEP103 Ion Instability Study for the ILC 3 km Damping Ring ion, damping, vacuum, emittance 1671
 
  • G.X. Xia
    MPI-P, München, Germany
 
  The ILC GDE is currently pushing the cost reduction for all subsystems of the ILC project for the Technique Design Phase 1. A short damping ring with circumference of 3.2 km was developed for this purpose. Based on this lattice, we performed a weak-strong simulation study of the ion instability in the electron damping ring for various beam parameters and vacuum pressures. The simulation results are given in this paper.  
 
WEP108 Application of Coherent Tune Shift Measurements to the Characterization of Electron Cloud Growth electron, photon, radiation, vacuum 1680
 
  • D.L. Kreinick, J.A. Crittenden, G. Dugan, M.A. Palmer, G. Ramirez
    CLASSE, Ithaca, New York, USA
  • M.A. Furman, M. Venturini
    LBNL, Berkeley, California, USA
  • R. Holtzapple, M. Randazzo
    CalPoly, San Luis Obispo, California, USA
 
  Funding: DOE = DE-FC02-08ER41538 NSF = PHY-0734867
Measurements of coherent tune shifts at the Cornell Electron Storage Ring Test Accelerator (CesrTA) have been made for electron and positron beams under a wide variety of beam energies, bunch charge, and bunch train configurations. Comparing the observed tunes with the predictions of several electron cloud simulation programs allows the evaluation of important parameters in these models. These simulations will be used to predict the behavior of the electron cloud in damping rings for future linear colliders. We outline recent improvements to the analysis techniques that should improve the fidelity of the modeling.
 
 
WEP109 Simulations of Electron Cloud Induced Instabilities and Emittance Growth for CesrTA emittance, electron, positron, synchrotron 1683
 
  • K.G. Sonnad, K.R. Butler
    Cornell University, Ithaca, New York, USA
  • G. Dugan, M.A. Palmer
    CLASSE, Ithaca, New York, USA
  • M.T.F. Pivi
    SLAC, Menlo Park, California, USA
 
  Funding: US Department of Energy DE-FC02-08ER41538, National Science Foundation PHY-0734867
We present results of a series of studies obtained using the simulation code CMAD to study how electron clouds affect the dynamics of positron beams in CesrTA. The study complements ongoing experiments dedicated for studying the same phenomena. The simulation involves tracking positrons through the CesrTA lattice and simultaneously computing the force exerted due to space charge of the electrons on each of the tracked positrons. The electrons themselves are allowed to evolve under the influence of the positrons. Several results bear a close resemblance to what has been observed experimentally.
 
 
WEP111 Beam Breakup in Dielectric Wakefield Accelerating Structures: Modeling and Experiments solenoid, wakefield, controls, focusing 1689
 
  • P. Schoessow, C.-J. Jing, A. Kanareykin, A.L. Kustov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A. Altmark
    LETI, Saint-Petersburg, Russia
  • W. Gai, J.G. Power
    ANL, Argonne, USA
 
  Funding: Work supported by USDOE SBIR program.
Beam breakup (BBU) effects resulting from parasitic wakefields limit considerably the intensity of the drive beam that can be transported through a dielectric accelerating structure and hence the accelerating field that can be achieved. We have been developing techniques to control BBU effects using a quadrupole channel or solenoid surrounding the wakefield device. We report here on the status of simulations and experiments on BBU and its mitigation, emphasizing an experiment at the Argonne Wakefield Accelerator facility using a 26 GHz dielectric wakefield device fitted with a solenoid to control BBU. We present calculations based on a particle-Green’s function beam dynamics code (BBU-3000) that we are developing. The code allows rapid, efficient simulation of BBU effects in advanced linear accelerators.
 
 
WEP112 Accurate Simulation of the Electron Cloud in the Fermilab Main Injector with VORPAL electron, dipole, proton, quadrupole 1692
 
  • P. Lebrun, P. Spentzouris
    Fermilab, Batavia, USA
  • J.R. Cary, P. Stolz, S.A. Veitzer
    Tech-X, Boulder, Colorado, USA
 
  Precision simulations of the electron cloud at the Fermilab Main Injector (MI) have been studied using the plasma simulation code VORPAL. Fully 3D and self consistent solutions that includes Yee-type E.M. field maps, electron spatial distributions and the time evolution of the cloud with respect to the bunch structure in the MI. The microwave absorption experiment has been simulated in detail and the response of the antennas has been derived from the VORPAL's pseudo-potential data. Based on the results of these simulations and the ongoing experimental program, two distinct new experimental techniques are proposed. The first one is based on the use BPM plates placed in dipole fields and that are made of material(s) for which the secondary emission is well characterized. The second technique would be based on the optical, or ultra-violet, detection of the radiation emitted (inverse photo-electric effect) when the cloud interacts with the inner surface of the beam pipe. As the microwave absorption experiment, this techique is non-invasise and has the advantage of providing spatial images of the cloud as well as accurate timing (ns) information.  
 
WEP116 Bucket Shaking Stops Bunch Dancing in Tevatron synchrotron, impedance, dipole, damping 1704
 
  • A.V. Burov, C.-Y. Tan
    Fermilab, Batavia, USA
 
  Bunches in Tevatron are known to be longitudinally unstable: their collective oscillations stay without any sign of decay. Typically, a feedback damper is used to stop these oscillations. Recently, it was theoretically predicted that the oscillations can be stabilized by means of small bucket shaking*. Detailed measurements in Tevatron have shown that this method does work. In this paper, an essential theory and specific observations of the related process are presented.
* A. Burov, “Dancing Bunches as van Kampen Modes”, this conference.
 
 
WEP123 Study on Low-Frequency Oscillations in a Gyrotron Using a 3D CFDTD PIC Method electron, gun, cathode, plasma 1713
 
  • M.C. Lin, D.N. Smithe
    Tech-X, Boulder, Colorado, USA
 
  Funding: Work supported by the U.S. Department of Energy under Grant No. DE-SC0004436.
Low-frequency oscillations (LFOs) have been observed in a high average power gyrotron and the trapped electron population contributing to the oscillation has been measured. As high average power gyrotrons are the most promising millimeter wave source for thermonuclear fusion research, it is important to get a better understanding of this parasitic phenomenon to avoid any deterioration of the electron beam quality thus reducing the gyrotron efficiency. 2D Particle-in-cell (PIC) simulations quasi-statically model the development of oscillations of the space charge in the adiabatic trap, but the physics of the electron dynamics in the adiabatic trap is only partially understood. Therefore, understanding of the LFOs remains incomplete and a full picture of this parasitic phenomenon has not been seen yet. In this work, we use a 3D conformal finite-difference time-domain (CFDTD) PIC method to accurately and efficiently study the LFOs in a high average power gyrotron. Complicated structures, such as a magnetron injection gun, can be well described. Employing a highly parallelized computation, the model can be simulated in time domain more realistically.
 
 
WEP126 Progress in Experimental Study of Current Filamentation Instability plasma, vacuum, electron, radiation 1719
 
  • B.A. Allen, P. Muggli
    USC, Los Angeles, California, USA
  • M. Babzien, M.G. Fedurin, K. Kusche, V. Yakimenko
    BNL, Upton, Long Island, New York, USA
  • C. Huang
    LANL, Los Alamos, New Mexico, USA
  • J.L. Martins, L.O. Silva
    IPFN, Lisbon, Portugal
  • W.B. Mori
    UCLA, Los Angeles, California, USA
 
  Funding: Work supported by Department of Energy and National Science Foundation
Current Filamentation Instability, CFI, is of central importance for the propagation of relativistic electron beams in plasmas. CFI could play an important role in the generation of magnetic fields and radiation in the after-glow of gamma ray bursts and also in energy transport for the fast-igniter inertial confinement fusion concept. Simulations were conducted with the particle-in-cell code QuickPIC* for e- beam and plasma parameters at the Brookhaven National Laboratory – Accelerator Test Facility, BNL-ATF. Results show that for a 2cm plasma the instability reaches near saturation. An experimental program was proposed and accepted at the BNL-ATF and an experiment is currently underway. There are three components to the experimental program: 1) imaging of the beam density/filaments at the exit from the plasma, 2) measurement and imaging of the transverse plasma density gradient and measurement of the magnetic field and 3) identifying the radiation spectrum of the instability. Preliminary results from phase one will be presented along with the progress and diagnostic design for the following phases of the experiment.
* C. Huang et. al. Journal of Computational Physics 217, 2(2006)
 
 
WEP130 Simulation Study of Transverse Spectrum in HIRFL-CSR electron, ion, accumulation, power-supply 1722
 
  • P. Li, L.J. Mao, J.W. Xia, J.C. Yang, D.Y. Yin, Y.J. Yuan
    IMP, Lanzhou, People's Republic of China
 
  Funding: Work supported by HIRFL-CSR project
Particles in a storage ring oscillate in the longitudinal and transverse dimensions. Therefore, the beam parameters, such as tune, momentum spread, emittance and their evolution can be obtained by analyzing the beam signals in frequency domain. In this paper, the simulation result of transverse beam spectrum in HIRFL-CSR is reported, including the influence of electron cooling, power supply ripple and the misalignment between ion and electron beams. Transverse coupling would occur if the longitudinal magnetic field of electron cooling device can not be compensated. And the distribution of ion beam in transverse space is a circle due to the misalignment between ion and electron beams. In this paper, main interest is focused on the effect of power supply ripple. The tune ripple form is the sine ware with the frequency of 50Hz which is equal to that of the industrial frequency in the simulation firstly. And then different forms of current ripple of power supply are simulated for comparative analysis. Tune shift will be induced by the power supply ripple. In this paper, those factors which may affect the accumulation of HIRFL-CSR are simulated in transverse beam spectrum.
 
 
WEP133 Adaptive Space-charge Meshing in the General Particle Tracer Code space-charge, electron, 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.  
 
WEP137 Performance Analysis on the IBM Blue Gene/P for Wakefield Calculations wakefield, cavity, plasma, electron 1737
 
  • M. Min, P.F. Fischer
    ANL, Argonne, USA
 
  Accurate and efficient simulations will significantly reduce the cost and the risk in the design process for various applications in accelerator design. We improved capability of the Argonne-developed high-fidelity wakefield simulation code, NekCEM, by upgrading pre-setup and communication subroutines for high-performance simulations beyond petascale. We present a detailed study of parallel performance of NekCEM on the IBM Blue Gene/P at Argonne. We demonstrate strong scaling up to P=131,072 cores using up to more than 1.1 billion grid points with the total number of elements up to E=273,000 and N=15 which gives 75% efficiency at 8,530 grid points per core compared to the base case of P =16,384 cores.  
 
WEP138 Developing Software Packages for Electromagnetic Simulations vacuum, electromagnetic-fields, radio-frequency, scattering 1740
 
  • J. Xu, M. Min, B. Mustapha
    ANL, Argonne, USA
 
  Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
In addition to previous developments on parallel beam dynamics software packages, our efforts have been extended to electromagnetic simulations. These efforts include developing new software packages solving the Maxwell equations in 2D and 3D. Scalable algorithms have been used for use of ALCF supercomputers. These new solvers are based on high order numerical methods. Comparative studies of structured and unstructured grids, continuous and discontinuous Galerkin methods will be discussed. The effects of bases will also be presented. Efficiency and challenges of new software packages will be presented. Some benchmarking and simulation results will be shown.
 
 
WEP142 Electron Cloud Modeling Results for Time-resolved Shielded Pickup Measurements at CesrTA electron, pick-up, positron, vacuum 1752
 
  • J.A. Crittenden, Y. Li, X. Liu, M.A. Palmer, J.P. Sikora
    CLASSE, Ithaca, New York, USA
  • S. Calatroni, G. Rumolo
    CERN, Geneva, Switzerland
 
  Funding: Support by DOE contract DE-FC02-08ER41538 and NSF contract PHY-0734867
The Cornell Electron Storage Ring Test Accelerator (CesrTA) program includes investigations into electron cloud buildup, applying various mitigation techniques in custom vacuum chambers. Among these are two 1.1 meter long sections located symmetrically in the east and west arc regions. These chambers are equipped with pickup detectors shielded against the direct beam-induced signal. Here we report on results from the ECLOUD modeling code which highlight the sensitivity of these measurements to model parameters such as the photoelectron energy distributions, and the secondary elastic yield value.
 
 
WEP146 A Quasi-3D Model of Electron Cyclotron Resonance Ion Source (ECRIS) ion, plasma, ECRIS, electron 1755
 
  • L. Zhao, B. Cluggish, J.S. Kim
    Far-Tech, Inc., San Diego, California, USA
 
  Funding: Grant supported by DOE office of Nuclear Physics
FAR-TECH, Inc is developing a hybrid, quasi-3D model to model charge breeding of an ion beam in an electron cyclotron resonance ion source. The model is a combination of 3D mapping of the plasma background calculated by GEM1D* and 3D tracking of the ion trajectories with MCBC**. The 3D electron distribution function and electric field of the background plasma are calculated self-consistently. The test beam ions are then tracked in it using MCBC which includes Coulomb, ionization and charge exchange collisions. The exact ion trajectories in the plasma and steady state 3D ion distribution at the extraction aperture are predicted and compared with previous simulations and experiments.
* D. H. Edgell et al., Rev. Sci. Instrum. 73, 641, 2002.
** J. S. Kim et al., Rev. Sci. Instrum. 79, 02B906, 2008.
 
 
WEP147 The Effect of Space-charge and Wake Fields in the Fermilab Booster impedance, booster, wakefield, coupling 1758
 
  • A. Macridin, J.F. Amundson, P. Spentzouris
    Fermilab, Batavia, USA
  • D.O. McCarron
    IIT, Chicago, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work was supported by the DOE contracts DE-AC02-07CH11359, DE-AC02-05CH11231 and DE-AC02-06CH11357 and the ComPASS project funded through the SciDAC.
We calculate the impedance and the wake functions for laminated structures with parallel-planes and circular geometries. We critically examine the approximations used in the literature for the coupling impedance in laminated chambers and find that most of them are not justified because the wall surface impedance is large. A comparison between the flat and the circular geometry impedance is presented. We use the wake fields calculated for the Fermilab Booster laminated magnets in realistic beam simulations using the Synergia code. We find good agreement between our calculation of the coherent tune shift at injection energy and the experimental measurements.
 
 
WEP150 GPU Computing for Particle Tracking optics, dynamic-aperture, lattice, storage-ring 1764
 
  • H. Nishimura, S. James, K. Muriki, Y. Qin, K. Song, C. Sun
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
This is a feasibility study of using a modern Graphics Processing Unit (GPU) to parallelize the accelerator particle tracking code. To demonstrate the massive parallelization features provided by GPU computing, a simplified TracyGPU program is developed for dynamic aperture calculation. Performances, issues, and challenges from introducing GPU are also discussed.
 
 
WEP152 Parallel Optimization of Beam-Beam Effects in High Energy Colliders luminosity, collider, beam-beam-effects, controls 1770
 
  • J. Qiang, R.D. Ryne
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
Beam-beam effects limit luminosity in high energy colliders. Parallel beam-beam simulation codes were developed to study those beam-beam effects and to help the collider design. In this paper, we will present a parallel optimization algorithm integrating together with the parallel beam-beam simulation to optimize the luminosity of the colliding beams. This algorithm is based on a differential evolutionary global optimization method and takes advantage of the two-level parallelization in both parallel search and parallel objective function evaluation. This significantly increases the scalability of the simulation on peta-scale supercomputers and reduces the time for finding the optimal working point.
 
 
WEP153 Simulation Results of a Feedback Control System to Damp Electron Cloud Single-Bunch Transverse Instabilities in the CERN SPS feedback, kicker, electron, controls 1773
 
  • R. Secondo, J.-L. Vay, M. Venturini
    LBNL, Berkeley, California, USA
  • J.D. Fox, C.H. Rivetta
    SLAC, Menlo Park, California, USA
  • W. Höfle
    CERN, Geneva, Switzerland
 
  Funding: Work supported by the US-DOE under Contract DE-AC02-05CH11231 and the US-LHC Accelerator Research Program (LARP).
Transverse Single-Bunch Instabilities due to Electron Cloud effect are limiting the operation at high current of the SPS at CERN. Recently a high-bandwidth Feedback System has been proposed as a possible solution to stabilize the beam and is currently under study. We analyze the dynamics of the bunch actively damped with a simple model of the Feedback in the macro-particle code WARP, in order to investigate the limitations of the System such as the minimum amount of power required to maintain stability. We discuss the feedback model, report on simulation results and present our plans for further development of the numerical model.
 
 
WEP154 Direct Numerical Modeling of E-Cloud Driven Instability of a Bunch Train in the CERN SPS electron, feedback, emittance, proton 1776
 
  • J.-L. Vay, M.A. Furman, M. Venturini
    LBNL, Berkeley, California, USA
 
  Funding: Supported by the US-DOE under Contract DE-AC02-05CH11231, the SciDAC program ComPASS and the US-LHC Accelerator Research Program (LARP). Used resources of NERSC and the Lawrencium cluster at LBNL.
Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. It has been proposed recently to use feedback systems operating in the GHz range to damp single-bunch transverse coherent electron cloud driven instabilities that may occur in relatively long, ns scale, proton bunches such as those in the CERN SPS. The simulation package WARP-POSINST was recently upgraded for handling multiple bunches and modeling concurrently the electron cloud buildup and its effect on the beam, allowing for direct self-consistent simulation of bunch trains generating, and interacting with, electron clouds. We have used the WARP-POSINST package on massively parallel supercomputers to study the growth rate and frequency patterns in space-time of the electron cloud driven transverse instability for a proton bunch train in the CERN SPS accelerator with, or without, feedback models (with various levels of idealization) for damping the instability. We will present our latest simulation results, contrast them with actual measurements and discuss the implications for the design of the actual feedback system.
 
 
WEP156 GPU-Accelerated 3D Time-Domain Simulation of RF Fields and Particle Interactions cavity, vacuum, coupling, electron 1779
 
  • S.J. Cooke, B. Levush, A.N. Vlasov
    NRL, Washington, DC, USA
  • T.M. Antonsen
    UMD, College Park, Maryland, USA
  • I.A. Chernyavskiy
    SAIC, McLean, USA
 
  Funding: This work is supported by the U.S. Office of Naval Research.
The numerical simulation of electromagnetic fields and particle interactions in accelerator components can consume considerable computational resources. By performing the same computation on fast, highly parallel GPU hardware instead of conventional CPUs it is possible to achieve a 20x reduction in simulation time for the traditional 3D FDTD algorithm. For structures that are small compared to the RF wavelength, however, or that require fine grids to resolve, the FDTD technique is constrained by the Courant condition to use very small time steps compared to the RF period. To avoid this constraint we have implemented an implicit, complex-envelope 3D ADI-FDTD algorithm for the GPU and demonstrate a further 5x reduction in simulation time, now two orders of magnitude faster than conventional FDTD codes. Recently, a GPU-based particle interaction model has been introduced, for which results will be reported. These algorithms form the basis of a new code, NEPTUNE, being developed to perform self-consistent 3D nonlinear simulations of vacuum electron devices.
 
 
WEP157 An Implementation of the Fast Multipole Method for High Accuracy Particle Tracking of Intense Beams multipole, space-charge, 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.  
 
WEP159 Improved Algorithms for Multipacting Simulation in the Analyst Code cavity, resonance, multipactoring, RF-structure 1785
 
  • J.F. DeFord, B.L. Held, K.J. Willis
    STAAR/AWR Corporation, Mequon, USA
 
  Funding: Work funded by the U.S. Dept. of Energy, Office of Science, SBIR Contract No. DE-FG02-05ER84373.
Electron multipacting is often deleterious in RF structures and must be controlled via modifications to the geometry, materials, or external fields. Recent improvements to the capabilities for modeling multipacting in the Analyst software package are presented in this paper. A backward difference scheme*, coupled with Newton-Raphson iteration, is used to integrate particle position/momentum, with integrations interrupted at element faces to minimize errors and lost particles. Support for the Furman-Pivi secondary emission model** has been implemented, with separate representations for low energy, re-diffused, and backscattered secondary particles, and multiple emissions per impact based upon a probability distribution. We have also developed a method to prune the tree of secondary particles resulting from an impact that minimizes particle count growth while maintaining important statistical information about the resonance. Finally, we have added support for volumetric sourcing of primaries, wherein the model volume is seeded with a population of particles with random positions and initial velocities. These improvements, along with benchmark calculations, will be presented.
* D. Darmofal, et al., Jour. Comp. Phys., 123, 1996, pp. 182-195.
** M. Furman, et al., LBNL-52807, June, 2003.
 
 
WEP161 Modeling and Simulations of Electron Emission from Diamond-Amplified Cathodes electron, vacuum, cathode, scattering 1791
 
  • D.A. Dimitrov, R. Busby, J.R. Cary, D.N. Smithe
    Tech-X, Boulder, Colorado, USA
  • I. Ben-Zvi, X. Chang, T. Rao, J. Smedley, E. Wang, Q. Wu
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work is supported by the U. S. Department of Energy under the DE-SC0004431 grant.
Emission of electrons from a diamond-amplified cathode was recently demonstrated*. This experiment was based on a promising new concept** for generation of high-current, high-brightness, and low thermal emittance electron beams. The measurements from transmission and emission experiments have shown the potential to realize the diamond-amplified cathode concept. However, the results indicate that the involved physical properties should be understood in greater detail to build diamond cathodes with optical properties. We have already made progress in understanding the secondary electron generation and charge transport in diamond with the models we implemented in the VORPAL computational framework. We have been implementing models for electron emission from diamond and will present results from 3D VORPAL simulations with the integrated capabilities on generating electrons and holes, initiated by energetic primary electrons, propagation of the charge clouds, and then the emission of electrons into diamond. We will discuss simulation results on the dependence of the electron emission on diamond surface properties.
* X. Chang et al., Electron Beam Emission from a Diamond-Amplified Cathodes, to appear in Phys. Rev. Lett. (2010).
** I. Ben-Zvi et al., Secondary emission enhanced photoinjector, Rep. C-A/AP/149, BNL (2004).
 
 
WEP162 Modeling of Diamond Based Devices for Beam Diagnostics electron, photon, diagnostics, scattering 1794
 
  • D.A. Dimitrov, R. Busby
    Tech-X, Boulder, Colorado, USA
  • I. Ben-Zvi, J.W. Keister, T. Rao, J. Smedley
    BNL, Upton, Long Island, New York, USA
  • E.M. Muller
    Stony Brook University, Stony Brook, USA
 
  Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under grants DE-SC0004584 (Tech-X Corp.) and DE-FG02-08ER41547 (BNL).
Beamlines at new light sources, such as the National Synchrotron Light Source II will operate at flux levels beyond the saturation level of existing diagnostics, necessitating the development of new devices. Currently, there is no detector which can span the entire flux range that is possible even in a second generation light source and will become crucial for next generation light sources. One new approach* is a diamond-based detector that will be able to monitor beam position, flux and timing to much better resolution. Furthermore, this detector also has linear response to flux over 11 orders of magnitude. However, the successful development of the detector requires thorough understanding and optimization of the physical processes involved. We will discuss the new modeling capabilities we have been implementing in the VORPAL 3D code to investigate the effects of charge generation due to absorption of x-ray photons, transport, and charge trapping. We will report results from VORPAL simulations on charge collection and how it depends on applied field, charge trapping, and the energy of absorbed photons.
*J. W. Keister, J. Smedley, D. A. Dimitrov, and R. Busby, Charge Collection and Propagation in Diamond X-ray Detectors, IEEE Transactions on Nuclear Science, 57, 2400 (2010).
 
 
WEP163 RF Cavity Characterization with VORPAL cavity, electron, radio-frequency, resonance 1797
 
  • C. Nieter, P.J. Mullowney, C. Roark, P. Stoltz, C.D. Zhou
    Tech-X, Boulder, Colorado, USA
  • F. Marhauser
    JLAB, Newport News, Virginia, USA
 
  When designing a radio frequency (RF) accelerating cavity structure various figures of merit are considered before coming to a final cavity design. These figures of merit include specific field and geometry based quantities such as the ratio of the shunt impedance to the quality factor (R/Q) or the normalized peak fields in the cavity. Other important measures of cavity performance include the peak surface fields as well as possible multipacting resonances in the cavity. High fidelity simulations of these structures can provide a good estimate of these important quantities before any cavity prototypes are built. We will present VORPAL simulations of a simple pillbox structure where these quantities can be calculated analytically and compare them to the results from the VORPAL simulations. We will then use VORPAL to calculate these figures of merit and potential multipacting resonances for two cavity designs under development at Jefferson National Lab for Project X.  
 
WEP164 Accelerating Beam Dynamics Simulations with GPUs quadrupole, collective-effects, acceleration, space-charge 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.
 
 
WEP165 Advanced Modeling of TE Microwave Diagnostics of Electron Clouds plasma, electron, diagnostics, vacuum 1803
 
  • S.A. Veitzer, D.N. Smithe, P. Stoltz
    Tech-X, Boulder, Colorado, USA
 
  Funding: Part of this work is being performed under the auspices of the U.S. Department of Energy as part of the ComPASS SciDAC project, #DE-FC02-07ER41499.
Numerical simulations of electron cloud buildup and in particular rf microwave diagnostics provide important insights into the dynamics of particle accelerators and the potential for mitigation of destabilizing effects of electron clouds on particle beams. Typical Particle-In-Cell (PIC) simulations may accurately model cloud dynamics; however, due to the large range of temporal scales needed to model side band production due to ecloud modulation, typical PIC models may not be the best choice. We present here preliminary results for advance numerical modeling of rf electron cloud diagnostics, where we replace kinetic particles with an equivalent plasma dielectric model. This model provides significant speedup and increased numerical stability, while still providing accurate models of rf phase shifts induced by electron cloud plasmas over long time scales.
 
 
WEP167 Searching for the Optimal Working Point of the MEIC at JLab Using an Evolutionary Algorithm luminosity, resonance, collider, betatron 1805
 
  • B. Terzić
    JLAB, Newport News, Virginia, USA
  • C. Jarvis
    Macalester, St. Paul, Minnesota, USA
  • M. Kramer
    UCB, Berkeley, California, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Supported in part by SciDAC collaboration.
The Medium-energy Electron Ion Collider (MEIC), a proposed medium-energy ring-ring electron-ion collider based on CEBAF at Jefferson Lab. The collider luminosity and stability are sensitive to the choice of a working point – the betatron and synchrotron tunes of the two colliding beams. Therefore, a careful selection of the working point is essential for stable operation of the collider, as well as for achieving high luminosity. Here we describe a novel approach for locating an optimal working point based on evolutionary algorithm techniques.
 
 
WEP174 Simulations and Calculations of Cavity-to-cavity Coupling for Elliptical SCRF Cavities in ESS cavity, coupling, linac, cryomodule 1813
 
  • R. Ainsworth, S. Molloy
    Royal Holloway, University of London, Surrey, United Kingdom
 
  The proton linac of the European Spallation Source (ESS) will rely on two families of superconducting cavities for the medium and high beta regions. Presented here are simulations of various cavity designs for different betas. The simulations are performed using the ACE3P codes developed at SLAC National Accelerator Laboratory, and the simulated eigenmode and R/Q spectrum will be shown for each design. Dangerous modes are identified. Of particular importance is the investigations of multiple cavity (cryomodule) configurations. From this, the simulated cavity-to-cavity coupling within a cryomodule is extracted. A theoretical model of this coupling based on the calculated cutoff frequencies, decay lengths, and resonance conditions, has also been developed, and a comparison made with the results of the simulation.  
 
WEP176 Loss Factor of Tapered Structures for Short Bunches impedance, vacuum, factory, electromagnetic-fields 1816
 
  • A. Blednykh, S. Krinsky
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by DOE contract DE-AC02-98CH10886
Using the electromagnetic simulation code ECHO, we have found* a simple phenomenological formula that accurately describes the loss factor for short bunches traversing an axisymmetric tapered collimator. In this paper, we consider tapered collimators with elliptical cross-section and use the GdfidL code to calculate the loss factor dependence on the geometric parameters for short bunches. The results for both axisymmetric and elliptical collimators are discussed.
* A. Blednykh and S. Krinsky, Phys. Rev. ST-AB 13, 064401 (2010).
 
 
WEP177 Radial Transmission Line Analysis of Multi-layer Circular Structures impedance, damping, cavity, gun 1819
 
  • H. Hahn, L.R. Hammons
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The analysis of multi-layer beam tubes is a frequent problem and is usually solved with axially propagating waves. This treatment is ill suited to a short multi-layer structure such as the present example of a ferrite covered ceramic break in the beam tube at the ERL photo-cathode electron gun. This paper demonstrates that such structures can better be treated by radial wave propagation. The theoretical method is presented and numerical results are compared with measured network analyser data and Microwave Studio generated simulations. The results confirm the concept of radial transmission lines as a valid analytical method.
 
 
WEP184 Cerenkov Radiator Driven by a Superconducting RF Electron Gun radiation, gun, electron, SRF 1831
 
  • B. R. Poole
    LLNL, Livermore, California, USA
  • J.R. Harris
    NPS, Monterey, California, USA
 
  Funding: Parts of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
The Naval Postgraduate School (NPS), Niowave, Inc., and Boeing have recently demonstrated operation of the first superconducting RF electron gun based on a quarter wave resonator structure. In preliminary tests, this gun has produced 10 ps-long bunches with charge in excess of 78 pC, and with beam energy up to 396 keV. Initial testing occurred at Niowave's Lansing, MI, facility, but the gun and its diagnostic beamline are planned for installation at NPS in the near future. The design of the diagnostic beamline is conducive to the addition of a Cerenkov radiator without interfering with other beamline operations. Design and simulations of a Cerenkov radiator, consisting of a dielectric lined waveguide will be presented. The dispersion relation for the structure is determined and the beam interaction is studied using numerical simulations. The characteristics of the microwave radiation produced in both the long and short bunch regimes will be examined.
 
 
WEP187 Simulation and Optimization of Project-X Main Injector Cavity cavity, HOM, dipole, impedance 1840
 
  • L. Xiao, C.-K. Ng
    SLAC, Menlo Park, California, USA
  • J.E. Dey, I. Kourbanis, Z. Qian
    Fermilab, Batavia, USA
 
  Project-X, a proposed high intensity proton facility to support a world-leading program in neutrino and flavor physics at Fermilab, plans to use the existing FNAL recycler and main injector (MI) complex, but requires upgrading the MI RF system. Currently there are two proposed 53MHz RF cavity designs for 6GeV to 120GeV operation. One design is a straight-line quarter wave resonant cavity, and the other a tapered quarter wave resonant cavity. The electromagnetic (EM) simulations of the two cavity designs are carried out by using SLAC finite element parallel code suit ACE3P. The EM simulation results for the RF parameters and higher-order-mode (HOM) properties have shown that the tapered cavity design has better RF performance than the straight one. The tapered cavity shape will then be optimized for the final design to meet the specified performance requirements for the Project-X. Possible multipacting zones in the cavity will be identified and the use of HOM dampers investigated for the optimized design.  
 
WEP190 Magnetic Field Expansion Out of a Plane: Application to Cyclotron Development cyclotron, vacuum, focusing, factory 1846
 
  • T. Hart, D.J. Summers
    UMiss, University, Mississippi, USA
  • K. Paul
    Tech-X, Boulder, Colorado, USA
 
  In studies of the dynamics of charged particles in a cyclotron magnetic field, the specified field is generally Bz in the z = 0 midplane where Br and Btheta are zero. Br(r,theta, z) and Btheta (r,theta, z) are usually determined through a linear expansion which assumes that Bz is independent of z. An expansion to only first order may not be sufficient for orbit simulations at small r and large z. This paper reviews the expansion of a specified Bz(r,theta, z = 0) out of the z = 0 midplane to arbitrary order, and shows simple examples worked out to 4th order.  
 
WEP192 Simulation Results for a Cavity BPM Design for the APS Storage Ring cavity, storage-ring, damping, linac 1849
 
  • X. Sun, G. Decker
    ANL, Argonne, USA
 
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A rectangular cavity BPM / tilt monitor for the APS storage ring has been designed to detect residual vertical-longitudinal tilt caused by the proposed short-pulse x-ray (SPX) project crab cavities. Electromagnetic simulations have been performed to verify the conceptual design and evaluate design alternatives. MAFIA and Microwave Studio have been applied to simulate the device in both time and frequency domains. The device geometry has been optimized to efficiently damp strongly driven lower- and higher-order modes while preserving the tilt-sensitive mode of interest. This mode is coupled out to the processing electronics using a waveguide geometry chosen to maximize isolation from the beam-driven modes.
 
 
WEP196 Single-Shot Longitudinal Phase Space Measurement Diagnostics Beamline Status at the Argonne Wakefield Accelerator diagnostics, cavity, quadrupole, dipole 1858
 
  • M.M. Rihaoui, D. Mihalcea, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • W. Gai, J.G. Power
    ANL, Argonne, USA
 
  A single-shot longitudinal phase space diagnostics experiment is currently being commissioned at Argonne Wakefield Accelerator. The diagnostic beamline consists of two magnetic dipoles that bend the beam horizontally followed by an rf deflecting cavity that streaks the beam vertically. Using this configuration, the incoming longitudinal phase space can be mapped to a final (x,y) plane which can be directly measured, e.g., using a YAG screen. In this paper we discuss the limitations of such longitudinal phase space diagnostics and present some preliminary measurements.  
 
WEP199 Estimation of Ecloud and TMCI Driven Vertical Instability Dynamics from SPS MD Measurements - Implications for Feedback Control feedback, controls, injection, synchrotron 1861
 
  • O. Turgut, A. Bullitt, J.D. Fox, G. Ndabashimiye, C.H. Rivetta, M. Swiatlowski
    SLAC, Menlo Park, California, USA
  • W. Höfle, B. Salvant
    CERN, Geneva, Switzerland
  • R. Secondo
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the U.S. Department of Energy under contract # DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
We present analysis of beam motion data obtained in high intensity SPS MD studies in 2009 and 2010. The single-bunch vertical E-cloud motion seen in parts of the bunch train after injection shows large tune shifts (roughly 0.02 above the 0.185 tune) developing between tail and head of unstable bunches. The unstable vertical motion has spectral content up to roughly 1.2 GHz and a quasi-periodic growth and decoherence relaxation oscillation effect is seen with time scales of hundred turns. Beam slice FFT and RMS techniques are illustrated to extract parameters important for the design of wide-band vertical feedback system, such as a growth rates of unstable motion, tune shifts within a single bunch and characterization of the bandwidth of the unstable structures within a bunch. We highlight the impact of synchrotron motion and injection transients on a proposed vertical processing channel. We present our MD plans including the beam driving process, developments in reduced model / identification techniques to extract dynamics from experimental and simulation data.
*J. Fox et al., ‘‘SPS Ecloud Instabilities - Analysis Of Machine Studies And Implications For Ecloud Feedback,'' IPAC'10, WEPEB052
 
 
WEP205 A Gap Clearing Kicker for Main Injector kicker, injection, booster, controls 1870
 
  • I. Kourbanis, P. Adamson, J. Biggs, B.C. Brown, D. Capista, C.C. Jensen, G.E. Krafczyk, D.K. Morris, D.J. Scott, K. Seiya, S.R. Ward, G.H. Wu, M.-J. Yang
    Fermilab, Batavia, USA
 
  Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Fermilab Main Injector has been operating at high Beam Power Levels since 2008 when multi-batch slip stacking became operational. In order to increase the beam power even further we have to address the localized beam loss due to beam left over in the Injection Kicker Gap during slip stacking. A set of Gap Clearing Kickers that kick any beam left in the injection gap to the beam abort have been installed during the summer of 2009 and became operational in October 2010. The kicker performance and its effect on beam losses will be described.
 
 
WEP210 Low Energy Beam Measurements Using PHIL Accelerator at LAL, Comparison with PARMELA Simulations solenoid, laser, gun, emittance 1885
 
  • J. Brossard, F. Blot, C. Bruni, S. Cavalier, J-N. Cayla, A. Gonnin, M. Joré, P. Lepercq, S.B. Letourneur, B.M. Mercier, H. Monard, C. Prevost, R. Roux, A. Variola
    LAL, Orsay, France
 
  PHIL (“PHoto-Injector at LAL") is a new electron beam accelerator at LAL. This accelerator is dedicated to test and characterize electron RF-guns and to deliver electron beam to users. This machine has been designed to produce and characterise low energy (E<10 MeV), small emittance (e<10 p.mm.mrad), high brilliance electrons bunch at low repetition frequency (n<10Hz). The first beam has been obtained on the 4th of November 2009. The current RF-gun tested on PHIL is the AlphaX gun, a 2.5 cell S-band cavity designed by LAL for the plasma accelerator studies performed at the Strathclyde university. This paper will present the first AlphaX RF-gun characterizations performed at LAL on PHIL accelerator, and will show comparisons between measurements and PARMELA simulations.  
 
WEP212 Development of a 325 MHz 4-Rod RFQ rfq, dipole, linac, resonance 1888
 
  • B. Koubek, U. Bartz, A. Schempp, J.S. Schmidt
    IAP, Frankfurt am Main, Germany
 
  A 4-Rod RFQ with a frequency of 325 MHz and an output energy of 3 MeV will be build as a part of the FAIR project of GSI. Design studies and model measurements on a short prototype of a 325 MHz 4-Rod RFQ model were made including simulations using CST Microwave Studio. The latest simulation results regarding the dipole field of this structure are presented in this paper.  
 
WEP214 Tuning Studies on 4-Rod RFQs rfq, linac, resonance, quadrupole 1894
 
  • J.S. Schmidt, B. Koubek, A. Schempp
    IAP, Frankfurt am Main, Germany
 
  For the optimization of Radio Frequency Quadrupole (RFQ) design parameters, a certain voltage distribution along the electrodes of an RFQ is assumed. Therefore an accurate tuning of the voltage distribution is very important for the beam dynamic properties of an RFQ. A variation can lead to particle losses and reduced beam quality. Our electrode design usually implies a constant longitudinal voltage distribution. For its adjustment tuning plates are used between the stems of the 4-Rod RFQ. Their optimal positions can be found by an iterative process. To structure this tuning process simulations with a NI LabVIEW based Tuning Software and CST Microwave ® are performed and compared to measurements of the ReA3-RFQ of the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The results of this studies are presented in this paper.  
 
WEP221 CW Room-Temperature Bunching Cavity for the Project X MEBT cavity, linac, bunching, proton 1900
 
  • G.V. Romanov, S. Barbanotti, E. Borissov, J.A. Coghill, I.G. Gonin, S. Kazakov, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
 
  The Project-X, a multi-MW proton source based on superconducting linac, is under development at Fermilab. The front end of the linac contains a CW room temperature MEBT section which comprises ion source, RFQ and high-bandwidth bunch selective chopper. The length of the chopper exceeds 10 m, so four re-bunching cavities are used to support the beam longitudinal dynamics. The RF and mechanical designs of the re-bunching cavity including stress and thermal analysis are reported.  
 
WEP225 H-Mode Accelerating Structures with PMQ Focusing for Low-Beta Beams focusing, ion, linac, quadrupole 1909
 
  • S.S. Kurennoy, J.F. O'Hara, E.R. Olivas, L. Rybarcyk
    LANL, Los Alamos, New Mexico, USA
 
  We report results of the project developing high-efficiency normal-conducting RF accelerating structures based on inter-digital H-mode (IH) cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of IH-PMQ structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. The H-PMQ accelerating structures following a short RFQ can be used both in the front end of ion linacs or in stand-alone applications. Results of the combined 3-D modeling – electromagnetic computations, beam-dynamics simulations with high currents, and thermal-stress analysis – for a full IH-PMQ accelerator tank are presented. The accelerating field profile in the tank is tuned to provide the best propagation of a 50-mA deuteron beam using coupled iterations of electromagnetic and beam-dynamics modeling. Multi-particle simulations with Parmela and CST Particle Studio have been used to confirm the design. Measurement results of a cold model of the IH-PMQ tank are in a good agreement with the calculations and will also be presented.  
 
WEP241 Beam Dynamics Simulations and Measurements at the Project X Test Facility rfq, dipole, quadrupole, focusing 1933
 
  • E. Gianfelice-Wendt, V.E. Scarpine, R.C. Webber
    Fermilab, Batavia, USA
 
  Funding: Work supported by Fermi Research Alliance, LLC under DE-AC02-07CH11359 with the U.S. DOE
Project X, under study at Fermilab, is a multi task SRF beam facility, aiming to provide high intensity protons for rare processes experiments and nuclear physics at low energy, and simultaneously for the production of neutrinos, as well as muon beams in the long term. A beam test facility - former known as High Intensity Neutrino Source (HINS) - is under commissioning for testing critical components of the project, e.g. a beam chopper. In this paper we describe the layout of the test facility and present beam dynamics simulations and measurements.
 
 
WEP248 Overview of the LBNE Neutrino Beam target, proton, remote-handling, shielding 1948
 
  • C.D. Moore, Y. He, P. Hurh, J. Hylen, B.G. Lundberg, M.W. McGee, J.R. Misek, N.V. Mokhov, V. Papadimitriou, R.K. Plunkett, R.P. Schultz, G. Velev, K.E. Williams, R.M. Zwaska
    Fermilab, Batavia, USA
 
  Funding: Work supported by Fermi Research Alliance, LLC, under contract DE-AC02-07CH11359 with the U.S. Department of Energy.
The Long Baseline Neutrino Experiment (LBNE) will utilize a neutrino beamline facility located at Fermilab. The facility will aim a beam of neutrinos toward a detector placed at the Deep Underground Science and Engineering Laboratory (DUSEL) in South Dakota. The neutrinos are produced in a three step process. First, protons from the Main Injector hit a solid target and produce mesons. Then, the charged mesons are focused by a set of focusing horns into the decay pipe, towards the far detector. Finally, the mesons that enter the decay pipe decay into neutrinos. The parameters of the facility were determined by an amalgam of the physics goals, the Monte Carlo modeling of the facility, and the experience gained by operating the NuMI facility at Fermilab. The initial beam power is expected to be ~700 kW, however some of the parameters were chosen to be able to deal with a beam power of 2.3 MW.
 
 
WEP249 Intense Muon Beams for Experiments at Project X target, collider, proton, linac 1951
 
  • C.M. Ankenbrandt, R.P. Johnson, C. Y. Yoshikawa
    Muons, Inc, Batavia, USA
  • V.S. Kashikhin, D.V. Neuffer
    Fermilab, Batavia, USA
  • J. Miller
    BUphy, Boston, Massachusetts, USA
  • R.A. Rimmer
    JLAB, Newport News, Virginia, USA
 
  Funding: Supported in part by DOE SBIR grant DE-SC00002739
A coherent approach for providing muon beams to several experiments for the intensity-frontier program at Project X is described. Concepts developed for the front end of a muon collider/neutrino factory facility, such as phase rotation and ionization cooling, are applied, but with significant differences. High-intensity experiments typically require high-duty-factor beams pulsed at a time interval commensurate with the muon lifetime. It is challenging to provide large RF voltages at high duty factor, especially in the presence of intense radiation and strong magnetic fields, which may preclude the use of superconducting RF cavities. As an alternative, cavities made of materials such as ultra-pure Al and Be, which become very good - but not super - conductors at cryogenic temperatures, can be used.
 
 
WEP254 Simulation of H Beam Chopping in a Solenoid-Based Low-Energy Beam Transport (LEBT) plasma, ion, solenoid, electron 1957
 
  • D.T. Abell, D.L. Bruhwiler, Y. Choi, S. Mahalingam, P. Stoltz
    Tech-X, Boulder, Colorado, USA
  • B. Han
    ORNL RAD, Oak Ridge, Tennessee, USA
  • M.P. Stockli
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work is supported by the US DOE Office of Science, Office of Basic Energy Sciences, including grant No. DE-SC0000844.
The H- linac for the Spallation Neutron Source (SNS) includes an electrostatic low-energy beam transport (LEBT) subsystem. The ion source group at SNS is developing a solenoid-based LEBT, which will include MHz frequency chopping of the partly-neutralized, 65~keV, 60~mA H- beam. Particle-in-cell (PIC) simulations using the parallel VORPAL framework are being used to explore the possibility of beam instabilities caused by the cloud of neutralizing ions generated from the background gas, or by other dynamical processes that could increase the emittance of the H- beam before it enters the radio-frequency quadrupole (RFQ) accelerator.
 
 
WEP256 Laser-Proton Acceleration as Compact Ion Source proton, laser, solenoid, electron 1960
 
  • S. Busold, O. Deppert, K. Harres, G. Hoffmeister, F. Nürnberg, M. Roth
    TU Darmstadt, Darmstadt, Germany
  • A. Almomani, C. Brabetz, M. Droba, O.K. Kester, U. Ratzinger
    IAP, Frankfurt am Main, Germany
  • V. Bagnoud, W.A. Barth, A. Blazevic, O. Boine-Frankenheim, P. Forck, I. Hofmann, A. Orzhekhovskaya, T. Stöhlker, A. Tauschwitz, W. Vinzenz, S.G. Yaramyshev
    GSI, Darmstadt, Germany
  • T.J. Burris-Mog, T.E. Cowan
    HZDR, Dresden, Germany
  • A. Gopal, S. Herzer, O. Jäckel, B. Zielbauer
    HIJ, Jena, Germany
  • T. Herrmannsdoerfer, M. Joost
    FZD, Dresden, Germany
  • M. Kaluza
    IOQ, Jena, Germany
 
  Preparatory work is presented in the context of the upcoming LIGHT project, which is dedicated to build up a test stand for injecting laser accelerated protons into conventional accelerator structures, located at GSI Helmholtzcenter for Heavy Ion Research (Darmstadt, Germany). In an experimental campaign in 2010, a beam of 8.4×109 protons with 170 ps pulse duration and (6.7±0.1) MeV particle energy could be focused with the use of a pulsed high-field solenoid. Collimation and transport of a 300 ps proton bunch containing 3×109 protons with (13.5±0.5) MeV particle energy over a distance of 407 mm was also demonstrated. Parallel simulation studies of the beam transport through the solenoid are in good agreement with the experiment.  
 
WEP274 Broadband Antenna Matching Network Design and Application for RF Plasma Ion Source impedance, ion, ion-source, plasma 1990
 
  • K.R. Shin
    ORNL RAD, Oak Ridge, Tennessee, USA
  • A.E. Fathy
    University of Tennessee, Knoxville, Tennessee, USA
  • Y.W. Kang, M.F. Piller
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The RF ion source at Spallation Neutron Source has been upgraded to meet higher beam power requirement. One important subsystem for efficient operation of the ion source is the 2MHz RF impedance matching network. The real part of the antenna impedance is very small and is affected by plasma density for 2MHz operating frequency. Previous impedance matching network for the antenna has limited tuning capability to cover this potential variation of the antenna impedance since it employed a single tuning element and an impedance transformer. A new matching network with two tunable capacitors has been built and tested. This network can allow precision matching and increase the tunable range without using a transformer. A 5-element broadband matching network also has been designed, built and tested. The 5-element network allows wide band matching up to 50 kHz bandwidth from the resonance center of 2 MHz. The design procedure, simulation and test results are presented.
 
 
WEP281 Beam Imaging of a High-Brightness Elliptic Electron Gun electron, gun, focusing, brightness 2008
 
  • T.M. Bemis, C. Chen, M.H. Lawrence, J.Z. Zhou
    Beam Power Technology, Inc., Chelmsford, MA, USA
 
  Funding: This work was funded in part by the Department of Energy, Grant No. DE-FG02-07ER84910.
An innovative research program is being carried out to experimentally demonstrate a high-brightness, space-charge-dominated elliptic electron beam using a non-axisymmetric permanent magnet focusing system. Results of the fabrication, initial testing and beam imaging of an elliptic electron gun are reported. Good agreement is found between the experimental measurements and simulation.
 
 
WEP283 Simulations of Transverse Stacking in the NSLS-II Booster booster, emittance, linac, lattice 2014
 
  • R.P. Fliller, T.V. Shaftan
    BNL, Upton, Long Island, New York, USA
 
  Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The linac needs to deliver 15 nC in 80 - 150 bunches to the booster every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source. We have developed a scheme to transversely stack two bunch trains in the NSLS-II booster in order to alleviate the charge requirements on the linac. This scheme has been outlined previously. In this paper we show particle tracking simulations of the tracking scheme. We show that the booster lattice has sufficient orbit correction and dynamic aperture at injection to maintain the charge and emittance of the first beam while it circulates waiting for the next train to arrive. We also show simulations of the booster ramp with a stacked beam for a variety of lattice errors and injected beam parameters. In all cases the performance of the proposed stacking method is sufficient to reduce the required charge from the linac. For this reason the injection system of the NSLS-II booster is being designed to include this feature.
 
 
WEP288 Optimizing the CEBAF Injector for Beam Operation with a Higher Voltage Electron Gun cavity, gun, electron, booster 2023
 
  • F.E. Hannon, A.S. Hofler, R. Kazimi
    JLAB, Newport News, Virginia, USA
 
  Recent developments in the DC gun technology used at CEBAF have allowed an increase in operational voltage from 100kV to 130kV. In the near future this will be extended further to 200kV with the purchase of a new power supply. The injector components and layout at this time have been designed specifically for 100kV operation. It is anticipated that with an increase in gun voltage and optimization of the layout and components for 200kV operation, that the electron bunch length and beam brightness can be improved upon. This paper explores some upgrade possibilities for a 200kV gun CEBAF injector through beam dynamic simulations.  
 
WEP297 A Conceptual Design of the 2+ MW LBNE Beam Absorber proton, shielding, target, hadron 2041
 
  • G. Velev, S.C. Childress, P. Hurh, J. Hylen, A.V. Makarov, N.V. Mokhov, C.D. Moore, I. Novitski
    Fermilab, Batavia, USA
 
  Funding: This work is supported by the U.S. Department of Energy.
The Long Baseline Neutrino Experiment (LBNE) will utilize a neutrino beamline facility located at Fermilab. The facility will aim a beam of neutrinos, produced by 60-120 GeV protons from the Fermilab Main Injector, toward a detector placed at the Deep Underground Science and Engineering Laboratory (DUSEL) in South Dakota. Secondary particles that do not decay into muons and neutrinos as well as any residual proton beam must be stopped at the end of the decay region to reduce noise/damage in the downstream muon monitors and reduce activation in the surrounding rock. This goal is achieved by placing an absorber structure at the end of the decay region. The requirements and conceptual design of such an absorber, capable of operating at 2+ MW primary proton beam power, is described.
 
 
THOBN1 R&D Toward a Neutrino Factory and Muon Collider collider, factory, cavity, target 2056
 
  • M.S. Zisman
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by U.S. Dept. of Energy, Office of High Energy Physics, under Contract No. DE-AC02-05CH11231.
Significant progress has been made in recent years in R&D towards a neutrino factory and muon collider. The U.S. Muon Accelerator Program (MAP) has been formed recently to expedite the R&D efforts. This talk will review the US MAP R&D programs for a neutrino factory and muon collider. Muon ionization cooling research is the key element of the program. The first muon ionization cooling demonstration experiment, MICE (Muon Ionization Cooling Experiment) is under construction now at RAL (Rutherford Appleton Laboratory) in UK. Status of MICE as well as the U.S. contribution to MICE will be presented.
 
slides icon Slides THOBN1 [1.987 MB]  
 
THOBN2 Muon Collider Final Cooling in 30-50 T Solenoids emittance, solenoid, acceleration, induction 2061
 
  • R. B. Palmer, R.C. Fernow
    BNL, Upton, Long Island, New York, USA
  • J.L. Lederman
    UCLA, Los Angeles, California, USA
 
  Muon ionization cooling to the required transverse emittance of 25 microns can be achieved with liquid hydrogen in high field solenoids, provided that the momenta are low enough. At low momenta, the longitudinal emittance rises because of the negative slope of energy loss versus energy. Assuming initial emittances that have been achieved in six dimensional cooling simulations, optimized designs are given using solenoid fields limited to 30, 40, and 50 T. The required final emittances are achieved for the two higher field cases.  
slides icon Slides THOBN2 [0.319 MB]  
 
THOBN4 Experiment to Demonstrate Acceleration in Optical Photonic Bandgap Structures laser, wakefield, electron, acceleration 2067
 
  • R.J. England, E.R. Colby, R. Laouar, C. McGuinness, D. Mendez, C.-K. Ng, J.S.T. Ng, R.J. Noble, K. Soong, J.E. Spencer, D.R. Walz, Z. Wu, D. Xu
    SLAC, Menlo Park, California, USA
  • E.A. Peralta
    Stanford University, Stanford, California, USA
 
  Funding: This work was funded by Department of Energy Grants DE-AC02-76SF00515, DE-FG06-97ER41276.
Optical scale dielectric structures offer a promising medium for high-gradient, compact, low-cost acceleration of charged particles. An experimental program is underway at the SLAC E163 facility to demonstrate acceleration in photonic bandgap structures driven by short laser pulses. We present initial experimental results, discuss structure and experimental design, and present first estimates of achievable gradient.
 
slides icon Slides THOBN4 [5.925 MB]  
 
THOBN6 Wakefield Breakdown Test of a Diamond-Loaded Accelerating Structure wakefield, vacuum, laser, acceleration 2074
 
  • S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, D.S. Doran, W. Gai, J.G. Power, Z.M. Yusof
    ANL, Argonne, USA
 
  Funding: DOE SBIR
Diamond has been proposed as a dielectric material for dielectric loaded accelerating (DLA) structures. It has a very low microwave loss tangent, the highest available thermoconductive coefficient and high RF breakdown field. In this paper we report the results from a wakefield breakdown test of diamond-loaded rectangular accelerating structure and development of a cylindrical diamond DLA. We expect to achieve field levels on the order of 100 MV/m in the structure using the 100nC beam at the Argonne Wakefield Accelerator Facility. Single crystal diamond plates produced by chemical vapor deposition (CVD) are used in the structure. The structure is designed to yield up to 0.5 GV/m fields on the diamond surface to test it for breakdown. A surface analysis of the diamond is performed before and after the beam test.
 
slides icon Slides THOBN6 [1.629 MB]  
 
THOCN7 Isochronous (CW) High Intensity Non-scaling FFAG Proton Drivers focusing, acceleration, cyclotron, proton 2116
 
  • C. Johnstone
    Fermilab, Batavia, USA
  • M. Berz, K. Makino
    MSU, East Lansing, Michigan, USA
  • S.R. Koscielniak
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  • P. Snopok
    IIT, Chicago, Illinois, USA
 
  Funding: Work supported in part under SBIR grant DE-FG02-08ER85222 and by Fermi Research Alliance, under contract DEAC02-07CH11359, both with the U.S. Dept. of Energy
The drive for higher beam power, duty cycle, and reliable beams at reasonable cost has focused world interest on fixed field accelerators, notably FFAGs. High-intensity GeV proton drivers encounter duty cycle and space-charge limits in the synchrotron and machine size concerns in cyclotrons. A 10-20 MW proton driver is challenging, if even technically feasible, with conventional circular accelerators. Recently, the concept of isochronous orbits has been developed for nonscaling FFAGs using powerful new methodologies in FFAG accelerator design. Isochronous orbits enable the simplicity of fixed RF and, by tailoring the field profile, the FFAG can remain isochronous beyond the energy reach of cyclotrons. With isochronous orbits, the machine proposed here has the high average current advantage and duty cycle of the cyclotron in combination with the strong focusing, smaller losses that are more typical of the synchrotron. With the cyclotron as the current industrial and medical standard, a competing CW FFAG would impact facilities using medical accelerators, proton drivers for neutron production, and accelerator-driven nuclear reactors. This work reports on these new advances.
 
slides icon Slides THOCN7 [2.429 MB]  
 
THP001 Hybrid Electron Linac Based on Magnetic Coupled Accelerating Structure linac, coupling, electron, impedance 2136
 
  • S.V. Kutsaev, K.I. Nikolskiy, N.P. Sobenin
    MEPhI, Moscow, Russia
 
  This paper presents the design of a hybrid linac which consists of a standing wave buncher and a travelling wave accelerating part. Both electric and magnetic-coupled disk-loaded waveguide (DLW) could be used as accelerating structure. The last one has better electrodynamical parameters comparing to classical DLW. Such an accelerator possesses the advantages of both standing wave and travelling wave linacs and has better output beam parameters.  
 
THP009 Collimator Design of 15 MeV Linear Accelerator Based Thermal Neutron Source for Radiography neutron, target, electron, linac 2154
 
  • B.J. Patil, V.N. Bhoraskar, S.D. Dhole
    University of Pune, Pune, India
  • S.T. Chavan, R. Krishnan, S.N. Pethe
    SAMEER, Mumbai, India
  • A.J. Patil
    DANA, Pune, India
 
  Neutron Radiography is a powerful non-destructive testing technique used for the analysis of objects which are widely used in security, medical, nuclear and industrial applications. Optimization of the thermal neutron radiography facility has been carried out using 15 MeV LINAC based neutron source. In this case, a neutron collimator has been designed along with g-n target, moderator, reflector and shielding. The g-n target has been optimized based on their photonuclear threshold. The moderating properties have been studied for few light elements to optimize best suitable moderator for radiography system. The major part of the design was to optimize the collimator for neutron beam which decides quality of the image given. To get best values of collimator parameters such as collimation ratio, gamma content, neuron flux, cadmium ratio, beam uniformity, etc. a FLUKA simulation was carried out. The collimator has been optimized with cadmium lining square cone to capture the scattered thermal neutrons and the collimation ratio to L/D=18. The neutron flux of the optimized facility obtained at the object plane is 1.0·10+5 n/(cm2-sec1) and neutron to gamma ratio is 1.0·10+5 n/(cm2-mR1).  
 
THP010 Optimization of Dual Scattering Foil for 6 to 20 MeV Electron Beam Radiotherapy electron, scattering, radiation, target 2157
 
  • B.J. Patil, V.N. Bhoraskar, S.D. Dhole
    University of Pune, Pune, India
  • S.T. Chavan, R. Krishnan, S.N. Pethe
    SAMEER, Mumbai, India
 
  From last 50 years, electron beam therapy has an important radiation therapy modality. The electron beam from the LINAC is of size ~ 2 mm, whereas the size required for actual treatment is usually larger than 2 X 2 cm2 up to 30 X 30 cm2 at the isocenter. In the present work, it is proposed to use dual scattering foil system for production of clinical electron beam. The foils for 6 to 20 MeV electrons were optimized using the Monte Carlo based FLUKA code. The material composition, thickness of primary foil, Gaussian width and thickness of secondary foil were optimized such that it should meet the design parameters such as Dose at iso-center, beam uniformity, admixture of bremsstrahlung, etc. A pencil beam of electrons passing through primary foil converted into Gaussian shape and falling at the centroid of secondary foil which experienced maximum scattering, whereas falling at the edge experienced the minimum scattering. This results into flat profile of electron at isocenter. In conclusion, the primary scattering foil has been optimized with high Z element (Ta) having uniform thickness, whereas the secondary foil has been optimized with low Z element (Al) having Gaussian shape.  
 
THP030 GEANT4 Studies of the Thorium Fuel Cycle proton, neutron, target, scattering 2178
 
  • C. Bungau
    Manchester University, Manchester, United Kingdom
  • R.J. Barlow
    UMAN, Manchester, United Kingdom
  • A. Bungau, R. Cywinski
    University of Huddersfield, Huddersfield, United Kingdom
 
  Thorium “fuel” has been proposed as an alternative to uranium fuel in nuclear reactors. New GEANT4 developments allow the Monte Carlo code to be used for the first time in order to simulate the time evolution of the concentration of isotopes present in the Thorium fuel cycle. A full study is performed in order to optimise the production of Uranium-233 starting with "pure" Thorium fuels, leading to levels of Uranium-233 which ensure the operation of the nuclear reactor in a regime close to criticality.  
 
THP041 Particle Dynamics Simulation in Wobbler System for Hollow High Energy Heavy Ion Beam Formation target, focusing, ion, heavy-ion 2193
 
  • S. Minaev, N.N. Alexeev, A. Golubev, G. Kropachev, T. Kulevoy, B.Y. Sharkov, A. Sitnikov, T. Tretyakova
    ITEP, Moscow, Russia
 
  Funding: Work supported by Rosatom contract #N.4е.45.90.10.1065
Intense heavy ion beam is an efficient tool to generate high energy density states in macroscopic amounts of matter. As result it enables to study astrophysical processes in the laboratory under controlled and reproducible conditions. For advanced experiments in high energy density physics the cylindrical target irradiated by hollow cylindrical beam is required. A new method for RF rotation of the ion beam is applied for the formation of the required hollow beam. The RF system consisting of two four-cell H-mode cavities with a resonant frequency of 297 MHz was chosen. The layout of the suggested rotating system for hollow beam formation including focusing elements is presented. The particle dynamics simulation was carried out for expecting beam parameters at ITEP Terawatt Accumulator project (ITEP TWAC). The results of simulation is considered in this paper.
 
 
THP046 Characterization of an SRF Gun: A 3D Full Wave Simulation gun, emittance, electron, SRF 2205
 
  • E. Wang
    PKU/IHIP, Beijing, People's Republic of China
  • I. Ben-Zvi
    BNL, Upton, Long Island, New York, USA
  • J. Wang
    CST of America, Wellesley Hills, Massachusetts, USA
 
  Funding: Work supported by Brookhaven science Associates, LLC Contract No.DE-AC02-98CH10886 with the U.S.DOE
We characterized a BNL 1.3GHz half-cell SRF gun is tested for GaAs photocathode. The gun already was simulated several years ago via two-dimensional (2D) numerical codes (i.e., Superfish and Parmela) with and without the beam. In this paper, we discuss our investigation of its characteristics using a three dimensional (3D) full-wave code (CST STUDIO SUITE™).The input/pickup couplers are sited symmetrically on the same side of the gun at an angle of 180⁰. In particular, the inner conductor of the pickup coupler is considerably shorter than that of the input coupler. We evaluated the cross-talk between the beam (trajectory) and the signal on the input coupler compared our findings with published results based on analytical models. The CST STUDIO SUITE™ also was used to predict the field within the cavity; particularly, a combination of transient/eigenmode solvers was employed to accurately construct the RF field for the particles, which also includes the effects of the couplers. Finally, we explored the beam’s dynamics with a particle in cell (PIC) simulation, validated the results and compare them with 2D code result.
 
 
THP051 An Overview of Normal Conducting Radio Frequency Projects and Manufacturing Capabilities at Radiabeam Technologies, LLC linac, gun, controls, radio-frequency 2214
 
  • R.B. Agustsson, S. Boucher, X.D. Ding, L. Faillace, P. Frigola, A.Y. Murokh, S. Storms
    RadiaBeam, Santa Monica, USA
 
  Radiabeam Technologies is currently designing, engineering and fabricating 8 different Normal Conducting Radio Frequency (NCRF) accelerating and diagnostic structures. These NCRF programs include compact X-band industrial systems, laboratory grade NCRF photoinjectors, deflecting cavities and High-Gradient structures. Nearly all aspects of these NCRF structures’ lifecycle are performed in house, including design, 3D electromagnetic and thermomechanical modeling, engineering, fabrication, cleaning and RF cold testing, tuning, and RF power testing. An overview of these varied projects along with references to more detailed publications presented in this conference are provided. Details concerning specific processes applicable to all of the above mentioned RF projects are also discussed.  
 
THP068 Multipacting Analysis for the Half-Wave Spoke Resonator Crab Cavity for LHC cavity, HOM, resonance, coupling 2258
 
  • Z. Li, L. Ge
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and was partially supported by the DOE through the US LHC Accelerator Research Program (LARP).
A compact 400-MHz half-wave spoke resonator (HWSR) superconducting crab cavity is being developed for the LHC upgrade. The cavity shape and the LOM/HOM couplers for such a design have been optimized to meet the space and beam dynamics requirements, and satisfactory RF parameters have been obtained. As it is known that multipacting is an issue of concern in a superconducting cavity which may limit the achievable gradient. Thus it is important in the cavity RF design to eliminate the potential MP conditions to save time and cost of cavity development. In this paper, we present the multipacting analysis for the HWSR crab cavity using the Track3P code developed at SLAC, and to discuss means to mitigate potential multipacting barriers.
 
 
THP073 Simulations of Emittance Measurement at CLIC emittance, collider, laser, quadrupole 2270
 
  • Yu.A. Kubyshin, H. Garcia
    UPC, Barcelona, Spain
  • E. Marin, D. Schulte, F. Stulle
    CERN, Geneva, Switzerland
 
  A proposal for a CLIC emittance measurement line using laser-wire beam profile monitors is presented. Results of simulations and optimizations are given. Estimates of the impact of beam size as well as statistical and machine-related errors on the measurement accuracy are discussed.  
 
THP087 G4Beamline and MARS Comparison for Muon Collider Backgrounds collider, background, electron, neutron 2297
 
  • M.A.C. Cummings, S.A. Kahn
    Muons, Inc, Batavia, USA
  • D. Hedin, A.O. Morris
    Northern Illinois University, DeKalb, Illinois, USA
  • J.F. Kozminski
    Lewis University, Romeoville, Illinois, USA
 
  Funding: Supported in part by SBIR Grant DE-SC0005447
Technological innovations in recent years have revived interest in muon colliders as the next generation energy frontier machine. The biggest challenge for muon colliders is that muons decay. Advances in muon cooling technology will make the focussing and acceleration of muons to TeV energies possible. The challenge for the detectors in such machines is overcoming the large backgrounds from muon decays in the colliding ring lattice that will inundate the interaction region (IR) and will make triggering and data reconstruction a challenge. Developing simulation tools that can reliably model the environment of the muon collider IR will be critical to physics analyses. We will need to expand the capabilities of current programs and use them to benchmark and verify results against each other. Here we are comparing an emerging capabiligy of G4beamline, an interface for physicists to GEANT4 code, with MARS, a mature program for particle fluences, in developing code for muon collider background studies
 
 
THP090 Physics Validation of Monte Carlo Simulations for Detector Backgrounds at a Muon Collider neutron, electron, background, collider 2303
 
  • A.O. Morris, D. Hedin
    Northern Illinois University, DeKalb, Illinois, USA
  • M.A.C. Cummings, S.A. Kahn, T.J. Roberts
    Muons, Inc, Batavia, USA
  • J.F. Kozminski
    Lewis University, Romeoville, Illinois, USA
 
  Muon colliders are considered to be an important future energy-frontier accelerator. A muon collider could be built as a circular accelerator into the TeV energy range as a result of the reduced synchrotron radiation expected from the larger rest mass of muons. For a muon collider with 750 GeV μ+ and μ- with 1012 μ per bunch, it can be expected that there would be 4.3×105 muon decays per meter per beam. These decays will produce very energetic off-momentum electrons that can produce detector backgrounds that can affect the physics. The main backgrounds include electrons from muon decays, synchrotron radiation from the decay electrons, hadrons produced by photonuclear interactions, coherent and incoherent beam-beam pair-production, and Bethe-Heitler muon production. In this paper we will discuss the simulation results in terms of observed physics processes in G4Beamline.  
 
THP101 The MERLIN Simulation Program: New Features used in Studies of the LHC Collimation System using MERLIN scattering, proton, collimation, target 2312
 
  • R.J. Barlow, R. Appleby, J. Molson, H.L. Owen, A.M. Toader
    UMAN, Manchester, United Kingdom
 
  We present recent developments in the MERLIN particle tracking simulation code, originally developed at DESY. Their use is illustrated by studies of the LHC collimation system. We make detailed comparisons of our results with those of other codes, and also, where possible, with the data. Different beam optics designs are studied, and the effect of new collimator materials for different upgrade scenarios is predicted.  
 
THP103 Spin Code Benchmarking at RHIC resonance, closed-orbit, synchrotron, status 2318
 
  • F. Méot, M. Bai, V. Ptitsyn
    BNL, Upton, Long Island, New York, USA
  • V.H. Ranjbar
    Tech-X, Boulder, Colorado, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Stepwise ray-tracing methods are being developed at C-AD, BNL, in view of benchmarking of existing spin codes and of spin dynamics simulations at RHIC. A status of that work is reported here.
 
 
THP127 Analysis of NSLS-II Touschek Lifetime betatron, synchrotron, closed-orbit, longitudinal-dynamics 2360
 
  • J. Choi, S.L. Kramer
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by DOE contract DE-AC02-98CH10886
As scrapers are adopted for the loss control of NSLS-II storage ring, Touschek lifetime estimations for various cases are required to assure the stable operation. However, to estimate the Touschek lifetime, momentum apertures should be measured all along the ring and, if we want to estimate the lifetime in various situations, it can take extremely long time. Thus, rather than simulating for each case, semi-analytic methods with the interpolations are used for the measurements of the momentum apertures. In this paper, we described the methods and showed the results.
 
 
THP131 Injection Straight Pulsed Magnet Error Tolerance Study for Top-off Injection injection, kicker, septum, betatron 2366
 
  • G.M. Wang, R.P. Fliller, R. Heese, S. Kowalski, B. Parker, T.V. Shaftan, F.J. Willeke
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886
NSLS II is designed to work in top-off injection mode. The goal is to minimize the disturbance of the injection transient on the users. The injection straight includes a septum and four fast kicker magnets. The pulsed magnet errors will excite a betatron oscillation. This paper gives the formulas of each error contribution to the oscillation amplitude at various source points in the ring. These are compared with simulation results. Based on the simple formulas, we can specify the error tolerances on the pulsed magnets and scale it to similar machines.
 
 
THP132 Beam Diagnostics using BPM Signals from Injected and Stored Beams in a Storage Ring injection, storage-ring, closed-orbit, betatron 2369
 
  • G.M. Wang, W.X. Cheng, R.P. Fliller, R. Heese, T.V. Shaftan, O. Singh, F.J. Willeke
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886
Many modern light sources are operating in top-off injection mode or are being upgraded to top-off injection mode. For top-off injection mode, the storage ring always has the stored beam and injected beam. So the BPM data is the mixture of both beam positions and the injected beam position cannot be measured directly. We propose to use a BPM with special electronics in NSLS II storage ring to retrieve the injected beam trajectory with the SVD method. The BPM has the capability to measure bunch-by-bunch beam position. We also need another system to measure the bunch-by-bunch beam current. The injected beam trajectory can be measured and monitored all the time without dumping the stored beam. We can adjust and optimize the injected beam trajectory to maximize the injection efficiency. We can also measure the storage ring acceptance by mapping the injected beam trajectory.
 
 
THP148 Experimental Investigation of Superradiance in a Tapered Free-Electron Laser Amplifier undulator, laser, electron, radiation 2396
 
  • Y. Hidaka, J.B. Murphy, B. Podobedov, S. Seletskiy, Y. Shen, X.J. Wang, X. Yang
    BNL, Upton, Long Island, New York, USA
 
  We report experimental studies of the effect of undulator tapering on superradiance in a single-pass high- gain free-electron laser (FEL) amplifier. The experiments were performed at the Source Development Laboratory (SDL) of National Synchrotron Light Source (NSLS). Efficiency was nearly tripled with tapering. Both the temporal and spectral properties of the superradiant FEL along the uniform and tapered undulator were experimentally characterized using frequency-resolved optical gating (FROG) images. Numerical studies predicted pulse broadening and spectral cleaning by undulator tapering Pulse broadening was experimentally verified. However, spectral cleanliness degraded with tapering.
* T. Watanabe et al, Phys. Rev. Lett. 98, 034802 (2007).
** X.J. Wang et al, Phys. Rev. Lett. 103, 154801 (2009).
 
 
THP164 Orbital Angular Momentum Light Generated via FEL at NLCTA undulator, laser, electron, bunching 2420
 
  • A. Knyazik, E. Hemsing, A. Marinelli, J.B. Rosenzweig
    UCLA, Los Angeles, USA
 
  A scheme to create coherent light with orbital angular momentum (OAM) using Free Electron Laser (FEL) at NLCTA is proposed. An 795 nm light co-propagating with relativistic unmodulated electron beam is fed through a helical undulator tuned to the second harmonic of the laser, which acts as a pre-buncher that helically micro-bunches the beam, modulating it in energy. The energy modulation is transferred to helical density modulation by propagating through a longitudinally dispersive section, such as a chicane. Finally the helical density 3-D modulated electron beam is sent through a second undulator resonant at light’s fundamental frequency, causing the electron beam to radiate OAM light. NLCTA facility has everything to make this experiment, including a planar undulator tuned to the fundamental frequency, except for a helical pre-bunching undulator, which can be easily constructed and installed to generate OAM light at NLCTA. According to simulations generated with Mathematica 7 and Genesis 1.3 a 3 period long pre-buncher will be enough to get out 140 MW of laser power from a seeded 10 MW, after transversing a 1.5 m long planar radiator using electron beam generated by NLCTA.  
 
THP171 Demonstration of 3D Effects with High Gain and Efficiency in a UV FEL Oscillator FEL, electron, wiggler, laser 2429
 
  • S.V. Benson, G.H. Biallas, K. Blackburn, J.R. Boyce, D.B. Bullard, J.L. Coleman, C. Dickover, D. Douglas, F.K. Ellingsworth, P. Evtushenko, C.W. Gould, J.G. Gubeli, D. Hardy, C. Hernandez-Garcia, K. Jordan, J.M. Klopf, J. Kortze, R.A. Legg, M. Marchlik, S.W. Moore, G. Neil, T. Powers, D.W. Sexton, M.D. Shinn, C. Tennant, R.L. Walker, A.M. Watson, G.P. Williams, F.G. Wilson, S. Zhang
    JLAB, Newport News, Virginia, USA
 
  Funding: This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences, the Office of Naval Research, and Joint Technology Office
We report on the performance of a high gain UV FEL oscillator operating on an energy recovery linac at Jefferson Lab. The high brightness of the electron beam leads to both gain and efficiency that cannot be reconciled with a one-dimensional model. Three-dimensional simulations do predict the performance with reasonable precision. Gain in excess of 100% per pass and an efficiency close to 1/2NW, where NW is the number of wiggler periods, is seen. The laser mirror tuning curves currently permit operation in the wavelength range of 438 to 362 nm. Another mirror set allows operation at longer wavelengths in the red with even higher gain and efficiency.
 
 
THP174 A Single Cavity Echo Scheme cavity, undulator, radiation, electron 2438
 
  • P.R. Gandhi, J.S. Wurtele
    UCB, Berkeley, California, USA
  • X.W. Gu
    UESTC, Chengdu, Sichuan, People's Republic of China
  • G. Penn, M.W. Reinsch
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the DIrector, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The possibility of implementing echo-enabled harmonic generation* (EEHG) within a single optical resonance cavity is explored both analytically and with numerical simulations. Two modulators of the same frequency are used so that the cavity radiation replaces the two seed lasers of conventional EEHG. Such a scheme has potential** to produce tunable radiation as in EEHG, but with the high repetition rate, longitudinal coherence, and narrow spectral bandwidth of an oscillator. These benefits, however, come with the complication that the beam must generate the radiation that modulates it. Analysis and GINGER simulations are presented for a specific example that takes advantage of robust multilayer mirror performance at 13.4 nm to produce radiation near or possibly even below 1 nm.
* G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009).
** J. Wurtele et al., Proc. of the 2010 FEL Conference, TUOC12.
 
 
THP175 The Effects of Mirror Surface Error on Coherent X-Ray Propagation in XFELO Cavity cavity, FEL, vacuum, undulator 2441
 
  • G.-T. Park
    University of Chicago, Chicago, Illinois, USA
  • K.-J. Kim, R.R. Lindberg
    ANL, Argonne, USA
 
  We study the propagation of coherent X-ray mode through optical cavity of X-ray FEL oscillator (XFELO) including rough grazing incidence mirror.
References
* K-J Kim, Y Shvyd'ko and S Reiche, Phys. Rev. Lett 100, 24802(2008)
** S. K. Sinha, E. B Sirota, S. Garoff, Phys. Rev. B38 2297 ((1988)
*** G. Park in preparation
 
 
THP178 Design of the MAX IV Ring Injector and SPF/FEL Driver linac, FEL, injection, electron 2447
 
  • S. Thorin, M. Eriksson, M.A.G. Johansson, D. Kumbaro, F. Lindau, L. Malmgren, J.H. Modéer, M. Sjöström, S. Werin
    MAX-lab, Lund, Sweden
  • D. Angal-Kalinin, J.W. McKenzie, B.L. Militsyn, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  The MAX IV linac will be used both for injection and top up into two storage rings, and as a high brightness injector for a Short Pulse Facility (SPF) and an FEL (in phase 2). Compression is done in two double achromats with positive R56. The natural second order momentum compaction, T566, from the achromats is used together with weak sextupoles to linearise longitudinal phase space, leaving no need for a linearising harmonic cavity. The design of the linac focuses on flexibility, simplicity and stability, while keeping the costs low. The accelerator structures have been ordered, as well as modulator/klystrons. The linac will be the first accelerator to be assembled and commissioned in the MAX IV project, starting mid 2012.  
 
THP180 Studies of a Linac Driver for a High Repetition Rate X-ray FEL linac, FEL, emittance, laser 2450
 
  • M. Venturini, J.N. Corlett, L.R. Doolittle, D. Filippetto, C. F. Papadopoulos, G. Penn, D. Prosnitz, J. Qiang, M.W. Reinsch, R.D. Ryne, F. Sannibale, J.W. Staples, R.P. Wells, J.S. Wurtele, M.S. Zolotorev
    LBNL, Berkeley, California, USA
  • A. Zholents
    ANL, Argonne, USA
 
  Funding: Work carried out under Department of Energy contract No. DE-AC02-0SCK11231
We report on on-going studies of a superconducting CW linac driver intended to support a high repetition rate FEL operating in the soft x-rays spectrum. We present a point-design for a 1.8 GeV machine tuned for 300~pC bunches and delivering low-emittance, low-energy spread beams as needed for the SASE and seeded beamlines.
 
 
THP183 Measurement of Femtosecond LCLS Bunches Using the SLAC A-line Spectrometer* linac, diagnostics, wakefield, electron 2459
 
  • Z. Huang, A. Baker, M. Boyes, J. Craft, F.-J. Decker, Y.T. Ding, P. Emma, J.C. Frisch, R.H. Iverson, J.J. Lipari, H. Loos, D.R. Walz
    SLAC, Menlo Park, California, USA
  • C. Behrens
    DESY, Hamburg, Germany
 
  We describe a novel technique and the preliminary experimental results to measure the ultrashort bunch length produced by the LCLS low-charge, highly compressed electron bunch. The technique involves adjusting the LCLS second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final 550-m of linac. As a result, the time coordinate of the bunch is directly mapped onto the energy coordinate at the end of the linac. A high-resolution energy spectrometer located at an existing transport line (A-line) is then commissioned to image the energy profile of the bunch in order to retrieve its temporal information. We present measurements of the single-digit femtosecond LCLS bunch length using the A-line as a spectrometer and compare the results with the transverse cavity measurement as well as numerical simulations.  
 
THP193 Study of Single and Coupled-Bunch Instabilities for NSLS-II wakefield, cavity, dipole, damping 2483
 
  • G. Bassi, A. Blednykh
    BNL, Upton, New York, USA
 
  We study single and coupled-bunch instabilities for the NSLS-II storage ring with a recently developed parallel tracking code. For accurate modelling of the coupled-bunch instability, we investigate improvements to current point-bunch models to take into account finite bunch-size effects.  
 
THP196 High Power Beam Test of a 1.6-cell Photocathode RF Gun at PAL gun, emittance, electron, coupling 2486
 
  • M.S. Chae, J.H. Hong, I.S. Ko, Y.W. Parc
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • C. Kim, S.J. Park
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Funding: This work was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST) (grant No. 2008-0059842)
The photocathode RF gun with four holes at the side of the full cell will be tested soon at the gun test stand which consists of a 1.6 cell cavity, a solenoid magnet, beam diagnostic components and auxiliary systems such as ICT, spectrometer, YAG scintillator and screens, Faraday cup, etc. Basic diagnostics such as the measurements of charge, energy and its spread, transverse emittance will be performed. It is expected that these diagnostics will confirm a successful fabrication of the RF gun. In this presentation, we will show the status of the RF gun aging in PAL and detail plan of measurements on various beam parameters. The results with the simulation code PARMELA will be presented to prepare measurement devices properly.
 
 
THP204 Corrections to Quantum Efficiency Predictions for Low Work Function Electron Sources electron, scattering, target, vacuum 2504
 
  • K. L. Jensen
    NRL, Washington, DC, USA
  • D.W. Feldman, E.J. Montgomery, P.G. O'Shea
    UMD, College Park, Maryland, USA
  • J.J. Petillo
    SAIC, Billerica, Massachusetts, USA
 
  Funding: Funding by the Joint Technology Office and the Office of Naval Research.
The Three-Step Model of Spicer, or the analogous Moments-based models, can be used to predict photoemission from metals and cesiated metals. In either, it is a convenient approximation to neglect electrons that have undergone scattering. Using Monte Carlo to follow scattered electrons, we assess the utility of the approximation particularly for low work function (cesiated) surfaces.
 
 
THP205 Modeling the Performance of a Diamond Current Amplifier for FELs electron, scattering, FEL, background 2507
 
  • K. L. Jensen, B. Pate, J.L. Shaw, J.E. Yater
    NRL, Washington, DC, USA
  • J.J. Petillo
    SAIC, Billerica, Massachusetts, USA
 
  Funding: We gratefully acknowledge funding by the Joint Technology Office and the Office of Naval Research.
A diamond current amplifier concept can reduce demands made of photocathodes under development for high performance Free Electron Lasers (FELs) by augmenting the charge per bunch (i.e., increasing the apparent QE of the photocathode) by employing secondary emission amplification in a diamond flake*. The characteristics of the bunch that emerges from the diamond flake is dependent on properties of the diamond (e.g., impurity concentrations) and the conditions under which it is operated (e.g., voltage drop, space charge, temperature)**. A study of the electron bunches produced by an incident 3-5 keV beam striking a very thin diamond and its transport under bias subject to scattering and space charge forces is considered. The quantities of greatest interest are then the yield, the transit time, emittance, and the rise/fall characteristics of the emerging bunch. These are simulated using Monte Carlo techniques, the application of which shall be described as it applies to the initial generation of the secondary electrons followed by their scattering and transport in the presence of band bending and space charge.
*J.E. Yater, et al., IEEE IVNC (2009); J. L. Shaw, et al., ibid.
**K.L. Jensen, et al. J. Appl. Phys. 108, 044509 (2010).
 
 
THP213 Traveling Wave Electron Linac for Synchrotron Injector linac, electron, synchrotron, injection 2519
 
  • S.V. Kutsaev, K.I. Nikolskiy, N.P. Sobenin
    MEPhI, Moscow, Russia
 
  In this paper the project design of a travelling wave electron linac used as an injector to synchrotron in Lebedev Physical Institute of the Russian Academy of Sciences (LPI RAS) is presented. The injected beam to the synchrotron should have very small emittance and energy spectrum. Thus, the buncher design is an essential question in this problem. One of the best output beam parameters can be achieved by using a waveguide buncher with the non-uniform parameters. The proposals of optimal buncher design and beam dynamics calculation results are presented.  
 
THP215 Performance of the Diagnostics for NSLS-II Linac Commissioning linac, booster, diagnostics, emittance 2525
 
  • R.P. Fliller, R. Heese, H.-C. Hseuh, M.P. Johanson, B.N. Kosciuk, D. Padrazo, I. Pinayev, J. Rose, T.V. Shaftan, O. Singh, G.M. Wang
    BNL, Upton, Long Island, New York, USA
 
  Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The National Synchrotron Light Source II (NSLS-II) is a state of the art 3 GeV third generation light source currently under construction at Brookhaven National Laboratory. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster synchrotron and associated transfer lines. The transfer lines not only provide a means to delivering the beam from one machine to another, they also provide a suite of diagnostics and utilities to measure the properties of the beam to be delivered. In this paper we discuss the suite of diagnostics that will be used to commission the NSLS-II linac and measure the beam properties. The linac to booster transfer line can measure the linac emittance with a three screens measurement or a quadrupole scan. Energy and energy spread are measured in a dispersive section. Total charge and charge uniformity are measured with wall current monitors in the linac and transformers in the transfer line. We show that the performance of the transfer line will be sufficient to ensure the linac meets its specifications and provides a means of trouble shooting and studying the linac in future operation.