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| WEPP133 |
High-gradient Multi-mode Two-beam Accelerating Structure
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2806 |
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- S. V. Kuzikov, M. E. Plotkin
IAP/RAS, Nizhny Novgorod
- J. L. Hirshfield
Yale University, Physics Department, New Haven, CT
- S. Kazakov
Omega-P, Inc., New Haven, Connecticut
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A new accelerating structure which is aimed to provide gradient >150 MV/m for next generation of multi-TeV linear colliders is suggested. The structure is based on periodic system of quasi-optical cavities*. Each of these cavities is excited in several equidistantly-spaced eigen modes by the drive beam in such a way that the RF fields reach peak values only during the short time intervals when an accelerating bunch is resident in the cavities, thus exposing the cavity surfaces to strong fields for only a small fraction of time. This feature is expected to raise the breakdown and pulse heating thresholds. The proposed structure embodies most of additional attractive properties: the cavity is an all metallic structure, no transfer or coupling structures are needed between the drive and acceleration channels, the cavity fields are symmetric around the axes of the drive beam and the accelerated beam, the cavity can exhibit high transformer ratio. Calculations of single quasi-optical rectangular cavity with parameters of drive and accelerating beams close to ones adopted for the CLIC project show that high gradient as well as high efficiency are achievable.
*S. V. Kuzikov et al. "Quasi-optical accelerating structure operated with a superposition of synchronized modes," Conf. Digest of Joint 32nd IRMMW Conf., Cardiff, UK, 2007, Vol.2, p.797-798.
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| WEPP146 |
Generation of Electron Microbunches Trains with Adjustable Sub-picosecond Spacing for PWFA and FEL applications
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2830 |
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- P. Muggli, E. Kallos
USC, Los Angeles, California
- M. Babzien, K. Kusche, V. Yakimenko
BNL, Upton, Long Island, New York
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We demonstrate that trains of subpicosecond electron microbunches, with subpicosecond spacing, can be produced by placing a mask in a large dispersion region of the beam line where the beam transverse size is dominated by the correlated energy spread. The particles are selected based on the scattering of their emittance at the mask. The electrons that hit the solid arts of the mask are subsequently lost. The mask spatial pattern is converted into a time pattern in the dispersion-free region of the beam line. The experiment was performed with the Brookhaven National Laboratory Accelerator Test Facility 60 MeV beam. We show that the number, length, and spacing of the microbunches can be controlled through the parameters of the beam and the mask. Trains with one to eight equidistant microbunches are produced. The microbunches spacing is adjusted in the 100 to 300 microns or 300 fs to 1 ps range and comparable microbunch length. The train structure is measured using CTR interferometry, and is stable in time and energy. Such microbunch trains can be further compressed and accelerated, and have applications to free electron lasers (FELs) and plasma wakefield accelerators (PWFAs).
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| WEPP147 |
Aberration-free Muon Transport Line for Extreme Ionization Cooling: a Study of Epicyclic Helical Channel
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2833 |
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- A. Afanasev, R. P. Johnson
Muons, Inc, Batavia
- Y. S. Derbenev
Jefferson Lab, Newport News, Virginia
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Once the normalized transverse emittances of a muon beam have been cooled to some hundreds of microns, new techniques such as Parametric-resonance Ionization Cooling and Reverse Emittance Exchange can be used to focus the beam very tightly on beryllium energy absorbers for further transverse emittance reduction. The transport lines for these techniques have stringent requirements for the betatron tunes so that resonance conditions are properly controlled and for the dispersion function so that the longitudinal emittance can be controlled by emittance exchange using wedge-shaped absorbers. The extreme angular divergence of the beam at the absorbers implies large beam extension between the absorbers such that these techniques are very sensitive to chromatic and spherical aberrations. In this work we describe general and specific solutions to the problem of compensating these aberrations for these new muon cooling channels.
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| WEPP148 |
Generation of High Gradient Wakefields in Dielectric Loaded Structures
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2835 |
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- M. E. Conde, S. P. Antipov, F. J. Franchini, W. Gai, F. Gao, R. Konecny, W. Liu, J. G. Power, Z. M. Yusof
ANL, Argonne, Illinois
- C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio
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Dielectric loaded wakefield structures have potential to be used as high gradient accelerator components. Using the high current drive beam at the Argonne Wakefield Accelerator Facility, we employed cylindrical dielectric loaded wakefield structures to generate accelerating fields of up to 100 MV/m. Short electron bunches (13 ps FWHM) of up to 86 nC are used to drive these fields, either as single bunches or as bunch trains. These recently tested standing-wave structures have a field probe near the outer edge of the dielectric to sample the RF fields generated by the electron bunches. Monitoring of these high intensity RF fields serves to verify the absence of electric breakdown.
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| WEPP149 |
Advances in Parametric-resonance Ionization Cooling
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2838 |
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- Y. S. Derbenev
Jefferson Lab, Newport News, Virginia
- R. P. Johnson
Muons, Inc, Batavia
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Parametric-resonance ionization cooling (PIC) is a muon-cooling technique that is useful for low-emittance muon colliders. This method requires a well-tuned focusing channel that is free of chromatic and spherical aberrations. The dispersion function of the channel must be large where the correction magnets are placed for aberration control but small and non-zero where the ionization cooling beryllium wedges are located to provide emittance exchange to maintain small momentum spread. In order to be of practical use in a muon collider, it also necessary that the focusing channel be as short as possible to minimize muon loss due to decay. A compact PIC focusing channel is described in which new magnet concepts are used to generate the required lattice functions.
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| WEPP151 |
Metallic Photonic Band Gap Accelerator Structure Experiments and Design
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2841 |
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- R. A. Marsh, M. A. Shapiro, R. J. Temkin
MIT/PSFC, Cambridge, Massachusetts
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Damping wakefields is a critical issue in the next generation of high gradient accelerators. Photonic bandgap (PBG) structures have unique properties that offer significant wakefield damping. The goal of this work is to quantify the higher order mode (HOM) wakefield content of a constructed metallic PBG accelerator structure, in order to test the theory of wakefield excitation in these structures and to provide direction for future structure design. Experimental measurements of wakefields excited by an 18 MeV electron beam in a 6 cell, 17.14 GHz metallic PBG traveling wave accelerator structure are reported. Because the electron beam used to generate wakefields in the PBG structure is bunched at the 17.14 GHz rf frequency, all wakefields observed were at integer multiples of 17.14 GHz. Using diode detectors, radiation has been observed at the input and output coupler ports as well as through a quartz window in the surrounding vacuum vessel. Estimates of wakefield radiation, made using HFSS and basic wakefield theory, compare well with experiment.
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| WEPP153 |
Status of the MANX Muon Cooling Experiment
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2844 |
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- K. Yonehara, D. R. Broemmelsiek, M. Hu, A. Jansson, V. Kashikhin, V. S. Kashikhin, M. J. Lamm, M. L. Lopes, V. D. Shiltsev, V. Yarba, M. Yu, A. V. Zlobin
Fermilab, Batavia, Illinois
- R. J. Abrams, M. A.C. Cummings, R. P. Johnson, S. A. Kahn, T. J. Roberts
Muons, Inc, Batavia
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MANX is an experiment to prove that effective six-dimensional (6D) muon beam cooling can be achieved a Helical Cooling Channel (HCC) using ionization-cooling with helical and solenoidal magnets in a novel configuration. The aim is to demonstrate that 6D muon beam cooling is understood well enough to plan intense neutrino factories and high-luminosity muon colliders. The experiment consists of the HCC magnets that envelop a liquid helium energy absorber, upstream and downstream instrumentation to measure the particle or beam parameters before and after cooling, and emittance matching sections between the detectors and the HCC. Studies are presented of the effects of detector resolution and magnetic field errors on the beam cooling measurements.
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| WEPP154 |
Linac-LHC ep Collider Options
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2847 |
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- F. Zimmermann, F. Bordry, H.-H. Braun, O. S. Brüning, H. Burkhardt, R. Garoby, T. P.R. Linnecar, K. H. Mess, J. A. Osborne, L. Rinolfi, D. Schulte, R. Tomas, J. Tuckmantel, A. de Roeck
CERN, Geneva
- H. Aksakal
N. U, Nigde
- S. Chattopadhyay
Cockcroft Institute, Warrington, Cheshire
- A. K. Ciftci
Ankara University, Faculty of Sciences, Tandogan/Ankara
- J. B. Dainton
Liverpool University, Science Faculty, Liverpool
- A. Eide
EPFL, Lausanne
- B. J. Holzer
DESY, Hamburg
- M. Klein
University of Liverpool, Liverpool
- S. Sultansoy
TOBB ETU, Ankara
- A. Vivoli
LAL, Orsay
- F. J. Willeke
BNL, Upton, New York
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We describe various parameter scenarios for a ring-linac ep collider based on LHC and an independent s.c. electron linac. Luminosities of order 1032/cm2/s can be achieved with a standard ILC-like linac, operated either in pulsed or cw mode, with acceptable beam power. Reaching much higher luminosities, up to 1034/cm2/s and beyond, would require the use of two linacs and the implementation of energy recovery. Advantages and challenges of a ring-linac ep collider vis-a-vis an alternative ring-ring collider are discussed.
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| WEPP155 |
Laser Driven Linear Collider
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2850 |
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- A. A. Mikhailichenko
Cornell University, Department of Physics, Ithaca, New York
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We continue detailed description of scheme allowing long term acceleration with >10 GeV/m in multi-cell microstructures side-illuminated by laser radiation. The basis of the scheme is a fast sweeping device for the laser bunch. After sweeping the laser bunch has a slope ~45° with respect to the direction of propagation. So the every cell of microstructure becomes excited locally only for the moments, when the particles are there. Self consistent parameters of collider based on this idea allow consideration this type of collider as a candidate for the near-future accelerator era.
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| FRXCGM01 |
High Quality GeV Electron Beams from Plasma-Laser Accelerators
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3733 |
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- W. Leemans
LBNL, Berkeley, California
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Accelerators are essential tools of discovery and have many practical uses. At the forefront of accelerator technology are the machines that deliver beams for particle physics, for synchrotron and free electron based radiation sources. The technology that drives these accelerators is extremely sophisticated but is limited by the maximum sustainable accelerating field. This impacts the size and cost of the device. More than two decades ago, lasers were proposed as power source for driving novel accelerators based on plasmas as the accelerating medium. An overview will be presented of what these devices can produce to date, including the 2004 demonstration of high quality electron beams* and the 2006 demonstration of GeV class beams from a 3 cm long accelerating structure**. We then discuss the key challenges for broad applicability of the technology and our goal of making a laser accelerator driven a VUV/soft x-ray free electron laser.
* C. G.R. Geddes et al., Nature 431, 538-541 (2004); S. P.D. Mangles et al., ibidem, p.535-538; J. Faure et al., ibidem, p. 541-544.
** W. P. Leemans et al., Nature Physics 2, 696-699 (2006).
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Slides
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