Author: O'Shea, B.D.
Paper Title Page
MOPMW040 Electron Beam Excitation of a Surface Wave in mm-Wave Open Accelerating Structures 494
  • M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, B.D. O'Shea, S.G. Tantawi, S.P. Weathersby
    SLAC, Menlo Park, California, USA
  • B. Spataro
    INFN/LNF, Frascati (Roma), Italy
  Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
As part of research on the physics of rf breakdowns we performed experiments with high gradient traveling-wave mm-wave accelerating structures. The accelerating structures are open, composed of two identical halves separated by an adjustable gap. The electromagnetic fields are excited by an ultra-relativistic electron beam. We observed that a confined travelling-wave mode exists in half of the accelerating structure. The experiments were conducted at FACET facility at SLAC National Accelerator Laboratory. Depending on the gap width, the accelerating structure had beam-synchronous frequencies that vary from 90 to 140 GHz. When we opened the gap by more than half wavelength the synchronous wave remains trapped. Its behavior is consistent with the so called "surface wave". We characterized this beam-wave interaction by several methods: measurement of the radiated rf energy with the pyro-detector, measurement of the spectrum with an interferometer, measurement of the beam deflection by using the beam position monitors and profile monitor.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW040  
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THPPA01 Demonstration of the Hollow Channel Plasma Wakefield Accelerator 3202
SUPSS117   use link to see paper's listing under its alternate paper code  
  • S.J. Gessner, J.M. Allen, C.I. Clarke, J.-P. Delahaye, J.T. Frederico, S.Z. Green, C. Hast, M.J. Hogan, N. Lipkowitz, M.D. Litos, B.D. O'Shea, D.R. Walz, V. Yakimenko, G. Yocky
    SLAC, Menlo Park, California, USA
  • E. Adli, C.A. Lindstrøm
    University of Oslo, Oslo, Norway
  • W. An, C.E. Clayton, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi
    UCLA, Los Angeles, California, USA
  • S. Corde, A. Doche
    LOA, Palaiseau, France
  • W. Lu
    TUB, Beijing, People's Republic of China
  Funding: Work supported by DOE contract DE-AC02-76SF00515.
Over the past decade, there has been enormous progress in the field of beam and laser-driven plasma acceleration of electron beams. However, in order for plasma wakefield acceleration to be useful for a high-energy e+e- collider, we need a technique for accelerating positrons in plasma as well. This is a unique challenge, because the plasma responds differently to electron and positron beams, with plasma electrons being pulled through the positron beam and creating a non-linear focusing force. Here, we demonstrate a technique called hollow channel acceleration that symmetrizes the wakefield response to beams of either charge. Using a transversely shaped laser pulse, we create an annular plasma with a fixed radius of 200 μm. We observe the acceleration of a positron bunch with energies up to 33.4 MeV in a 25 cm long channel, indicating an effective gradient greater than 100 MeV/m. This is the first demonstration of a technique that way be used for staged acceleration of positron beams in plasma.
slides icon Slides THPPA01 [5.647 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPPA01  
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