Author: Clayton, C.E.
Paper Title Page
TUOBN1 Laser Wakefield Acceleration Beyond 1 GeV using Ionization Induced Injection 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]  
 
TUOBN4 Plasma Wakefield Experiments at FACET 715
 
  • M.J. Hogan, R.J. England, J.T. Frederico, C. Hast, S.Z. Li, M.D. Litos, D.R. Walz
    SLAC, Menlo Park, California, USA
  • W. An, C.E. Clayton, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori, S. Tochitsky
    UCLA, Los Angeles, California, USA
  • P. Muggli, S.F. Pinkerton, Y. Shi
    USC, Los Angeles, 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 beginning in summer 2011. The nominal FACET parameters are 23GeV, 3nC electron bunches compressed to ~20μm long and focused to ~10μm wide. The intense fields of the FACET bunches will be used to field ionize neutral lithium or cesium vapor produced in a heat pipe oven. Previous experiments at SLAC demonstrated 50GeV/m gradients in an 85cm field ionized lithium plasma where the interaction distance was limited by head erosion. Simulations indicate the lower ionization potential of cesium will decrease the rate of head erosion and increase single stage performance. The initial experimental program will compare the performance of lithium and cesium plasma sources with single and double bunches. Later experiments will investigate improved performance with a pre-ionized cesium plasma. The status of the experiments and expected performance are reviewed.
 
slides icon Slides TUOBN4 [13.080 MB]  
 
WEOBS3 The Effects of a Density Mismatch in a Two-State LWFA 1421
 
  • B.B. Pollock, F. Albert, C. Filip, D.H. Froula, S.H. Glenzer, J.E. Ralph
    LLNL, Livermore, California, USA
  • C.E. Clayton, C. Joshi, K.A. Marsh, J. Meinecke, A.E. Pak, J.L. Shaw
    UCLA, Los Angeles, California, USA
  • K.L. Herpoldt
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • G.R. Tynan
    UCSD, La Jolla, California, USA
 
  Funding: Work performed under U.S. DOE Contract DE-AC52-07NA27344 and was partially funded by the Laboratory Directed Research and Development Program under project tracking code 06-ERD-056.
A two-stage Laser Wakefield Accelerator (LWFA) has been developed, which utilizes the ionization induced injection mechanism to produce high energy, narrow energy spread electron beams when the electron density is equal in both stages. However, when the densities are not equal these high quality beams are not observed. As the electron density varies across the interface between the adjacent stages the size of the ion cavity is expected to change; this results in either a reduction of the peak electron energy (for a density decrease), or in the exclusion of previously trapped charge from the first wake period (for a density increase). The latter case can be overcome if the interaction length before the density interface exceeds a threshold determined by the densities in each stage, and may provide a mechanism for enhanced energy gain.