TOPA  —  Advanced Concepts   (17-May-05   13:50—17:40)

Chair: C. Pellegrini, UCLA, Los Angeles, California

Paper Title Page
TOPA001 Mono Energetic Beams from Laser Plasma Interactions 69
  • C.G.R. Geddes, E. Esarey, W. Leemans, C.B. Schroeder, C. Toth
    LBNL, Berkeley, California
  • J.R. Cary, C. Nieter
    Tech-X, Boulder, Colorado
  • J. Van Tilborg
    TUE, Eindhoven
  Funding: Supported by U.S. Dept. of Energy contracts DE-AC03-76SF00098, DE-FG03-95ER40926, DE-FG02-01ER41178, DE-FG02-03ER83857, SciDAC, and NSF 0113907. C. Geddes is also supported by the Hertz foundation.

A laser driven wakefield accelerator has been tuned to produce high energy electron bunches with low emittance and energy spread by extending the interaction length using a plasma channel. Wakefield accelerators support gradients thousands of times those achievable in RF accelerators, but short acceleration distance, limited by diffraction, has resulted in low energy beams with 100% electron energy spread. In the present experiments on the L’OASIS laser,* the relativistically intense drive pulse was guided over 10 diffraction ranges by a plasma channel. At a drive pulse power of 9 TW, electrons were trapped from the plasma and beams of percent energy spread containing >200pC charge above 80 MeV and with normalized emittance estimated at < 2 pi -mm-mrad were produced.** Data and simulations (VORPAL***) show the high quality bunch was formed when beam loading turned off injection after initial trapping, and when the particles were extracted as they dephased from the wake. Up to 4TW was guided without trapping, potentially providing a platform for controlled injection. The plasma channel technique forms the basis of a new class of accelerators, with high gradients and high beam quality.

*W.P. Leemans et al., Phys. Plasmas 5, 1615-23 (1998). **C.G.R. Geddes et al., Nature 431, 538-41 (2004). ***C. Nieter et al., J. Comp. Phys. 196, 448-73 (2004).

TOPA002 Review of Beam-Driven Plasma Wakefield Experiments at SLAC
  • M.J. Hogan, C.D. Barnes, F.-J. Decker, P. Emma, R.H. Iverson, P. Krejcik, C.L. O'Connell, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • C.E. Clayton, C. Huang, D.K. Johnson, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori
    UCLA, Los Angeles, California
  • S. Deng, T.C. Katsouleas, P. Muggli, E. Oz
    USC, Los Angeles, California
  Funding: Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DE-FG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.

In the plasma wakefield accelerator, a short relativistic-electron bunch drives a large amplitude plasma wave or wake. In experiment E-164X, we use the 28.5 GeV, ultra-short (?80 femtosecond), high peak-current (?30 kiloamperes) bunch now available at the Stanford Linear Accelerator Center Final Focus Test Beam facility. The head of this bunch fieldionizes a lithium vapor and excites the wake, and the tail samples the accelerating field. The latter is accomplished by setting the plasma density to match the plasma wavelength to the bunch length. After the plasma, the bunch is dispersed in energy by an imaging magnetic-spectrometer. Preliminary analysis shows that gradients in excess of 15 GeV/m are excited over a plasma length of approximately 10 cm, leading to energy gain on the order of of 1.5 GeV, or about an order of magnitude larger than energy gains reported to date. This gradient is also three orders of magnitude larger than that in the three-kilometer long Stanford linear accelerator that produces the incoming beam. These results are obtained in a new regime for beam-driven plasma accelerators in which the electron bunch creates its own plasma. The current status of the experiment as well as future plans will be discussed.

TOPA003 Optical Injection into Laser Wake Field Accelerators
  • J.R. Cary, D.L. Bruhwiler, J.R. Cary, R. Giacone, C. Nieter
    Tech-X, Boulder, Colorado
  • E. Esarey, C.G.R. Geddes, W. Leemans
    LBNL, Berkeley, California
  Funding: This work supported by the U.S. Department of Energy grants DE-FG02-04ER41317, DE-FG02-01ER41178, aand DE-FG02-03ER83857, and NSF grant 0113907.

The accelerating gradient of laser-generated wake fields in plasmas can be orders of magnitude greater than the gradients obtainable in traditional, rf structures. One of the hurdles to overcome on the road to practical utilization of said plasma wake fields for production of high energy particles is the creation of quality beams having significant charge, low emittance, and narrow energy spread. To generate appropriate beams, various injection methods have been proposed. Injection by conventional means of beam prepartion using conventional technology is very difficult, as the accelerating buckets are only tens of microns long. Therefore, the field has turned to all-optical injection schemes, which include injection by colliding pulses, plasma ramps, wave breaking, and self-trapping through pulse evolution. This talk will review the various concepts proposed for injection, including plasma ramps, colliding pulses, and self trapping. The results of simulations and experiments will be discussed along with proposed mechanisms for improving the generated beams. Parameter studies to find optimal beam generation scenarios will be presented.

TOPA005 Left-Handed Metamaterials Studies and their Application to Accelerator Physics 458
  • S.P. Antipov, W. Liu, J.G. Power
    ANL, Argonne, Illinois
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois
  Funding: DOE grant NSF grant

Recently, there has been a growing interest in applying artificial materials, known as Left-Handed Metamaterials (LHM), to accelerator physics. These materials have both negative permittivity and permeability and therefore possess several unusual properties: the index of refraction is negative and the direction of the group velocity is antiparallel to the direction of the phase velocity (along k). These properties lead to a reverse Cherenkov effect, which has potential beam diagnostic applications, in addition to accelerator applications. Several LHM devices with different configurations are being experimentally and theoretically studied at Argonne. In this paper, we describe permittivity and permeability retrieval techniques that we have developed and applied to these devices. We have also investigated the possibility of building a Cherenkov detector based on LHM and propose an experiment to observe the reverse radiation generated by an electron beam passing through a LHM. The potential advantage of a LHM detector is that the radiation in this case is emitted in the direction reversed to the direction of the beam, so it could be easier to get a clean measurement.

TOPA006 High Energy Gain IFEL at UCLA Neptune Laboratory 500
  • P. Musumeci, S. Boucher, C.E. Clayton, A. Doyuran, R.J. England, C. Joshi, C. Pellegrini, J.E. Ralph, J.B. Rosenzweig, C. Sung, S. Tochitsky, G. Travish, R.B. Yoder
    UCLA, Los Angeles, California
  • S.V. Tolmachev, A. Varfolomeev, A. Varfolomeev, T.V. Yarovoi
    RRC Kurchatov Institute, Moscow
  We report the observation of energy gain in excess of 20 MeV at the Inverse Free Electron Laser Accelerator experiment at the Neptune Laboratory at UCLA. A 14.5 MeV electron beam is injected in an undulator strongly tapered in period and field amplitude. The IFEL driver is a CO2 10.6 mkm laser with power larger than 400 GW. The Rayleigh range of the laser, ~ 1.8 cm, is much shorter than the undulator length so that the interaction is diffraction dominated. A few per cent of the injected particles are trapped in a stable accelerating bucket. Electrons with energies up to 35 MeV are measured by a magnetic spectrometer. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV/m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator.  
TOPA007 Proton Acceleration and High-Energy Density Physics from Laser Foil Interactions 573
  • P.A. Norreys
    CCLRC/RAL, Chilton, Didcot, Oxon
  • F.N. Beg
    UCSD, La Jolla, California
  • A.E. Dangor, K.M. Krushelnick, M. Wei
    Imperial College of Science and Technology, Department of Physics, London
  • M. Tatarakis
  • M. Zepf
    Queen's University of Belfast, Belfast, Northern Ireland
  Intense laser plasma interactions have long been shown to be a source of very energetic ions - from the first experiments in the 1970's. However, there has been a recent revival of interest in the production of protons and ions from the such plasmas - primarily from the observation of collimated beams of protons and heavier ions which were observed at the rear thin foil targets irradiated by ultra-high intensity laser pulses (such that I > 1018 W/cm2). These ion beams have unique properties which may make them suitable for a variety of applications such as for probing high density plasmas, for fast ignition in inertial confinement fusion, as an ion source for subsequent acceleration stages in a particle accelerator or potentially for medical applications. Recent experimental results will be reviewed and the potential for such future applications will be highlighted.  
TOPA008 First Observation of Laser-Driven Acceleration of Relativistic Electrons in a Semi-Infinite Vacuum Space 650
  • T. Plettner, R.L. Byer, T.I. Smith
    Stanford University, Stanford, Califormia
  • E.R. Colby, B.M. Cowan, C.M.S. Sears, R. Siemann, J.E. Spencer
    SLAC, Menlo Park, California
  Funding: Department of Energy DE-FG03-97ER41043.

We have observed acceleration of relativistic electrons in vacuum driven by a linearly polarized laser beam incident on a thin gold-coated reflective boundary. The observed energy modulation effect follows all the characteristics expected for linear acceleration caused by a longitudinal electric field. As predicted by the Lawson-Woodward theorem the laser driven modulation only appears in the presence of the boundary. It shows a linear dependence with the strength of the electric field of the laser beam and also it is critically dependent on the laser polarization. Finally, it appears to follow the expected angular dependence of the inverse transition radiation process.

TOPA009 Photonic Band Gap Accelerator Demonstration at Ku-Band. 656
  • E.I. Smirnova, L.M. Earley, R.L. Edwards
    LANL, Los Alamos, New Mexico
  • A.S. Kesar, I. Mastovsky, M.A. Shapiro, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts
  Funding: The research is supported by DOE High Energy Physics, Contract No. DE-FG02-91ER40648.

We report progress on the design and cold test of a metal Ku-band PBG accelerator structure. The 17.140 GHz 6-cell PBG accelerator structure with reduced long-range wakefields was designed for the experiment. The copper structure was electroformed and cold-tested. Tuning was performed through chemical etching of the rods. Final cold test measurements were found to be in very good agreement with the design. The structure will be installed on the beam line at the accelerator laboratory at Massachusetts Institute of Technology and will be powered with 3 MW of peak power from the Haimson 17.14 GHz klystron. Results of the design, fabrication, cold test and hot test on the Haimson accelerator will be presented.

TOPA010 Photonic Crystal Laser-Driven Accelerator Structures 731
  • B.M. Cowan
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy contract DE-AC03-76SF00515 (SLAC).

We discuss simulated photonic crystal structure designs, including two- and three-dimensional planar structures and fibers. The discussion of 2D structures demonstrates guiding of a speed-of-light accelerating mode by a defect in a photonic crystal lattice and reveals design considerations and trade-offs. With a three-dimensional lattice, we introduce a candidate geometry and discuss beam dynamics, coupling, and manufacturing techniques for that structure. In addition we discuss W-band scale tests of photonic crystal structures. The computational methods are also discussed.

TOPA011 Self Consistent Scheme for Obtaining Electron-Positron Collisions with Multi-TeV Energy 740
  • A.A. Mikhailichenko
    Cornell University, Department of Physics, Ithaca, New York
  We describe here a self-consistent scheme for arrangement of multi-TeV collisions of electrons and positrons by using laser burst swept along microstructures with stable rate of acceleration ~10GeV/m. Shown that all component of the scheme are within present day technology. For energy ~1TeV luminosity could reach 1035 /cm2/s with wall-plug power of few tens of kW only.