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Panasenko, D.

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WEOBKI01 Stable Electron Beams with Low Absolute Energy Spread from a Laser Wakefield Accelerator with Plasma Density Ramp Controlled Injection 1916
  • C. G.R. Geddes, E. Esarey, W. Leemans, K. Nakamura, D. Panasenko, G. R.D. Plateau, C. B. Schroeder, C. Toth
    LBNL, Berkeley, California
  • J. R. Cary
    Tech-X, Boulder, Colorado
  • E. Cormier-Michel
    University of Nevada, Reno, Reno, Nevada
  Funding: Supported by DOE, including grant DE-AC02-05CH11231, DARPA, and by an INCITE computational award.

Laser wakefield accelerators produce accelerating gradients up to hundreds of GeV/m and narrow energy spread, and have recently demonstrated energies up to GeV and improved stability [*,**] using electrons self trapped from the plasma. Controlled injection and staging can further improve beam quality by circumventing tradeoffs between energy, stability, and energy spread/emittance. We present experiments demonstrating production of a stable electron beam near 1 MeV with 100 keV level energy spread and central energy stability by using the plasma density profile to control self injection, and supporting simulations. A 10 TW laser pulse was focused near the downstream edge of a mm-long hydrogen gas jet. The plasma density near focus is decreasing in the laser propagation direction, which changes the wake phase velocity and reduces the trapping threshold. This allows stable self trapping and low absolute energy spread. Simulations indicate that such beams can be post accelerated to form high energy, high quality, stable beams, and experiments are under investigation.

* Geddes et al, Nature v431 no7008, 538 (2004).** Leemans et al, Nature Physics v2 no10, p696 (2006)

slides icon Slides  
THPMN112 Colliding Pulse Injection Experiments in Non-Collinear Geometry for Controlled Laser Plasma Wakefield Acceleration of Electrons 2975
  • C. Toth, E. Esarey, C. G.R. Geddes, W. Leemans, K. Nakamura, D. Panasenko, C. B. Schroeder
    LBNL, Berkeley, California
  • D. L. Bruhwiler, J. R. Cary
    Tech-X, Boulder, Colorado
  Funding: Supported by DOE grant DE-AC02-05CH11231, DARPA, and and INCITE computational grant.

Colliding laser pulses* have been proposed as a method for controlling injection of electrons into a laser wakefield accelerator (LWFA) and hence producing high quality relativistic electron beams with energy spread below 1% and normalized emittances below 1 micron. The original proposal relied on three coaxial pulsesI. One pulse excites a plasma wake, and a collinear pulse following behind it collides with a counterpropagating pulse forming a beat pattern that boosts background electrons into accelerating phase. A variation of this method uses only two laser pulses** which may be non-collinear. The first pulse drives the wake, and beating of the trailing edge of this pulse with the colliding pulse injects electrons. Non-collinear injection avoids optical elements on the electron beam path (avoiding emittance growth). We report on progress of non-collinear experiments at LBNL, using the Ti:Sapphire laser at the LOASIS facility of LBNL. Preliminary results indicate that electron beam properties are affected by the second beam. Details of the experiment will be presented.

* E. Esarey, et al, Phys. Rev. Lett 79, 2682 (1997).** G. Fubiani, Phys. Rev. E 70, 016402 (2004).

THPMN113 Performance of Capillary Discharge Guided Laser Plasma Wakefield Accelerator 2978
  • K. Nakamura, E. Esarey, C. G.R. Geddes, A. J. Gonsalves, W. Leemans, D. Panasenko, C. B. Schroeder, C. Toth
    LBNL, Berkeley, California
  • S. M. Hooker
    OXFORDphysics, Oxford, Oxon
  Funding: This work is supported by US DoE office of High Energy Physics under contract DE-AC02-05CH11231 and DARPA.

A GeV-class laser-driven plasma-based wakefield accelerator has been realized at the Lawrence Berkeley National Laboratory (LBNL). The device consists of a 100 TW-class high repetition rate Ti:sapphire LOASIS laser system of LBNL and a gas-filled capillary discharge waveguide developed at Oxford University. Results will be presented on the generation of GeV-class electron beams with a 3.3 cm long preformed plasma channel. The use of a discharge-based waveguide permitted operation at an order of magnitude lower density and 15 times longer distance than in previous experiments that relied on laser-preformed plasma channels. Laser pulses with peak power ranging from 10-50 TW were guided over more than 20 Rayleigh ranges and high-quality electron beams with energy up to 1 GeV were obtained. The dependence of the electron beam characteristics on plasma channel properties and laser parameters are discussed.