A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

Toth, C.

Paper Title Page
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.

 
THPMN114 Recent Progress at LBNL on Characterization of Laser Wakefield Accelerated Electron Bunches Using Coherent Transition Radiation 2981
 
  • W. Leemans, E. Esarey, C. G.R. Geddes, N. H. Matlis, G. R.D. Plateau, C. B. Schroeder, C. Toth, J. Van Tilborg
    LBNL, Berkeley, California
 
  Funding: Work supported by US DoE Office of High Energy Physics under contract DE-AC03-76SF0098 and DARPA.

At LBNL, laser wakefield accelerators (LWFA) now produce ultra-short electron bunches with energies up to 1 GeV[1]. As femtosecond electron bunches exit the plasma they radiate a strong burst in the terahertz range[2,3], via coherent transition radiation (CTR). Measuring the CTR properties allows non-invasive bunch-length diagnostics[4], a key to continuing rapid advance in LWFA technology. In addition, this method of CTR generation provides very high peak power that can lead novel THz-based applications. Experimental bunch length characterizations through electro-optic sampling as well as bolometric analysis are presented. Measurements demonstrate both the shot-by-shot stability of bunch parameters, and femtosecond synchronization between bunch, THz pulse, and laser beam.

[1] W. P. Leemans et al., Nature Physics 2, 696(2006)[2] W. P. Leemans et al., PRL 91, 074802(2003)[3] C. B. Schroeder et al., PRE 69, 016501(2004)[4] J. van Tilborg et al., PRL 96, 014801(2006)

 
WEYKI02 Experimental Demonstration of 1 GeV Energy Gain in a Laser Wakefield Accelerator 1911
 
  • A. J. Gonsalves, S. M. Hooker
    OXFORDphysics, Oxford, Oxon
  • D. L. Bruhwiler, J. R. Cary
    Tech-X, Boulder, Colorado
  • E. Cormier-Michel
    University of Nevada, Reno, Reno, Nevada
  • E. Esarey, C. G.R. Geddes, W. Leemans, K. Nakamura, C. B. Schroeder, C. Toth
    LBNL, Berkeley, California
 
  GeV-class electron accelerators have a broad range of uses, including synchrotron facilities, free electron lasers, and high-energy particle physics. The accelerating gradient achievable with conventional radio frequency (RF) accelerators is limited by electrical breakdown within the accelerating cavity to a few tens of MeV, so the production of energetic beams requires large, expensive accelerators. One promising technology to reduce the cost and size of these accelerators (and to push the energy frontier for high-energy physics) is the laser-wakefield accelerator (LWFA), since these devices can sustain electric fields of hundreds of GV/m. In this talk, results will be presented on the first demonstration of GeV-class beams using an intense laser beam. Laser pulses with peak power ranging from 10-40TW were guided in a 3.3 cm long gas-filled capillary discharge waveguide, allowing the production of high-quality electron beams with energy up to 1 GeV. The electron beam characteristics and laser guiding, and their dependence on laser and plasma parameters will be discussed and compared to simulations.  
slides icon Slides