On the production of flat electron bunches for laser wakefield acceleration
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TOMS, MOLECULES, OPTICS
On the Production of Flat Electron Bunches for Laser Wakefield Acceleration1 M. Kandoa, Y. Fukudaa, H. Kotakia, J. Kogaa, S. V. Bulanova, e, T. Tajimaa, A. Chaob, R. Pitthanb, K.-P. Schulerc, A. G. Zhidkovd, and K. Nemotod a
Kansai Photon Science Institute, Japan Atomic Energy Agency, Kyoto, 619-0215 Japan b Stanford Linear Accelerator Center, Palo Alto, CA 94025, USA c DESY, Deutsches Elektronen-Synchrotron, Hamburg, 22603 Germany d Central Research Institute of Electric Power Industry, Kanagawa, 240-0196 Japan e Prokhorov Institute of General Physics, Russian Academy of Sciences, Moscow, 119991 Russia e-mail: [email protected] Received April 3, 2007
Abstract—We suggest a novel method for the injection of electrons into the acceleration phase of particle accelerators, producing low-emittance beams appropriate even for the demanding high-energy linear collider specifications. We discuss the injection mechanism into the acceleration phase of the wakefield in a plasma behind a high-intensity laser pulse, which takes advantage of the laser polarization and focusing. The scheme uses the structurally stable regime of transverse wakewave breaking, when the electron trajectory self-intersection leads to the formation of a flat electron bunch. As shown in three-dimensional particle-in-cell simulations of the interaction of a laser pulse elongated in the transverse direction with an underdense plasma, the electrons injected via the transverse wakewave breaking and accelerated by the wakewave perform betatron oscillations with different amplitudes and frequencies along the two transverse coordinates. The polarization and focusing geometry lead to a way to produce relativistic electron bunches with an asymmetric emittance (flat beam). An approach for generating flat laser-accelerated ion beams is briefly discussed. PACS numbers: 53.38.Kd, 41.75.Jv, 52.38.Hb, 52.38.-r DOI: 10.1134/S1063776107110064 1
1. INTRODUCTION
Electron accelerators with energies of many gigaelectronvolts and low emittance are needed for coherent light sources and linear colliders. The laser acceleration of charged particles provides a promising approach toward such development in a compact way, avoiding some of the complications arising due to the additional requirements of asymmetric emittance for linear colliders, as outlined below. In the laser wakefield accelerator (LWFA) concept, electrons are accelerated by the longitudinal electric field created in an underdense plasma by a high-intensity short laser pulse [1]. Electrons injected by conventional accelerators, self-injected by nonlinear wakewave breaking (for details, see papers [2–4] and review articles [5] and the references therein) or injected in the multiple laser pulse configuration [6] can achieve energies substantially higher than the initial injection energies. Although the understanding and production of highintensity (≈nC) and low-emittance (≈2–3 mm mrad) electron beams via laser plasma interaction has made rapid progress [5, 7–12], applications to co
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