• W. Lu, C. Joshi, W. B. Mori, F. S. Tsung, M. Tzoufras
  UCLA, Los Angeles, California
• S. Fonseca, L. O. Silva, J. H. Vieira
  Instituto Superior Tecnico, Lisbon

The extraordinary ability of space-charge waves in plasmas to accelerate charged particles at gradients that are orders of magnitude greater than that in current accelerators has been well documented. We develop a phenomenological framework for Laser Wakefield Acceleration (LWFA) in the 3D nonlinear regime, in which the plasma electrons are expelled by the radiation pressure of a short pulse laser, leading to nearly complete blowout. This theory provides a recipe for designing a LWFA for given laser and plasma parameters and estimates the number and the energy of the accelerated electrons whether self-injected or externally injected. These formulas apply for self-guided as well as externally guided pulses (e.g. by plasma channels). Based on this theory, we will present scenarios on how to build a single stage accelerator with output energies from GeV to TeV. Particle-In-Cell (PIC) simulations are used to verify our theory. This work was supported by DOE and NSF under grant Nos. DE-FG03-92ER40727, DE-FC02-01ER41179, DE-FG02-03ER54721, and NSF-Phy-0321345.

• M. Tzoufras, C. Huang, W. Lu, W. B. Mori, F. S. Tsung
  UCLA, Los Angeles, California
• S. Fonseca, L. O. Silva, J. H. Vieira
  Instituto Superior Tecnico, Lisbon

The realization of high quality LWFA-produced electron beams requires laser pulses that remain focused for distances exceeding the Rayleigh length. It is often thought that a short pulse laser cannot be self-guided and some form of external optical guiding is needed. As short pulse lasers with higher power are rapidly coming online to test the LWFA concept it is vital to understand the nature of their propagation through centimeters of plasma. We argue that a degree of self-guiding is possible for short ultra-intense pulses that have been shown to lead to complete ponderomotive expulsion of plasma electrons. Furthermore, the generation of a high quality electron beam requires proper loading of the wake. We have developed a theoretical framework which predicts the maximum number of electrons which can be loaded in the wake, as well as the optimal charge density profile for beam loading. Using the PIC codes OSIRIS and QuickPIC we present designs of LWFA accelerators that verify our theoretical estimates as well as demonstrate the potential of LWFA to produce high energy electron beams with high beam quality.