Self-trapped electron acceleration from the nonlinear interplay between Raman forward scattering, self-focusing, and hosing

Abstract

The generation of high current (>kA), relativistic beams from the wave breaking of plasma waves that result from a high-power (>5 TW), short-pulse (<ps) laser propagating through an underdense plasma is studied in detail using the fully explicit particle-in-cell model PEGASUS [K.-C. Tzeng et al., Phys. Rev. Lett. 76, 3332 (1996)]. The plasma waves and the self-trapped acceleration are due to a highly nonlinear interplay between Raman forward scattering, self-focusing, laser heating, hosing, and wave breaking. The resulting beams have a continuous energy spread with a maximum energy exceeding simple dephasing estimates. For a 5 J laser, a total of 2×1011 electrons are accelerated to relativistic energies with 2×108 of these at 50±1 MeV with a normalized emittance of 13π mm mrad. Details in the correlation of anti-Stokes generation and electron acceleration, the meaning of wave breaking, and the maximum electron energies are presented. A plasma wave accordion mechanism and multibunch beamloading can occur after wave breaking, and these are offered as an explanation for how higher than expected energies are observed. Comparisons to published experimental results are also given.