Magnetic Field and Radiation Production in Laser-Driven Electron Beams
John Peterson, Stanford University
Modern high-power lasers incident on gas jets can accelerate electron beams to relativistic energies. The high current density in these beams produces strong magnetic fields accompanied by intense x-ray synchrotron emission. We use experiment and simulation to explore magnetic field dynamics and x-ray production with picosecond and femtosecond laser plasma accelerators. First, in the picosecond, self-modulated laser wakefield accelerator, our experimental radiographs and particle-in-cell simulations reveal strong and unexpectedly long-lived electromagnetic fields after the laser has left the gas jet. Theory and simulation demonstrate that these fields are sustained by an inductive acceleration process for 10s of picoseconds. Second, we simulate a GeV electron beam typical of a femtosecond, bubble-regime laser wakefield accelerator as it propagates through a secondary plasma target. The beam quickly becomes unstable and breaks into small micron-scale current filaments surrounded by strong magnetic fields. We predict that the high fluxes of focused synchrotron x-rays produced in this regime could outperform other compact x-ray sources in the 100s-keV to MeV energy range—an important advance for high-energy-density radiography.
Abstract Author(s): J. Ryan Peterson, Nuno Lemos, Siegfried Glenzer, and Frederico Fiuza