Simulation of electron postacceleration in a two-stage laser wakefield accelerator

Abstract

Electron bunches produced in self-modulated laser wakefield experiments usually have a broad energy distribution, with most electrons at low energy (1-3 MeV) and only a small fraction at high energy. We propose and investigate further acceleration of such bunches in a channel-guided resonant laser wakefield accelerator. Two-dimensional simulations with and without the effects of self-consistent beam loading are performed and compared. These results indicate that it is possible to trap about 40% of the injected bunch charge and accelerate this fraction to an average energy of about 50 MeV in a plasma channel of a few mm.

Terahertz radiation from laser accelerated electron bunches

“…This could be done by focusing a laser beam with cylindrical optics to produce a vertical mm-scale sheet-like plasma through which the electron beam propagates. Increasing the mean energy of the electron beam to the few 10's of MeV with, e.g., a channel-guided LWFA, 29 could further increase the pulse energy to the few 100 J level in a 0.1 rad cone. Such intense terahertz radiation will provide access to nonlinear regimes and highly nonequilibrium processes using MV/cm field strengths.…”

Progress on laser plasma accelerator development using transversely and longitudinally shaped plasmas

“…Experiments underway at LBNL are now focusing on a staged LWFA approach in which a down-ramp electron injector is coupled to a capillary discharge plasma channel for acceleration to high energy [15]. Here we report progress on the design and physics of such a staged approached using the results of PIC simulations with the VORPAL [28] framework.…”

“…This is important for many applications, which desire momentum spreads below those of present experiments (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) MeV/c or few % longitudinal spread and ~0.2-2 MeV/c transverse spread). The short plasma wave wavelength X p = ^jtc 2 m/e 2 n e , typically ~ 10-100 um, determines the size requirement for the injected bunch, where n e is the plasma density.…”

“…Future LWFA experiments are likely to use a staged approach [15]. In the first stage -the injection stage -a relatively low energy, high quality electron bunch is generated using a laser injection method.…”

Laser guiding at > 1018 W/cm2 in plasma channels formed by the ignitor heater method

“…Simulations indicate guiding the laser pulse with a plasma channel can substantially increase particle energy and reduce energy spread by increasing length over which the laser remains intense [3]. We have used channels formed by hydrodynamic shock to guide acceleration relevant intensities of 10 18 W/cm 2 in initial experiments.…”