Electron trajectories in the magnetic field of capillary discharge: Application to laser wakefield accelerators in plasma channel

Abstract

Capillary discharge plasma channels have demonstrated guiding of laser beams and may be employed to extend the length of laser-driven accelerators. However, the magnetic field associated with the discharge current may affect the injection of electrons into the capillary. A model for magnetic field generation is presented and analyzed. For a wide range of parameters of interest the magnetic field outside the channel is well described by a diffusion equation. Analytical solutions of the diffusion equation are obtained and compared with numerical solutions. Trajectories, for test electrons starting from outside the capillary, are described and discussed. For typical parameters the deflection of electrons by the magnetic field is small compared with the acceptance of the wakefield.