Laser-driven relativistic electron dynamics in a cylindrical plasma channel

Abstract

The energy and trajectory of the electron, which is irradiated by a high-power laser pulse in a cylindrical plasma channel with a uniform positive charge and a uniform negative current, have been analyzed in terms of a single-electron model of direct laser acceleration. We find that the energy and trajectory of the electron strongly depend on the positive charge density, the negative current density, and the intensity of the laser pulse. The electron can be accelerated significantly only when the positive charge density, the negative current density, and the intensity of the laser pulse are in suitable ranges due to the dephasing rate between the wave and electron motion. Particularly, when their values satisfy a critical condition, the electron can stay in phase with the laser and gain the largest energy from the laser. With the enhancement of the electron energy, strong modulations of the relativistic factor cause a considerable enhancement of the electron transverse oscillations across the channel, which makes the electron trajectory become essentially three-dimensional, even if it is flat at the early stage of the acceleration.

Scaling laws for direct laser acceleration in a radiation-reaction dominated regime

“…Analytical predictions of the maximum electron energy as a function of channel density and electron initial radial position are provided by equations (9) and (21) using radiation-reaction reduced value of I given by the lowest estimate from equations (24) and (25). The required acceleration distance to achieve this energy can be estimated through equation (13).…”

“…Both equations (24) and (25) predict an asymptotic value that particles with a large initial value of I 0 would tend to after a resonant cycle. If the predicted asymptotic I is much smaller for one of the limits (RR due to the laser or due to the channel fields), it means that this limit represents the dominant contribution to the radiation reaction.…”

“…A fraction of these particles eventually does converge towards the predicted values in the example with a longer propagation distance. (24). (b) Comparison with data points from test-particle simulations at the moment when the electron reaches the maximum energy.…”

“…They have the same laser intensity 13without radiation reaction (considering I0). Orange lines are obtained using equations (9) and (21) with radiation reaction (considering I given by equation (24)). Crosses show the corresponding results from 2D PIC simulations.…”

“…This regime of electron acceleration is referred to as the direct laser acceleration (DLA) [7]. The rich physics of this setup has raised a keen interest among researchers in the past few years [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. It was reported that the efficiency of DLA may be enhanced using various strategies: parametric amplification of betatron oscillations [26][27][28][29], applying additional longitudinal electric field [30,31] or by "breaking of the adiabaticity that precludes electron energy retention" [32].…”