Energy boost in laser wakefield accelerators using sharp density transitions

TL;DR

This paper explores how sharp plasma density transitions can enhance energy gain in laser wakefield accelerators by enabling rapid rephasing, supported by models and simulations.

Contribution

It introduces a new approach using sharp density transitions for rephasing in nonlinear wakefield regimes, extending previous phase-locking concepts.

Findings

Analytical expressions for energy gain in sharp density profiles

Simulation validation of rephasing effects

Potential for multi-stage acceleration improvements

Abstract

The energy gain in laser wakefield accelerators is limited by dephasing between the driving laser pulse and the highly relativistic electrons in its wake. Since this phase depends on both the driver and the cavity length, the effects of dephasing can be mitigated with appropriate tailoring of the plasma density along propagation. Preceding studies have discussed the prospects of continuous phase-locking in the linear wakefield regime. However, most experiments are performed in the highly non-linear regime and rely on self-guiding of the laser pulse. Due to the complexity of the driver evolution in this regime it is much more difficult to achieve phase locking. As an alternative we study the scenario of rapid rephasing in sharp density transitions, as was recently demonstrated experimentally. Starting from a phenomenological model we deduce expressions for the electron energy gain in such density profiles. The results are in accordance with particle-in-cell simulations and we present gain estimations for single and multiple stages of rephasing.