Electron Self-Injection in Multidimensional Relativistic-Plasma Wake Fields

Abstract

We present an analytical model for electron self-injection in a nonlinear, multidimensional plasma wave excited by a short laser pulse in the bubble regime or by a short electron beam in the blowout regime. In these regimes, which are typical for electron acceleration, the laser radiation pressure or the electron beam charge pushes out background plasma electrons forming a plasma cavity--bubble--with a huge ion charge. The plasma electrons can be trapped in the bubble and accelerated by the plasma wakefields up to very high energies. The model predicts the condition for electron trapping and the trapping cross section in terms of the bubble radius and the bubble velocity. The obtained results are in a good agreement with results of 3D particle-in-cell simulations.

Physics of Quasi-Monoenergetic Laser-Plasma Acceleration of Electrons in the Blowout Regime

“…2(f) gives p z max ≈ 21m e c > γ g m e c,a n d|p r max |≈4m e c. The large longitudinal momentum of these electrons makes them the best injection candidates; their promotion to fully dynamic macroparticles may result in their self-injection and acceleration (Morshed et al, 2010). Longitudinal synchronization of sheath electrons, p z ≥ γ g m e c, is necessary and, in highdensity plasmas (such as γ g ≈ k p R b ), also sufficient for their injection (Kostyukov et al, 2009). In the opposite limit of strongly rarefied plasmas, γ g > 10k p R b , the sheath electrons do not synchronize with (and thus cannot be injected into) a non-evolving bubble (i.e.…”

Analytic model of electron self-injection in a plasma wakefield accelerator in the strongly nonlinear bubble regime

“…Previous works [15,16] have shown using a phenomenological non-evolving spherical bubble model that trapping is possible for large enough blowout radii, where the critical blowout radius for trapping scales linearly with the bubble relativistic factor γ 0 . Other authors [17] have found empirically (from PIC simulations) that when the radius exceeds several collisionless skip depths trapping always occurs for non-evolving bubbles regardless of the bubble velocity.…”

Energy Spread Reduction of Electron Beams Produced via Laser Wake

“…There have been several numerical studies of this trapping process [29,30], which predict density thresholds for self-trapping of few-10 18 -10 20 cm −3 for the blowout condition 2<a 0 <4. This thesis will present data indicating that in He plasmas this threshold occurs at 4x10 18 cm −3 for laser powers of 60 TW.…”