Electron self-injection into an evolving plasma bubble: Quasi-monoenergetic laser-plasma acceleration in the blowout regime

Authors

Serguei Y. Kalmykov, University of Nebraska-LincolnFollow
A. Beck, CEA, DAM, DIF, Arpajon F-91297, France
S. A. Yi, University of Texas at Austin
V. N. Khudik, University of Texas at Austin
Michael C. Downer, University of Texas at AustinFollow
E. Lefebvre, CEA, DAM, DIF, Arpajon F-91297, France
Bradley Allan Shadwick, University of Nebraska-LincolnFollow
Donald Umstadter, University of Nebraska - LincolnFollow

Date of this Version

2011

Citation

PHYSICS OF PLASMAS 18, 056704 (2011); doi:10.1063/1.3566062

Comments

Copyright 2011 American Institute of Physics. Used by permission.

Abstract

An electron density bubble driven in a rarefied uniform plasma by a slowly evolving laser pulse goes through periods of adiabatically slow expansions and contractions. Bubble expansion causes robust self-injection of initially quiescent plasma electrons, whereas stabilization and contraction terminate self-injection thus limiting injected charge; concomitant phase space rotation reduces the bunch energy spread. In regimes relevant to experiments with hundred terawatt- to petawatt-class lasers, bubble dynamics and, hence, the self-injection process are governed primarily by the driver evolution. Collective transverse fields of the trapped electron bunch reduce the accelerating gradient and slow down phase space rotation. Bubble expansion followed by stabilization and contraction suppresses the low-energy background and creates a collimated quasi-monoenergetic electron bunch long before dephasing. Nonlinear evolution of the laser pulse (spot size oscillations, self-compression, and front steepening) can also cause continuous self-injection, resulting in a large dark current, degrading the electron beam quality.