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

S. Y. Kalmykov, A. Beck, S. A. Yi, V. N. Khudik, M. C. Downer, E. Lefebvre, B. A. Shadwick, D. P. Umstadter

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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.

Original languageEnglish (US)
Article number056704
JournalPhysics of Plasmas
Volume18
Issue number5
DOIs
Publication statusPublished - May 1 2011

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ASJC Scopus subject areas

  • Condensed Matter Physics

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