Zhao, T. Z. and Behm, K. and Dong, C. F. and Davoine, X. and Kalmykov, S. Y. and Petrov, V. and Chvykov, V. and Cummings, P. and Hou, B. and Maksimchuk, A. and Nees, J. A. and Yanovsky, V. and Thomas, A. G. R. and Krushelnick, K. (2016) High-Flux Femtosecond X-Ray Emission from Controlled Generation of Annular Electron Beams in a Laser Wakefield Accelerator. Physical review letters, 117 (9): 094801. ISSN 0031-9007
Electron_Halo_Paper.pdf - Accepted Version
Available under License Creative Commons Attribution-NonCommercial.
Download (2MB)
Abstract
Annular quasimonoenergetic electron beams with a mean energy in the range 200-400 MeV and charge on the order of several picocoulombs were generated in a laser wakefield accelerator and subsequently accelerated using a plasma afterburner in a two-stage gas cell. Generation of these beams is associated with injection occurring on the density down ramp between the stages. This well-localized injection produces a bunch of electrons performing coherent betatron oscillations in the wakefield, resulting in a significant increase in the x-ray yield. Annular electron distributions are detected in 40% of shots under optimal conditions. Simultaneous control of the pulse duration and frequency chirp enables optimization of both the energy and the energy spread of the annular beam and boosts the radiant energy per unit charge by almost an order of magnitude. These well-defined annular distributions of electrons are a promising source of high-brightness laser plasma-based x rays.