We propose to use a combination of Hermite-Gaussian laser modes to generate a nonlinear ring bubble with a large longitudinal accelerating field and a transverse focusing field suitable for positron beam focusing and acceleration. The nonlinear bubble can provide higher accelerating gradients compared with a linear plasma wake. PIC simulations have been used to demonstrate control of the focusing force by changing the relative intensity ratio of the two laser modes, enabling matched positron beam propagation for emittance preservation. In addition, in order to improve phase space characteristics of laser wakefield produced electron beams, in particular, to reduce their transverse emittance, we propose to generate femtosecond electron beams with ultralow emittance using a two-color laser-ionization injection method. By controlling the amplitude and the duration of the injection pulse, the emittance can be controlled to the level of 10^-2 mm mrad.

Date Published: 14 May 2015
PDF: 8 pages
Proc. SPIE 9514, Laser Acceleration of Electrons, Protons, and Ions III; and Medical Applications of Laser-Generated Beams of Particles III, 95140P (14 May 2015); doi: 10.1117/12.2178882

Published in SPIE Proceedings Vol. 9514:
Laser Acceleration of Electrons, Protons, and Ions III; and Medical Applications of Laser-Generated Beams of Particles III
Kenneth W. D. Ledingham; Eric Esarey; Carl B. Schroeder; Klaus Spohr; Paul McKenna; Florian J. Grüner; Paul R. Bolton, Editor(s)