Simulation of monoenergetic electron generation via laser wakefield accelerators for 5–25TW lasers

In 2004, using a 3D particle-in-cell (PIC) model F. S. Tsung et al., Phys. Rev. Lett. 93, 185004 (2004), it was predicted that a 16.5TW, 50fs laser propagating through nearly 0.5cm of 3×1018cm−3 preformed plasma channel would generate a monoenergetic bunch of electrons with a central energy of 240MeV after 0.5cm of propagation. In addition, electrons out to 840MeV were seen if the laser propagated through 0.8cm of the same plasma. The simulations showed that self-injection occurs after the laser intensity increases due to a combination of photon deceleration, group velocity dispersion, and self-focusing. The monoenergetic beam is produced because the injection process is clamped by beam loading and the rotation in phase space that results as the beam dephases. Nearly simultaneously S. P. D. Mangles et al., Nature 431, 535 (2004); C. G. R. Geddes et al., ibid. 431, 538 (2004); J. Faure et al., ibid. 431, 541 (2004) three experimental groups from around the world reported the generation of near nano-Coulomb of low emittance, monoenergetic electron beams using similar laser powers and pulse lengths as those reported in our simulations. Each of these experiments is modeled using the same 3D PIC code OSIRIS. The simulations indicate that although these experiments use a range of plasma parameters, density profiles, laser powers, and spot sizes; there are some commonalities to the mechanism for the generation of monoenergetic beams. Comments are given on how the energy and beam quality can be improved in the future.