Include rayleigh taylor like instability of the foil

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ssibility of a self-regulated regime where the transverse expansion of the foil decreases the density along the axis [while the frequency downshift in the foil frame compensates the effect of decreasing  on Rð!0 Þ], allowing for an increase of the ion energy at the expense of the total number of accelerated ions (Bulanov et al., 2010a, 2010b). For a 3D expansion, theory predicts an asymptotic scaling with time of kinetic energy KðtÞ=mc2 ’ ð3tÞ3=5 that is more favorable than for plane acceleration. This effect has recently been confirmed by 3D simulations (Tamburini et al., 2012) showing a higher peak energy than found in lower dimensionality simulations. Rev. Mod. Phys., Vol. 85, No. 2, April–June 2013 FIG. 26 (color online). Three-dimensional simulations of thin-foil acceleration in the radiation pressure dominant regime (see text for parameters). Top: Snapshots at t ¼ 40 T of ion density isosurface and Poynting vector in the y ¼ 0 plane. Bottom: The maximum ion kinetic energy vs time and the ion phase-space projection (x; px ) at t ¼ 80 T. The solid line corresponds to the analytical calculation according to the LS model. From Esirkepov et al., 2004. The ultrahigh intensities needed for RPD acceleration are still above present-day laser technology. However, after the proposal of Esirkepov et al. (2004) it was realized that exploring the concept using pulses with circular polarization (CP) at normal laser incidence would enable an investigation of a RPD regime at lower intensities as theoretically discussed by Macchi et al. (2005) in thick targets. Three papers (Zhang, Shen, Li et al., 2007; Klimo et al., 2008; Robinson et al., 2008) independently showed that the use of CP allowed an optimal coupling with an ultrathin foil target as well as rather monoenergetic spectra. Much theoretical work has been devoted to LS-RPA with CP pulses, unfolding a dynamics that is much richer than what is included in the simple ‘‘accelerating mirror’’ model. In particular, formation of a monoenergetic ion distribution is not straightforward (Eliasson et al., 2009; Macchi, Veghini, and Pegoraro, 2009; Macchi et al., 2010) and may require one to control and engineer both the pulse and target properties (Qiao et al., 2009, 2010; T.-P. Yu et al., 2010; Grech et al., 2011). Several multidimensional simulation studies suggested using flattop transverse profiles to keep a quasi-1D geometry (Klimo et al., 2008; Liseykina et al., 2008; Robinson et al., 2008; Qiao et al., 2009) in order to avoid target deformation that would favor electron heating, to prevent early pulse breakthrough due to transverse expansion, and to keep a monoenergetic spectrum against the inhomogeneous distribution of the laser intensity; to address this last issue, a target Andrea Macchi, Marco Borghesi, and Matteo Passoni: Ion acceleration by superintense laser-plasma . . . FIG. 27 (color online). (a) Three typical narrow-band spectra for Z=A ¼ 1=2 impurity ions observed from...
View Full Document

Ask a homework question - tutors are online