Simulation studies of radiation pressure-driven light sail and shock acceleration

Abstract

Simulation results are reported for two ion acceleration mechanisms driven by radiation pressure. Threedimensional (3D) simulations of the acceleration of thin foils by circularly polarized pulses ("light sail" regime) at ultra-relativistic intensities (a 0 > 100) show an ion energy that is higher than observed in 1D and 2D simulations, presumably due to density rarefaction and self-wrapping of the laser pulse as the foil is deformed. Simulations of the interaction of linearly polarized pulses with long-scalelength, moderately overdense plasmas at mildly relativistic intensities (a 0 = 1÷ 10) show radiation-pressure driven formation of both solitary and shock waves leading to ion acceleration in the target bulk. In 1D simulations, the spectrum of the accelerated ions is monoenergetic within some range of the initial ion temperature. In 2D simulations, the onset of rippling at the shock surface apparently leads to broadening of the energy spectrum.

Ion shock acceleration by large amplitude slow ion acoustic double layers in laser-produced plasmas

“…The electrons are assumed to be isothermal so that the electron number density obeys the Boltzmann distribution of the form [45] n e (φ, φ max ) = n i (0, φ max ) exp(φ/θ), (7) where θ = T e /T i . Equation (7) ensures that n e = n i when φ = 0. It should be noted that kinetic models for the electrons have been used both in the non-relativistic [32,47] and relativistic [49,50] regimes; to obtain Eq.…”

“…is Dawson's integral. The electrons are assumed to be isothermal so that the electron number density obeys the Boltzmann distribution of the form [45] n e (φ, φ max ) = n i (0, φ max ) exp(φ/θ), (7) where θ = T e /T i . Equation (7) ensures that n e = n i when φ = 0.…”

“…The condition ∂V /∂φ = 0 at φ = φ max is equivalent to the quasi-neutrality condition n e = n i at x = −∞, where it also holds that n i (φ max , φ max ) = 1. Using this together with the expression (7) for the electron density, we have…”

“…Laser accelerated ions have important potential applications in the fields of cancer therapy [1][2][3], inertial confinement fusion [4], etc., where well defined energies of the protons are of great importance. A number of ion acceleration methods have been considered [5][6][7]. The interaction of an intense laser beam with an underdense plasma can lead to rapid heating of the electrons and acceleration of ions [8,9].…”