Relativistic laser piston model: Ponderomotive ion acceleration in dense plasmas using ultraintense laser pulses

Abstract

A high-efficiency overmoded klystron-like relativistic backward wave oscillator with low guiding magnetic field Phys. Plasmas 19, 093102 (2012) Relativistic plasmas in uniform magnetic fields. I. General off-axis coupling methods J. Math. Phys. 53, 083302 (2012) Derivation of nonlinear Schrödinger equation for electrostatic and electromagnetic waves in fully relativistic twofluid plasmas by the reductive perturbation method Phys. Plasmas 19, 082303 (2012) Parametric decays in relativistic magnetized electron-positron plasmas with relativistic temperatures Laser ponderomotive force at superhigh intensities provides an efficient ion acceleration in bulk dense targets and evacuates a channel enabling further laser beam propagation. The developed quasistationary model of a laser piston-a double layer structure supported by the radiation pressure-predicts the general parameters of the acceleration process in homogeneous and inhomogeneous overdense plasmas. Particle-in-cell simulations confirm the estimated characteristics in a wide range of laser intensities and ion densities and show advantages of circularly polarized laser pulses. Two nonstationary effects are identified in the simulations. First, oscillations of the piston velocity and of the thickness of the ion charge separation layer broaden the energy spectrum of accelerated ions. Second, the electrons accelerated toward the incoming laser wave emit strong high-frequency radiation, enabling a cooling effect, which helps to sustain high charge neutrality in the piston and to maintain an efficient ion acceleration.

Relativistic hole boring and fast ion ignition with ultra-intense laser pulses

“…Numerical simulations of ion acceleration One-dimensional PIC simulations [2] confirm the analytical predictions of the piston model. Two-dimensional [1,3] and three-dimensional [4] PIC simulations of the ponderomotive ion acceleration with intense laser pulses provide an additional information about the angular divergence of the accelerated ions and the stability of the hole boring process.…”

Numerical studies of acceleration of thorium ions by a laser pulse of ultra-relativistic intensity

“…The beam intensity was equal to 1.0*10 23 W/cm 2 for the flat target and 1.1*10 22 W/cm 2 for the hemispherical one. For both considered cases the laser pulse parameters correspond to the radiation pressure acceleration (RPA) mechanism domination range [10,11,12,13]. However, for the flat target the relativistic transparency [14,15] of the target is observed (Fig.1c) since the electron density in the interaction area decreases below the relativistic critical density (e* n crrel =3.0*10 4 C/cm 3 ).…”

Reaching high flux in laser-driven ion acceleration

“…The acceleration mechanism relies on the laser pulse piling up a thin electron spike, pushed forward by the ponderomotive force at the so-called piston velocity v piston = cΞ/(1 + Ξ), where the parameter Ξ = I/(m p n 0 c 3 ) [29] is introduced.…”

“…Among the standard of these novel acceleration schemes is, e.g., Coulomb explosion (CE) of clusters [20][21][22] and double-layered targets [23][24][25][26], designed to provide narrow energy spreads for the generated ion beams. Next to these schemes, which still rely on an expanding electron cloud due to local plasma heating, new schemes were introduced promising a more direct energy transfer from the laser pulse to an accelerated ion bunch, such as collisionless shock acceleration [27,28], hole boring (HB) [29] or laser piston, also referred to as light sail (LS) [30][31][32][33][34], or entirely new approaches [35]. Hole boring and light sail acceleration schemes aim at directly employing the laser's light pressure to move the plasma electrons, which subsequently pull the heavier ions by the Coulomb field, thus promising a more controllable energy transfer and hence more easily tunable ion bunch properties as well as a higher efficiency.…”