Plasma ion evolution in the wake of a high-intensity ultrashort laser pulse.

Experimental investigations of the late-time ion structures formed in the wake of an ultrashort, intense laser pulse propagating in a tenuous plasma have been performed using the proton imaging technique. The pattern found in the wake of the laser pulse shows unexpectedly regular modulations inside a long, finite width channel. On the basis of extensive particle in cell simulations of the plasma evolution in the wake of the pulse, we interpret this pattern as due to ion modulations developed during a two-stream instability excited by the return electric current generated by the wakefield.

Small-scale electron density and magnetic-field structures in the wake of an ultraintense laser pulse.

We investigate the interaction of a high intensity ultrashort laser pulse with an underdense collisionless plasma in the regime where the Langmuir wake wave excited behind the laser pulse is loaded by fast particle beams, formed during the wake wave breaking. The beam loading causes the deterioration of the central part of the wake wave near the pulse axis, and the formation of bunches of sharply focalized ultrarelativistic electrons. The bunches of electrons generate a fast propagating magnetic field, which we interpret in terms of the magnetic component of the Lienard-Wiechert potential of a moving electric charge.

Surface oscillations in overdense plasmas irradiated by ultrashort laser pulses.

The generation of electron surface oscillations in overdense plasmas irradiated at normal incidence by an intense laser pulse is investigated. Two-dimensional (2D) particle-in-cell simulations show a transition from a planar, electrostatic oscillation at 2 omega, with omega the laser frequency, to a 2D electromagnetic oscillation at frequency omega and wave vector k > omega/c. A new electron parametric instability, involving the decay of a 1D electrostatic oscillation into two surface waves, is introduced to explain the basic features of the 2D oscillations.

High density collimated beams of relativistic ions produced by petawatt laser pulses in plasmas.

Under optimal interaction conditions ions can be accelerated up to relativistic energies by a petawatt laser pulse in both underdense and overdense plasmas. Two-dimensional particle in cell simulations show that the laser pulse drills a channel through an underdense plasma slab due to relativistic self-focusing. Both ions and electrons are accelerated in the head region of the channel.