V. A. Vshivkov

Ion acceleration by superintense laser pulses in plasmas

Ion acceleration by petawatt laser radiation in underdense and overdense plasmas is studied with 2D3V-PIC (Particle in Cell) numerical simulations. These simulations show that the laser pulse drills a channel through the plasma slab, and electrons and ions expand in vacuum. Fast electrons escape first from the electron-ion cloud. Later, ions gain a high energy on account of the Coulomb explosion of the cloud and the inductive electric field which appears due to fast change of the magnetic field generated by the laser pulse. Similarly, when a superintense laser pulse interacts with a thin slab of overdense plasma, its ponderomotive pressure blows all the electrons away from a finite-diameter spot on the slab. Then, due to the Coulomb explosion, ions gain an energy as high as 1 GeV.

Generation of subcycle relativistic solitons by super intense laser pulses in plasmas

Abstract 2D and 3D particle in cell simulations of the interaction of ultra-short, high-intensity laser pulses with inhomogeneous plasmas show the formation of long-lived electromagnetic solitons. These solitons consist of electron density depressions and intense electromagnetic field concentrations with a bigger amplitude and a lower frequency than those of the laser pulse. A significant portion of the electromagnetic energy is trapped in the form of solitons. Due to the plasma inhomogeneity, the solitons propagate toward the plasma–vacuum interface where they radiate away their energy in the form of bursts of low frequency electromagnetic radiation.

Magnetic fields from high-intensity laser pulses in plasmas

In a plasma interacting with ultra-short, high-intensity laser pulses, the magnetic part of the Lorentz force on the electrons can become as important as the electric part. In this case, we can expect the magnetic field to change the pattern of the nonlinear laser-pulse - plasma interaction drastically. The relativistic nonlinearities introduced by the magnetic interaction are of general interest in relation to the field of ultra-strong electromagnetic waves propagating in media, high-energy space plasmas and laser - plasma interaction under laboratory conditions. We present a summary of analytical and numerical results concerning the generation of quasi-static magnetic fields by high-intensity laser pulses in underdense plasmas and in thin plasma foils, and discuss the dynamical effects of these fields on the plasma motion and on the pulse propagation. This analysis indicates that phenomena such as current pinching, reconnection of magnetic-field lines and vortex propagation etc, that have been previously discussed in the case of space and laboratory plasmas, are also important for laser - plasma interactions.

Relativistic electromagnetic solitons produced by ultrastrong laser pulses in plasmas

Low frequency, relativistic sub‐cycle localised (soliton‐like) concentrations of the electromagnetic (em) energy are found in two‐dimensional (2D) and in three‐dimensional (3D) Particle in Cell simulations of the interaction of ultra‐short, high‐intensity laser pulses with homogeneous and inhomogeneous plasmas. These solitons consist of electron and ion density depressions and intense em field concentrations with a frequency definitely lower than that of the laser pulse. The downshift of the pulse frequency, due to the depletion of the pulse energy, causes a significant portion of the pulse em energy to become trapped as solitons, slowly propagating inside the plasma. In an earlier phase solitons are formed due to the trapping of the em radiation inside an electron cavity, while ions can be assumed to remain at rest. Later on, after (mi/me)1/2 times the laser period, ions start to move and the ion depletion occurs producing a slowly growing hole in the plasma density. In inhomogeneous plasmas the solitons are accelerated toward the plasma vacuum interface where they radiate away their energy in the form of bursts of low frequency em radiation. In the frame of a 1D cold hydrodynamic model for an electron‐ion plasma, the existence of multipeaked em solitons has been investigated both analytically and numerically. The analytical expression for a sub‐cycle relativistic soliton has been derived for circularly polarized pulses in a cold isotropic plasma, and in the presence of an externally applied magnetic field. Recently, em relativistic solitons in a hot multi‐component plasma have been investigated in the frame of an hydrodynamic (adiabatic) model and of a kinetic (isothermal) model. An overview of the most recent analytical and numerical results on the soliton dynamics is given.Low frequency, relativistic sub‐cycle localised (soliton‐like) concentrations of the electromagnetic (em) energy are found in two‐dimensional (2D) and in three‐dimensional (3D) Particle in Cell simulations of the interaction of ultra‐short, high‐intensity laser pulses with homogeneous and inhomogeneous plasmas. These solitons consist of electron and ion density depressions and intense em field concentrations with a frequency definitely lower than that of the laser pulse. The downshift of the pulse frequency, due to the depletion of the pulse energy, causes a significant portion of the pulse em energy to become trapped as solitons, slowly propagating inside the plasma. In an earlier phase solitons are formed due to the trapping of the em radiation inside an electron cavity, while ions can be assumed to remain at rest. Later on, after (mi/me)1/2 times the laser period, ions start to move and the ion depletion occurs producing a slowly growing hole in the plasma density. In inhomogeneous plasmas the solitons...

Ultra intense magnetic fields in laser plasma interaction: their generation and influence on light propagation

Extremely large, quasi-stationary magnetic fields can be generated in plasmas by high intensity laser pulses. These fields can change the plasma dynamics and the pulse propagation. Several aspects of their generation and of their effect on the plasma and on the laser pulse are discussed in the relativistic pulse amplitude regime: (a) the formation of magnetic wakes, (b) the development of longitudinal and transverse Langmuir wake wavebreaks and (c) the magnetic field generation on a thin foil, viewed as a model for overdense plasmas with sharp boundaries.