Exact charge conservation scheme for Particle-in-Cell simulations for a big class of form-factors

As an alternative to solving of Poisson equation in Particle-in-Cell methods, a new construction of current density exactly satisfying continuity equation in finite differences is developed. This procedure called density decomposition is proved to be the only possible linear procedure for defining the current density associated with the motion of a particle. Density decomposition is valid at least for any n-dimensional form-factor which is the product of one-dimensional form-factors. The algorithm is demonstrated for parabolic spline form-factor.Comment: 13 pages, Latex 2.09, no figures, bibliography 10 entrie

Fundamental Physics and Relativistic Laboratory Astrophysics with Extreme Power Lasers

The prospects of using extreme relativistic laser-matter interactions for laboratory astrophysics are discussed. Laser-driven process simulation of matter dynamics at ultra-high energy density is proposed for the studies of astrophysical compact objects and the early universe.Comment: 12 pages, 15 figures. Invited talk at European Conference on Laboratory Astrophysics (ECLA), 26-30 September, 2011, Paris, France. Submitted to European Astronomical Society Publications Serie

Ultrahigh Light Intensification by a Counter-Propagating Breaking Plasma Wave - Relativistic Flying Parabolic Mirror

A method to generate ultrahigh intense electromagnetic fields is suggested, based on the laser pulse compression, carrier frequency upshift and focusing by a counter-propagating breaking plasma wave, relativistic flying parabolic mirror. This method allows us to achieve the quantum electrodynamics critical field (Schwinger limit) with present day laser systems.Comment: 5 pages, 2 figures; http://wwwapr.apr.jaeri.go.jp/aprc/e/results/simulation/timur/mirror

Bow wave from ultra-intense electromagnetic pulses in plasmas

We show a new effect of the bow wave excitation by an intense short laser pulse propagating in underdense plasma. Due to spreading of the laser pulse energy in transverse direction, the bow wave causes a large-scale transverse modulation of the electron density. This can significantly increase the electric potential of the wake wave since the wake wave is generated in the region much wider than the laser pulse waist.Comment: 6 pages, 4 figure

Relativistic Mirrors in Laser Plasmas (Analytical Methods)

Relativistic flying mirrors in plasmas are realized as thin dense electron (or electron-ion) layers accelerated by high-intensity electromagnetic waves to velocities close to the speed of light in vacuum. The reflection of an electromagnetic wave from the relativistic mirror results in its energy and frequency changing. In a counter-propagation configuration, the frequency of the reflected wave is multiplied by the factor proportional to the Lorentz factor squared. This scientific area promises the development of sources of ultrashort X-ray pulses in the attosecond range. The expected intensity will reach the level at which the effects predicted by nonlinear quantum electrodynamics start to play a key role.Comment: 24 pages, 8 figures, This review article is based on the materials of the plenary lecture presented at the ICPIG-2015 conference (Iasi, Romania, 2015) by S.V.

Similarity of magnetized plasma wake channels behind relativistic laser pulses with different wavelengths

Using particle-in-cell simulations of relativistic laser plasma wakes in the presence of an external magnetic field, we demonstrate that there exists a parameter window where the dynamics of the magnetized wake channel are largely independent of the laser wavelength $\lambda_{\rm las}$. One condition for this manifestation of "limited similarity" is that the electron density $n_{\rm e}$ is highly subcritical, so that the plasma does not affect the laser. The freedom to choose a convenient laser wavelength can be useful in experiments and simulations. In simulations, an up-scaled wavelength (and, thus, a coarser mesh and larger time steps) reduces the computational effort, while limited similarity ensures that the overall structure and evolutionary phases of the wake channel are preserved. In our demonstrative example, we begin with a terrawatt$\cdot$picosecond pulse from a ${\rm CO}_2$ laser with $\lambda_{\rm las} = 10\,\mu{\rm m}$, whose field reaches a relativistic amplitude at the center of a sub-millimeter-sized focal spot. The laser is shot into a sparse deuterium gas ($n_{\rm e} \sim 10^{13}\,{\rm cm}^{-3}$) in the presence of a tesla-scale magnetic field. Limited similarity is demonstrated in 2D for $4\,\mu{\rm m} \leq \lambda_{\rm las} \leq 40\,\mu{\rm m}$ and is expected to extend to shorter wavelengths. Assuming that this limited similarity also holds in 3D, increasing the wavelength to $40\,\mu{\rm m}$ enables us to simulate the after-glow dynamics of the wake channel all the way into the nanosecond regime.Comment: 27 pages, 21 figure

On annihilation of the relativistic electron vortex pair in collisionless plasmas

In contrast to hydrodynamic vortices, vortices in plasma contain an electric current circulating around the center of the vortex, which generates a magnetic field localized inside. Using computer simulations, we demonstrate that the magnetic field associated with the vortex gives rise to a mechanism of dissipation of the vortex pair in a collisionless plasma, leading to fast annihilation of the magnetic field with its energy transforming into the energy of fast electrons, secondary vortices, and plasma waves. Two major contributors to the energy damping of double vortex system, namely, magnetic field annihilation and secondary vortex formation, are regulated by the size of the vortex with respect to the electron skin depth, which scales with the electron gamma-factor, $\gamma_e$, as $R/d_e \propto \gamma_e^{1/2}$. Magnetic field annihilation appears to be dominant in mildly relativistic vortices, while for the ultrarelativistic case, secondary vortex formation is the main channel for damping of the initial double vortex system.Comment: 6 pages, 4 figure

Directed Coulomb explosion effect on proton acceleration by an intense laser pulse from a double-layer target

We examine ion acceleration by irradiating a hundred TW laser pulse on a double-layer target. It is shown analytically and by three-dimensional particle-in-cell simulations that higher energy protons are obtained by using material with a high charge-to-mass ratio in the first layer of a double-layer target, because a strong Coulomb explosion occurs in such a material. As a result, the protons keep accelerating for a longer time. Using the optimal conditions for the target, it is shown that high energy and high quality protons can be generated.Comment: 6 pages, 5 figure

Relativistic Whistle: High Order Harmonics Induced by the Ultra-Intense Laser Pulse Propagating inside the Fiber

A propagation of an ultra-intense short laser pulse in a fiber is investigated with two dimensional Particle-in-Cell simulations. The fiber is a narrow hollow channel with walls consisting of overdense plasma. In the nonlinear interaction of the laser pulse with fiber walls high order harmonics are generated. Sufficiently high harmonics, for which the fiber walls are transparent, propagate outwards at certain angle. This is a scheme of a generator of ultra-short pulses of coherent light with a very short wavelength.Comment: 6 pages, 6 figure

Wakefield Excited by Ultrashort Laser Pulses in Near-Critical Density Plasmas

Laser wakefield acceleration (LWFA) using high repetition rate mJ-class laser systems brings unique opportunities for a broad range of applications. In order to meet the conditions required for the electron acceleration with lasers operating at lower energies, one has to use high density plasmas and ultrashort pulses. In the case of a few-cycle pulse, the dispersion and the carrier envelope phase effects can no longer be neglected. In this work, the properties of the wake waves generated by ultrashort pulse lasers in near-critical density plasmas are investigated. The results obtained may lead to enhancement of the quality of LWFA electron beams using kHz laser systems.Comment: 9 pages; presented at SPIE Optics + Optoelectronics, 2019, Prague, Czech Republi