Plasma-grating-based laser pulse compressor.

To avoid damage in high-power laser systems, a chirped plasma-based grating is proposed for compressing laser pulses that have been previously stretched and amplified. This chirped grating is generated through the interaction of chirped pump laser pulses in a plasma slab. Particle-in-cell (PIC) simulations demonstrate that the grating exists for a duration sufficient to be utilized in the final chirped pulse amplification (CPA) stage.

Formation and properties of spatially inhomogeneous plasma density gratings.

Volume plasma density gratings receive increasing interest since, compared to solid-state optical media, they posses significantly higher damage thresholds. The gratings are produced by counterpropagating laser pulses in underdense plasma. When analyzing their optical properties, usually they are assumed to be homogeneous in space.

Plasma volume holograms for focusing and mode conversion of ultraintense laser pulses.

Beating of a broad laser reference beam with a quite general focused object beam inside a plasma volume generates a dynamic plasma hologram. Both beams may be of moderate intensity. The volume hologram can be read out by an ultraintense main beam (of similar structure as the reference beam) producing an object beam replica.

Plasma-based polarizer and waveplate at large laser intensity.

A plasma photonic crystal consists of a plasma density grating which is created in underdense plasma by counterpropagating laser beams. When a high-power laser pulse impinges the crystal, it might be reflected or transmitted. So far only one type of pulse polarization, namely the so-called s wave (or TE mode) was investigated (when the electric field vector is perpendicular to the plane of incidence).

Parametric pulse amplification by acoustic quasimodes in electron-positron plasma.

In a recent paper, M. R. Edwards, N.

Transient Plasma Photonic Crystals for High-Power Lasers.

A new type of transient photonic crystals for high-power lasers is presented. The crystal is produced by counterpropagating laser beams in plasma. Trapped electrons and electrically forced ions generate a strong density grating.

Pulse shaping during Raman-seed amplification for short laser pulses.

Raman-seed pulse amplification in a one-dimensional backscattering geometry is investigated with the help of numerical simulations and analytical estimates. The significant dependence of the initial amplification on the pulse form is revisited on the basis of a three-wave interaction as well as a kinetic Vlasov model. It is shown how the short duration of the input seed pulse influences its subsequent behavior, depending on plasma density and pump strength.

Phase-space contraction and attractors for ultrarelativistic electrons.

Ultrashort-pulse laser intensities can reach 10(22) W/cm(2). In this case the electron motion becomes ultrarelativistic and significant bremsstrahlung occurs. The radiation causes a dissipative effect, which is called a radiation reaction.

Diffusion in a collisional standard map.

Test particle evaluation of the diffusion coefficient in the presence of magnetic field fluctuations and binary collisions is presented. Chaotic magnetic field lines originate from resonant magnetic perturbations (RMPs). To lowest order, charged particles follow magnetic field lines.

Energy gain of an electron by a laser pulse in the presence of radiation reaction.

A well-known no-energy-gain theorem states that an electron cannot gain energy when being overrun by a plane (transverse) laser pulse of finite length. The theorem is based on symmetries which are broken when radiation reaction (RR) is included. It is shown here that an electron, e.

Poincaré analysis of wave motion in ultrarelativistic electron-ion plasmas.

Based on a relativistic Maxwell-fluid description, the existence of ultrarelativistic laser-induced periodic waves in an electron-ion plasma is investigated. Within a one-dimensional propagation geometry nonlinear coupling of the electromagnetic and electrostatic components occurs that makes the fourth-order problem nonintegrable. A Hamiltonian description is derived, and the manifolds of periodic solutions are studied by Poincaré section plots.

Numerical modeling of edge-localized-mode filaments on divertor plates based on thermoelectric currents.

Edge localized modes (ELMs) are qualitatively and quantitatively modeled in tokamaks using current bursts which have been observed in the scrape-off-layer (SOL) during an ELM crash. During the initial phase of an ELM, a heat pulse causes thermoelectric currents. They first flow in short connection length flux tubes which are initially established by error fields or other nonaxisymmetric magnetic perturbations.

Directed chaotic transport in the tokamap with mixed phase space.

On the basis of the tokamap, characteristic features of magnetic field lines and zeroth-order guiding-center particle motion in the whole body of a magnetically confined plasma, e.g., a tokamak plasma, are investigated.

Sheared plasma rotation in partially stochastic magnetic fields.

It is shown that resonant magnetic perturbations generate sheared flow velocities in magnetized plasmas. Stochastic magnetic fields in incomplete chaos influence the drift motion of electrons and ions differently. Using a fast mapping technique, it is demonstrated that a radial electric field is generated due to the different behavior of passing particles (electrons and ions) in tokamak geometry; magnetic trapping of ions is neglected.

Improved confinement due to open ergodic field lines imposed by the dynamic ergodic divertor in TEXTOR.

The ergodization of the magnetic field lines imposed by the dynamic ergodic diverter (DED) in TEXTOR can lead both to confinement improvement and to confinement deterioration. The cases of substantial improvement are in resonant ways related to particular conditions in which magnetic flux tubes starting at the X points of induced islands are connected with the wall. This opening process is connected with a characteristic modification of the heat deposition pattern at the divertor target plate and leads to a substantial increase and steepening of the core plasma density and pressure.

Diffusion of test particles in stochastic magnetic fields in the percolative regime.

For stochastic magnetic flux functions with percolative contours the test particle transport is investigated. The calculations make use of the stochastic Liouville approach. They start from the so-called A-Langevin equations, including stochastic magnetic field components and binary collisions.

Diffusion of test particles in stochastic magnetic fields for small Kubo numbers.

Motion of charged particles in a collisional plasma with stochastic magnetic field lines is investigated on the basis of the so-called A-Langevin equation. Compared to the previously used A-Langevin model, here finite Larmor radius effects are taken into account. The A-Langevin equation is solved under the assumption that the Lagrangian correlation function for the magnetic field fluctuations is related to the Eulerian correlation function (in Gaussian form) via the Corrsin approximation.

Change of the magnetic-field topology by an ergodic divertor and the effect on the plasma structure and transport.

The magnetic-field perturbation produced by the dynamic ergodic divertor in TEXTOR changes the topology of the magnetic field in the plasma edge, creating an open chaotic system. The perturbation spectrum contains only a few dominant harmonics and therefore it can be described by an analytical model. The modeling is performed in the vacuum approximation without assuming a backreaction of the plasma and does not rely on any experimentally obtained parameters.

Toroidal plasma rotation induced by the dynamic ergodic divertor in the TEXTOR tokamak.

The first results of the Dynamic Ergodic Divertor in TEXTOR, when operating in the m/n=3/1 mode configuration, are presented. The deeply penetrating external magnetic field perturbation of this configuration increases the toroidal plasma rotation. Staying below the excitation threshold for the m/n=2/1 tearing mode, this toroidal rotation is always in the direction of the plasma current, even if the toroidal projection of the rotating magnetic field perturbation is in the opposite direction.

Chirped solitons as attractors for short light pulses.

Nonlinear chirped pulse solutions are shown to exist as stable attractors for short light pulses in driven and damped systems. The attractors are determined for systems of different complexity, from simple gain and damping modelings up to the inclusion of higher-order dispersion, Raman processes, and delayed nonlinear responses. The chirped attractors, their stability, as well as the attractor basins can be determined analytically.

Averaged dynamics of optical pulses described by a nonlinear Schrödinger equation with periodic coefficients.

A nonlinear Schrödinger equation with periodic coefficients, as it appears, e.g., in nonlinear optics, is considered.

Chirped femtosecond solitonlike laser pulse form with self-frequency shift.

Ultrashort laser pulse propagation in a generalized nonconservative system is considered. Slopes appearing in the form of the third-order time derivative for narrow pulse widths, nonlinear dispersion, and self-frequency shift arising from stimulated Raman scattering are taken into account. An exact analytical solitonlike solution is presented for a femtosecond solitary laser pulse.

Gray optical dips in the subpicosecond regime.

Narrow optical dip solutions are investigated when, besides self-phase modulation and group velocity dispersion, also third-order dispersion, nonlinear dispersion, and stimulated Raman scattering are taken into account. By using the inverse scattering transform for the higher-order optical nonlinear Schrödinger (HNLS) equation under Hirota parameter conditions, the dark N-soliton solution is constructed. The explicit forms of the one- and two-soliton solutions are investigated in detail.

Rescaling invariance and anomalous transport in a stochastic layer.

The anomalous chaotic transport in a one-degree-of-freedom Hamiltonian system subjected to a small time-periodic perturbation is investigated. Strong quasiperiodic dependencies of the statistical properties of the motion on log epsilon are found, where epsilon is a perturbation parameter. The period log lambda depends on the rescaling parameter lambda, which is determined only by the frequency of perturbation and behavior of unperturbed Hamiltonian near a saddle point.

Angular transport in a nonperiodic Chirikov-Taylor map.

Transport in angular direction is considered for a nonperiodic Chirikov-Taylor (standard) map. In the limit of large stochasticity parameter, depending on the boundary conditions of the action variable, either superdiffusive of diffusive behavior is found. In both cases characteristic oscillations in the transport coefficients occur.