Thin Plasma Foil Research Articles

Plasma concept for generating circularly polarized electromagnetic waves with relativistic amplitude

Propagation features of circularly polarized (CP) electromagnetic waves in magnetized plasmas are determined by the plasma density and the magnetic field strength. This property can be applied to design a unique plasma photonic device for intense short-pulse lasers. We have demonstrated by numerical simulations that a thin plasma foil under an external magnetic field works as a polarizing plate to separate a linearly polarized laser into two CP waves traveling in the opposite direction. This plasma photonic device has an advantage for generating intense CP waves even with a relativistic amplitude. For various research purposes, intense CP lights are strongly required to create high energy density plasmas in the laboratory.

Unstable longitudinal expansion of plasma foils accelerated by circularly polarized laser pulses in non-transparent regimes

Relativistic opaqueness has been considered to be a sufficient condition for the stable compression and acceleration of a negligibly thin plasma foil by a circularly polarized laser pulse. However, in our simulations, we observed that finite-thick plasma foils, which are still relativistically nontransparent to the laser pulse, can be subject to sudden and rapid expansion of the foil even when the pulse intensity is expected to be high enough to suppress the electrostatic Coulomb expansion. Analyzing the “distribution” of the ponderomotive force over the finite thickness of a slab-like foil, we found a theoretical condition to avoid the new expansion mechanism. Relations between this expansion and the relativistic electron heating and self-induced transparency are discussed.

Generation of attosecond electron packets in the interaction of ultraintense Laguerre – Gaussian laser beams with plasma

The interaction of a thin plasma foil with two counterpropagating circularly polarised Laguerre – Gaussian laser beams of ultra-high intensity is studied using pwarticle-in-cell simulations in a fully three-dimensional geometry. It is found that within the course of the interaction, bunched electron packets are generated from the plasma target. Each packet has a duration of about 830 attoseconds, and adjacent bunches are spatially separated by one laser wavelength. The emitted electron packets move at ultrarelativistic velocities along the axis of laser propagation.

Nonlinear interaction of ultraintense laser pulse with relativistic thin plasma foil in the radiation pressure-dominant regime

We present a study of the effect of laser pulse temporal profile on the energy /momentum acquired by the ions as a result of the ultraintense laser pulse focussed on a thin plasma layer in the radiation pressure-dominant (RPD) regime. In the RPD regime, the plasma foil is pushed by ultraintense laser pulse when the radiation cannot propagate through the foil, while the electron and ion layers move together. The nonlinear character of laser–matter interaction is exhibited in the relativistic frequency shift, and also change in the wave amplitude as the EM wave gets reflected by the relativistically moving thin dense plasma layer. Relativistic effects in a high-energy plasma provide matching conditions that make it possible to exchange very effectively ordered kinetic energy and momentum between the EM fields and the plasma. When matter moves at relativistic velocities, the efficiency of the energy transfer from the radiation to thin plasma foil is more than 30% and in ultrarelativistic case it approaches one. The momentum /energy transfer to the ions is found to depend on the temporal profile of the laser pulse. Our numerical results show that for the same laser and plasma parameters, a Lorentzian pulse can accelerate ions upto 0.2 GeV within 10 fs which is 1.5 times larger than that a Gaussian pulse can.

激光与等离子体薄膜作用中的陡峭上升沿激光脉冲的产生

激光与等离子体薄膜作用中的陡峭上升沿激光脉冲的产生

Spatiotemporal evolution of a thin plasma foil with Kappa distribution

AbstractThe one-dimensional behavior of a thin plasma foil heated by laser is studied, emphasizing on the fully kinetic effects associated with initial energetic electrons using a relativistic kinetic 1D3V Particle-In-Cell code. For this purpose, the generalized Lorentzian (Kappa) function inclusive the high energy tail is employed for initial electron distribution. The presence of the initially high-energy electrons leads to a different ion energy spectrum than the initially Maxwellian distribution. It is shown for the smaller Kappa parameter k where the high energy tail of the electron distribution function becomes more significant, the electron cooling rate increases. Moreover, the spatiotemporal evolution of electric field is strongly affected by the initial super-thermal electrons.

Radiation-pressure-dominant acceleration: Polarization and radiation reaction effects and energy increase in three-dimensional simulations

Polarization and radiation reaction (RR) effects in the interaction of a superintense laser pulse (I>10(23) W cm-2) with a thin plasma foil are investigated with three dimensional particle-in-cell (PIC) simulations. For a linearly polarized laser pulse, strong anisotropies such as the formation of two high-energy clumps in the plane perpendicular to the propagation direction and significant radiation reactions effects are observed. On the contrary, neither anisotropies nor significant radiation reaction effects are observed using circularly polarized laser pulses, for which the maximum ion energy exceeds the value obtained in simulations of lower dimensionality. The dynamical bending of the initially flat plasma foil leads to the self-formation of a quasiparabolic shell that focuses the impinging laser pulse strongly increasing its energy and momentum densities.

Radiation reaction effects on electron nonlinear dynamics and ion acceleration in laser–solid interaction

Radiation Reaction (RR) effects in the interaction of an ultra-intense laser pulse with a thin plasma foil are investigated analytically and by two-dimensional (2D3P) Particle-In-Cell (PIC) simulations. It is found that the radiation reaction force leads to a significant electron cooling and to an increased spatial bunching of both electrons and ions. A fully relativistic kinetic equation including RR effects is discussed and it is shown that RR leads to a contraction of the available phase space volume. The results of our PIC simulations are in qualitative agreement with the predictions of the kinetic theory.

Radiation reaction effects on radiation pressure acceleration

Radiation reaction (RR) effects on the acceleration of a thin plasma foil by a superintense laser pulse in the radiation pressure-dominated regime are investigated theoretically. A simple suitable approximation of the Landau–Lifshitz equation for the RR force and a novel leap-frog pusher for its inclusion in particle-in-cell simulations are provided. Simulations for both linear and circular polarization of the laser pulse are performed and compared. It is found that at intensities exceeding 1023 W cm− 2 the RR force strongly affects the dynamics for a linearly polarized laser pulse, reducing the maximum ion energy but also the width of the spectrum. In contrast, no significant effect is found for circularly polarized laser pulses whenever the laser pulse does not break through the foil.

Influence of the Weibel instability on the expansion of a plasma slab into a vacuum

The development of the Weibel instability during the expansion of a thin plasma foil heated by an intense laser pulse is investigated, using both analytical models and relativistic particle-in-cell simulations. When the plasma has initially an anisotropic electron distribution, this electromagnetic instability develops from the beginning of the expansion. Then it contributes to suppress the anisotropy and eventually saturates. After the saturation, the strength of the magnetic field decreases because of the plasma expansion until it becomes too weak to maintain the distribution isotropic. For this time, the anisotropy rises as electrons give progressively their longitudinal energy to ions, so that a new instability can develop.

Rarefaction Acceleration and Kinetic Effects in Thin-Foil Expansion into a Vacuum

The collisionless expansion into a vacuum of a thin plasma foil adiabatically cooling down is studied with a particular emphasis on the evolution of the electron distribution function. It is shown that during the expansion the bulk of the distribution function evolves towards a top-hat distribution. As a result, while the electrons globally lose energy in favor of the ions, the rarefaction wave accelerates until it reaches the center of the foil. The electron temperature becomes strongly inhomogeneous, with a maximum in the center of the foil, a strong dip in the outer part of the foil, and a constancy of the initial temperature in the far corona.

Stability of a plasma foil in the radiation pressure dominated regime

The stability of a thin plasma foil accelerated to relativistic velocities by the radiation pressure of an ultra high intensity electromagnetic pulse is investigated. The effects of the onset of a Rayleigh-Taylor-like instability are discussed in the context of the ion acceleration process during the interaction of the laser pulse with the plasma. It is stressed that the experimental study of this advanced laser plasma interaction regime will be accessible within the framework of the ELI experiment and will be of relevance for our understanding of high energy astrophysical phenomena.

Ion acceleration and stability in the radiation pressure dominated regime

We investigate the stability against the onset of Rayleigh-Taylor modes of a thin plasma foil accelerated by the radiation pressure. We are interested in the process of ion acceleration in the interaction between a plasma foil and an ultraintense laser pulse in the so-called Radiation Pressure Dominated Regime. We show that in the relativistic regime the Rayleigh-Taylor instability develops more slowly than in the non-relativistic regime. We show that the onset of the Rayleigh-Taylor-like instability leads to the formation of high-density, high-energy plasma clumps and to a relatively higher rate of ion acceleration in the regions between the clumps.

Photon Bubbles and Ion Acceleration in a Plasma Dominated by the Radiation Pressure of an Electromagnetic Pulse

The stability of a thin plasma foil accelerated by the radiation pressure of a high intensity electromagnetic (e.m.) pulse is investigated analytically and with particle in cell numerical simulations. It is shown that the onset of a Rayleigh-Taylor-like instability can lead to transverse bunching of the foil and to broadening of the energy spectrum of fast ions. The use of a properly tailored e.m. pulse with a sharp intensity rise can stabilize the foil acceleration.

High-order Harmonic Generation in Ultra Thin Plasma Foil

Via l-D Particle In Cell (PIC) simulations, we investigated the high-order harmonic emission from flim plasma foils irradiated by two circular- polarized, counter-propagating laser pulses with their electrical vectors rotating in different directions. More than 200 harmonics can be generated with a laser intensity of 1021 W/cm2. When the duration of laser gets shorter, the frequencies of harmonics were severely modulated due to the Doppler shift caused by the movement of the plasma boundary when the foil is being compressed. The Doppler shift can be estimated by the simulation results, and this effect can also be reduced or modified by introducing frequency chirping to the pump pulse.