The reflection and transmission of a few-cycle femtosecond Ti:Sa laser pulse impinging on a metal nano-layer have been analysed. The thickness of the layer was assumed to be of order of 2-10 nm, and the metallic free electrons were represented by a surface current density distributed at the plane boundary of a dielectric substrate. The target studied this way can be imagined, for instance, as a semi-transparent mirror produced by evapotating a thin aluminum layer on the surface of a glass plate. The exact analytic solution has been given for the system of the coupled Maxwell-Lorentz equations decribing the dynamics of the surface current and the scattered radiation fields. It has been shown that in general a non-oscillatoty frozen-in wake-field appears following the main pulse with an exponential decay and with a definite sign of the electric field. The characteristic time of these wake-fields is inversely proportional with the square of the plasma frequency and with the thickness of the metal nano-layer, and can be larger than the original pulse duration. The magnitude of these wake-fields is proportional with the incoming field strength, and the definite sign of them governed by the cosine of the carrier-envelope phase difference of the incoming ultrashort laser pulse. As a consequence, when we let such a wake-field excite the electrons of a secondary target (say an electron beam, a metal plate or a gas jet), we obtain 100 percent modulation in the electron signal in a given direction, as we vary the carrier-envelope phase difference. This scheeme can perhaps serve as a basis for the construction of a robust linear carrier-envelope phase difference meter.
In the present work, we demonstrate for the first time a proof-of-principle experiment for nanoparticle-assisted laser wakefield acceleration. The nanoparticles, generated through laser ablation of aluminium, were introduced into the plasma and used to trigger the injection of electrons into the nonlinear plasma wake excited by a high power femtosecond laser. In this experiment, a significant enhancement of the electron beam energy, energy spread and divergence is obtained compared with the case when electrons are self-injected. The best quality electron bunches presented peak energy up to 338…
We present a theoretical investigation of the excitation of multiple electrostatic wakefields by the ponderomotive force of a short electromagnetic pulse propagating through a dense plasma. It is found that the inclusion of the quantum statistical pressure and quantum electron tunneling effects can qualitatively change the classical behavior of the wakefield. In addition to the well known plasma oscillation wakefield, with a wavelength of the order of the electron skin depth, which in a dense plasma is of the order of several nanometers, wakefields in dense plasmas with a shorter wavelength ar…
Generation of wake fields by a short electromagnetic pulse in a plasma with an inhomogeneous background magnetic field and density profile is considered, and a wave equation is derived. Transmission and reflection coefficients are calculated in a medium with sharp discontinuities. Particular attention is focused on examples where the longitudinal part of the electromagnetic field is amplified for the transmitted wave. Furthermore, it is noted that the wake field can propagate out of the plasma and thereby provide information about the electron density profile. A method for reconstructing the b…
Metre-scale plasma wakefield accelerators have imparted energy gain approaching 10 gigaelectronvolts to single nano-Coulomb electron bunches. To reach useful average currents, however, the enormous energy density that the driver deposits into the wake must be removed efficiently between shots. Yet mechanisms by which wakes dissipate their energy into surrounding plasma remain poorly understood. Here, we report ps-time-resolved, grazing-angle optical shadowgraphic measurements and large-scale particle-in-cell simulations of ion channels emerging from broken wakes that electron bunches from the …
Significant proton fluxes were detected in the near wake region of the Moon by an ion mass spectrometer on board Chandrayaan-1. The energy of these nightside protons is slightly higher than the energy of the solar wind protons. The protons are detected close to the lunar equatorial plane at a $140^{\circ}$ solar zenith angle, i.e., ~50$^{\circ}$ behind the terminator at a height of 100 km. The protons come from just above the local horizon, and move along the magnetic field in the solar wind reference frame. We compared the observed proton flux with the predictions from analytical models of an…
Recently NAano-Plasmonic, Laser Inertial Fusion Experiments (NAPLIFE) were proposed, as an improved way to achieve laser driven fusion. The improvement is the combination of two basic research discoveries: (i) The possibility of detonations on space-time hyper-surfaces with time-like normal (i.e. simultaneous detonation in a whole volume) and (ii) to increase this volume to the whole target, by regulating the laser light absorption using nano-shells or nano-rods as antennas. These principles can be realized in an in-line, one dimensional configuration, in the simplest way with two opposing las…
Ionization injection triggered by short wavelength laser pulses inside a nonlinear wakefield driven by a longer wavelength laser is examined via multi-dimensional particle-in-cell simulations. We find that very bright electron beams can be generated through this two-color scheme in either collinear propagating or transverse colliding geometry. For a fixed laser intensity $I$, lasers with longer/shorter wavelength $λ$ have larger/smaller ponderomotive potential ($\propto I λ^2$). The two color scheme utilizes this property to separate the injection process from the wakefield excitation process.…
Ionization injection is attractive as a controllable injection scheme for generating high quality electron beams using plasma-based wakefield acceleration. Due to the phase dependent tunneling ionization rate and the trapping dynamics within a nonlinear wake, the discrete injection of electrons within the wake is nonlinearly mapped to discrete final phase space structure of the beam at the location where the electrons are trapped. This phenomenon is theoretically analyzed and examined by three-dimensional particle-in-cell simulations which show that three dimensional effects limit the wave num…
It has been shown that in the scattered radiation, generated by an ultrashort laser pulse impinging on a metal nano-layer, non-oscillatory wake-fields appear with a definite sign. The magnitude of these wake-fields is proportional with the incoming field strength, and a sign of them is governed by the cosine of the carrier-envelope phase difference of the incoming pulse. At relativistic laser intensities the target is considered as a plasma layer in vacuum, produced from a thin foil by a pre-pulse, which is followed by the main high-intensity laser pulse. The nonlinearities stemming from the r…
Pulsed laser intensity dependence of crater formation and light reflection in the UDMA-TEGDMA copolymer nanocomposite, doped with resonant plasmonic gold nanorods
Achieving High Efficiency And Enhanced Beam Quality In Laser Wakefield Acceleration
Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS)（中国科学院上海光学精密机械研究所）
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 $λ_{\rm las}$. 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, thu…
