A new concept of laser fusion driver is proposed, which uses a beam combination technique with stimulated Brillouin scattering phase conjugate mirror (SBS-PCM). It is constructed systematically with a cross-type amplifier as a basic unit. In the first part of this paper, we introduce the cross-type laser amplifier using SBS-PCM, with several advantages by experimental results. These advantages are the ideal properties for practical laser fusion driver, such as the perfect isolation of leak beam, the compensation of thermally induced birefringence through the amplifiers, the easy maintenance and alignment insensitiveness, and the freely-scale-up energy. Next, some successful results for the phase control of SBS-PCM are presented, which is one of the main problems in the current beam combination laser using SBS-PCM. Particularly, a new technique for controlling the phase of SBS-PCM, “self-density modulation,” is introduced, which is the simplest ever among those reported. With the advantages of the cross-type amplifier using SBS-PCM and the novel method for controlling the phase of SBS-PCM, the proposed beam combination laser system is presented as the most promising one, which can contribute to the realization of high energy laser that can operate with high repetition rate over 10 Hz, even in the case of huge output energy over MJ.

A scheme for electron acceleration by two crossing chirped lasers has been proposed. An important effect of a frequency chirp of the laser is investigated. Two high intensity chirped lasers, with the same amplitude and frequency, crossing at an arbitrary angle in a vacuum, interfere, causing modulation of laser intensity. An electron experiences a ponderomotive force due to the resultant field of lasers and gains considerable energy. For a certain crossing angle, the electron gains maximum energy due to the constructive interference. A frequency chirp of the laser plays an important role during the electron acceleration in a vacuum. The electron momentum increases due to the frequency chirp. Hence, the electron energy is enhanced during acceleration.

Bifurcation phenomenon in the energy-angular correlation spectrum of the vacuum laser acceleration has been observed with computer simulation. Concerning a focused laser pulse, the classical single-valued energy-angular correlation spectrum for a plane wave is, besides broadened to a band, bifurcated with the classical value in between the two branches. Analytic expression to describe the correlation has been derived and physical explanations based on the ponderomotive potential model and Lorentz-Newton force analyses are presented. The theoretical results are supported by numerical simulations which have been compared with the experimental results. This study is helpful in designing vacuum laser acceleration experiments.

Nitrogen lasers have been used for many years to make dye solutions lase. A nitrogen laser, which transverse electrical discharge in gas at atmospheric pressure has been built in our laboratory. It has been characterized and applied to pump different dyes: Rhodamine 6G, Coumarin 440, DOTCI, and pyranine in simple “on axis” geometric configuration. It has been shown that pyranine can lase in the absence of any optical external mirror cavity, this happens at very low threshold, and in different solvents. Dyes under consideration can be grouped into two major classes according to their lasing behavior independently on their concentration in the solvent: Rhodamine 6G and DOTCI can lase both axially or transversally and Coumarin 440 and pyranine can lase only axially. Other intriguing features have been observed that span from simultaneous multiple beam generation, to super fluorescence and to distribute axial pumping of dye solutions. A preliminary basis for understanding and controlling such processes is the spatial energy distribution and the energy density of the beam.

Laser plasma interaction experiments have been performed using an fs Titanium Sapphire laser. Plasmas have been generated from planar PMMA targets using single laser pulses with 3.3 mJ pulse energy, 50 fs pulse duration at 800 nm wavelength. The electron density distributions of the plasmas in different delay times have been characterized by means of Nomarski Interferometry. Experimental data were compared with hydrodynamic simulation. First results to characterize the plasma density and temperature as a function of space and time are obtained. This work aims to generate plasmas in the warm dense matter (WDM) regime at near solid-density in an ultra-fast laser target interaction process. Plasmas under these conditions can serve as targets to develop X-ray Thomson scattering as a plasma diagnostic tool, e.g., using the Vacuum ultraviolet (VUV) free-electron laser (FLASH) at Dentsches Elektronen-Synchrotron (DESY) Hamburg.

Magnetic confinement fusion (MCF) based on neutral particle beam irradiation reached the highest gains with JET and is discussed in relation to the ITER project for a possible re-orientation with respect to the ignition process. Ignition plays a similar role for inertial confinement fusion (ICF). After a short review about specific ICF developments, the fast igniter development offered a re-consideration of igniting DT fuel at modest or low compression. The observation of extreme anomalies (Sauerbrey 1996, Zhang et al., 1998 and Badziak et al., 1999) at interaction of picosecond (ps) laser pulses above TW power could be explained as a skin layer mechanism based on earlier computations (Hora et al., 2002) with nonlinear (ponderomotive) force acceleration. The resulting very high ion current density space charge neutral plasma blocks interacting as pistons to ignite DT may lead to a new scheme of laser fusion with low cost energy generation.

Three dimensional Particle-in-Cell (3D-PIC) simulations of electron acceleration in vacuum with radially polarized ultra-intense laser beams have been performed. It is shown that single-cycle laser pulses efficiently accelerate a single attosecond electron bunch to GeV energies. When multi-cycle laser pulses are used, one has to employ ionization of high-Z materials to inject electrons in the accelerating phase at the laser pulse maximum. In this case, a train of highly collimated attosecond electron bunches with a quasi-monoenergetic spectra is produced. A comparison with electron acceleration by Gaussian laser pulses has been done. It is shown that the radially polarized laser pulses are superior both in the maximum energy gain and in the quality of the produced electron beams.

Results of theoretical calculations and experimental measurements of the equation of state (EOS) at extreme conditions are discussed and applied to aluminum. It is pointed out that the available high pressure and temperature information covers a broad range of the phase diagram, but only irregularly and, as a rule, is not thermodynamically complete; its generalization can be done only in the form of a thermodynamically complete EOS. A multi-phase EOS model is presented, accounting for solid, liquid, gas, and plasma states, as well as two-phase regions of melting and evaporation. The thermodynamic properties of aluminum and its phase diagram are calculated with the use of this model. Theoretical calculations of thermodynamic properties of the solid, liquid, and plasma phases, and of the critical point, are compared with results of static and dynamic experiments. The analysis deals with thermodynamic properties of solid aluminum at T = 0 and 298 K from different band-structure theories, static compression experiments in diamond anvil cells, and the information obtained in isentropic-compression and shock-wave experiments. Thermodynamic data in the liquid state, resulting from traditional thermophysical measurements, “exploding wire” experiments, and evaluations of the critical point are presented. Numerous shock-wave experiments for aluminum have been done to measure shock adiabats of crystal and porous samples, release isentropes, and sound speed in shocked metal. These data are analyzed in a self-consistent manner together with all other available data at high pressure.

The model's results are shown for the principal shock adiabat, the high-pressure melting and evaporation regions and the critical point of aluminum. New experimental and theoretical data helped to improve the description of the high-pressure, high-temperature aluminum liquid. The present EOS describes with high accuracy and reliability the complete set of available information.

The inertial confinement fusion (ICF) philosophy is based on high compression. The reasoning is that (a) it is cheaper (energetically) to compress than to heat and (b) nuclear reactions are proportional to density square, therefore the more you compress the better you are in ICF. Of course the only limitations of compression are the hydrodynamic instabilities (like Rayleigh-Taylor, etc). Many of the references in the literature require extremely high compression and in particular the pB11 needs extremely huge compressions. In this paper it is shown that there is an optimum of compression, namely gain G is maximum for a definite compression. The value of this density (for a given fuel mass and particular ICF scheme) depends on the equation of state (EOS). We calculate this value for fast ignition (FI) schemes and compare it with the central spark ignition (CSI) model. The gain calculations are based on the ideal gas for the ions and the Fermi-Dirac EOS for the electrons with an effective alpha, as usually suggested from simulations. The “optimum compression” idea is easily understood from the following argument: From EOS data one needs an infinite energy to compress to an infinite density. Since the energy output is finite it is clear that G is zero for infinite compression. On the other hand for normal density with small fuel mass (~ few mg) the gain is also zero. Therefore a maximum should exist somewhere. For the deuterium-tritium fuel with a mass of few mg one gets an optimum at few hundred g/cc. If you compress more then the gain is going down. So there is a desired maximum compression fixed by EOS. Last but not least, bremsstrahlung losses in degenerate plasma are discussed and the clean fusion (i.e., without neutrons) of proton + B11 → 4α is analyzed.

For decades the analysis of interferometry have relied on the approximation that the index of refraction in plasmas is due solely to the free electrons. This general assumption makes the index of refraction always less than one. However, recent soft x-ray laser interferometry experiments with Aluminum plasmas at wavelengths of 14.7 nm and 13.9 nm have shown fringes that bend the opposite direction than would be expected when using that approximation. Analysis of the data demonstrated that this effect is due to bound electrons that contribute significantly to the index of refraction of multiply ionized plasmas, and that this should be encountered in other plasmas at different wavelengths. Recent studies of Silver and Tin plasmas using a 46.9 nm probe beam generated by a Ne-like Ar capillary discharge soft-ray laser identified plasmas with an index of refraction greater than one, as was predicted by computer calculations. In this paper we present new interferometric results obtained with Carbon plasmas at 46.9 nm probe wavelength that clearly show plasma regions with an index of refraction greater than one. Computations suggest that in this case the phenomenon is due to the dominant contribution of bound electrons from doubly ionized carbon ions to the index of refraction. The results reaffirm that bound electrons can strongly influence the index of refraction of numerous plasmas over a broad range of soft x-ray wavelengths.

Investigations of a high resolution X-ray emission spectrum in the range 0.66–0.75 nm obtained by irradiating a Germanium target with high-power p-polarized, 40 picosecond laser radiation at 532 nm wavelength was done. Spectra in the wavelength region of 2l-4l′ and 2l-5l′ L-shell transitions in F-like, Ne-like and Na-like germanium ions were recorded using the FSSR-2D spectrometer equipped with a spherically bent quartz crystal with a spectral resolution λ/Δλ better than 5000. Spectral lines were compared with theoretical values obtained using the LANL plasma kinetic code ATOMIC. Fair agreement between experimental and theoretical spectral lines has been observed, which allowed to measure enough high bulk electron temperature values of 560 eV and electron density of ∼1021 cm−3 in Ge plasma irradiated by rather small commercial high repetition rate Nd:YAG laser system.

It has been shown that in the scattered radiation, generated by an ultrashort laser pulse impinging on a metal nano-layer, non-oscillatory wakefields appears with a definite sign. The magnitude of these wakefields is proportional to the incoming field strength, and the definite sign of them is governed by the cosine of the carrier-envelope phase difference of the incoming pulse. When we let such a Wakefield excite the electrons of a secondary target (say an electron beam, a metal surface or a gas jet), we can obtain 100 percent modulation in the electron signal in a given direction. This scheme can serve as a basis for the construction of a robust linear carrier-envelope phase difference meter. At relativistic laser intensities, the target is considered as a plasma layer in vacuum produced from a thin foil by a prepulse, which is followed by the main high-intensity laser pulse. The nonlinearities stemming from the relativistic kinematics lead to the appearance of higher-order harmonics in the scattered spectra. In general, the harmonic peaks are downshifted due to the presence of an intensity-dependent factor. This phenomenon is analogous to the famous intensity-dependent frequency shift in the nonlinear Thomson scattering on a single electron. In our analysis, an attention has also been paid to the role of the carrier-envelope phase difference of the incoming few-cycle laser pulse. It is also shown that the spectrum has a long tail where the heights of the peaks vary practically within one order of magnitude forming a quasi-continuum. Fourier synthesizing the components from this plateau region attosecond pulses has obtained.

The general issue of the spectral selection of a portion of the wide extreme-ultraviolet spectrum obtained via extreme nonlinear processes as high order harmonic generation includes the problem of maintaining the ultrafast temporal duration of the pulses. In this paper, we present an instrument in which the pulse selection is operated in the wide wavelength range from 17 nm to above 60 nm, which is the central portion of the high-harmonics spectrum, with an instrumental function of about three femtoseconds. The design of the monochromator is based on the conical diffraction, which realizes very high diffraction efficiency by exploiting the specular reflection on the grating facets long-wise illuminated. The optical layout makes use of two gratings in the compensated-monochromator scheme already presented by the authors. The discussion of the residual aberration is also presented, with the aims to investigate the ultimate temporal resolution obtainable by this scheme.

The model of plasma production by laser radiation onto a solid target was developed taking into account plasma heating by the emitted electrons and target heating by ion bombardment, as well as by the laser radiation. The near target plasma structure was analyzed. The space charge sheath was studied solving the Poisson equation and taking into account the volume charge of accelerated electrons and ions. The kinetics of atoms evaporated from the target and the back-flow of atoms and ions from the plasma towards the surface was analyzed. A system of equations, including equations for solid heat conduction, plasma generation and the plasma expansion was formulated. The calculation for Cu target, laser spot radius 100 μm, pulse duration 1 ms, 103, 10, 1ns and laser power density qL = 10−3–1 GW/cm2 was conducted. The ratio of net evaporation rate to the total evaporated mass flux was determined. It was shown that the plasma mainly generated in the electron emission beam relaxation region and there the plasma flow is subsonic. The electric field at the target surface is relatively large and therefore the ion current to the surface in the space region is large and comparable with the electron emission current. A large contribution of the plasma energy flux in the target heat regime was obtained, showing that the laser generated plasma significantly converts the absorbed laser energy to kinetic and potential energy of the plasma particles, which transport part of the energy through the electrostatic sheath to the solid surface.

An electron-beam accelerator based on spiral water pulse forming line which consists of a primary storage capacitor system, an air core spiral strip transformer, a spiral pulse forming line of water dielectric, and a field-emission diode, is described. The experimental results showed that the diode voltage is more than 500 kV, the electron beam current of diode is about 24 kA, and the pulse duration is about 200 ns. The main parameters of the accelerator were calculated theoretically. The distributions for electrical field in the pulse forming line were obtained by the simulations. In addition, the process of the accelerator charging a spiral pulse forming line was simulated through the Pspice software to get the waveforms of charging voltage of pulse forming line, the diode voltage and diode current of accelerator. The theoretical and simulated results agree with the experimental results. This accelerator is very compact and works stably and reliably.

Concerning laser-driven electron acceleration in vacuum, a comparison was made between using circularly polarized (CP) laser field and linearly polarized (LP) field. It has been found that the main advantage for using CP field is that its acceleration channel occupies relatively larger phase space, which can give rise to greater acceleration efficiency. This feature chiefly comes from the difference in the distribution of the longitudinal electric components of these two kinds of fields. One of the disadvantages with CP field is the “energy saturation” phenomenon as the laser intensity is sufficiently high, resulting from the enhanced Lorentz force component in CP field. Physical explanations of these characteristics are addressed as well.

An oscillating two-stream instability (OTSI) is investigated in plasma, which has hot and cold positive ions, negative ions, and the electrons. For this, a long wavelength plasma wave is considered to be driven by two copropagating lasers with frequencies ωL1 and ωL2, such that their difference is almost equal to the electron plasma frequency ωp. In the present mechanism, this plasma beat wave (ωb, kb) is taken to grow in amplitude, so that it becomes susceptible to the OTSI and produces a low frequency electrostatic mode (ω, k), and two shorter wavelength Langmuir wave sidebands (ω1, k1) and (ω2, k2) with ω1 = ω − ωb, ω2 = ω + ωb, k1 = k − kb, and k2 = k + kb in the plasma. The effects of charge number Z, mass, temperature, and density of the ions are studied on the growth rate of the instability, and the amplitudes and phases of the sideband waves generated during the OTSI. It is found that the effects of charge number and mass of the ions are significant on the instability.

This work describes the application of laser ion source (LIS) for fabrication of semiconductor nanostructures, as well as relevant equipment completed and tested in the IPPLM for the EU STREP “SEMINANO” project and the obtained experimental results. A repetitive pulse laser system of parameters: energy of ∼0.8 J in a 3.5 ns-pulse, wavelength of 1.06 μm, repetition rate of up to 10 Hz and intensity on the target of up to 1011 W/cm2, has been employed to produce Ge ions intended for ion implantation into SiO2 substrate. Simultaneously, laser-ablated material (atoms clusters debris) was deposited on the substrate surface. The parameters of the Ge ion streams (energy and angular distributions, charge states, and ion current densities) were measured with the use of several ion collectors and an electrostatic ion energy analyzer. The SiO2 films of thickness from 20–400 nm prepared on substrates of a single Si crystal were deposited and implanted with the use of laser-produced germanium of different properties. The modified SiO2 layers and sample surface properties were characterized with the use of different methods: X-ray photoelectron and Auger electron spectroscopy (XPS+AES), Raman scattering spectroscopy (RSS) and scanning electron microscopy (SEM). The production of the Ge nano-crystallites has been demonstrated for annealed samples prepared in different experimental conditions.

The dependence of calcium ion subshell populations on the target density during the ion stopping process was analyzed using a five charge-state collisional-radiative model. The model, which consists of the ground and three excited states for every ion charge, was successfully compared with the experiment. The gas-solid difference of calcium ion charge state distribution has been numerically demonstrated. For Ca projectiles with energies of 4–11 MeV/u, the increase of the mean ion charge in solid target is explained by the increase of the total ionization rate and by suppression of the bound electron capture process at high densities of the stopping medium.

In this paper, we present a novel kind of electron acceleration mechanism when the trapped electrons are in a wake of plasma with adiabatically attenuating density. Accompanied with the increase of phase velocity βp of the wake owing to the plasma density attenuating adiabatically, the trapped electrons synchronized with the wake will get an additional acceleration besides the synchrotron oscillating acceleration just like in an accelerating elevator. The additional energy gain of the trapped electrons is determined by the value of the relativistic factor γpf = ω/ωp(zf) at the exit zf of the plasma wake. Moreover, the acceleration length is not limited by the dephasing deterministically any more, instead, it is mainly determined by the survivability of the wake. In other words, it is dependent upon the wake instability and its involving energy from driving source.