By sophisticated application of particle-in-cell simulations, we demonstrate the ultimate role of non-linear pulse evolutions in accelerating electrons during the entrance of an intense laser pulse into a preformed density profile. As a key point in our discussions, the non-linear pulse evolutions are found to be very fast even at very low plasma densities, provided that the pulse length exceeds the local plasma wavelength. Therefore, these evolutions are sufficiently developed during the propagation of typical short density scale lengths occurred at high contrast ratios of the pulse, and lead to plasma heating via stochastic acceleration in multi-waves. Further analysis of simulation data at different physical parameters indicates that the rate of evolutions increases with the plasma density leading to higher plasma heating and overgrown energetic electrons. In the same way, shortening the density scale length results into increase in the evolution rate and, simultaneously, decrease in the interaction time. This behavior can describe the observed optimum value of pre-plasma scale length for the maximum electron heating.

Evidence will first be presented in favor of the usefulness of coordination number-dependent equations of state of metallic plasmas. After some theoretical discussion of the way such an equation of state may be related to dimer properties, with specific regard to Na and Al, critical point predictions for the alkalis will be brought into contact with experiments. In this context, some results on W will also be surveyed. Structural properties, static and dynamic, will then be considered in relation to transport in both Cu and H plasmas. This will embrace experiments on electrical resistivity in both examples. For H, a simple inference can be extracted about the structure factor, and the discussion will finally be generalized to treat the metalization of solid H.

The uniform side-on emission of second harmonic radiation has recently been measured from the corona of a laser irradiated plasma with large electron density gradients. A theoretical model has been developed to study the internal electric fields and double layers in such strongly inhomogeneous plasmas. The analytical model shows immediately a density-independent second harmonic term which reproduces very closely the measured intensity of the second harmonic. A detailed numerical evaluation of the term, for a plasma with a linear density profile (permitting Airy solutions), results in a net intensity with small spatial variation but also with both long and short wavelength periodicities exactly as measured. The observed vanishing of the periodicity, when broad band laser sources are used, can then immediately be explained from integration of the standing-wave like oscillations.

Effects of solid nanolayers embedded in a near-critical density plasma on the laser-driven collisionless shock acceleration are investigated by using two-dimensional particle-in-cell simulations. Due to the interaction of nanolayers and the incident laser, an additional number of hot electrons are generated and an inhomogeneous magnetic field is induced. As a result, the collisionless shock is reinforced within the nanolayer gaps compared to the target without the structured nanolayers. When the laser intensity is 9.8 × 1019 W/cm2, the amplitude of the electrostatic field is increased by 30% and the shock velocity is increased from 0.079c to 0.091c, leading to an enhancement of the peak energy and the cutoff energy of accelerated protons, from 6.9 MeV to 9.1 MeV and 12.2 MeV to 20.0 MeV, respectively. Furthermore, the effects of the width of the nanolayer gaps are studied, by adjusting the gap width of nanolayers, and optimal nanolayer setups for collisionless shock acceleration can be acquired.

Study of even harmonic generation resulting from propagation of whistler pulse in homogeneous high-density quantum plasma immersed in an externally applied magnetic field, using the recently developed quantum hydrodynamic model is presented. The effects of quantum Bohm potential, quantum statistical pressure, and electron spin have been taken into account. The field amplitude of even harmonic of the whistler with respect to fundamental wave and the conversion efficiency for phase-mismatch has been analyzed. The conversion efficiency of harmonic radiation depends on the plasma electron density, magnetic field strength as well as the intensity of whistler pulse. The efficiency increases significantly with an increase in plasma density, magnetic field and whistler wave intensity. Higher conversion efficiency is observed in degenerate plasma for lower values of the static magnetic field as compared with classical plasma.

In this paper, the occurrence of the stimulated Raman scattering (SRS) and its effects on stimulated Brillouin scattering (SBS) pulse compression in FC-40 are investigated. As the experimental medium, the characteristics of FC-40 are suitable for pulse compression. Firstly, the frequency shifts and the threshold of SRS in FC-40 are studied with a mode-locked laser system as pump source, without taking the SBS effect into account. On the basis of the experimental results, the competition between SRS and SBS as well as its effect on pulse compression is investigated. Results show that SRS gets higher gain and grows rapidly with the increase of the laser intensity by pump effect, which will result in decreasing of SBS energy reflection.

The coefficients Ai, that enter the fit formula for the stopping power (6), are given incorrectly in table 1. The table gives expressions for the quantities Ai2, rather than the coefficients Ai as printed. Therefore, the square root of the given expressions should be computed to obtain Ai. The given accuracy of the fit is reported correctly since it was obtained using the correct coefficients.

A 32-year-old hypothesis of the formation of barred-spiral galaxies (Bostick 1957, 1958, 1986; Laurence, 1956) which become coherent-self-exciting homopolar generators has recently gained confirmative support from 3-D, particle-in-cell computer simulations (Nielsen et al. 1979; Buneman et al. 1980; Peratt et al. 1980, 1984, 1986). Such galaxies should be able to convert an appreciable fraction, f, of the energy from their gravitationally-collapsing plasmas to coherently-increasing magnetic energy via their coherent, self-exciting, homopolar-generator action. The following simple calculation shows that the resulting mutually-induced magnetic repulsions (Len's law) between neighboring galaxies is greater than the gravitational attractive forces between the galaxies. The observed expansion of the Universe can be thus simply accounted for without recourse to the ‘Big Bang’ hypothesis, with its unaccounted-for mysteries.

Recent experimental and theoretical research on intense pulsed particle beams involving the ETIGO Project at the Technological University of Nagaoka is reviewed. Experimentally, we review the following: (1) studies on local divergence angle in parameter space, (2) development of self-magnetically insulated “Plasma-Focus Diode,” (3) beam focusing by z-discharged plasma channel, (3) measurement of ablation process of beam-target interaction, (4) time-resolvable measurement of energy and species, (5) inductive postacceleration of highly neutralized ion beam, (6) construction of new pulse-power machine, and pulse-compression experiment by plasma erosion opening switch. A brief summary is also given on the development of 2.5-dimensional particle-in-cell computer simulation code.

A high-frequency surface plasma wave (SPW) excited over metallic surface irradiated by a laser beam, can undergo stimulated Compton scattering if phase velocity of daughter plasma wave is equal to the Fermi velocity for metal. The pump SPW ${\rm (}{{\rm \omega} _0},{\vec k_{0{\rm z}}})$ parametrically excites a quasi-electrostatic plasma wave ${\rm (\omega}, {\vec k_{\rm z}})$ and a backscattered sideband SPW ${\rm (}{{\rm \omega} _1},{\vec k_{1{\rm z}}})$ at resonance ω0 = ω − ω1 and ${\vec k_{0{\rm z}}} = {\vec k_{\rm z}} - {\vec k_{1{\rm z}}}$. The growth rate of Compton process increases with the frequency of incident laser and turns out to be 5.425 × 1010 rad/s at laser frequency ω0 = 0.7595 × 1015 rad/s for incident laser amplitude A0L = 11 × 1011 V/m, laser spot size b = 1.38 × 10−5 m, and free electron density of metal n0 = 5.85 × 1028/m3. The excitation of highly damped quasi-electrostatic plasma wave in this parametric process provide a better nonlinear option for surface heating as compared with direct laser heating. The process can also be used for diagnostics purposes.

This is a short summary of research on the self-magnetically Bθ-insulated ion diode originally proposed by K. Zieher (1981, 1983, 1984, 1984a). We report the most recent progress. For detailed discussions see the forthcoming publications (Schimassek 1989; Westermann 1989). After the exploratory work of Zieher the efforts of recent years have concentrated on the numerical simulation (Westermann 1988; 1988a; 1988b), the development of detailed diagnostic tools (Rogner & Schultheiss 1986; Kühn & Rogner 1985; Klumpp & Bluhm 1986) and the focusing properties of the Bθ-diode (Citron et al. 1986; Bauer et al. 1987; Schimassek et al. 1988; Westermann 1988c). Experiments and numerical simulations on three modifications of the diode will be reported (version I, II, III).

In this article, we present the results of the laser ion source (LIS) for heavy ion high charge state Institute of Theoretical and Experimental Physics terawatt accumulator facility. This LIS is a duty ion source of C+4 for the injector. The main parameters of CO2 laser, vacuum target chamber, ion beam high voltage extraction system, and low energy beam transport line are shown. The stability of the LIS operation is discussed and measured ion beam parameters (ion current, pulse duration, emittance) for different charge states are presented. After the upgrading of the laser cavity, high voltage capacitors, and spark gaps and the installation of a new catalyst regenerator system, the CO2 laser became much more stable and allows long term operation. LIS works about 1 × 106 shots without intervention.

A one-dimensional (1D) numerical model for studying enhanced terahertz (THz) radiation generation by mixing of ordinary and extraordinary modes of two-color laser pulses propagating in magnetized plasma has been presented. The direction of the static external magnetic field is such that one of the two laser pulses propagates in the extraordinary mode, while the other pulse propagates in the ordinary mode, through homogeneous plasma. A transverse electromagnetic wave with frequency in the THz range is generated due to the presence of the external magnetic field. It is observed that larger amplitude THz radiation can be generated by mixing of the ordinary and extraordinary modes of the two-color laser pulses as compared with the single laser pulse propagating in the extraordinary mode. Further, 2D simulations using the XOOPIC code show that the fields obtained via simulation study are compatible with those obtained from the numerical model.

Emissions from the rear side of the targets were temporally resolved by irradiating an ultraviolet (UV) laser on Al and Au thin targets. A difference was clearly observed between the above two targets. Given the fact that absorbed laser energy is converted with a very high efficiency to soft x-rays in a high Z plasma, a characteristic emission peak only observed for Au targets was attributed to the effect of soft x-ray energy transport. The ablation pressures estimated from the emissions indicate that the pressure scaling for Au is close to the one by x-ray radiation rather than by a UV laser. With soft x-ray irradiation, energy transport in A1 foils was also studied. An ablation pressure was estimated by the shock speed.

We have developed a compact, 14.7 nm, sub-5 ps X-ray laser source at Lawrence Livermore National Laboratory (LLNL) together with a Mach-Zehnder type diffraction grating interferometer built at Colorado State University for probing dense, high intensity laser-produced plasmas. The short wavelength and pulse length of the probe reduces refraction, absorption effects within the plasma and minimizes plasma motion blurring. This unique diagnostic capability gives precise two-dimensional (2D) density profile snapshots and is generating new data for rapidly evolving laser-heated plasmas. A review of the results from dense, mm-scale line focus plasma experiments will be described with detailed comparisons to hydrodynamic simulations.

Periodical short pulse trains were observed in the oscillation of the waveguide mode free electron laser, which could be explained as a self mode-lock oscillation of the free electron laser.

The spectra of the spontaneous emission and the induced absorption were observed, which were in good agreement with theoretical calculations.

The energy spread of the relativistic electron beam was measured using Thomson back scattering from a high power CO2, laser.

It is expected (Hora & Handel 1987) that the energy spectra of electrons emitted from laserirradiated atoms in low-density gases would be fundamentally different for laser intensities above and below the threshold of a correspondence principle. Below such a threshold, the emission is a quantum mechanical interaction while, in contrast, above the threshold it is a classical process. Both of our earlier experiments (Boreham & Hora 1979; Boreham & Luther-Davies 1979) and those of several others, including some very recent results (Monot et al. 1993) confirm—after some controversy—the existence of such a correspondence principle. Details are discussed.

The acceleration of an electron beam by surface plasma waves (SPW), in the presence of external magnetic field parallel to surface and perpendicular to direction of propagation of SPW has been studied. This wave propagating along the $\hat z$-axis is excited using Kretschmann geometry, having maximum amplitude at the metal–vacuum interface. Equations of motion have been solved for electron energy and trajectory. The electron gains and retains energy in the form of cyclotron oscillations due to the combined effect of the static magnetic field and SPW field. The energy gained by the beam increases with the strength of magnetic field and laser intensity. In the present scheme, electron beams can achieve ~15 KeV energy for the SPW amplitude A1 = 1.6 × 1011 V/m, plasma frequency ωp = 1.3 × 1016 rad/s and cyclotron frequency ωc/ωp = 0.003.

The interaction of femtosecond ultra-intense laser pulses with clusters increases absorption of the incident laser light compared with the interaction with solid targets and leads to enhanced generation of different quantum beams with unique parameters. Future investigations of such interaction urgently need detailed modeling and optimization of cluster parameters, for instance, in order to obtain the clusters with desired size, or some specific spatial configuration of the target etc. A numerical model of gas-cluster targets production by the nozzle flows of gases and binary mixtures is presented. Some previous results of the model utilization are summarized, and some new results are given. Techniques of experimental verification of the numerical results are discussed.

Porous materials have peculiar characteristics that are relevant for inertial confinement fusion (ICF). Among them, chemically produced foams are proved to be able to smooth the laser inhomogeneities and to increase the coupling of the laser with the target. Foams realized with other elements and techniques may prove useful as well for ICF applications. In this work, we explore the potential of a novel class of porous materials for ICF, namely, carbon nanofoams produced with the pulsed laser deposition (PLD) technique, by means of hydrodynamic numerical simulations. By comparison with a simulation of solid-density carbon, PLD nanofoams show a higher pressure at the shock front, which could make them potential good candidates as ablators for a capsule for direct-drive fusion.