It is shown that a powerful laser beam is capable of the ponderomotive confinement of plasma with electron density exceeding the critical density for the radiation under review. The theory describing force and heat balances of the plasma together with the propagation of the laser radiation is developed. The laws of the dense plasma scaling for controlled thermonuclear fusion (CTF) and other applications are formulated.

We describe the mathematical basis and organization of Crunch, a ID shock-hydrodynamics code to analyze pulsed-power experiments at Los Alamos National Laboratory. The program uses finite-element methods that preserve stability during material collisions and shock convergence on axis. It handles coupled calculations of nonlinear magnetic diffusion to simulate imploding liners. These calculations may be driven by multiple current waveforms or a selfconsistent current variation derived from a pulsed-power generator model. Crunch incorporates elastic material contributions and calculates element break and melt points. The primary goal in program development was effective use by experimentalists. Crunch is controlled by a streamlined script language and runs on standard personal computers. An interactive graphical postprocessor expedites analysis of results. To support the program we have assembled data resources in machine-independent format including Sesame equation-of-state tables, a material strength library and a library of temperature-dependent conductivities.

The Precision Phebus program, started in 1993, emphasizes a series of laser and target experiment objectives on the two-beam Phebus Nd-phosphate glass laser. Recently, three major objectives that are also very important issues for megajoule-class lasers have been met: First, the balance of the incident beam-to-beam 3ω power is shown to be in the range from 5 to 12% for 3-ns, 3ω-shaped pulses of reproducible high-energy shots; second, the smoothing uniformity of the laser energy deposited on the target, that is, the contrast of the spatial beam modulations, can be kept lower than 5%; and, finally, the tight control of the beam targeting leads to a pointing precision of less than 10 μrd on the target at the target chamber center (TCC) and of 80 μrd on X-ray sources located up to 3 cm from the TCC to improve the space- and time-resolved X-ray shadowgraphy techniques performed for target physics experiments such as implosion and hydrodynamical instability studies.

Some characteristics of the picosecond laser produced plasma expanding across an externally applied magnetic field (0.6T) have been reported. Two to three times enhancement in X-ray emission from copper plasma has been observed for the laser intensity range ∼5 X 1011 to 5 X 1012 W/cm2. The X-ray yield has been found to increase with an increase in the magnetic field intensity. Enhancement in X-ray emission is correlated with confinement of expanding plasma either in external magnetic field or in high ambient gas pressure. Generation of some highfrequency instability and fast ions was also observed in the plasma along with bouncing of plasma near the β = 1 surface where kinetic pressure of plasma equals magnetic pressure.

A review of the AVLIS (atomic vapor laser isotope separation) development performed by GPI and LAD Ltd. (Moscow, Russia) during the last 4–5 years is presented. The processes of laser isotope separation of ytterbium (Yb) have been studied analytically, with numerical simulations, and experimentally. The basic attention is given to the following topics: the selectivity of ionization; the laser beams arrangement in a cavity; the forming of a vapor flux; and the extraction of ions from plasma. Installations to produce highly enriched 168Yb in industrial scales were created. The content of 168Yb in the laser-produced plasma reached 90–95%, in the material deposited on the ion collector up to 62%, and in the washing liquid up to 45%. The rate of the enriched Yb production was up to 5–10 mg/h. For the first time a profitable commodity was produced by the AVLIS method.

The paper presents experimental results on the application of microsecond plasma opening switch (MPOS) technology for materials surface modification. The ion beam parameters generated by the MPOS are up to 250 keV energy and current density and energy densities of up to 150 A/cm2 and 2.2 J/cm2, respectively. Characterization of the treated samples showed structural changes to a depth of several microns. The small ion range (few microns) and fast cooling of the upper melted layer (up to 1010 K/s) result in formation of fine-grain structures characterized by improved corrosion and erosion properties. Measurements indicate an increase in microhardness of a factor of about 3 for carbon steel samples. Corrosion resistance increase for the treated samples of at least 3, as measured by mass loss and potentiodynamic methods, has been measured for Al alloys. Microstructural changes in the surface morphology indicate a reduction in grain size for the treated samples and the appearance of shallow craters. Results of numeric simulations are given for the temperature distribution in materials due to ion beam heating.

Free-electron lasers exploiting media with periodically modulated refractive indices are studied. The regime of large modulation is considered, and the conditions of its realization are discussed. Two types of media with periodically modulated refractive indices are analyzed: a gas-plasma medium with a periodically varying degree of ionization and a superlattice-like medium. The gain, saturation field, and efficiency of these free-electron lasers are found. For any given frequency, the gain is optimized with respect to the choice of electron energy, direction of motion, and other parameters. Its relationship with other types of free-electron lasers (e.g., the Cherenkov laser) is discussed.

Maximum charge states of ions registered in the far expansion zone from laser-produced plasma of Al, Co, Ni, Cu, Ta, W, Pt, Au, Pb, and Bi are presented. The Thomson parabola spectrometer was used to display a general view of the ion species of an expanding plasma while detailed ion charge-energy spectra were determined by the cylindrical electrostatic ion energy analyzer. The current densities of highly charged ion groups above 20 mA/cm2 were measured by use of an ion collector at a distance of ∼1 m from the target. The photodissociation iodine laser system PERUN (λ = 1.315 μm, power density up to ∼1015 W cm−2) was employed as a driver.

The results of a high-resolution processing, based on techniques of fractal dimension analysis, of experimental data from earlier experiments on the linear Z-pinches are presented, which prove the electric current-carrying plasmas to be a random fractal medium. The basic building block of this medium is identified to be an almost-closed helical filamentary magnetoplasma configuration (we call it heteromac). The heteromacs are coupled together through long-range self-sustained filamentation and, thus, form a dynamical percolating network with dissipation. The results (i) extend recently identified phenomenon of the 3D large-scale (up to several centimeter size) helical filamentary plasma structures (Kukushkin et al. 1994, 1995, 1997a) in plasma focus gaseous discharges to the case of Z-pinch gaseous discharges and (ii) provide a novel view into the dynamics of Z-pinch's necks, plasma spikes, and magnetic bubbles as well as into generic features of electric current-carrying plasmas varying from low-electric current laboratory plasmas to cosmic plasmas. This covers about 30 orders of magnitude of length scale and suggests unprecedented opportunities for interpolating between and extrapolating from well-understood phenomena. A magnetoplasma universe model is suggested.

Analytic analysis of collisionless Weibel modes in laser-created plasmas is presented. The heat flux (HF), the plasma expansion (PE), and the inverse bremsstrahlung absorption (IBA) sources have been investigated. It has been shown that for short laser wavelengths (λL < 1 µm) and high laser fluxes (I > 1014 W/cm2), the inverse bremsstrahlung absorption is the most efficient Weibel mechanism for producing strong magnetic fields in the vicinity of the critical layer. For large laser wavelengths (λL < 10 µm), the production of the magnetic fields in the vicinity of the critical layer, due to the plasma expansion mechanism, is as important as the ones due to the thermal transport and the inverse bremsstrahlung absorption mechanisms. Useful scaling laws of convective e-foldings, with respect to the laser and the plasma parameters, are also derived.

We have analyzed the shock wave propagation experiments performed at LULI and presented at ECLIM'94. The targets were aluminium foils with thickness from 5 to 25 μm. Simulations were performed with the SARA-1D multigroup radiation code. We have shown a small level of preheating caused by the absorption of X-rays with energies close to the K-edge of aluminum. Several sets of opacities were used in order to study this effect, including experimental values for cold aluminum. Simulations show a small level of visible emission induced by X-ray preheating before the arrival of the shock.

Proton-boron-11 is the clean fusion reaction par excellence, but it is very difficult to exploit it because of the very high ignition temperature of this reaction and its moderate fusion yield. In this paper, a proposal is made to induce these reactions by a heat-detonation wave that expands across a compressed target. The front of the wave has a double-layer structure, with a first front driven by electron heat conduction and a second front heated by α-particle energy deposition. Both fronts create a hot plasma where the stopping power is dominated by ions. The wave is originated by an ignitor triggered by an ultraintense lightning beam. This beam can be made of photons (laser), plasma (ramjets), or ions (proton beams, borane clusters). Proton beam shots of 1022. W/cm2 and several GA for some picoseconds would be needed for this purpose. The supersonic propagation of the fusion wave and the ignitor requirements are analyzed in this paper. The main conclusion is that the burning wave can only propagate if a substantial fraction of the radiation losses from the already burning fuel is reabsorbed in the colder fuel. It is calculated that for densities larger than few thousands g/cm3 most of the bremsstrahlung radiation created in the hot plasma can be reabsorbed by the Compton effect in a region of 1 g/cm2 optical thickness of the surrounding compressed and cold fuel.

The generation of poloidal magnetic field in an inhomogeneous cold, collisionless plasma by an elliptically polarized Gaussian laser beam is discussed. A field in the range of megagauss is induced by the laser inhomogeneity effect even for a normal incident beam. This field scales as I0 λ, where I0 and λ are the intensity and wavelength of the laser beam, respectively, and is independent of the density profile structure. The small angular correction factor due to focal spot asymmetry scales as ∼I0λ3 and may be significant for a small-sized plasma with a steep density profile. The limitation of our model is discussed, with possible implications.

Intense electron beams are known to produce surface plasmas when they strike typical target materials. The beam space charge then draws an ion current that can substantially affect the beam dynamics. We consider these effects for two intense-beam sources: (1) a needle-tip cathode immersed in a strong magnetic field, and (2) an induction accelerator-produced beam that is focused onto a field-free target. For the first case, the dominant effect is an electrostatic dipole instability between the beam and the ions. A sufficiently large magnetic field can keep the oscillation amplitude to a low level. For the second case, the dominant effect is that the focal length changes in time. For the “worst case” of space-charge-limited proton emission, the predicted effect is severe. The actual abundance and charge state of the target-plasma ions will need to be measured or inferred from planned experiments. Mitigation schemes also are discussed briefly.

Coherent control of molecular processes provides a means of controlling the dynamics of molecules, and of molecular processes, via laser-induced quantum interference. We briefly review this approach, provide relevant references, and highlight recent advances in the control of molecular processes.

We create hot (Te > 200 eV) and dense (Ne > 1023 cm−3) plasmas in the colliding zone of two thin foils accelerated by two laser beams of the LULI facilities. Three spectroscopic diagnostics (two 1D space-resolved spectrographs and a 2D monochromatic imaging) are used to drive the efficiency of the compression. We show that 2D effects are important. Realistic simulations of these experiments must be done, taking into account the inhomogeneity of the laser intensity in the focal spot, the foil distorsion, the plasma lateral expansion, and the lateral thermal conduction. Two-dimensional LASNEX code results are in good agreement with our experimental results. The optimized compressed plasmas generated are favorable for the exhibition of dense plasma effects due to molecular formations, and they reproduce in laboratory some astrophysical situations.

Laser plasma experiments reveal rich interplay between laser plasma instabilities. The growth of stimulated Brillouin scattering (SBS) is one of the most significant constraints of laser fusion experiments. In this paper, a mechanism of stabilization of SBS process due to magnetic anisotropy has been presented. Magnetic anisotropy induced by the temporally exponentially growing nonoscillating magnetic moment from inverse Faraday effect (IFE) has been studied.It has been shown that for interaction of Nd laser (λ = 1.06 μm) on solid deuterium target the SBS growth rate (y) ∼ 3.45 ps and the phase velocities of the incident and scattered electromagnetic (EM) waves have been shown to decay exponentially (∼e∼λ1) in this SBS process resulting in wave-number mismatch.