A key issue in the design of an HIF reactor cavity is the transport of the heavy ion beam from final focusing, across the cavity, to the target. Previous estimates have indicated that streaming instabilities will disrupt the beam transport for a background chamber gas pressure of 10−4 to 10−1 torr. The most attractive liquid lithium first wall reactor cavity designs produce a background gas density in just this pressure range. A detailed analysis of the streaming instabilities has now demonstrated that the beam can be transported through this background. The important fact that had been neglected is that a mode with a given wave number will grow for only a small fraction of the transport time, due to the changing beam and electron densities during transport. This analysis opens wide an attractive window for reactor cavity design.

This paper presents numerical simulations of thermodynamic and hydrodynamic response for solid targets that are irradiated with strongly bunched, highly focused, intense beams of energetic uranium ions. The main purpose of this work is to study the behavior of thermal stress waves induced in such targets by the incident ion beam. These theoretical studies will complement the experimental investigations that will be carried out in the near future at the Gesellschaft für Schwerionenforschung (GSI) plasma physics experimental area. These experiments will be performed using the existing heavy ion synchrotron, SIS18, which delivers 4 × 109 uranium ions in a single bunch with a length of about 125 ns. Other time structures, for example, a pulse that consists of a series of bunches, are also possible. The particle energy is on the order of 400 MeV/u and the beam can be focused to sub millimeter radius. This information concerning material response under intense beam loading will have important implications on designing a viable production target for the superconducting fragment separator, Super-FRS, which is going to be constructed at the future facility for antiproton and ion research (FAIR), Darmstadt, Germany, for the production and separation of exotic nuclei.

The National Ignition Facility (NIF) is a MJ-class glass laser-based facility funded by the Department of Energy which has achieved thermonuclear ignition and moderate gain as one of its main objectives. In the summer of 1998, the project was about 40% complete, and design and construction was on schedule and on cost. The NIF will start firing onto targets in 2001, and will achieve full energy in 2004. The Lawrence Livermore National Laboratory (LLNL) together with the Los Alamos National Laboratory (LANL) have the main responsibility for achieving X-ray driven ignition on the NIF. In the 1990s, a comprehensive series of experiments on Nova at LLNL, followed by recent experiments on the Omega laser at the University of Rochester, demonstrated confidence in understanding the physics of X-ray drive implosions. The same physics at equivalent scales is used in calculations to predict target performance on the NIF, giving credence to calculations of ignition on the NIF. An integrated program of work in preparing the NIF for X-ray driven ignition in about 2007, and the key issues being addressed on the current Inertial Confinement Fusion (ICF) facilities [(Nova, Omega, Z at Sandia National Laboratory (SNL) and NIKE at the Naval Research Laboratory (NRL)], are described.

A new type of ion-beam diode, self-magnetically insulated, spherical plasma focus diode (SPFD), was developed. With the SPFD, three-dimensional focusing of an intense pulsed light-ion beam was obtained. Experiments and simulations were carried out to study the behavior of the SPFD. In the experiments, diagnostic results of the Rutherford scattering pinhole camera and the shadow-box showed that the ion beam was focused into a small cylindrical area with ∽0.5 mm in diameter and ∽2.5 mm in length. The average ion-beam current density at the anode surface was found to be ∽2 kA/cm2. In the simulations, it was observed that most of the diode gap is well insulated by the self-magnetic field induced by the diode current. The electron sheath in the diode gap significantly enhances the ion flow from the anode. As a result, the ion current density is several times higher than the single-species space-charge limited value.

With the advent of ultrashort (subpicosecond) high-power lasers it is now possible to create intense bursts of X-rays with subpicosecond durations. An analysis of the temporal response of diffraction of such X-rays by crystals in both the dynamical and kinematic regime is presented. It is also shown that under certain conditions the temporal resolution can be determined by the response of the crystal.

The multi-petawatt (PW) lasers currently being built in Europe as part of the Extreme Light Infrastructure (ELI) project will be capable of generating femtosecond light pulses of ultra-relativistic intensities (~1023–1024 W/cm2) that have been unattainable so far. Such laser pulses can be used for the production of high-energy ion beams with unique features that could be applied in various fields of scientific and technological research. In this paper, the prospect of producing ultra-intense (intensity ≥1020 W/cm2) ultra-short (pico- or femtosecond) high-energy ion beams using multi-PW lasers is outlined. The results of numerical studies on the acceleration of light (carbon) ions, medium-heavy (copper) ions and super-heavy (lead) ions driven by a femtosecond laser pulse of ultra-relativistic intensity, performed with the use of a multi-dimensional (2D3 V) particle-in-cell code, are presented, and the ion acceleration mechanisms and properties of the generated ion beams are discussed. It is shown that both in the case of light ions and in the case of medium-heavy and super-heavy ions, ultra-intense femtosecond multi-GeV ion beams with a beam intensity much higher (by a factor ~102) and ion pulse durations much shorter (by a factor ~104–105) than achievable presently in conventional radio frequency-driven accelerators can be produced at laser intensities of 1023 W/cm2 predicted for the ELI lasers. Such ion beams can open the door to new areas of research in high-energy density physics, nuclear physics and inertial confinement fusion.

To produce pulses with good flat-top quality, pulse-forming lines (PFLs) have been widely used in the field of Tesla-type pulse generators. To shorten the physical length of the PFL, a double-width PFL (DWPFL) is proposed that doubles the output pulse width while maintaining flat-top quality. A repetitively 10 GW Tesla-type long-pulse generator producing pulses with flat-top width of about 110 ns was developed with a coaxial DWPFL to produce high-current electron beams. Electron beams of about 10 GW with flat-top widths of about 110 ns were obtained on a planar vacuum diode load. With this pulse generator and a C-band high-power microwave system, microwaves of ~2.2 GW power and full-width at half-maximum of 101 ns were generated. The experiment demonstrates the feasibility and ideal output waveform quality of the DWPFL.

In this study, an atmospheric pressure cold plasma jet has been generated based on dielectric barrier discharge plasma. The double ring electrode configuration is used and analysis has been performed subjected to wide range of supply frequencies up to 25 kHz and supply voltage up to 6 kV. The electrical characterization of the plasma jet has been carried out using a high voltage probe. The V-I characteristics of the developed cold plasma jet have been studied and the consumption of the power has been analyzed at various input combinations of supply frequency and applied voltage. Consequently, the supply voltage and supply frequency are optimized with respect to the discharge current and jet length for optimum power consumption. The peak power consumed for glow discharge operation has been found to be 1.27 W in the optimized configuration.

The recent progress of laser fusion research has been remarkable in obtaining the high density of more than 100 times solid density (Nakai et al. 1988) and high temperature plasma producing thermonuclear neutrons of 1013 per shot (pellet gain of 0·2%) (Yamanaka et al. 1986a) and in the understanding of the implosion physics. The data bases of the laser fusion are rapidly being accumulated and the technologies for the advanced experiments have been developed, both of which enable us to proceed toward the fusion ignition experiment and the achievement of the breakeven conditions.

In this paper we propose the coherent amplification of gamma radiation of a system of parapositronium atoms. The nonlinear optics of positronium media is suggested. The induced annihilation transitions for the electron-positron plasma are compared with those of the positronium medium. It is suggested in this paper that the Bose–Einstein condensation could play a crucial role in the estimation of the induced annihilation of electron-positron pairs for dense (n ≳ 1016cm−3) and cold (T ≲ 104 °K) positronium systems. The calculated effects of the induced positron-electron decays might be observed in astrophysical objects such as pulsars, white dwarf stars etc. Furthermore, these transitions might play an important role in Klein–Alfven cosmology. Finally, with the further advancement of the positron technology, a gamma ray laser may be constructed.

In this experimental study, the ablative Richtmyer–Meshkov (RM) and the Rayleigh–Taylor (RT) instabilities were generated by the laser pulse of Gaussian-like power profile. The initial multi-modal perturbation, the inhomogeneous momentum transfer and different Atwood numbers generate different shapes of spikes and bubbles in the central region (CR) and the near-central region (NCR) of the spot. A one-dimensional Gaussian-like power profile causes the formation of the wavy-like rows of aperiodic spikes. The periodic spike segments inside the rows appear due to locally coherent flow. In the NCR, the mushroom-shape spikes tend to the organization on the isotropic square and the anisotropic rhombic lattices. The increase of the lattice periods two, three, or four times indicates formation of superstructures. The growth of sharp asymmetric RM/RT spikes in the CR is fast, uncorrelated and linear, while the growth of the symmetric mushroom-shape ones in the NCR is slow, correlated, and nonlinear.

A computer kinetics model has been developed to predict the steady state behaviour of e-beam-pumped KrF lasers. The model can be used to calculate species densities, gain, loss and laser efficiency. Close agreement is obtained between the model predictions and a wide range of experimental measurements of optical gain, loss, and laser efficiency as a function of e-beam pump power, taken at various laboratories.

Characteristics of annular wire array z pinches as a function of wire number and at high wire number are reviewed. The data, taken primarily using aluminum wires on Saturn, are comprehensive. The experiments have provided important insights into the features of wire-array dynamics critical for high X-ray power generation, and have initiated a renaissance in z pinches when high numbers of wires are used. In this regime, for example, radiation environments characteristic of those encountered during the early pulses required for indirect-drive ICF ignition on the NIF have been produced in hohlraums driven by X rays from a z pinch, and are commented on here.

We consider beams that are described by a four-dimensional (4D) transverse distribution f (x, y, x′, y′), where x′ ≡ px /pz and z is the axial coordinate. A two-slit scanner is commonly employed to measure, over a sequence of shots, a two-dimensional (2D) projection of such a beam's phase space, for example, f (x, x′). Another scanner might yield f (y, y′) or, using crossed slits, f (x, y). A small set of such 2D scans does not uniquely specify f (x, y, x′, y′). We have developed “tomographic” techniques to synthesize a “reasonable” set of particles in a 4D phase space having 2D densities consistent with the experimental data. We briefly summarize one method and describe progress in validating it, using simulations of the High Current Experiment at Lawrence Berkeley National Laboratory.

The paper presets the results of a study on a self-magnetically insulated ion diode with an explosive-emission potential electrode. The experiments have been carried out using the TEMP-4M accelerator, operating in a double-pulse mode: the first negative pulse (300–500 ns, 100–150 kV) followed by the second positive pulse (150 ns, 250–300 kV). The ion beam energy density was 0.3–2.5 J/cm2; the beam was composed from carbon ions (80–85%) and protons. We studied several geometries of the diode: planar and focusing strip arrangement, annular and spiral geometries. It was shown that during the second voltage pulse, a condition of magnetic insulation in the diode gap is fulfilled (B/Bcr ≥3). Using the new spiral geometry of the diode, it was possible to increase the efficiency of ion current generation due to the suppression of the electron component of the total diode current by increasing the electron transit time in the gap. We have increased the efficiency of carbon ion generation from 5–9% (in the planar strip diodes) up to 17–20% in the spiral diode. The spiral geometry of the diode makes it possible to increase the efficiency of C+ ion generation 25–30 times compared to the space-charge-limited current (Childe-Langmuir limit). This is more than two times higher than in other known geometries of self-magnetically insulated diodes. The spiral diode has a resource of more than 107 pulses.

Integrated simulation results of femtosecond laser ablation of copper were compared with new experimental data. The numerical analysis was performed using our newly developed FEMTO-2D computer package based on the solution of the two-temperature model. Thermal dependence of target optical and thermodynamic processes was carefully considered. The experimental work was conducted with our 40 fs 800 nm Ti:sapphire laser in the energy range from 0.14 mJ to 0.77 mJ. Comparison of measured ablation profiles with simulation predictions based on phase explosion criterion has demonstrated that more than one ablation mechanisms contribute to the total material removal even in the laser intensity range where explosive boiling is dominating. Good correlation between experimental and simulation results was observed for skin depth and hot electron diffusion depth – two parameters commonly considered to identify two ablation regimes in metal. Analysis of the development dynamics for electron–lattice coupling and electron thermal conduction allowed explaining different ablation regimes because of the interplay of the two parameters.

This paper examines the necessity of including ion viscosity in modeling laser fusion implosions. Using the Naval Research Laboratory one-half Mega Joule laser fusion target as an example, it is shown that for virtually the entire implosion up to maximum compression, and the entire rebound after the implosion, ion viscosity is unimportant. However for about half a nanosecond before peak implosion, ion viscosity can have a significant, but by no means dominant effect on both the one-dimensional flow and on the Rayleigh-Taylor instability.

We present results of X-ray emission by the rear side of gold thin targets irradiated by the Phebus laser at λ = 0.35 μm, τ = 0.7 and 1.3 ns, and EL = 1.5 kJ. A streak camera coupled with a transmission grating gave the time-resolved X-ray emission of the rear side. Also, a streak camera coupled with a slit allowed us to obtain information about the space and time evolution of the plasma. Some other diagnostics gave information about the energy balance and the X-ray conversion efficiency. The results are in good agreement with previous ones obtained with the Octal laser, particularly on optimum thicknesses for X-ray conversion efficiencies. Values of the thermal flux limiter are deduced. Simulations with FCI 1 code with multigroup radiative transfer and non-LTE ionization reproduce the experimental results only about some points. A number of reasons, such as 2-D effects and problems of opacity, are invoked.

From the neodymium glass laser system Novette with two beams of 74 cm diameter and 18 kJ energy per pulse output in the nanosecond range, the design, the steps of the construction, and results of the system are reported. The two beams are synchronized to 5 psec and conversion to green light up to 78% has been realized. Conversion to four times the laser frequency is measured with more than 25% conversion. Simulation and measurement of laser beam properties at several locations permit an analysis to define the final Nova configuration. About half of Novette's experiments were to study short wave length laser–plasma interactions for the then better coupling by inverse bremsstrahlung mechanisms for inertial confinement fusion with laser intensities up to 1017 W/cm2. Experiments were divided between high density implosion research and non-local thermodynamic equilibrium plasma conditions.

For operation of an ion source in an intense ion beam diode, it is desirable to form a localized and robust source of high purity. A cryogenically operated ion source has great promise, since the ions are formed from a condensed high-purity gas, which has been confined to a relatively thin ice layer on the anode surface. Previous experiments have established the principles of operation of such an ion source, but have been limited in repetitive duration due to the use of short-lived liquid He cooling of the anode surface. We detail here the successful development of a “Cryo-Diode” in which the cooling was achieved with a closed-cycle cryo-pump. This results in an ion source design that can potentially be operated for an indefinite duration. Time-of-flight measurements with Faraday cups indicate that the resultant ion beam is of high-purity, and composed of singly charged ions formed out of the gas frozen out on the anode surface.