A maximum electric field E = 2.65 GV/m with an accelerated electron current of 1 KA has been obtained, for pulse lengths of 130 ps, in an electron gun based on Pulse Power Technology. This is the highest accelerating field ever achieved in the presence of such a large current. Measurements of beam emittance and energy from 0.4 to 2.65 MeV show that the scaling of the invariant emittance with electric field and with beam current is consistent with theoretical predictions. A few applications of high-gradient acceleration are discussed.

On the basis of coupled neutronic/hydrodynamic calculations, we examine the neutron heating effects on the ignition and burn propagation in laser-imploded D-T pellets. The fusionproduced neutrons deposit their energy all over the pellet region since the mean-free-path of the neutron is long. The fraction of neutron energies deposited to the central spark region during the ignition phase is too small to reduce the threshold energy of the laser for ignition. In the burn phase, the neutron heating decreases the maximum compression ratio and accelerates the plasma expansion. The inclusion of neutron heating hence decreases the pellet gain from the value in the case without neutron heating. Calculations neglecting the transport of neutron recoils overestimate the neutron heating rate in the reactor-grade pellets.

Within the grand canonical ensemble, we use a general quantum statistical formula and the thermodynamic Green's functions to derive a perturbation expansion for the pressure of a multicomponent plasma. Different contributions to the equation of state (EOS) are given analytically and by numerical calculations. Exact results for the EOS are presented in the shape of a low-density expansion up to the order (ne2)5/2, including ladder-type contributions and “beyond Montroll–Ward” terms.

The dynamic model of plasma open switches is proposed in this article. It is based on the initiation and development of force instabilities (pinches and necks) in spatially inhomogeneous plasma accelerated by the magnetic field pressure. The model proposed does not require the consideration of subtle effects at the pinch implosion stage. It allows one to account for main features of the operation of plasma current open switches within the framework of magnetic hydrodynamics. It also provides quantitative estimates in good agreement with experimental results.

Experiments have been performed to investigate charge state and energy loss of 5.9-MeV/u uranium ions in a partially ionized dense argon plasma with 1017 ≤ ne ≤ 1019 cm−3 and 1 ≤ Te ≤ 10 eV. The charge state of the ions was found to be equal to the equilibrium charge state in cold gas. The energy loss offered a useful tool for plasma density diagnostics. Spectroscopic measurements using the electron collision broadening of ArII- and ArIII-lines in the visible and UV spectral region confirm this plasma density data.

The work begins with a presentation of results concerning periodic Rayleigh-Taylor (RT)and Richtmyer–Meshkov (RM) dynamics. The periodic RT flows are considered in 2D and 3D cases. The periodic RM flows are considered in a 2D case. Nonstationary and steadystate statements of RT and RM problems are given. Nonstationary statements of RT and RM problems are given in the2D case. Steady-state statements of RT and RM problems are considered in the 2D and 3D cases (RT) and in the 2D case (RM). Questions about turbulence are given in the second part of the work. In the nonstationary statement, the beginning of a transition from an equilibrium close to hydrostatics and behavior of a dynamic system when it is close to the steady-state solution are considered. To study the smooth evolution of the dynamic system in the RT case (at last during an initial of order of unity t ≃ 1 stage) we have to cut of f an inverse turbulent cascade incoming from the small scales (inverse means that the typical k decreases in time during the cascade). The cascade starts from some small scale k ≫ 1 (here g = 1) and appears in the scales k ≃ 1 after time t ≃ 1 after start. We have to consider exponentially smoothed initial data to cut it off. This means that amplitudes of initial spectrum of perturbations have to be exponentially decreased in the direction of high k. The steadystates have been studied in two ways. In both of them the spectral decomposition of a velocity field and an elevation of the contact surface has been used. In one of them, corresponding to the nonstationary situation, the ordinary differential system for time dependent spectral components has been integrated. The other solutions of the algebraic equations for constant components have been studied. These results have been compared with a computer simulation that has been done by large particles and artificial compressibility methods. High-order nonlinear terms corresponding to the interaction of a wide spectrum of harmonics are considered in both ways. The spatial structure of the many dimensional periodic solutions is studied. It is known that there are two important features in the flows under consideration: the bubble envelope and the jet “phase.” Spatial structures of the 2D and 3D flows are compared in the report. It is shown that the apices of the bubbles are isolated points and the bubble envelopes in both flows are qualitatively similar; the difference has a quantitative character. On the contrary, the jet “phases” differ qualitatively in the 2D and 3D cases. In the 2D case in the plane picture, the jets are separated from each other. In this picture they are isolated fingers. In the 3D case, near the bubble envelope after some time of development following after cos kx cos qy type initial perturbation, they are not the isolated fingers. They form a structure of the intersecting walls. We see, thus, that the 2D and 3D cases are topologically different. Most powerful ejections of dense fluid are in the points where these wall jets intersect each other.

The concept of fast ignitor is intimately connected with the fundamental phenomenon of ultra-intense light beam propagation through dense matter in which kinetic effects combine with radiation pressure dominated hydrodynamics to form a complex scenario of extremely non-linear physics. In this paper, the fluid dynamic aspect of channel formation in a highly over-dense plasma is studied and possible attenuation mechanisms of the propagating pulse are evaluated in one dimension. Under the assumption that mass ablation reaches a quasistationary state, the radiation-assisted ablation pressure, the speed of the bow shock, and the density steepening around the critical point are determined self-consistently from the ID fluid conservation relations and the electromagnetic wave equation. Due to ponderomotive profile steepening, the ablation pressure is reduced by 40% in the subsonic region and is dominated by the radiation pressure in the supersonic domain. Channel lengths are calculated for various intensities and pellet compression ratios. Likewise, the nonlinear propagation of a superintense electromagnetic wave in an underdense plasma channel is investigated for the ID case with the help of a relativistic fluid model.

Direct-drive laser fusion received a number of setbacks from the experimental observation in the 1960s and 1970s of very complex interactions in laser plasma experiments caused by a number of nonlinear and anomalous phenomena. Although smoothing methods were introduced intuitively or empirically–succeeding in reducing these difficulties–it was not until a few years ago that the 20-ps stochastic pulsation mechanism was discovered. We assume here that this 20-ps stochastic pulsation may be the major obstacle to achieving direct-drive fusion, even though it is now generally assumed that the major challenge to the achievement of direct-drive fusion is the Rayleigh-Taylor instability. While we do not discount the importance of the Rayleigh-Taylor mechanisms, we concentrate here on the analysis of the pulsation process. A method of analysis was developed, using time-dependent real-time computations employing a genuine two-fluid model, which includes the interior electric fields and the very large amplitude longitudinal plasma oscillations that are driven by the laser field. These mechanisms, which were first suggested in 1974, reveal themselves now as self-generated von-Laue gratings, preventing the propagation of laser radiation through the outermost plasma corona and preventing energy deposition by temporal interruption caused by thermal relaxation and the subsequent reestablishment of these gratings, and so on. The abolition of this pulsation by broad-band laser irradiation or other smoothing methods is now well understood. A synopsis of these developments is presented here, consistent with Rubbia's proposition of using the MJ drivers for laser fusion, the technology for which is now available.

A review of work done on laser generated shocks in solids using a high-peak-power Nd:glass laser in the Laser and Plasma Technology Division of the Bhabha Atomic Research Centre is presented in this paper. The 20-J/5-ns Nd:glass laser used in the experiments is able to produce focused laser intensities in the range of 5 × 1011-1013 W/cm2 and a shock pressure in the range of 0.1–5 Mbar. A l-J/100-ps Nd:glass laser is also being developed for laser shock studies, details of which are presented. Several diagnostics have been developed for laser shock studies of which the main diagnostics are optical shadowgraphy, optical interferometry, and laser velocity interferometry for particle velocity measurement. The measurement of ablation pressure in various types of targets, the scaling of ablation pressure with laser intensity, the effect of laser beam nonuniformity on shockfront or ablation pressure uniformity, the smoothing of shockfront and pressure profiles in high-Z coated and high-Z doped targets, and so on, are the various experimental studies conducted. We have tried to study X-ray driven ablation in aluminum and plastic targets using gold and copper as X-ray producing targets. Uniform pressure of about 0.1 Mbar has been generated over an area of 4 mm2

The interaction of relativistic electrons produced by ultrafast lasers and focussing them on strongly precompressed thermonuclear fuel is analytically modelled. Energy loss to target electrons is treated through binary collisions and Langmuir wave excitation. The overall penetration depth is determined by quasielastic and multiple scattering on target ions. Thus, it appears possible to ignite efficient hot spots in a target with density larger than 300 g/cc.

Light ion beam inertial confinement fusion (ICF) is a concept in which intense beams of low atomic number ions would be used to drive ICF targets to ignition and gain. Here, results from numerical simulations are presented describing the operation of an indirect-drive light-ion ICF target designed for a commercial power plant application. The simulations indicate that the ICF target, consisting of an X-ray-driven capsule embedded in a spherical foam-filled hohlraum, will produce a fusion energy output of over 500 MJ when driven with lithium ion beams containing a total input energy of 8 MJ.

Under certain restrictions imposed on the plasma parameters, an analytical 2D solution to the magnetohydrodynamic equations, taking into account the Hall effect [of the HMHD (Hall magnetohydrodynamic) equations], is found for the case when plasma flows across a magnetic field. This solution has the form of the sum of a rather arbitrary steady flow and a small time-dependent disturbance. We show that waves of a purely acoustic nature can propagate against the background of the flow. The magnetic field manifests itself in this process only in that it produces an effective gravity force, the “gravitational” acceleration being proportional ωeτe. Like acoustic-gravity waves in the atmosphere, such quasiacoustic-gravity (QAG) waves in a plasma increase greatly in their amplitude as they propagate “upward,” that is, in this case, to the anode of an accelerating plasma channel. The existence of a rather general dimensionless similarity criterion is also shown. It can be found directly from the structure of the HMHD equations without any restrictions as to the plasma parameters.

In doing research on the turbulent mixing (TM) of two gases different in density, it is of great interest to study experimentally the 3D density distribution pattern of chemically nonreactive gases in the TM zone. For this purpose, noncontact and, particularly, optical techniques to obtain experimental data may be attractive. This article discusses the possibility of using pulsed laser interferometry in this application. Based on this technique, the experiment should result in the mixture density distribution integrated along the light path. Requirements for high-quality interference patterns have been analyzed in application to typical experimental conditions, to show that they may be produced with specific restrictions set on the mixture constitution. Generally, the TM zone has no symmetry. Therefore, the problem of reconstructing 3D density distributions (TDD) of gases can be solved by sufficiently providing many TM zone integral projections (or aspects). It is technically difficult and expensive to achieve this large number of aspects (N> 10). Therefore, it is essential that a reconstruction method be selected to allow the solution of the problem with the least possible number of aspects. Given that the experiment data are incomplete, the reconstruction methods that are based on the concept of maximum data entropy did well. Information a priori about the solution to be sought for an isobaric gas mixture is that its each constituent has invariable density. Thus, a functional data entropy can be defined that is similar to Fermi gas in statistical physics. An algorithm has been suggested for reconstruction as a modified maximum-bounded entropy procedure (Bashurin et al. 1995). This makes reasonable good reconstruction achievable even with as few aspects as N = 4. Experiments on the study of TM of a propane jet in air using a four-aspects laser interferometer were provided and reconstruction of propane concentration distribution was conducted. The results allow determination of the TM zone spectral characteristics.

A high-power Nd3+:glass laser system has been constructed and tested. This system consists of a master oscillator, a four-pass amplifier for preamplification, and five-stage amplifiers. The system has been demonstrated in excess of 80 J (2 TW) at 40-ps pulse duration. Final laser beam quality was quite good due to the compensation of the polarization distortion in the four-pass preamplifier, the minimization of the diffraction effect by the image relaying, and the elimination of high spatial frequency components by the spatial filtering. This enables us to obtain high laser output power without any severe spatial spiking effects. Gains and spatial profiles of output pulses were measured after each amplifier stage.

The very clean nuclear fusion reaction of hydrogen and boron-11 by inertial confinement arrives at conditions for power stations by volume ignition only at compressions to 100,000 times the solid state. The earlier (numerically) observed anomaly of decreasing gain at increasing density (retrograde behavior) is analyzed and the reason clarified: the strong stopping power mechanism, based on Gabor's collective model, is reaching its limit of too small Debye lengths at the extremely high densities because of the optimum temperature in the range of 30 keV due to the reabsorption of the bremsstrahlung. The relativistic correction of the bremsstrahlung for the always much higher temperatures after volume ignition is included from Maxon's model.

This study was devoted to the investigation of the shock-induced intensification of the turbulent mixing zone. Our data were compared with those reported by the authors from the United States and France. The experiments were performed in a shock tube of square section filled with the two gases, which were separated with a thin lavsan film. The working gases were helium, argon, krypton, xenon, and their combinations. This allowed us to perform the studies for the Atwood numbers ranging from 0.095 to 0.91 in magnitude. The incident shock wave passed from light to heavy gas and vice versa. The initial pressure of 0.5 atm and Mach number of the incident shock wave 3% were chosen as the working parameters because under these conditions the experimental x, t-diagram coincided with the calculated x, t-diagram within the 3% experimental error. The process was visualized by the Schlieren method with the IAB-451 device using continuous recording or recording in frames. We studied the shock-induced intensification of the turbulent zone, the effect of initial conditions on this intensification, and the influence of the turbulent zone on the intensification of the shock passed through the zone.

This paper discusses the implications of using different fuels, including pure deuterium, deuterium–tritium, deuterium–helium3, and proton–boron11, on safety and environmental compatibility of the fusion reactor, as well as on the driver requirements. Due to present-day technology limitations, it seems likely that the first generation of the fusion reactors will be based on a deuterium–tritium cycle. Such a scheme, however, would pose serious problems, including neutron activation and tritium handling. We show that by developing low-level tritium inertial fusion targets, one may substantially reduce the daily use of tritium in the reactor that may ultimately lead to a reduction in the overall tritium inventory in the power plant. Such reduced tritium targets will still generate sufficient energy to run the power plant economically.

A method is proposed to evaluate the power brightness of an intense pulsed ion beam by using a Thomson parabola spectrometer (TPS). In the method, the time-dependent power brightness of each ion species can be determined independently from the density profile of ion tracks. The method is successfully utilized to evaluate the power brightness of ion beams produced in point pinch diode. The brightness of highly ionized carbons of 660 keV and oxygens of 880 keV, and singly ionized molecular ions of 400 keV, are evaluated independently. The total brightness is evaluated to be 3.2 GW/cm2/sr for highly ionized ions, and 1.9 GW/cm2/sr for molecular ions.