A review of theoretical works on the laboratory X-ray laser (XRL) research performed at RFNC–VNIITF for the last few yearsis presented. Three potential photopumped XRL schemes with relatively short laser wavelengths (44, 23, and 64 Å) have been investigated. Theoretical studies of lasing plasma parameters for some of the published recombination and resonantly photopumped XRL schemes have been performed using our kinetics and line-profile codes.

An experimental investigation into the asymptotic stage of the separation of the turbulized mixtures of two fluids with densities ratio n = 3 has been carried out. The turbulized mixtures resulted from Rayleigh–Taylor instability when the contact boundary between two fluids was moved under an acceleration. At a certain instant of time, the system changes from the gravitationally unstable mode to the gravitationally stable one by the way of changing of the acceleration sign. During the ampoule motion with the investigated fluids at the gravitationally stable mode, the depth of penetration of the heavy fluid into the light one was registered with the photographic method. The length of the ampoule way at the gravitationally stable mode has been fixed so that the final (asymptotic) stage of the separation could be registered. At the result of themeasurements, it has been determined the separation process at the asymptotic stage has the same dimensionless velocity asat the initial stage.

An experimental investigation into inertial properties of the developed Rayleigh–Taylor instability with the different initial values of the kinetic energy of turbulence has been performed. The experiments were performed by using two fluids having different densities with density ration n = 3. Fluids were placed in an ampoule. At the unstable stage of motion, the ampoule was moving under an acceleration. At a certain instant of time the acceleration was removed and the ampoule moved under the force of inertia. By means of pulsed X-ray photography, the mixing region size and the time-space distributionof the average density of matter in the turbulent mixing region have been determined at different instants of time. The time-space distributions are compared with those obtained by semiempirical theories of mixing.

The results of numerical and analytical investigation of the ultra-intense laser pulse's interaction with overdense plasma are presented. The mechanisms of the wave field energy transformation into the overdense plasma energy are discussed. The effects of radiation propagation deep into plasma as well as long-living vortex formation, plasma boundary instability, and the surface structures formation are obtained. The basic mechanisms for the absorption of incident radiation and the role played by polarization of the radiation are studied. Nonlinear theory of plasma surface instability in the field of the strong electromagnetic wave is developed.

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.

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.

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.

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.

On the basis of Lagrangian representation for equation of thin-liquid-layer dynamics, analytic solutions of the Rayleigh–Taylor instability problem at the nonlinear stage in the observer's space are found. Evolution of various perturbation types, in the layer shape and in layer velocity components, is considered. It is shown that there are both exponentially growing and limited oscillating solutions. The results of the theoretic considerations are substantiated with numerical calculations that use the complete system of the law of conservation.

In this article, the results of experimental and numerical studies of the behavior of perturbed interface between air and helium are presented. The interface is initially accelerated by the incident shock wave coming from air to helium and then decelerated by a series of reflected shock waves. Two types of initial interface perturbations like “saw” and “step” are considered.

This article considers one of the simplest shear flows–ID time-dependent plane mixing layer. Under certain conditions, many more complicated flows are similar to it: timeindependent plane mixing layer, initial portion of plane and round jets, initial mixing phase in cylindrical vortex, etc. This application was previously studied in a 2D approximation. In this computation the turbulence was treated as the result of random perturbations initially applied to the interface of two flows. Numerical simulation used a 2D EGAK code. The computational results were interpreted using the version of semi-empirical turbulent theory with isotropic Reynolds tensor (model 1). This article continues the studies by Bakhrakh; in addition, a similar approach is implemented based on 3D simulation with the TREK method. The data interpretation uses the version of semi-empirical theory with and without Reynolds tensor anisotropy (models 1 and 2, respectively).

The MAGO concept using the thermonuclear target with DT gas preliminary heating up to kiloelectronvolt range temperatures, which sufficiently enables the reduction of requirements of the compression rate (to 10 km/s) and the compression degree (to several hundreds) of the target, is investigated. The MAGO chamber with the Laval supersonic annular nozzle is used for plasma preheating. In this chamber magnetized plasma is accelerated up to 1000-km/s velocities and heated by collisionless shock waves. Systems with liner and magnetic compression are considered for the subsequent plasma compression. Energizing of a real-size system can be supplied by the magnetic flux compression generators with energy 100−500 MJ. Experiments close to the threshold of ignition can be conducted proportionally in 2−3 times reduced systems. Then the energy required will be 10–30 times less than in a real-size system.

Powerful pulse installations are usually used to produce large yields of X-ray radiation. With an increase of the stored energy up to 100 MJ, the costof a single experiment on these installations becomes comparable to the cost of a shot with explosive magnetic generators (EMG), according to expert estimates. The physical scheme of a device with a changeable mass liner forlarge soft X-ray (in the range of 0.3 to 0.5 keV) yields eneration is investigated. The scheme investigated is substantially free from difficulties connected with high precision liners and fast switches for current pulse sharpening.

The results of numerical simulations of fast electrons interaction with matter, calculated yield and angular distribution of bremsstrahlung and fluorescence K-α X-ray radiation and generation of electromagnetic fields, carried out by ERA, PM2D, and PRIZMA codes for the state of experiments on interaction of ultra-short laser pulses with high-Z targets at intensity of 1016−1018 W/cm2 are presented. Spherical targets with conical hollows and conical targets of high-Z matter are proposed for experiments with picosecond lasers to increase the brightness of hard X-ray sources.

The results of ID-ERA and 2D-TIGR, OMEGA codes calculations of compression and burn of indirect-driven targets for the thermonuclear ignition and Engineering Test Facility are presented. The possibility to obtain high-energy yield of G > 100 with driver energy of Ed = 5−10 MJ by using the heavy-ion one-beam accelerator as the main driver and powerful laser for fast ignition of thermonuclear detonation of cylindrical targets is pointed out.

One of the difficulties of light ion beam fusion is to propagate the beam in the reactor cavity and to focus the beam on the target. The light ion beam has some local divergence angle because there are several causes for divergence at the diode. The ion beam propagates with a speed of one tenth of light speed. With this high speed, the leading edge of the ion beam cannot be charge-neutralized due to the delay of neutralization by the inertia of thermal electrons in the background plasma. The electrostatic force induced by this mechanism at the leading edge causes the beam divergence during propagation. To confine the beam in a small radius during propagation, the magnetic field must play a role. Here the electron beam is proposed to be launched simultaneously with the launch of a proton beam. If the electron beam has the excess current, the beam induces the magnetic field in the negative azimuthal direction, which confines the ion beam in a small radius by the electrostatic field, as well as the electron beam by the Lorentz force. The metal guide around the beam path helps the beam confinement and reduces the total amount of magnetic field energy induced by the electron current. Simulation shows that the proton beam with the comoving electron beam propagates in a small radius confined in the metal guide.

Compton scattering of laser light by an electron beam at large angles, in particular at 90°, produces coherent hard radiation if the density of the electron beam is high enough. In this case, the intensity of the scattered radiation is greatly enhanced in a small cone around the forward direction of propagation of the electron beam. As an example, the production of 1-KeV coherent X rays is discussed.

A classical linear theory is used to compare large synchrotron sources to a rf linear accelerator employed as a VUV/X-ray source. Comparisons are made on a per-pulse basis. It is demonstrated that the linear accelerator as an X-ray source is comparable to large synchrotron accelerators with wiggler insertion devices at the experiment. Applications to lithography, X-ray microscopy, X-ray spectroscopy and detector calibration are examined. Excluding lithography, the linear accelerator with an appropriate laser source is a useful source of X rays for these applications. As verification, classical results are compared with quantum mechanical results and are shown to be in good agreement.