The collisional recombination process in highly ionized plasma and relevant reheating of the plasma are analyzed in the parameter regime appropriate for X-ray lasing. A method for describing the rate of collisional recombination is proposed based on a compact threelevel atomic model. Reheating of the plasma due to collisional recombination is described by a time-dependent adiabatic exponent γ. Using a self-similar description of the free expanding plasma, the gain of recombination lasing is investigated. In comparison with an open two-level atomic model, the present model gives lower gains appearing later in time. The inclusion of plasma reheating reduces the peak gain and shifts it to later times. Although the three-level model is shown to give a good qualitative description of the atomic processes, a considerable discrepancy was observed when compared with simulations for hydrogenlike carbon.

A three-term equation of state is used for the simulation of hydrodynamic shock phenomena. The reliability of it is tested by comparing the isotherms and shock Hugoniots obtained from it with available experimental data. This is illustrated for three typical materials Al, Pt and Au, which are of considerable interest for inertially confined thermonuclear fusion studies. We observe that reliable equation of state (EOS) data can be generated for nonmetallic substances like CH2. The EOS is used in the simulations of laser-driven shocks in double-layered target aluminum on gold (Al-Au) using hydrodynamic code employing a simplified laser-absorption model. The output from it is compared with the recent laser-driven shock experiments of Koeniget al.

Experimental results on the determination of the color temperature in shock waves produced with lasers are presented. The method is based on imaging the target rear side in two different spectral windows and on using phased zone plates to produce high-quality shocks. The shock velocity is also measured, allowing, with the use of the equation of state, the real shock temperature to be deduced and compared with the measured color temperature.

In a self-consistent manner, the total power for linear inverse Compton scattering between a Gaussian electron beam colliding head on with a Gaussian laser beam is obtained. The theory is shown to agree with well-known limiting cases. Coupling among harmonic modes is explicitly shown in the resultant power relation. Even so, for the parameters of interest, harmonic modes are negligible compared to the fundamental mode. Total power calculations are of importance in detector calibration. The theory is applied using practical linear accelerator and laser parameters.

One of the most crucial problems of a heavy ion fusion (HIF) driver is the transport of the beam from the final focusing system to the fusion target. The conventional focusing scheme is based on ballistic transport, assuming that all space charge effects can be kept sufficiently small. To achieve a space charge neutralized beam transport, other more sophisticated schemes like beam transport in a plasma channel have been suggested. Inspired by the results of the first experiments on the generation of adequate discharge-driven plasmas, we suggest applying a pulsed supersonic gas jet for the high-current discharge channel creation, thereby improving the plasma channel stability. The supersonic jet is produced by a gas expansion into the reactor chamber through a converging-diverging nozzle that has a hollow inner tube on its axis for both heavy ion and UV laser beam injection.

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 injection-locking excimer laser beam with a pulse duration of 25 ns is focused on the surface of a polymide film. The laser beam that passes through the etching film is shorter than the original one. By optimizing the thickness of the film and the beam powerdensity, a pulse with a 3-ns pulse duration can be obtained using this switch technology.

This paper presents a simple but complete 2D model for helical flux-compression generators that overcomes many of the limitations present in existing zero-dimensional models. The generator circuit is effectively decomposed into separate z and; current carrying circuits, with each of the; circuits (rings) corresponding to a different current. Use is also made of a technique by which these rings are sequentially switched out of circuit. The approach proposed opens the way to a full understanding of the behavior of cascade systems of generators inductively coupled by dynamic transformers using the so-called flux-trapping technique. In addition, the model can also yield an important insight into the phenomena that differentiates the performance of small generators when primed by a capacitor, a battery, or an externally produced magnetic field. Finally, the numerical code developed in the paper can readily be adapted to model high-energy and high-current generators in which the helical coil and the armature are of variable geometry. Valuable design information is provided on the magnetic and the electric field distributions within the generator and on the likely radial and axial movements of the stator turns.

The problem of hydrodynamic stability is important for inertial confinement fusion (ICF) systems based upon high compression of fuel before its ignition. This problem for the case of complicated multilayer foils has been studied here by a new approach describing the development of Rayleigh-Taylor or interchange instability in compressible media with inhomogeneous distribution of “entropy”s = ρ/ρk, ∂ where K = (∂ In ρ/∂ In ρ)s is an adiabatic derivative taken in the local hydrostatic values of ρ and ρ. Inhomogeneous distribution of s simulates the dynamics of development of perturbations of multilayer flyer foils and shells. Besides instability, the same approach has been used for analysis of ID pulsations of a levitated foil. The problem of pulsations is real in the case of foils. Indeed, (1) an ablative acceleration is equivalent to an effective gravity field, which causes the appearance of an atmospheric-type distribution of thermodynamic functions, (2) the duration of ablative flight of foil is at least several times larger than the time that is necessary for an acoustic wave to travel from one side of the foil to another side, and (3) there is a strong initial impulse that initiates the motion of foil. This impulse together with (1, 2) is a reason for the powerful pulsations of foils. The period of pulsations is defined by the velocity of sound in the foil material, which is dependent on the derivatives of an equation of state (EOS). The check of the derivatives gives us finer information concerning the current state of matter and the EOS than the usual measurements of material velocity and pressure that are rougher measures. Therefore, an analysis of pulsations seems to be a promising tool for tracking the dynamics of flyer foil and for the definition of thermodynamic properties of matter.

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.

In a number of single-shot applications and experiments at remote locations where flux-compression generators provide the most practicable power source, it may be necessary to use cascaded generators with inductive coupling between them to provide the required power amplification. The complexity of the resulting system appears to have so far inhibited the development of any simple but complete numerical code, and has prevented a full understanding of the complex action of the overall system. The present paper meets these requirements, by extending an existing simple 2D helical generator code, and shows how this can be used to solve problems arising from the design stage of a prototype system.

The design and constructional aspects of a novel pulse power generator for use in dense plasma research presently under construction are presented. The generator consists of two Marx capacitor banks, each of 0.25 μF, 480 kV, and 28.8 kJ. Each Marx generator drives a water transmission line, in which the live electrode is the central conductor. The transmission lines consist of a constant impedance section followed by a multielectrode gas linegap followed by an exponential taper to the load section. The novel feature is the use of an auxiliary exponential line coupled at the load. This line controls both the voltage and the effective impedance at the load section. In addition, by leaving this line circuit open, energy not coupled to the plasma in the initial high-impedance phase may be reflected back and deposited into the discharge, increasing the peak current by 50%. Circuit simulations using a real-time-varying load impedance show that the current pulse rises in an approximately linear way to a maximum of 1.2 MA at 250 ns. The current falls to zero in the following 250 ns. The current waveform may be flattened simply by disconnecting the auxiliary line, giving a rectangular pulse of 350 ns with a maximum value of 950 kA. The overall impedance of the entire system may be adjusted by varying the separation between the conductors. The equivalent source impedance at the load is 0.8 Ω. This low value is by virtue of the auxiliary line, which limits the voltage at the load section and reduces the insulator constraints. We present simulations of the generator under real load conditions. The model also is checked against analytical solutions of exponential line behavior and against other published models of pulse power generators.

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 stopping power of dense nonideal plasmas is calculated in different approximations. The T-matrix approximation for binary collisions is compared with the random phase approximation (RPA) approximation for dielectric fluctuations. Within a microscopic model, the dynamical evolution of the velocity of the projectile is calculated. It reproduces well experimental values for the stopping of fast heavy ions. Further improvements due to correlations are discussed. Both concepts, cluster decomposition and memory, are compared and it is found that they lead to the same quantum virial corrections of the Beth-Uhlenbeck type in equilibrium. However, memory in the kinetic equation causes an additional renormalization of the effective energy transfer in nonequilibrium.

Space-resolved spectra of line-shaped laser-produced magnesium plasmas in the normal direction of the target have been obtained using a pinhole crystal spectrograph. These spectra are treated by a spectrum analyzing code for obtaining the true spectra and fine structures of overlapped lines. The spatial distributions of electron temperature and density along the normal direction of the target surface have been obtained with different spectral diagnostic techniques. Especially, the electron density plateaus beyond the critical surface in line-shaped magnesium plasmas have been obtained with a fitting technique applied to the Stark-broadened Ly-α wings of hydrogenic ions. The difference of plasma parameters between those obtained by different diagnostic techniques is discussed. Other phenomena, such as plasma satellites, population inversion, etc., which are observed in magnesium plasmas, are also presented.

An expression for the stopping power is derived in the quantum T-matrix approximation. The transport cross sections needed for a numerical evaluation are calculated using a scattering phase-shift analysis. Numerical results are given for the stopping power of an electron beam running into an electron gas. The temperature and density dependencies of the stopping power are discussed. Finally, dynamical screening is included in the weak coupling limit according to a kinetic equation proposed by H.A. Gould and H.E. DeWitt.

A fast-charging, discharge-switch-free Blumlein pulse forming line has been developed for high-voltage pulsed power generation. In the BL, a saturable charging inductor (CI) of amorphous metallic core is utilized and, as a result, fast-charging (charging time ≈220 ns) is obtained with a reduced prepulse. In addition, by using CI as a step-up transformer, the impedance of the output pulse can be converted to 4Z, Z, Z/4. By using the BL with a Marx generator of 300 kV and 1.1 kJ, an output of —580 kV at 24 kA and a pulse length of 60 ns are obtained, with a current rise time of less than 16 ns. The energy transfer efficiency of the line (output pulse energy/charging energy of a pulse forming line) is evaluated to be more than 92%.

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.