Experimental study of the radiation scattered at the laser heating of low-density foam targets and transmitted through the targets is presented. The scattered and transmitted radiations were investigated using spectrometers and streak cameras providing spatial, angular, spectral and temporal resolutions that enabled us to study the dynamics of the process of burning-through of the thick foam targets, the velocities of the plasma critical density motion as well as mass velocity of the plasma.

The experimental results of the activation spectra, dose rate measurements, and the residual nuclide production cross sections obtained after the irradiation of the NatCu and 59Co targets by 12C ion beams at ITEP and GSI are presented in this paper. These results are compared with simulations by the CASCADE and LAQGSM codes.

Modeling plus simulations using the one-dimensional Lagrangian radiation-hydrodynamics code HYADES are compared with data from classical and ablative Rayleigh–Taylor experiments conducted on the Nova laser. Comparisons between the experiments and modeling for both the gross hydrodynamic motion and the perturbation evolution are made and show good agreement. A third order perturbation analysis is applied to demonstrate the onset of nonlinearity. A simple, physically intuitive saturation model is used to describe the growth further into the nonlinear regime. Finally, we present the first comparison of the Betti ablation front theory with indirect-drive RT data and obtain good agreement.

A kinetic model of electron cascade growth in the electromagnetic field of a focused intense laser pulse as used for laser spark generation in gases has been numerically implemented in Visual C code. The effects considered comprise Drude absorption, diffusive kinetic and inelastic losses as well as (three-particle) electron recombination. The objectives were to illustrate the dynamic process of gas ionization, and to clarify the pressure dependence of known breakdown thresholds within a range of about 2 × 104 to 2 × 106 Pa of initial pressure. Two-dimensional (cylindric coordinates) simulations of the optical breakdown in nitrogen were conducted on a commercial PC, using constant values for the collision cross section (2 × 10−19 m2), prevalent electronic excitation states (~4.8 eV), and a laser wavelength of 1064 nm. A certain aerosol concentration on the order of 3 ppb was assumed in order to provide initial electrons for cascade growth. Exemplary results with laser pulse energy of 26 mJ, pulse duration of 14 ns and an 18 µm focal spot size illustrate the dynamic process of ionization within a very short time period of less than 0.5 ns. The kinetic energy of the electrons is found to increase sharply up to more than 100,000 K on breakdown. A series of simulations considered the minimum pulse energy of breakdown (MPE) under variation of initial pressure. Identical laser parameters as in experiments conducted previously were used and the results are in excellent agreement with respect to curve shapes, i.e., MPE ~1/p0.4 in the first experiment and MPE ~1/p0.3 in the second one. The absolute values lie within a factor of two, which is explained by model abstraction and input data uncertainties.

The X-ray image of a compressed shell (enhanced by high-Z doping) was used in recent experiments to diagnose the effect of shell-fuel mixing. The emission ring (due to the limb effect) moves toward smaller radii due to mixing. We show here that using backlighting imaging can greatly enhance future imaging experiments. In addition to the emission ring, a backlighting absorption ring can appear around it. The absorption ring is virtually unaffected by mixing. Thus, the relative position of the two rings constitutes a mixing signature. In other words, the absorption ring delineates the colder part of the shell and is a true signature of the compression, whereas the emission ring reflects the shell material motion due to mixing.

An analytical formalism of laser absorption in a nanorod embedded dielectric surface has been developed. Nanorods lie in the plane of the dielectric, in the form of a planar array. A laser, impinged on them with an electric field perpendicular to the lengths of the nanorods, imparts oscillatory velocity to nanorod electrons. As the free electrons of a nanorod are displaced, a space charge field is developed in the nanorod that exerts restoration force on the electrons and their drift velocity shows a resonance at ${\rm \omega} = {\rm \omega} _{\rm p}/\sqrt 2 $, where ωp denotes the plasma frequency of free electrons inside the nanorod. It is inhibited by collisions and nanorod expansion. At the resonance, the electrons are efficiently heated by the laser and laser energy is strongly absorbed, resulting in significant reduction in laser transmissivity. The transmissivity decreases with laser intensity.

The interaction of electromagnetic radiation with plasmas is studied in relativistic four-vector formalism. A gauge and Lorentz invariant ponderomotive four-force is derived from the time dependent nonlinear three-force of Hora (1985). This four-force, due to its Lorentz invariance, contains new magnetic field terms. A new gauge and Lorentz invariant model of the response of plasma to electromagnetic radiation is then devised. An expression for the dispersion relation is obtained from this model. It is then proved that the magnetic permeability of plasma is unity for a general reference frame. This is an important result since it has been previously assumed in many plasma models.

This paper considers the heating of a target in a shock wave created in a planar geometry by the ponderomotive force induced by a short laser pulse with intensity higher than 1018 W/cm2. The shock parameters were calculated using the relativistic Rankine–Hugoniot equations coupled to a laser piston model. The temperatures of the electrons and the ions were calculated as a function of time by using the energy conservation separately for ions and electrons. These equations are supplemented by the ideal gas equations of state (with one or three degrees of freedom) separately for ions and electrons. The efficiency of the transition of the work done by the laser piston into internal thermal energy is calculated in the context of the Hugoniot equations by taking into account the binary collisions during the shock wave formation from the target initial condition to the compressed domain. It is shown that for each laser intensity there is threshold pulse duration for the formation of a shock wave. The explicit calculations are done for an aluminum target.

A comparative analysis of a fast atom beam and ion beam effect on a metal target in the binary collision model is performed. Irradiation by fast atoms has been shown to more closely correspond to neutron radiation in a nuclear reactor, in terms of the primary knocked-on atom spectrum and the efficiency and mechanism of the radiation defect formation. It was found that upon irradiation by fast carbon atoms with an energy of 0.2-0.3 MeV, the average number of radiation defects in the displacement cascade of one atom is four to five times higher than the calculated values using the SRIM program for ions with the same energy. It is shown that during penetration in the target, the probability of ionization of atoms with energies less than 0.4 MeV is negligible.

In preparation for an experiment with a laser-generated intense proton beam at the Laser Fusion Research Center at Mianyang to investigate the 11B(p,α)2α reaction, we performed a measurement at very low proton energy between 140 keV and 172 keV using the high-voltage platform at the Institute of Modern Physics, Lanzhou. The aim of the experiment was to test the ability to use CR-39 track detectors for cross-section measurements and to remeasure the cross-section of this reaction close to the first resonance using the thick target approach. We obtained the cross-section σ = 45.6 ± 12.5 mb near 156 keV. Our result confirms the feasibility of CR-39 type track detector for nuclear reaction measurement also in low-energy regions.

The one-dimensional behavior of a thin plasma foil heated by laser is studied, emphasizing on the fully kinetic effects associated with initial energetic electrons using a relativistic kinetic 1D3V Particle-In-Cell code. For this purpose, the generalized Lorentzian (Kappa) function inclusive the high energy tail is employed for initial electron distribution. The presence of the initially high-energy electrons leads to a different ion energy spectrum than the initially Maxwellian distribution. It is shown for the smaller Kappa parameter k where the high energy tail of the electron distribution function becomes more significant, the electron cooling rate increases. Moreover, the spatiotemporal evolution of electric field is strongly affected by the initial super-thermal electrons.

Cylindrical magnetrons with rotating cathodes have found wide application in the thin-film coating deposition technologies owing to a higher degree of the target utilization and used power level as compared with planar magnetrons. The aim of this work was to increase the efficiency of cylindrical magnetrons. It is known that the region of uniform coatings deposition with extended magnetrons is essentially lower than the sputtered cathode length. The actual achievable cathode utilization degree is limited, with the regions at cathode ends having a higher wear rate than the central part. To eliminate these shortcomings, experiments were carried out on the creation of a magnetic system to allow an increase of the coating deposition uniformity and target utilization. Resulting from the investigations that were carried out, a magnetic system design with an increased magnetic field at its ends (by 5–15%) and modified turn-around parts has been developed. This magnetic system design allows extending the coating deposition region with the uniformity of ±1% by 12.5 cm and completely eliminating accelerated erosion of the end cathode parts. The obtained results are promising for use in technologies of deposition of thin-film coatings with a high degree of uniformity (no worse than ±1%) onto large-area substrates.

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.

Unconventional, promising approaches to inertial fusion energy (IFE) proposed and studied in the framework of IFE keep-in-touch activity at Frascati EURATOM-ENEA Association will be reconsidered for the present more advanced technological context associated to a planned large installations scenario. Then the possibility to generate laser-produced fast heavy-ion sources (e.g., Bi ions, tens GeV) will be explored taking as reference results obtained in the FIGEX experiment scaled toward thermonuclear regimes. A possible dimensioning of such sources will be also given as well as the associated laser requirements.

Strong electromagnetic fields are radiated during the operation of the intense electron-beam accelerator (IEBA), and it is investigated in this paper. It is obtained that the triggered spark-gap switch and the main switch of the IEBA are the radiation resources. Here, the radiation of the triggered spark-gap switch is researched carefully. Firstly, circuit simulation is used to simulate the current going through the switch. The electric fields generated by the current and its frequency spectra are both calculated. The electric fields of the IEBA are measured by using a bi-cone antenna. When the primary capacitor of the IEBA is charged to 20 kV, the radiation field with amplitude of 753.4 V/m, dominant frequency of 20.8 MHz and high frequency 100 MHz is obtained. The experiment results show reasonable agreements with the analysis. It is believed that the gas-gap switch is a new method to achieve wide-band radiation.

A parameter study of implosion, burn, and gain of D–T ignitor/D3He fuel pellets is presented for a D3He inertial confinement fusion reactor. It is found from burn simulation that attaining a quasi-isobaric state with a temperature of 4 keV and pR value of 2.5 g/cm2 for the D–T ignitor and 0.8 keV and 9.5 g/cm2 for the D3He main fuel would suffice to obtain a pellet gain of ∼40–50 required for the D3He reactor. With 30-MJ laser irradiation and the coupling efficiency of 10%, the density of the target is assumed to be imploded to 5,000 times the liquid density. However, in the implosion simulation to realize the above configuration it is found that after void closure the central hot D–T ignitor region is ignited, while the bulk of the D3He main fuel is still imploding with high velocities. This preignition of the D–T ignitor leads to a low compression of the main fuel and prevents the D–T/D3He pellet from obtaining the required pellet gain. The pellet gain obtained is only ∼3.

The generation of high-order harmonics in ultraviolet spectral range by targets of periodic modulation interacting with relativistic, high contrast laser pulse (Iλ2 = 1020 W/cm2 · μm2) was investigated experimentally and numerically. The spectral intensity of the 2nd- and 3rd-order harmonic emission from grating of different periodicities (250, 410, and 480 nm) is presented. The enhancement of the 3rd harmonic order compared with 2nd was observed for a grating of 480 nm periodicity. The experimental results indicate the role of the grating periodicity on the emission efficiency of different higher order harmonics in the UV spectral range. The higher order harmonics are emitted at the grating surface separated from the specular reflection of the laser pulse, due of the interference effects. In addition, 2D numerical PIC simulations demonstrate a complex angular distribution of the higher harmonics (HH) spectral intensity and confirm the strong dependence of the HH efficiency of a specific order on the grating periodicity, as observed experimentally. These special features of the high harmonic emission by periodically modulated targets open the route toward the control of HH spectral composition and of the emission efficiency of the lower order harmonics.

Results in some directions of the target technology for research on high energy density and laser fusion at the Russian Federal Nuclear Centre–All-Russia Research Institute of Experimental Physics for the last three years are presented. The results of development of optical and X-ray methods of characterization and manufacturing techniques of targets for studying the equation-of-state at high pressures and the condensed rare gas targets for the influence of pulse-repeated laser irradiation are given.

Plasma focus is one type of ion source with energy up to few MeV. While some efforts have been made to understand the physics of ion beam acceleration in plasma focus devices (PFD), an acceptable clarification does not exist yet. In this work, the procedure of ions) electrons) acceleration in PFDs to the MeV energy is investigated theoretically. Moreover, the trajectory of electrons (ions) and their angular distribution are studied. The simulations are carried out by COMSOL Multiphysics version 5.2 for a 4.5 kJ Mather type PFD. The results of simulations and calculations show that trapped ions in the negative potential of electrons, their movement toward the top of the anode and the drift motion due to electrical and magnetic fields near the top of the anode are the main causes of high energy electrons (ions) production and acceleration.