A conical-pinched electron-beam diode has been studied with the objective of increasing the brightness of this inherently high current ion beam. Experiments and calculations are described that suggest it may be possible to obtain powers as high as 1013W/cm2 at 4MV from a carefully designed insulated-anode-type pinched-electron beam diode.

Time and space-resolved emission spectroscopy measurements were performed to investigate plasma dynamics during laser evaporation of a graphite target in an ambient inert atmosphere. Intense molecular emission is found to occur behind a front separating the plasma from the foreign gas. Two stages of expansion are found and are well described, using a viscous drag force model for the first one and a delayed ideal blast wave model for the second. The vibrational temperature estimated using the Swan band in helium at different pressures is presented.

We theoretically and experimentally investigate the conditions of obtaining a narrowband flat-top Brillouin gain spectrum (BGS) based on single-frequency and multi-frequency phase modulations. Using the unequal-amplitude spectral lines, the flat-top BGS can be realized by controlling the intensity ratio and the frequency separation between them. In experiment, we obtain the flat-top gain spectra with the bandwidths of 40 MHz and 125 MHz, and with the top fluctuation of less than 0.21 dB. Based on this, we also achieve low distortion Brillouin amplification of a probe signal pulse and spectrum.

The acceleration of transparent charged macroparticles by the repeated radiation pressure of a laser beam is considered. A radial electric field allows a motion along a closed path, on a stable orbit. For macroparticles made out of carborundum, of radius r = 0.5 μm, velocities above 100 km/s look feasible, allowing the production of high densities of energy.

We generate self-phase-stabilized pulses by difference-frequency generation of a hollow-fibre broadened supercontinuum followed by two-stage optical parametric amplification. This system allows the production of broadband pulses widely tuneable in the near-IR wavelength region. Energies up to 0.2 mJ with 15 fs pulse width are demonstrated. These characteristics make this source suitable as a driver for attosecond pulse generation.

The goal of the experiments on “Module A-5” and S-300 machines for some 15 years was to study the “liner-converter” inertial confinement fusion (ICF) scheme. A new class of fast instabilities of z pinches was studied both in experiments and in analytical theory. Stabilization of the light liner has been achieved by means of an extrinsic magnetic field. Formation of thin overheated current-carrying shells has been predicted analytically and seems to be really observed. Both theory and simulations predict growing Te and heat flux onto the converter by using heterogeneous z pinches with spatially separated regions of efficient energy exchange and of efficient heat conductivity. In our first experiments of this kind, impurities were inserted by means of placing thin glass fibers into a He jet. Growing intensity of the spectral lines of He-like chlorine from the cathode surface confirms the growth of heat flux. Theoretical investigations and 2.5-D simulations were devoted to some basic points of this program.

The energy problem is an open issue becoming increasingly pressing. The possibility to use nuclear fusion as an alternative energy source is thus acquiring progressively more importance and many investors are pushing to achieve the goal of an electric plant based on fusion. The most studied reaction is the deuterium-tritium one, but this poses several technical issues related to the handling of the radioactive fuel and neutron generation. In this frame, the aneutronic 11B(p, α)2α fusion reaction has attracted the interest of many researchers. Despite a fusion reactor based on pB is still a long-term goal, the study of this reaction is important both for astrophysics research and for its possible employment in schemes of high brightness source of α particles for applications, as for instance in medicine. Nevertheless, the univocal identification of the produced alphas is a well-known challenging task when the reaction is triggered by high-intensity lasers. Indeed, due to the multifaceted emission typical of laser-matter interactions, the signal coming from alphas is often superimposed to that generated by protons and by other ions, and in many cases, it is therefore hardly recognizable. In this work, we analysed the possibility of employing a Thomson spectrometer (TS) with an adequate differential filtering system for the exclusion from the α-particle trace, the contribution of all other ionic species. Moreover, for the energy ranges where the filtering method cannot be successfully applied, we investigated the feasibility of integrating in the TS assembly a particle detector for time-of-flight (TOF) measurements.

The third-order nonlinear optical properties of three hydrazone derivatives, namely, ethyl 2-((2E)-2-(4-(dimethylamino)benzylidene]hydrazinyl)-5-nitrobenzoate, ethyl 2-((2E)-2-(4-chlorobenzylidene)hydrazino)-5-nitrobenzoate, and methyl 5-nitro-2-((2E)-2-(4-nitrobenzylidene)hydrazino)benzoate were investigated by the single beam Z-scan technique with nanosecond laser pulses at 532 nm. The compounds were doped into PMMA (poly (methyl methacrylate)), and their third-order nonlinearity was studied with a prospective of reaching a compromise between processability and high nonlinear optical behavior. The optical limiting study of the samples was carried out at 532 nm. The measured values of the third-order nonlinear susceptibility, χ(3), and the nonlinear refractive index, n2, are of the order of 10−13 esu and 10−11 esu, respectively. The nonlinear absorption in materials was attributed to reverse saturable absorption. The results are quite promising for possible applications in photonic devices.

With the development of high-power microwave technology, the output power of the pulse generator is required more and more higher. In this paper, it is realized by increasing the output power of the module while the output impedance of the module changes little. The module of the generator is based on pulse forming network (PFN) and linear transformer (LT). Four Blumlein PFNs with arc-type configuration and 24 Ω characteristic impedance were connected symmetrically to the primary coil of the LTD and driven by two identical laser triggered spark switches to ensure four Blumlein PFNs synchronizing operation. On this basis, a two-stage high-power pulse generator based on PFN-LT is developed. The following technical parameters of the generator were achieved on a 12 Ω high-power solid resistor: output voltage amplitude of ∼250 kV and output power of ∼5.2 GW at a repetition rate of 5 Hz.

The main purpose of this work is to describe the construction and operation of the low energy accelerator with energy in the range from (zero to 100 KeV). This accelerator includes an ion source of the cold cathode Penning type (with pierce geometry for ion beam extraction), an accelerating tube (with 8 electrodes) and Faraday cup (FC) for measuring ion current. A vacuum system which gives vacuum of the order 3.0 × 10−8 Torr is used. A palladium tube is used to supply the source with pure hydrogen atoms. It was possible to operate this accelerator with an energy 50 KeV at minimum hydrogen pressure, 6.3 × 10−6 Torr. The total resistance applied between the accelerating electrodes RT = 31.5 MΩ. These data include the influence of the pressure in the accelerating tube, the magnetic field of the ion source, the extraction potential and the accelerating potential on the collector ion current. It was possible to accelerate protons with an energy 50 KeV with current about 100 μA at pressure 6.3 × 10−6 Torr, the source magnetic field = 110 G (IB = 2 A), the arc current = 0.4 A and the extraction potential = 10 KV.

Classical molecular dynamics of the ions and quantum treatment of the electrons are combined in the study of the properties of hot, dense plasmas. An effective ionic interaction potential is used in the molecular dynamics simulations. The electronic density of states is calculated using the equation of motion method. Special attention is given to the broadening of resonances in the electronic density of states, which may have important effects on the thermodynamic properties of the plasma.

To predict the gain in a lasing transition in ions of a laser-produced plasma, it is essential to calculate the amount of the reabsorption of radiation emitted in the transition from the lower laser level to the ground state. An important quantity influencing the reabsorption is the plasma geometry as resulting from the design of the laser and target system. Modeling a nonaxially symmetrical geometry of the plasma arising from a target irradiated by line-focused laser beams, we consider the plasma in the form of a longitudinally cut-out circular cylinder, with central angle ø, and the length of the plasma much larger than its transversal extension. Accounting for the effect of resonance line trapping via the escape probability approach, and taking the absorption profile in the line center approximation, an explicit formula for the photon escape probability depending on the radial and angular coordinates of an interior point in the plasma is derived. This function is averaged over the angular variable to obtain an only radially varying mean escape probability.

We investigated several examples of ion beam targets that utilize the energy efficiency of direct drive while optimizing on the symmetry requirements. Heavy-ion beams of charge state Z ≥ 3 at 5–10 GeV have ≲15–20 m bending radii with 3.5-T fields. Beams like these could be used with targets involving direct drive. Control of asymmetries in direct-drive ion beam targets depends on control of the effects of residual target asymmetries after an appropriate illumination scheme has been adopted. In this paper, we outline results of our investigations into ion beam target concepts in which the effects of residual asymmetries are ameliorated. The beams are placed according to our axially symmetric Gaussian-quadrature illumination scheme (Mark 1986). The targets survive the effects of residual asymmetries in our recent 2-D hydrodynamic simulations. We also briefly discuss the additional positive effects of polarized DT fuel on ion beam targets.

We present the results of the theoretical studies of the plasma heating in the flows which converge toward the axis of cylindrical cavity. We show that as a result of the shock wave reflection from the axis, the narrow hot filament is formed. This phenomenon is important for the interpretation of the dynamic processes in the electric discharges used for X-ray generation. We notice that the plasma parameters which can be of interest for inertial confinement fusion (ICF) can be reached in such the processes.

We report results from a study of the integrated column density and expansion dynamics of ground-state-selected Ba+ ions in a laser–plasma plume using a new experimental system—VPIF (vacuum-ultraviolet photoabsorption imaging facility). The ions are tracked by recording the attenuation of a pulsed and collimated vacuum ultraviolet beam, tuned to the 5p–6d inner-shell resonance of singly ionized barium, as the expanding plasma plume moves across it. The attenuated beam is allowed to fall on a CCD array where the spatial distribution of the absorption is recorded. Time-resolved ion velocity and integrated column density maps are readily extracted from the photoionization images.

A fundamental problem for the realization of laser fusion through the implosion of a spherical target is Kidder's E−1/6 law, where E is the energy needed for ignition, proportional to the 6th power of the ratio R/R0, where R0 and R are the initial and final implosion radii, respectively. This law implies that the ignition energy is very sensitive to the ratio R0/R, or vice versa, the ratio R0/R is very insensitive to the energy input, with R0/R limited by the Rayleigh–Taylor instability. According to still classified data of the Centurion–Halite experiment at the Nevada Test Site, ignition would require an energy of ${\rm E}\simeq 50\,{\rm MJ}$, 25 times larger than the 2 MJ laser at the National Ignition Facility (NIF) reported in the New York Times. This means that even a tenfold increase from 2 to 20 MJ would only decrease the R/R0 ratio by an insignificant factor of 10−1/6 ≃ 0.7. To overcome this problem, it is proposed that the spherical target is replaced with a hollowed-out, rapidly rotating, cm-size ferromagnetic target, accelerated by a rotating traveling magnetic wave to a rotational velocity of ~1 km/s, at the limit of its tensile strength. In a rotating reference system, the general theory of relativity predicts the occurrence of negative gravitational field masses in the center of rotation, with their source located in the Coriolis force field. The density of this negative gravitational field mass can be larger than the magnitude of the positive mass density of a neutron star. The repulsive gravitational force causes the centrifugal force. For a magnetized plasma placed in the rapidly spinning, hollowed-out target chamber, this repulsive force can be balanced by the magnetic force generated by thermomagnetic currents of the Nernst effect. Such a configuration does not suffer from the Rayleigh–Taylor instability, but becomes a small magnetohydrodynamic generator, amplifying the magnetic field to values about equal to those of the Nernst effect, axially confining the plasma. By placing the spinning target in the center of a lithium vortex, the fusion neutrons absorbed in the vortex can breed tritium, and at the same time remove heat from the target chamber to sustain the Nernst effect. A hot spot is thereby produced in the target chamber, which launches a thermonuclear burn wave into a cylindrical deuterium–tritium configuration. With the stability of a rapidly rotating target greatly increased, and the range of 10 MeV electrons in the wall of the cm-size ferromagnetic target, an intense 10 MeV relativistic electron beam drawn from a 10 MJ Marx generator should be sufficient to implode the target for thermonuclear ignition.

A Gw-level high-power CO2 laser system has been developed. A short laser pulse is cut out with a double Pockels cell electrooptical shutter from a hybrid CO2 laser oscillator and amplified with a three-stage dual-path TEA preamplifier, a two-stage TEA preamplifier, a large aperture TEA amplifier, and an electron beam-controlled final amplifier. All parts of the laser system are controlled with a control system. The laser output power is up to 3.2 × 109 W and laser pulse width is 4 ns full width at half maximum.

Nonstationarity of stimulated Raman backscattering in a finite homogeneous plasma slab is examined. Slowly varying envelope equations are analyzed taking into account a damping and a convection of an electron plasma wave, with a nonzero source boundary condition assumed. The linear analysis method is used for examination of stability of saturated stationary amplitude solutions. When linear wave damping is sufficiently small or absent, these solutions are spatially periodic and appear linearly unstable to small perturbations. However, a direct numerical simulation of the backscattering process in a lossless case shows that the system tends to quasistationary state with maximum reflectivity (R → 1). If the electron plasma wave damping exceeds a certain critical value, a spatially aperiodic solution raises and the Raman backscattering process becomes stable.

The acceleration of electrons in a laser plasma at the densities below the critical one is investigated by a particle simulation. It is shown that the stabilization of parametric instability and limitation of the energies of the accelerated electrons take place. The structure of the plasma electron distribution function is examined.

By using a linear analysis, a new type of thermal self-focusing instability without inverse bremsstrahlung absorption is analyzed. In the model it is assumed that part of the light is absorbed only at the critical surface and that the heat conduction is restricted to a layer on the target. Perturbations with wavelengths comparable to target radius are studied.