An advanced cone-nanolayer target with nanolayers on both inside and outside of the hollow-cone tip is proposed. Two-dimensional particle-in-cell simulations show that laser interaction with such cone-nanolayer targets can efficiently produce fast electron beams with manageable spotsize, and the beams can propagate for a relatively long distance in the vacuum beyond the cone tip.

We consider spontaneous thermalization of free photon field (in a vacuum) due to self-interaction, mediated by the virtual e−e+ field at ultra-high concentrations of the electromagnetic energy. That nonlinear, attractive, short-range interaction between photons triggers spontaneous evolution of the initial, low-frequency spectrum toward the maximum-entropy spectral distribution peaking in the gamma range of frequencies. Collimation and the total power of the photon beam (pulse) are hardly affected by the process of spontaneous thermalization. We estimate the threshold intensity that triggers spectral evolution of the photon field, the necessary power of the laser beam, the minimum size of the interaction region, parameters of the fully thermalized photon field, and discuss the near-threshold behavior of the electromagnetic field. Possible applications of thermalized photon beams are suggested, for example, they can serve as the pump field to attain gamma-lasing or facilitate ignition in the fusion pellet.

In review, general results obtained by Institute of Physics and Power Engineering (IPPE) during 1981–1992 are presented in the field of physics of nuclear-induced plasmas in the following directions: processes of primary ionization of different media by nuclear reaction products; function of electron distribution in nuclear-induced plasmas; processes of excitation and relaxation; track structure of nuclear-induced plasmas. Prospects of study progress are discussed with a view to improve the current concepts of physics of elementary processes occurring in nuclear-induced plasmas and obtain experimental and theoretical data on process constants needed to calculate the nuclear-pumped lasers.

The results of the development of the ITEP accelerator carbon ion injector based on a repetition-rate CO2 laser ion source are described. The improvement includes a modified pulsed HV-feeding generator for the discharge formation in the laser gas mixture. The advanced discharge module ensures essential increase of the laser active volume and specific electrical deposition energy. The comparative computer simulations of the discharge characteristics for the improved and the prototype lasers are applied. The design and the output spatial-temporal parameters of the free-running laser “Malish-M” are shown, so the significant increase of the laser power is reached. The spatial characteristics of the laser beam obtained with diffraction calculations are compared to measured radial distribution of the energy density. The target laser intensity and the different channels of the energy loss of the laser beam in the optical scheme are estimated. Finally, the output C4+ current trace of heavy ion injector as well as the injector scheme are shown.

In this paper, a method of two-dimensional fine-scanning with charge coupled device has been conducted to precisely measure spatial position and intensity distribution of small-scale focal spot (diameter in microns). The measurement accuracy of the small-scale focal spot position is better than 1 µm when the fluctuations of the light energy and background noise are relatively small. The theoretical analysis is consistent with the experimental results.

It is proposed that single attosecond pulses be generated via electron's Thomson scattering of two counter-propagating laser pulses. In the case of linear polarization, the generation of a single attosecond pulse is highly sensitive to the carrier envelope phase (CEP). However, in the case of circular polarization, it is completely independent on the CEP, which will make circular polarization favorable to generate a stable attosecond X-ray pulse. For either linear or circular polarization, the radiation obtained by using two counter-propagating pulses can be much more intense than that obtained by only using one of these two pulses.

The algorithm and results of calculating the integral and differential energy spectra of a pulsed electron beam (350–500 keV, 80 ns), generated by direct-action accelerators, are presented. The electron spectrum was calculated using the oscillograms of the accelerating voltage, electron current, total current of the diode, and the one-dimensional Child–Langmuir (1D CL) ratio. It was found that the discrepancy in the integrated electron beam energy spectrum, when measured using the total current in the diode and using the electron beam current, did not exceed 15% for 80%–95% of the electrons generated in a diode with graphite, carbon fabric, and multipoint cathodes. When calculating the electron spectrum using the 1D CL, the error was much higher.

Because of the large number of X-ray photons which will be emitted per unit solid angle and wavelength interval, laser generated plasmas have good prospects as X-ray sources for time-resolved diffraction experiments in solid state research. Starting from this a modified two-crystal diffractometer will be described, which uses the particular advantages of laser plasmas as X-ray flash sources. Requirements for the source will be determined and discussed.

Intense light-ion beam (LIB) propagation through a plasma channel is numerically investigated by using a two-dimensional simulation code. Analyses are given for the LIB propagation which couples with the motion of the channel plasma. Although the electron back current neutralizes the LIB current under typical beam and channel plasma conditions, the Lorentz force of the electron back current expands the LIB radially. The expansion of the LIB depends strongly on the density of the channel plasma. A strong current of the order of 1 MA is shown to propagate stably in an argon plasma channel.

We describe a funnel cone for concentrating an ion beam on a target. The cone utilizes the reflection characteristic of ion beams on solid walls to focus the incident beam and increase beam intensity on target. The cone has been modeled with the TRIM code. A prototype has been tested and installed for use in the 350-keV K+ NDCX target chamber.

In inertial confinement fusion experiments that involve short-laser pulses such as fast ignition (FI), diagnosis of neutrons is usually very challenging because high-intensity γ rays generated by short-laser pulses would mask the much weaker neutron signal. In this paper, fast-response scintillators with low afterglow and gated microchannel plate photomultiplier tubes are combined to build neutron time-of-flight (nTOF) spectrometers for such experiments. Direct-drive implosion experiments of deuterium-gas-filled capsules were performed at the Shenguang-II Upgrade (SG-II-UP) laser facility to study the compressed fuel areal density (〈ρR〉) and evaluate the performance of such nTOF diagnostics. Two newly developed quenched liquid scintillator detectors and a gated ultrafast plastic scintillator detector were used to measure the secondary DT neutrons and primary DD neutrons, respectively. The secondary neutron signals were clearly discriminated from the γ rays from (n, γ) reactions, and the compressed fuel areal density obtained with the yield-ratio method agrees well with the simulations. Additionally, a small scintillator decay tail and a clear DD neutron signal were observed in an integrated FI experiment as a result of the low afterglow of the oxygen-quenched liquid scintillator.

In this paper, a scheme of compound optical limiting based on nonlinear material dissolved into Brillouin medium is proposed. Both nonlinear material and Brillouin medium used as the solvent play roles of optical limiting, so the proposed optical limiting scheme presents a lower output clamp value and flatter output energy compared with the single stimulated Brillouin scattering (SBS). Compound optical limiting of F16PCCu/acetone is prepared and output energy characteristic based on it is studied in this paper. Both the theoretical and experimental results indicate that the output clamp value and output energy based on the compound method is lower and flatter than that based on single SBS optical limiting. Some properties of the compound optical limiting, such as limiting energy range, limiting waveband, response speed, limiting threshold and damage threshold, also are analyzed and discussed in the later part of this paper.

The kinetic stability properties of relativistic nonneutral electron flow in planar diode geometry are examined for extraordinary-mode perturbations about the self-consistent Vlasov equilibrium . Here, the cathode is located at x = 0; the anode is located at x = d the outer edge of the electron layer is located at is the equilibrium flow velocity in the x-direction; n^b is the electron density at the cathode (x = 0); and is the axial magnetic field, with const. in the vacuum region (xb < x ≤ d). The extraordinary-mode eigenvalue equation, derived in a companion paper for low-frequency, long-wavelength perturbations, is solved exactly. This leads to a formal dispersion relation, which can be used to determine the complex eigenfrequency ω over a wide range of system parameters and wavenumber k in the y-direction. The formal dispersion relation is further simplified for and , assuming low-frequency perturbations about a tenuous electron layer with and . Here, , and , where denotes the average equilibrium orbit, and [γ(x) − 1]mc2 is the average kinematic energy of an electron fluid element. The resulting approximate dispersion relation is solved numerically over a wide range of system parameters to determine the detailed dependence of stability properties on electromagnetic effects, layer thickness, and electron energy, as measured by , and γb − 1, respectively. Here, γb = γ(xb) denotes the electron energy at the outer edge of the electron layer. As a general remark, it is found that increasing the electron energy (γb − 1), increasing the strength of electromagnetic effects , and/or decreasing the layer thickness (xb/d) all have a stabilizing influence.

The first experimental study of the propagation of electrons created by an intense laser in shock-compressed matter has been performed with the VULCAN laser facility at the Rutherford Appleton Laboratory, to investigate one of the fundamental phases of the fast ignitor concept for inertial confinement fusion. Plastic plane targets were irradiated on one side with two pulsed laser beams, each with I ≈ 1014 W/cm2, t ≈ 2 ns, E ≈ 80 J per pulse, to generate a planar shock wave; on the opposite side of the target, a chirped pulse amplification (CPA) laser beam (I ≈ 1016 W/cm2, t ≈ 3 ps, E ≈ 10 J) was focused to generate the fast electrons. The results show an increase of hot electron penetration in compressed matter with respect to an ordinary one. Experimental results have been analyzed with computer simulations.

The paper presents experimental results on the application of microsecond plasma opening switch (MPOS) technology for materials surface modification. The ion beam parameters generated by the MPOS are up to 250 keV energy and current density and energy densities of up to 150 A/cm2 and 2.2 J/cm2, respectively. Characterization of the treated samples showed structural changes to a depth of several microns. The small ion range (few microns) and fast cooling of the upper melted layer (up to 1010 K/s) result in formation of fine-grain structures characterized by improved corrosion and erosion properties. Measurements indicate an increase in microhardness of a factor of about 3 for carbon steel samples. Corrosion resistance increase for the treated samples of at least 3, as measured by mass loss and potentiodynamic methods, has been measured for Al alloys. Microstructural changes in the surface morphology indicate a reduction in grain size for the treated samples and the appearance of shallow craters. Results of numeric simulations are given for the temperature distribution in materials due to ion beam heating.

The X-ray emission from hollow atoms produced by collisions of multiply charged ions accelerated by a short pulse laser with a solid or foil is studied theoretically. The possibility of obtaining a high conversion efficiency X-ray source in an ultrafast atomic process (∼1 fs) is demonstrated using the multistep-capture-and-loss (MSCL) model. Such an X-ray source has a clear advantage for the spectral range around a few kiloelectron volts over the conventional Kα X-ray source. Namely, the number of X-ray photons increases as the laser energy becomes larger and could reach 3 × 1011 photons for a laser energy of about 10 J.

In Russia, the Iskra-6 laser facility with pulse energy of up to 300 kJ and nanosecond pulse duration was being planned (Kirillov et al., 2000). The possibility of thermonuclear ignition with this laser energy was a goal of the theoretical investigation at RFNC-VNIITF. Results of one-dimensional (1D) and two-dimensional (2D) modeling of indirect-driven targets for ignition on the Iskra-6 laser facility are presented. Sensitivity of cryogenic single-shell and non-cryogenic double-shell targets to radiation flux non-uniformity and shells roughness are studied.

A study of the space-time structure of the light reflected when a plastic target (CH)n is irradiated at a maximum power of 1012 watt/cm2 by a Nd glass laser pulse of nanosecond duration is described. The reflected light has been used for time integrated spot imaging, whereas the time dependence of the reflected power at different angles has been studied by optical guides of different length coupled with a single fast photodiode. It has been found that: 1) the spot images are formed by a high contrast stationary speckle pattern, indicating the presence of a random phase mixing in the back-scattered light; 2) the interaction is characterized by a high reflection in the initial stages (t ≤ 0·3 ns) followed by almost complete absorption.

A nonparaxial investigation for propagation characteristics of q-Gaussian laser beam in rippled density plasma is studied by considering the relativistic nonlinearity. The field distribution in the medium is expressed in terms of q parameter and beam width parameter f. Nonlinear parabolic partial differential equation governing the evolution of complex envelope in slowly varying approximation is solved in a modulated density profile. Analytical theory of self-focusing including higher order terms in the expansion of dielectric function up to fourth order is developed and the variation of beam width parameter f with the distance of propagation for different parameters is studied. One may note that increased value of density ripple, laser intensity and depth of modulation, increases self-focusing whereas a lower value of q shows strong self-focusing. A comparative study between paraxial and nonparaxial study has also conducted. This study is useful for research in high energy density physics.