The late-time growth rate of the Richtmyer–Meshkov instability was experimentally studied at different Atwood numbers with two-dimensional (2D) and three-dimensional (3D) single-mode initial perturbations. The results of these experiments were found to be in good agreement with the results of the theoretical model and numerical simulations. In another set of experiments a bubble-competition phenomenon, which was observed in previous work for 2D initial perturbation (Sadot et al., 1998), was shown to exist also when the initial perturbation is of a 3D nature.

We present two-dimensional simulation results of the formation and evolution of a diffuse plasma channel in the XeCl pumping discharge. Channel formation was initiated by metallic convexity at the cathode surface with a characteristic dimension of ∼0.1 cm. Two pumping regimes were considered. Initial voltage in the second regime was increased 1.6 times and impedance was decreased 2 times in contrast with the first regime. Evolutions and spatial distributions are presented for electron density, electric field, and frequencies of the main process. In the first regime, the diffuse plasma channel forms. The main processes causing development of the plasma channel are inhomogeneous distribution of the electric field, increase of the stepwise ionization frequency at ne ∼ 1015 cm−3, and depletion of HCl. Increasing of the initial voltage and decreasing of the impedance in the second regime results in a quick rise of the discharge current and electron density in the discharge gap, and uniform discharge takes place during the current pulse.

In this article, we discuss the modifications that occur in the brightness and gain of a longitudinal wiggler-free electron laser with the aid of induced betatron oscillation. Two novel approaches have been discussed to improve the gain of the system. In the first scheme, an auxiliary undulator field with betatron oscillations brings in additional bunching and results in enhanced gain. In the second scheme, an axial magnetic field is tuned to provide additional bunching for gain enhancement.

Low-frequency, relativistic, subcycle solitary waves are found in two-dimensional and three-dimensional particle-in-cell (PIC) numerical simulations, as a result of the interaction of ultrashort, high-intensity laser pulses with plasmas. Moreover, nondrifting, subcycle relativistic electromagnetic solitons have been obtained as solutions of the hydrodynamic equations for an electron–ion warm plasma, by assuming the quasi-neutrality character of the plasma response. In addition, the formation of long-living macroscopic soliton-like structures has been experimentally observed by means of the proton imaging diagnostics. Several common features result from these investigations, as, for example, the quasi-neutral plasma response to the soliton radiation, in the long-term evolution of the system, which leads to the almost complete expulsion of the plasma from the region where the electromagnetic radiation is concentrated, even at subrelativistic field intensity. The results of the theoretical investigations are reviewed with special attention to these similarities.

High-current electron beams with a current density of up to 100 A/cm2 generated by a plasma-cathode gas-filled diode at low accelerating voltages are studied. Two types of gas discharges are used to produce plasma in the cathode. With glow and arc discharges, beam currents of up to 150 A and 400 A, respectively, have been obtained at an accelerating voltage of 16 kV and at a pressure of 1–3·10−2 Pa in the acceleration gap. The ions resulting from ionization of gas molecules by electrons of the beam neutralize the beam charge. The charge-neutralized electron beam almost without losses is transported over a distance of 30 cm in a drift channel which is in the axial magnetic field induced by Helmholtz coils. The results of calculations for the motion of electrons of the charge-neutralized beam with and without axial external field are presented and compared with those of experiments.

We have performed an initial assessment of the feasibility of producing heavy negative ion beams as drivers for an inertial confinement fusion reactor. Negative ion beams offer the potentially important advantages relative to positive ions that they will not draw electrons from surfaces and the target chamber plasma during acceleration, compression, and focusing, and they will not have a low energy tail. Intense negative ion beams could also be efficiently converted to atomically neutral beams by photodetachment prior to entering the target chamber. Depending on the target chamber pressure, this atomic beam will undergo ionization as it crosses the chamber, but at chamber pressures at least as high as 1.3 × 10−4 torr, there may still be significant improvements in the beam spot size on the target, due to the reduction in path-averaged self-field perveance. The halogens, with their large electron affinities, are the best negative ion candidates. Fluorine and chlorine are the easiest halogens to use for near-term source experiments, whereas bromine and iodine best meet present expectations of driver mass. With regard to ion sources and photodetachment neutralizers, this approach should be feasible with existing technology. Except for the target chamber, the vacuum requirements for accelerating and transporting high energy negative ions are essentially the same as for positive ions.

Experiments conducted on the EKAP facility at the Russian Federal Nuclear Center–VNIITF concerning the stabilization of Rayleigh–Taylor instability-induced mixing in miscible liquids by the formation of a molecular diffusion (or transitional) layer between the liquids initially were described. The experiments had an Atwood number of 1/3. The acceleration was 3500 times that of Earth's gravity, and several values of diffusion layer thickness were considered. The experiments showed that the growth of the turbulent mixing zone could be delayed by adjusting the amplitude of the initial perturbations and the characteristic thickness of the diffusion layer. This has been observed in experiments conducted with water and mercury. The mixing layer evolution was imaged using X-ray radiography.

Ablation depths of stainless steel targets irradiated by 80-fs laser pulses at a flux F ≤ 40 J/cm2 (intensity ≤ 5 × 1014 W/cm2) in the presence of air at atmospheric pressure are experimentally measured. These values are lower than the theoretical predictions for metal targets in vacuum. Results are analyzed on the basis of the role of the ambient gas and of crater formation on the behavior of the ablated material.

The assembly of the Paul Trap Simulator Experiment (PTSX) is now complete and experimental operations have begun. The purpose of PTSX, a compact laboratory facility, is to simulate the nonlinear dynamics of intense charged particle beam propagation over a large distance through an alternating-gradient transport system. The simulation is possible because the quadrupole electric fields of the cylindrical Paul trap exert radial forces on the charged particles that are analogous to the radial forces that a periodic focusing quadrupole magnetic field exert on the beam particles in the beam frame. By controlling the waveform applied to the walls of the trap, PTSX will explore physics issues such as beam mismatch, envelope instabilities, halo particle production, compression techniques, collective wave excitations, and beam profile effects.

This article presents two types of a hollow-cathode plasma source based on an arc discharge where the electrons emitted either by a hot filament or by a surface-discharge-based trigger system initiate a gas arc discharge. The sources produce gas plasmas of densities 1010–1012 cm−3 in large volumes of up to 0.5 m3 at a discharge current of 100–200 A and at a pressure of 10−1–10−2 Pa. Consideration is given to some peculiarities of the operation of the plasma sources with various working gases (Ar, N2, O2). The erosion rate of the cold hollow cathode in the designed plasma sources is shown to be 10 times lower than that found in an ordinary one. The sources are employed for plasma-assisted surface modification of solids.

Experiments conducted on the SOM facility at the Russian Federal Nuclear Center–VNIITF, concerning the turbulent mixing induced by the Rayleigh–Taylor instability in a three-layer system of immiscible liquids are described. The fluids are contained in a small tank 6.4 cm × 5.4 cm × 12 cm, which is accelerated vertically downward by a gas gun. The mixing layer evolution was imaged by seeding one of the fluids with particles and using a bidirectional light sheet method (refractive index matching was used to minimize measurement errors). Experiments were performed for two different accelerations (g = 350 g0 and g = 100 g0, where g0 = 980 cm/s2, and the acceleration decreases with distance traveled), and with aqueous solutions of glycerin and benzene (with density ratio 1.6). The lower, middle, and upper layers were a sodium hyposulfite–glycerin solution, a water–glycerin solution, and benzene, respectively. The glycerin solution was seeded with particles. The principal objective of the experiments was to obtain the distribution of fluid particle sizes arising from the mixing of the immiscible fluids.

The laser-induced plasma obtained from the liquid target and expanding across a steady magnetic field has been studied using atomic emission spectroscopy. The line emission from the plasma was enhanced (>1.5 times) in the presence of a magnetic field, whereas background emission decreases. Enhancement in line intensity was found to be mainly a function of plasma beta (β). An increased rate of three-body recombination in plasma particles due to the cooling of the plasma during its expansion and an increase in effective plasma density as a result of its confinement seems to be the reason behind this enhancement.

We describe the next set of experiments proposed in the U.S. Heavy Ion Fusion Virtual National Laboratory, the so-called Integrated Beam Experiment (IBX). The purpose of IBX is to investigate in an integrated manner the processes and manipulations necessary for a heavy ion fusion induction accelerator. The IBX experiment will demonstrate injection, acceleration, compression, bending, and final focus of a heavy ion beam at significant line charge density. Preliminary conceptual designs are presented and issues and trade-offs are discussed. Plans are also described for the step after IBX, the Integrated Research Experiment (IRE), which will carry out significant target experiments.

The design, operation, and functionality of the multifunctional shock tube (MST) facility at the Russian Federal Nuclear Center–VNIITF are described. When complete, the versatile MST consists of three different driver sections that permit the execution of three different classes of experiments on the compressible turbulent mixing of gases induced by the (1) Richtmyer–Meshkov instability (generated by a stationary shock wave with shock Mach numbers <5), (2) Rayleigh–Taylor instability (generated by compression wave such that acceleration of the interface is <105g0, where g0 = 9.8 m/s2), and (3) combined Richtmyer–Meshkov and Rayleigh–Taylor instability (generated by a nonstationary shock wave with initial pressure at the front 5 × 106 Pa and acceleration of ≤106g0 of the interface). For each of these types of experiments, the density ratio of the gases is ρ2 /ρ1 ≤ 34. Perturbations are imposed on a thin membrane, embedded in a thin wire array of microconductors that is destroyed by an electric current. In addition, various limitations of experimental techniques used in the study of interfacial instability generated turbulent mixing are also briefly discussed.

A double shell z-pinch with an axial magnetic field is considered as a K-shell plasma radiation source. One-dimensional radiation-hydrodynamics calculations performed suggest that this scheme holds promise for the production of the K-shell radiation of krypton (hν ≈ 12–17 keV). As a first step in verifying the advantages of this scheme, experiments have been performed to optimize a neon double-shell gas puff with an axial magnetic yield for the K-shell yield and power. The experiments show that the application of an axial magnetic field makes it possible to increase the K-shell radiation power and reduce the shot-to-shot spread in the K-shell yield. Comparisons between the experiments and modeling are made and show good agreement.

The high precision X-ray spectroscopy studies of plasma created from the CO2 clusters in gas jet targets by the ultrashort laser pulses (35 and 60 fs duration) were performed at the intensities IL ∼ 1017–1018 W cm−2. The spectral line shape of the H-like and He-like oxygen ions gains an asymmetry with increasing the laser pulse intensity. Theoretical modeling of the line shape shows that the asymmetry can be explained by absorption of the Doppler-shifted line radiation from the essential fraction of ions (over 10−3) with energies above 1 MeV due to photoionization of inner shells of carbon ions. The results obtained demonstrate measurement capabilities of the X-ray spectral measurements of multicharged ions accelerated during the interaction with a laser radiation.

Experiments on self-similar Rayleigh–Taylor instability-induced mixing in gases in the Earth's gravity conducted on the OSA facility at the Russian Federal Nuclear Center–VNIITF are described. These experiments are distinguished from other experiments, usually performed with immiscible liquids in a tank or with miscible liquids initially separated by a solid barrier that is retracted, in that a membrane (of ∼1 μm thickness) with liquid soap film embedded in a thin wire array (with microconductors of diameter 20 μm and with a spacing of 4 mm) initially separates the fluids. An electric current to initiate the fluid interpenetration and mixing destroys the membrane. Experiments performed for three different Atwood numbers are described: in SF6-Ar with A = 0.54, in SF6-He with A = 0.94, and in Kr-Ar with A = 0.35. Various parameters of the mixing were measured from Schlieren photographs. In particular, the dimensionless rate of mixing front growth is α = 0.078.

By means of a new two-dimensional three-temperature hydrodynamical code we considered the burning of the deuterium fuel with a small amount of a catalytic 3He in a cylindrical channel. To reduce the requirements for an ignition heavy ion beam we used an irradiated DT tablet (Jbeam = 4·106 TW/g, Ebeam = 0.5 MJ). We received the steady burning wave for the parameter ρr [gsim ] 8–10 g/cm2 with a gain coefficient G [gsim ] 30 in comparison with such parameters for the DT fuel G ∼ 140 at ρr = 0.5 g/cm2. Upon reducing the parameter ρr ∼ 4 g/cm2, the burning wave disappears moving along a channel. A part of the deuterium fuel burns with a reduced gain coefficient of 3–5. In the case of large fuel densities ρ = 100 g/cm3, our estimates show extremely large requirements for a compression beam 450–750 MJ for ρr ∼ 4 g/cm2.

The interaction of Xe (λ ∼ 1.73 μm) and XeCl (0.308 μm) laser radiation with surfaces of metal and TiN-ceramic coatings on glass and steel substrates has been studied. Correlation between parameters of surface erosion versus laser-specific energy was investigated. Monitoring of laser-induced erosion on smooth polished surfaces was performed using optical microscopy. The correlation has been revealed between characteristic zones of thin coatings damaged by irradiation and energy distribution over the laser beam cross section allowing evaluation of defects and adhesion of coatings. The interaction of pulsed periodical CO2 (λ ∼ 10.6 μm), and Xe (λ ∼ 1.73 μm) laser radiation with surfaces of teflon (polytetrafluoroethylene—PTFE) has been studied. Monitoring of erosion track on surfaces was performed through optical microscopy. It has been shown that at pulsed periodical CO2-radiation interaction with teflon the sputtering of polymer with formation of submicron-size particles occurs. Dependencies of particle sizes, form, and sputtering velocity on laser pulse duration and target temperature have been obtained.

It is shown that beyond a virtual cathode the current of a magnetized steady-state thin annular electron beam in a drift tube may range from zero to the limiting current of the tube.