A condition for the transition of the electron beam produced in a coaxial rod-pinch diode to the mode of magnetic insulation has been established from the law of conservation of particle and field momentum fluxes. The magnetic field of the external current has been shown to contribute twice as much to magnetic insulation of the beam as the magnetic field of the electron beam self-current. Based on the relations derived, a model has been constructed for magnetic insulation of the electron flow in high-current rod-pinch diodes, which are used for radiography of high speed phenomena. The obtained theoretical results agree well with the results of numerical calculations and with experimental data gained at the Naval Research Laboratory (USA).

This article presents an effect of cross focusing of two laser beams on the growth of a laser ripple in laser-produced plasmas. The mechanism of nonlinearity is assumed to be ponderomotive force, arising because of the Gaussian intensity distribution of the laser beams. The dynamical equation governing the laser ripple intensity has been set up and a numerical solution has been presented for typical laser plasma parameters. It is found that the change in the intensity of the second laser beam can affect the growth of the laser ripple significantly.

This study reports on the optimization of the radio frequency capture phase during the operational cycle of the SIS-18 synchrotron at Gesellschaft für Schwerionenforschung, Darmstadt, Germany. The ion species studied were 238U+28 and 238U73+ at an injection energy of 11.4 MeV/u. The longitudinal relative momentum spread derived from Schottky spectra of the coasting beam at injection provides a value of |Δp/p0|full-width ∼ 5 × 10−3. Simulation results from the synchrotron tracking code ESME (FermiLab) were compared with beam-current profile measurements obtained from a pickup. To gain further insight, the Tomography program (European Organization for Nuclear Research) has been used to derive the longitudinal phase space development from waterfall plots of the measured beam current profile, which may then be compared against simulation. Possible causes of this nonadiabaticity are discussed and solutions are proposed.

Experiments conducted at the OSA shock tube facility at the Russian Federal Nuclear Center–VNIITF to investigate the compressible turbulent mixing of argon and krypton gases induced by the Rayleigh–Taylor instability are described. A liquid soap film membrane of thickness ∼1 micrometer embedded in an array of microconductors is used, on which specified initial perturbations can be applied. The shock is piston driven by compressed gas. The gas interface was accelerated with an acceleration g′4 3104 m0s2. The membrane is disintegrated at the beginning of the experiment by a strong electric explosion. Imaging is performed using Schlieren photography. The dimensionless growth rate of the mixing zone was determined to be 0.04.

The interaction of the mixing zone between two gases of different densities with compression waves and shock waves has been investigated. The characteristics of the mixing zone in which the Rayleigh–Taylor instability is developing have been analyzed. The evolution of the mixing zone volume and mass during the accelerated motion has been defined. A qualitative distinction in the evolution of the mixing zone under the influence of a continuous deceleration resulting from the interaction with the reflected compression wave—shockless deceleration—is revealed as compared to deceleration that is accompanied by appearance of a shock wave moving through the mixing zone—shock-induced deceleration.

Energetic protons are emitted from thin foils irradiated by short laser pulses at high intensities. One- and two-dimensional particle-in-cell simulations have been used to study the influence of initial proton position, laser irradiance, and target density profile on this ion acceleration. These simulations bring additional support to the idea that protons are mainly accelerated from the rear side of the target, by electrostatic fields associated with hot electrons escaping into vacuum. The density scale length at the front of the target appears to be the main parameter to increase proton energies when the laser irradiance is fixed.

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.

We analyze the influence of a high-intensity laser field in the inverse mean free path of electrons moving through a degenerate electron gas. Our calculations are based on the random-phase-approximation formalism, in terms of the dielectric function of the medium, where the effects of the laser field are included in the dynamical response. The main effects on the slowing down of the electrons are studied as a function of the intensity and frequency of the laser field, as well as a function of the projectile velocity. A modification of the electron inverse mean free path for plasmon and electron-hole excitations is obtained due to multiphoton-exchange processes.

This article reports the first Richtmyer–Meshkov instability experiments using an improved version of the Atomic Weapons Establishment convergent shock tube. These investigate the shock-induced turbulent mixing across the interfaces of an air/dense gas/air region. Multipoint ignition of a detonatable gas mixture produces a cylindrically convergent shock that travels into a test cell containing the dense gas region. The mixing process is imaged with shadowgraphy. Sample results are presented from an unperturbed experiment and one with a notch perturbation imposed on one of the dense gas interfaces. The unperturbed experiment shows the mixing across the dense gas boundaries and the motion of the bulk dense gas region. Imposition of the notch perturbation produces a mushroom-shaped air void penetrating the dense gas region. Three-dimensional simulations performed using the AWE TURMOIL3D code are presented and compared with the sample experimental results. A very good agreement is demonstrated. Conducting these first turbulent mixing experiments has highlighted a number of areas for future development of the convergent shock-tube facility; these are also presented.

The general possibility of the extended (∼30 cm) closed-drift ion source application for deposition of wear-resistant amorphous hydrogenated carbon (a-C:H) films on large-area dielectric substrates, in particular, on carbon-fiber plastic, is shown. Parameters of the “ion” and the “plasma” regimes of the ion source operation in argon and methane are defined. It is shown that the ion current nonuniformity is in the range of ±5–15% depending on the operation mode. Optimum conditions for the substrate precleaning in argon and hard, well-adhered a-C:H films deposition from methane are determined. The films are characterized by high hardness (∼11 GPa) and low surface roughness (∼0.13 nm) that leads to a several times lower friction coefficient (0.05) and wear rate (0.001 μm3m−1N−1) compared to glass and carbon-fiber plastic substrates.

The optical emission spectra of the plasma generated by a 1.06-μm Nd:YAG laser irradiation of Al target in air was recorded and analyzed in a spatially resolved manner. Electron temperatures and densities in the plasma were obtained using the relative emission intensities and the Stark-broadened linewidths of Al(I) emission lines, respectively. The dependence of the electron density and temperature on the distance from the target surface and on the laser irradiance were manifested. We also discussed how the air takes part in the plasma evolution process and confirmed that the ignition of the air plasma was by the collisions between the energetic electrons and the nitrogen atoms through a cascade avalanche process.

The excitation of large-amplitude plasma waves by intense few-cycle laser pulses in thin overdense plasma layers is studied using one-dimensional particle-in-cell simulation. P-polarized pulses generate relativistic electron pulses (jets) at the irradiated surface that penetrate the layer and then oscillate back and forth due to reflection by self-generated space charge fields building up in front of the surfaces. Counterpropagating plasmons of large amplitude are excited and start to emit radiation at 2ωp and other harmonics of the plasma frequency. The analogy to type III solar radio emission that is driven by electron bursts from deeper layers of the solar corona is pointed out; it highlights the present topic as another example of laboratory astrophysics with lasers.

By using an effective dielectric constant to modify the nanoplasma model, the interactions of large Ar clusters with high-intensity femtosecond laser pulses have been studied. It is shown that the resonance absorption mechanism plays a predominant role in the production of highly energetic argon ions, and the calculated mean kinetic energy of Ar ions is in good agreement with our previous experimental results. The scaling of mean kinetic energy and charge states of Ar ions against cluster size and laser intensity has also been analyzed. The results indicate the existence of optimum cluster sizes and optimum laser intensities where the best coupling efficiency of the laser energy can be obtained.

Good adhesion of thin films to the substrate is obviously necessary for any practical applications. Ion beam and plasma treatment are used to establish enhanced adhesion of thin films at dielectric substrates. It was supposed that both these processes could lead either to removal of contaminant layers as a result of surface heating and desorption or to production of stable chemical bonding within the metal–substrate interface. The article shows that the second process is the dominant factor.

Conclusive demonstration of electron-beam enhancement of ion charge states for the Metal Vapor Vacuum Arc (MEVVA) ion source was recently achieved using an external electron beam (E-MEVVA) in experiments performed jointly among the Institute for Theoretical and Experimental Physics (ITEP), Moscow, Russia, the High Current Electronics Institute (HCEI), Tomsk, Russia, and Brookhaven National Laboratory (BNL), USA. The E-MEVVA experiments were performed in Moscow and Tomsk with nearly the same design of ion sources. Results for lead and bismuth cathodes yielded maximum ion charge states of Pb7+ and Bi8+ for E-MEVVA, as compared to Pb2+ and Bi2+ for conventional MEVVA operation. Additional encouraging results were also obtained using a Z-discharge to produce an internal electron-beam (Z-MEVVA and LIZ-MEV).

This article reports on the latest experiments in the series of Richtmyer–Meshkov instability (RMI) shock-tube experiments. Previous work described a double-bump experiment that evidenced some degree of unrepeatability. The present work features an enlarged perturbation introduced to improve repeatability. In common with the previous work, the experiments were conducted at shock Mach number 1.26 (70 kPa overpressure), using the Atomic Weapons Establishment 200 × 100 mm shock tube with a three-zone test cell arrangement of air/sulphur hexafluoride/air. The sulphur hexafluoride gas (SF6) was chosen for its high density (5.1 relative to air) providing an Atwood number of 0.67. Gas separation was by means of microfilm membranes, supported by fine wire meshes. A double-bump perturbation of two-dimensional geometry was superimposed on the downstream membrane representing a 0.6% addition to the dense gas volume. Visualization of the turbulent gas mixing was by laser sheet illumination of the seeded SF6 gas using a copper vapor laser pulsing at 12.5 kHz. Mie scattered light was recorded using a 35-mm rotating drum camera to capture a sequence of 50 images per experiment. Sample experimental results shown alongside corresponding three-dimensional hydrocode calculations highlight the problems in both analysis and comparison caused by multiple scattering arising from the necessary use of a high seeding concentration. Included is a demonstration of the effectiveness of introducing into the hydrocode a Monte Carlo-based simulation of the multiple scattering process. The results so derived yield greatly improved qualitative agreement with the experimental images. Quantitative analysis took the form of deriving relative intensity data from line-outs through experimental images and their code equivalents. A comparison revealed substantial agreement on major features.

Bremsstrahlung is one of the most important energy loss mechanisms in achieving ignition, which is only possible above a threshold in temperature for a given fusion reaction and plasma conditions. A detailed analysis of the bremsstrahlung process in degenerate plasma points out that radiation energy loss is much smaller than the value given by the classical formulation. This fact seems not useful to relax ignition requirements in self-ignited targets, because it is only relevant at extremely high densities. On the contrary, it can be very positive in the fast ignition scheme, where the target is compressed to very high densities at a minimum temperature, before the igniting beamlet is sent in.

On hand of 3D PIC simulations we show that in a strongly magnetized plasma a relativistic electron beam can be forced to emit highly coherent radio emission by self-induced nonlinear density fluctuations. Such slowly moving nonlinear structures oscillate with the local plasma frequency at which the relativistic electrons are scattered. Beam electrons dissipate a significant amount of their kinetic energy by inverse Compton radiation at a frequency of about γ2ωpe. Since the beam is sliced into pancake structures which experience the same electric field the inverse Compton scattering is coherent. Such a process is a very promising candidate for the coherent radio emission of pulsars.

Primary storages based on a linear transformer scheme were developed long ago. In this scheme, the secondary turn only has to be insulated from the high output voltage. Seven years ago at the High Current Electronics Institute (HCEI) a primary storage based on a linear transformer scheme and called the Linear Transformer Driver (LTD) stage was designed. In LTD stages, the primary turn, the storage capacitors with the switches, the core, and the outer conductor of the secondary turn are integrated into the stage cavity representing one separate building block of the primary storage. The body of the LTD cavity keeps ground potential during the shot allowing us to assemble them in series or in parallel depending on load requirements. Such flexibility of the storage structure and high output power of the LTD stages allows us to replace for some applications the traditional water line technology with LTD-based primary storages that are connected directly to the load (Direct Drive Scheme—DDS). In this article, we present the design of several LTD stages developed at HCEI and give examples of high-power energy storages produced by using the LTD technology.

This article investigates the molecular mixing caused by Rayleigh–Taylor (RT) instability of a gravitationally unstable density interface tilted at a small angle to the horizontal. The mixing is measured by the increase in background potential energy, and the mixing efficiency, or fraction of energy irreversibly lost to fluid motion doing work against gravity, is calculated. Laboratory experiments are carried out using saline and fresh water, and modeled with compressible numerical simulations, with a suitable choice of parameters and initial conditions. The experiments show that the high cumulative efficiency of mixing in RT instability at a horizontal interface is only slightly reduced by an interface tilt of up to 10°, despite the strong overturning that occurs. Instantaneous mixing efficiencies as high as 0.5–0.6 are measured, when RT instability is active, with lower values of about 0.35 during the subsequent overturning. The numerical simulations capture the most unstable scales and the overturning motion well, but generate more mixing than the experiments, with the instantaneous mixing efficiency remaining at 0.5 for most of the run. The difference may be due to restratification at small scales in the high Prandtl number experiments.