A two-dimensional particle-in-cell (PIC) simulation is carried out to study the wakefield and stopping power for a hydrogen ion beam pulse with low drift velocity propagation in hydrogen plasmas. The plasma is assumed to be collisionless, uniform, non-magnetized, and in a steady state. Both the pulse ions and plasma particles are treated by the PIC method. The effects of the beam density on the wakefield and stopping power are then obtained and discussed. It is found that as the beam densities increase, the oscillation wakefield induced by the beam become stronger. Besides, the first oscillation wakefield behind the bunch is particularly stronger than others. Moreover, it is found that the stationary stopping power increases linearly with the increase of the beam density in the linear/semilinear region.

The hydrodynamic efficiency of conversion of the energy of fast charged particles into the kinetic energy of the bulk motion of plane-parallel shells is investigated in the framework of two simple models–one based on the stepwise density profile and the other employing a self-similar solution. The analytical estimates obtained are substantiated with ID hydrodynamic calculations. In case of spherical shells, the three key dimensionless parameters determining the values of the hydrodynamic efficiency are pointed out; the dependence of the hydrodynamic efficiency on these parameters has been explored numerically. The effects of a nonuniform energy deposition (increasing by the end of the fast particle ranges) and of a nonuniform absorber composition are also discussed.

A steady-state analytical model is used to calculate the operational parameters of a coaxial-type, self-magnetically insulated ion-beam diode, called a plasma focus diode (PFD). The electrons are described by nonlaminar flow with a constant radial density distribution instead of the density profile determined self-consistently by one-dimensional laminar flow. The calculated results were compared with the experimental results obtained at the peak power, and good agreement was obtained between them. From the theoretical understanding of the PFD we obtained the scaling relations of diode impedance and the ion-current efficiency and used them to discuss the possible ways to increase the coupling efficiency and the ion-current efficiency and to reduce the instabilities in the diode operation.

Experiments have been performed at the Central Laser Facility, Rutherford Appleton Lab., UK. using novel techniques in which laser produced plasmas have been diagnosed by measurements of the charged thermonuclear reaction products. Two types of experiment are being reported here. Firstly, thermonuclear alpha particles from an exploding pusher target have been used to determine the growth of the Rayleigh–Taylor instability in a separate laser driven planar foil. The resulting alpha particle range loss distributions provide a direct measurement of the foil thickness distribution and hence the instability. The R–T instability has been observed in a number of foils with range losses varying between almost zero to over lOμm. Secondly, a thermonuclear particle backlighting technique has been used in the measurement of the stopping power of hot plasma for different materials. The ratio of plasma stopping power to that of the cold material is measured and compared to a value obtained from theoretical modelling. The solid state nuclear track detector CR–39 has been used as a diagnostic for these experiments. A sophisticated image analysis system has been developed to enhance and improve data recovery.

In this paper, we study the excitation of Gould–Trivelpiece (TG) waves by streaming ions in dusty plasma and derive the dispersion relation of the excited waves using first-order perturbation theory. The motion of charged particles is controlled by electromagnetic fields in plasma. The energy transfer processes which occur in this collisionless plasma are believed to be based on wave–particle interactions. We have found that the TG waves may be generated in a streaming ion plasma via Cerenkov interaction, and the ions may be accelerated by TG waves via cyclotron interaction, which enable energy and momentum transfer. The variation in the growth rate of TG wave with dust grain size and relative density of negatively charged dust grains is also studied. The dust can cause an unstable TG mode to be stable in Doppler resonance, and can induce an instability in Cerenkov interaction.

The paper presents experimental and theoretical research data on the generation, transport, and extraction of a large cross-section (750 × 150 mm2) electron beam into the air through a thin metal foil in an accelerator with a mesh plasma cathode on the bases of a low-pressure arc and with a multi-aperture two-electrode electron-optical system. When the burning conditions of the arc discharge, responsible for the generation of the emission plasma, is changed, the characteristics of this plasma were investigated, including under the conditions of the selection of electrons from it. Our experiments show that at an accelerating voltage of 200 kV, current in the accelerating gap of up to 30 A, and full width at half maximum of up to 100 µm, the average extracted power is ≈4 kW and the extracted beam current is ≈85% from the common current into the accelerating gap. Our numerical estimates give a good correlation between the arc and emission plasma parameters depending on the electrode configuration in the discharge system and on the mechanism of electron beam generation. Analysis of the emission plasma parameters under different arc conditions and of the mechanisms responsible for the beam energy loss suggests that most of the energy in the accelerator is lost at the support grid and at the output foil due to defocusing of the beam and partial electron reflection from the foil. Other mechanisms that decrease the extracted beam energy are discussed.

The proton–boron ${}^{11}{\text{B}}\left( {p,\alpha } \right)2\alpha $ reaction (p-11B) is an interesting alternative to the D-T reaction ${\text{D}}\left( {{\text{T}},{\text{n}}} \right)\alpha $ for fusion energy, since the primary reaction channel is aneutronic and all reaction partners are stable isotopes. We measured the α production yield using protons in the 120–260 keV energy range impinging onto a hydrogen–boron-mixed target, and for the first time present experimental evidence of an increase of α-particle yield relative to a pure boron target. The measured enhancement factor is approximately 30%. The experiment results indicate a higher reactivity, and that may lower the condition for p-11B fusion ignition.

It is demonstrated that finite pressure gradients can be maintained in the lowest free energy state (‘relaxed state’) of a plasma configuration. The pressure forces are supported by the Magnus Force in a compressible adiabatic plasma if mass motions are considered. It has been demonstrated elsewhere that these forces can be of the same order of magnitude as the Lorentz forces in some laboratory plasmas.

This paper presents cross-sections and collision strengths for proton-impact excitation of optically forbidden transitions in Al10+. These data, calculated in the impact-parameter formalism, covering the expected range of energies/temperature in laser-produced plasmas, are believed to represent the first such detailed treatment of this system. The cross-sections decrease with energy as E−1, while the collision strengths tend to finite limits as the energy of colliding proton becomes infinitely great. This high-energy limiting value has been evaluated combining results from the semi-classical treatment of ion-impact excitation processes and the Born approximation for high-energy behavior of the collision strength. The effective target size has been estimated from the calculated high-energy limit of the collision strength in the Born approximation.

In an earlier preliminary design study, we proposed a novel nuclear-pumped laser-driven (NPL) inertial confinement fusion (ICF) power reactor that represents an important variation on the “neutron feedback” concept for ICF. This NPL-driven ICF concept also included an advanced, DT-seeded, D3He-fueled pellet and magnetic protection of the first wall of the reactor chamber. Advantages that were demonstrated for this approach included increased efficiency for laser-to-target energy coupling, increased efficiency for thermalto-electric energy conversion, and reduced neutron activation and waste. The coupling efficiency is enhanced because a nuclear-pumped flashlamp is directly pumped by fission fragments from uranium micropellets within the lamp medium. The thermal conversion efficiency is greater because a large fraction of the ICF pellet&s fusion yield is in charged Finally, the fraction of the fusion yield carried by neutrons is significantly reduced in comparison with pure D-T-fueled pellets; thus, neutron-induced activity in the first wall is decreased and safety is increased. The initial study indicated these factors could result in a required driver energy of 5 MJ (vice 10 MJ currently projected) and a pellet gain of only 50 (vice 100 currently projected) for a feasible l,000-MWe power reactor operating with approximately six pellets per second. The current study includes a refined analysis of an NPL-driven ICF power reactor of this type. A cylindrical design for the fission/NPL blanket is selected as a “natural” geometry for pumping the NPL. Required enrichments and criticalities are then predicted for the multiplication of the fusion neutron yield needed to pump the NPL. Based upon these results, we report a more detailed parametric study of the efficiencies for converting neutron, X-ray, and plasma yields from advanced ICF pellets into electrical and optical energy flows required in this concept. We also examined breeding tritium in a lithium blanket layer. Results from these studies help define topics and parameter spaces for further research on this unique reactor concept.

Numerical simulation of active media nuclear-pumped lasers on noble gases and their mixtures with metal vapors are presented. Prospects of creation of high-power short-wavelength nuclear-pumped excimer lasers are discussed.

A scaling model for hot spherical ablative implosions in direct-drive mode is presented. The model results have been compared with experiments from LLE, ILE, and LLNL. Reduction of the neutron yield due to illumination nonuniformities is taken into account by the assumption that the neutron emission is cut off when the gas shock wave reflected off the center meets the incoming pusher, i.e., at a time when the probability of shell breakup is greatly enhanced. The main advantage of this semiempirical scaling model is that it elucidates the principal features of these simple implosions and permits one to estimate very quickly the performance of a high-aspect-ratio direct-drive target illuminated by short-wavelength laser light.

An atomic model of the laser-produced Al plasma has been developed and used to analyze excitation processes of recombination pumping soft X-ray lasers. A soft X-ray gain for H-like Balmer-α line and He-like 3d-2p transition in short-pulse intense KrF laser (IL = 1014–1015 W/cm2, T = 10–100 ps)-produced Al plasmas are calculated for various laser temporal pulse shapes to find the condition for efficient production of population inversion. Results from different models are compared and requirements for the atomic model for X-ray laser design are discussed.

We have proposed an extension of the Model Microfield Method to the case of ionic radiators. Special attention is given to the accurate treatment of plasma mixtures in terms of static and dynamic statistical properties of the plasma microfield. Line shapes of one electron Carbon and Argon illustrate the influence of ion dynamic effects.

An experimental investigation on X-ray emission from laser-produced plasmas is presented and the properties of such an emission of interest for application purposes are examined. Plasmas were generated by focusing 1 μm, 3 ns Nd laser pulses onto Al and Cu targets at an intensity of 1013 W/cm2. The temporal evolution of the emission and its spectral features were investigated by using an X-ray streak-camera and an X-ray photodiode. In the case of Cu targets, the analysis of the emission showed two spectral components. The main component was centered at ≈ 1.2 keV and a minor component, whose intensity was measured to be 10-3 of the previous component, was observed at ≈7 keV. The X-ray conversion efficiency, in the investigated spectral region, was measured to be 1% for Cu targets and 0.3% for Al targets.

For ultrafast material analyses, we constructed the time-resolved X-ray diffraction system utilizing ultrashort X-rays from laser-produced plasma generated by the 12-TW–50-fs laser at the Nuclear Engineering Research Laboratory. Ultrafast transient changes in laser-irradiated GaAs crystals were observed as X-ray diffraction patterns. Experimental results were compared with numerical analyses.

The paper considers the equation for heterogeneity coefficient within the turbulent mixing area in the approximation of big Reynolds numbers and small Mach numbers. A mechanism is studied of the heterogeneity coefficient dissipation due to molecular diffusion. The Kolmogorov's hypothesis on developed turbulence is used to calculate a dissipative term. The model presented allows us to take into account the heterogeneity degree in LV- and KE-models of turbulent mixing. A system of equations allowing us to calculate directly the heterogeneity degree is derived for the case of the LV-model with the turbulent diffusion coefficient which is constant over the turbulent mixing area. A self-similar solution is derived for the heterogeneity coefficient which is in good agreement with the results of experiments and direct numerical simulations. The heterogeneity coefficient averaged over the mixing area is shown to depend weakly on the density drop between the mixing materials. Thus, it is kH = 0.25 at the drop n = 1–3, and at the drop n = 20 − kH = 0.23.

A model of an electron beam interacting with neutral argon was developed by solving the chemical kinetic rate equations for the time-dependent populations of ground and excited levels of Arl and Aril as well as the populations of electron energy groups. Intensities of spectral lines were calculated, from predicted population densities and Einstein coefficients, and compared to experimental results.

The thermal plasma is generated during the beam pulse and persists for some time after the pulse is terminated. Low energy levels of Arii with a 4s or 4p valence electron have similar time profiles to the plasma density. However, high energy levels of Aril with a 4p′ or 4p′ valence electron have similar temporal profiles as the beam current. They are populated predominantly by direct ionization and exceed levels populated by thermal electrons. The 4p′ levels decay rapidly to 4s′ levels, which have very high beam deposition efficiencies for being pumped back to the 4p′ levels. In this way, certain transitions such as 4s′–4p′ in ArII are pumped directly by the electron beam. Without direct ionization, these transitions would be negligible compared to those transitions which have lower energy levels.

The synchrotron emission from relativistic electrons in a thermal plasma with large-scale random magnetic fields is considered. In this case, the spectral synchrotron power of a single electron can be given in closed form allowing exact analytical expressions for the synchrotron emissivity, absorption coefficient, intensity and total energy loss of particles to be derived. The influence of various physical parameters such as gas density, magnetic field strength, particle's Lorentz factor on the resulting emissivities, intensities and energy loss is discussed in detail. Below the Razin– Tsytovich frequency vR = 20 Hz (ne/l cm−3) (B/l Gauss)−1, the spectral appearance of synchrotron radiation both in the optically thin and thick case is quite different than the vacuum behaviour. Since in the quasar broad line regions, vR is of the order 1011 Hz the suppression of synchrotron radiation may explain why most quasars are radio quiet. Likewise, the necessary physical conditions for the occurrence of synchrotron masering in the optically thick case are given. We obtain optical depth |τ|>1 for compact nonthermal sources. The total energy loss of a single particle is shown to be exponentially reduced at Lorentz factors less than γR = 2·1. 10−3 (ne/1 cm−3)½ (B/1 Gauss)−1.