Models for the prediction of electron pedestal temperatures at the edge of type I ELMy H-mode plasmas are developed. These models are based on theory motivated concepts for pedestal width and pressure gradient. The pedestal pressure gradient is assumed to be limited by high n ballooning mode instabilities, where both the first and second stability limits are considered. The effect of the bootstrap current, which reduces the magnetic shear in the steep pressure gradient region at the edge of the H-mode plasma, can result in access to the second stability of ballooning mode. In these pedestal models, the magnetic shear and safety factor are calculated at one pedestal width away from separatrix. The predictions of these models are compared with the experimental electron pedestal temperatures for type I ELMy H-mode discharges obtained from the latest public version (version 3.2) in the International Tokamak Physics Activity Edge (ITPA) Pedestal Database.

In doing research on the turbulent mixing (TM) of two gases different in density, it is of great interest to study experimentally the 3D density distribution pattern of chemically nonreactive gases in the TM zone. For this purpose, noncontact and, particularly, optical techniques to obtain experimental data may be attractive. This article discusses the possibility of using pulsed laser interferometry in this application. Based on this technique, the experiment should result in the mixture density distribution integrated along the light path. Requirements for high-quality interference patterns have been analyzed in application to typical experimental conditions, to show that they may be produced with specific restrictions set on the mixture constitution. Generally, the TM zone has no symmetry. Therefore, the problem of reconstructing 3D density distributions (TDD) of gases can be solved by sufficiently providing many TM zone integral projections (or aspects). It is technically difficult and expensive to achieve this large number of aspects (N> 10). Therefore, it is essential that a reconstruction method be selected to allow the solution of the problem with the least possible number of aspects. Given that the experiment data are incomplete, the reconstruction methods that are based on the concept of maximum data entropy did well. Information a priori about the solution to be sought for an isobaric gas mixture is that its each constituent has invariable density. Thus, a functional data entropy can be defined that is similar to Fermi gas in statistical physics. An algorithm has been suggested for reconstruction as a modified maximum-bounded entropy procedure (Bashurin et al. 1995). This makes reasonable good reconstruction achievable even with as few aspects as N = 4. Experiments on the study of TM of a propane jet in air using a four-aspects laser interferometer were provided and reconstruction of propane concentration distribution was conducted. The results allow determination of the TM zone spectral characteristics.

A low-energy proton accelerator named pulsed synchronous linear accelerator (PSLA) is proposed and developed at the Institute of Fluid Physics, which is driven by unipolar-pulsed high voltages. Pulsed-accelerating electric fields and low-energy ion beams are precisely synchronized on temporal and spatial positions for continuous acceleration. The operating mode and the features of the PSLA are introduced. At present, the feasibility of a low-energy proton PSLA has been verified in principle. An average accelerating gradient up to 3 MV/m for protons is achieved.

Compton scattering of laser light by an electron beam at large angles, in particular at 90°, produces coherent hard radiation if the density of the electron beam is high enough. In this case, the intensity of the scattered radiation is greatly enhanced in a small cone around the forward direction of propagation of the electron beam. As an example, the production of 1-KeV coherent X rays is discussed.

The coherence of the laser radiation limits the average beam fluence in high power laser installations. The disadvantages of present optical schemes are analysed. A new optical scheme with controlled spatial coherence is described and its consequences are shown.

Scattered emission from the laser plasma created in shell target heating experiments using the Delfin-1 laser has been studied. It is shown that the ω0 spherical harmonics can be used to determine both the plasma temperature in the nc/4 region and also the plasma flow through this region.

Stimulated Raman scattering driven by intense subpicosecond laser drivers is analyzed, in particular, the effects of the pulse shape and relativity on the instability and its characteristic spectra. The analysis is carried out in the pulse group velocity frame (Lorentz transformed) where growth rates for backscattering are decreased relative to their values when analyzed in the laboratory frame, while forward-scattered growth rates have greatly enhanced values. A range of intensities and densities is considered, appropriate to recent experiments, which ranges from strongly coupled scattering at high densities (even for forwardscattering) to stimulated Compton scattering regimes for backscattering and relativistically trapped forwardscattering at low densities. The inhomogeneities in intensity and density cause mode conversion between waves inside and outside the pulse. This can be at a modest level, as for backscattering, or extreme as in the case of forwardscattering when the Raman scattered light can be trapped within the laser pulse. The consequent feedback between modes within the pulse allows solutions, absolutely growing in the pulse frame, to be found.

The interaction of a plasma produced by irradiation of perforated foils with laser pulses was studied. The laser beam of the first harmonics of the iodine laser (λ = 1.315 μm) system PERUN was focused by anf/2 optics (f = 20 cm) on a hole in the foil target of high-Z material. The laser energy and the temporal shape of the pulses were monitored both before and behind the hole. Foils of two different materials (Pb, Cu) were used, and a series of hole diameters 2rH ranging from 100 μm to 500 μm were tested. The diameter of the laser focal spot 2r0 was about 150 μm. For hole diameters smaller than 300 μm, a shortening of the laser pulse was observed, demonstrating the effect of plasma shutter. The pulse shortening, which depends on the hole diameter, corresponds to the reduction in the pulse energy passing through the hole. An analysis of the experimental data is based on hydrodynamic computations, and the physics of the process is illustrated by a simple analytical model.

We have identified a general final compression section for HIF drivers, the section between accelerator and the target. The beams are given a head to tail velocity tilt at the beginning of the section for longitudinal compression, while going through bends that direct it to the target at specific angle. The aim is to get the beams compressed while maintaining a small centroid off-set after the bends. We used a specific example, 1 MJ driver with 500 MeV Rubidium + 1 ion beams. We studied the effect of minimizing dispersion using different bend strategies, and came up with a beamline point design with adiabatic bends. We also identified some factors that lead to emittance growth as well as the minimum pulse length and spot size on the target.

A γ-ray laser would stimulate the emission of radiation of wavelengths below 1 Å from excited states of nuclei. However, the anticipation of a need for high pump powers tended to discourage early research and the difficulties in demonstrating a device were first assumed to be insurmountable. Over the past decade, advances in pulsed-power technology have changed these perceptions and studies have built a strong momentum. A nuclear analog of the ruby laser has been proposed and many of the component steps for pumping the nuclei have been demonstrated experimentally. A quantitative model based upon the new data and concepts has shown the γ-ray laser to be feasible if some real isotope has its properties sufficiently close to the ideals modeled. The greatest positive impact upon feasibility has come from the discovery of giant resonances for pumping nuclei that greatly reduce the levels of pump power needed.

Recent progress on accelerator and systems studies carried out in the framework of a national program on heavy ion fusion is reviewed. Plans for future investigations aiming at the basic aspects of inertial confinement with heavy ion beams are discussed.

Free electron lasers (FELs) place very stringent requirements on the quality of electron beams. Present techniques for commissioning and operating electron accelerators may not be optimized to produce the high brightness beams needed. Therefore, it is proposed to minimize the beamline errors in electron accelerator transport systems by minimizing the deviations between the experimentally measured and design transport matrices of each beamline section. The transport matrix for each section is measured using evoked responses. In addition, the transverse phase space of the beam is reconstructed by measuring the spatial distribution of the electrons at a number of different betatron phases and applying tomographic techniques developed for medical imaging.

Taking into account the stochastic excitation of the atoms (as quantum structures), we can suggest an absolutely new conception of a wide spectrum of processes in a femtosecond laser produced plasma. The electromagnetic fields being achieved with the modern laser technique exceed intraatomic fields by several orders. This fundamentally changes the physics of their interaction with the atomic structures. The atom effectively transforms the energy of radiation falling on it into fluxes on the nucleus. Quantum systems spin interaction with vector potential field being to play the essential role.

It is cylindrical converters that are generally considered for the purpose of changing the ion beam energy into X rays, with their irradiation to be provided through the cylinder end. This article studies a target having a disk-shaped converter to be irradiated sideways. It may be practical when one fails to overcome difficulties with the focusing of ion beams into a spot of a diameter smaller than a few millimeters.

Two methods of target technology for investigation of X-ray laser–plasma emission are presented. The first deals with steel and gold microcapillary targets. They are about 200 μm in inner diameter and about 500 μm in length. The second method deals with metal plus plastic targets of reduced and controlled density in the range of 1.6–8.1 g/cm3 for Cu + polyethylene (PE) and 1.6–7.6 g/cm3 for Fe + PE.

At the start of a new volume I want to take the opportunity to thank the associate editors and the editorial board members whose terms ended recently for their many years of service to the scientific community and to this journal especially. I personally had a lot of help from all of them, and I dare to ask for their continued support for this journal. The attentive reader may notice quite a change in the editorial team. Therefore this is also the opportunity to welcome the new board members and to wish them success for their editorial work.

The paper addresses Rayleigh–Taylor instability (RTI) problems and presents a method of describing an interface with markers on a Eulerian mesh, which is implemented in the MAH-3 code. The proposed method allows a more accurate description of the evolution of the interface caused by Rayleigh–Taylor perturbations and preserves symmetry of the interface under appropriate symmetry of the problem (planar, cylindrical, and spherical). The method employs an unstructured triangular mesh of makers. Method capabilities are demonstrated on 2D and 3D Rayleigh–Taylor instability problems.

We study strongly correlated plasmas far from equilibrium with the ultimate aim of describing the cooling of heavy ion beams by electrons. With the help of molecular dynamics (MD) computer simulations, we conclude that the relaxation of a two-component plasma depends strongly upon the preparation of the initial configuration. If the initial data have no intercomponent correlations, such will build up during the evolution so that the intercomponent potential energy decreases while the kinetic energy increases. These effects become more pronounced for strongly coupled plasmas and limit the efficiency of electron cooling. We cannot confirm certain mean-field predictions on the influence of an external magnetic field on the cooling process. A study of the relaxation of anisotropic velocity distributions for a one-component plasma shows deviations from meanfield results for strongly coupled plasmas.