Direct-drive implosion experiments on the GEKKO XII laser (9 kJ, 0.5 μm, 2 ns) with deuterium and tritium (DT) exchanged plastic hollow shell targets demonstrated fuel areal densities (ρR) of ˜0.1 g/cm2 and fuel densities of ˜600 times liquid density at fuel temperatures of ˜0.3 keV. (The density and ρR values refer only to DT and do not include carbons in the plastic targets.) These values are to be compared with thermonuclear ignition conditions, i.e., fuel densities of 500–1000 times liquid density, fuel areal densities greater than 0.3 g/cm2, and fuel temperatures greater than 5 keV. The irradiation nonuniformity in these experiments was significantly reduced to a level of <5% in root mean square by introducing random-phase plates. The target irregularity was controlled to a 1% level. The fuel ρR was directly measured with the neutron activation of Si, which was originally compounded in the plastic targets. The fuel densities were estimated from the ρR values using the mass conservation relation, where the ablated mass was separately measured using the time-dependent X-ray emission from multilayer targets. Although the observed densities were in agreement with one-dimensional calculation results with convergence ratios of 25–30, the observed neutron yields were significantly lower than those of the calculations. This suggests the implosion uniformity is not sufficient to create a hot spark in which most neutrons should be generated.

A kinetic model for KrF is presented that, by neglecting all but the most important kinetic processes, adequately describes the performance of electron-beam-pumped KrF lasers by a few, simple analytical expressions. The expression for the saturation intensity as a function of pump rate and gas composition is checked by measurements of gain saturation in both argon-rich and krypton-rich laser mixtures. The effects of fluorine burn-up are considered and are shown to impose a fundamental relationship between output fluence and efficiency of KrF laser amplifiers.

Dissociative excitation of the HgI (B–X) band system and atomic mercury lines was observed during collisions of CO+ ions with CH3HgI molecules in the laboratory kinetic energy range 100–1000 eV. By the use of the integrated intensity of the most intense band of the (B–X) transition of the HgI radical at 445 nm, emission cross sections were measured at different kinetic energies of these ions.

This article presents a review of X-ray spectroscopic diagnostic and measurement techniques as applied to laser plasma interaction and laser fusion studies. As a matter of definition we restrict our attention to the range of a several hundred eV to about 100 keV. We deal with both the basic measurement concepts and the instrumental techniques. First a brief review of the physical phenomena and parameter ranges involved is given. We then deal with specific X-ray spectroscopic instruments and methods that are useful in laser plasma X-ray spectroscopy. A discussion is given of various modeling techniques and how they can be compared with experimental measurements.

A method of absolutely unfolding the atomic spectrum by a pinhole transmission grating spectrometer (TGS) is discussed in detail. The numerical process considers both the factors of higher-dispersive-order overlapping of TGS and source-size widening effects. Real soft-X-ray spectra of aluminum, copper, and gold plasmas are presented of experiments performed on the Six-Beam Laser Facility at the Shanghai Institute of Optics and Fine Mechanics.

Recent improvements to the Nova laser and target experiments addressing laser–plasma interaction physics, hydrodynamic stability, implosion physics, and X-ray laser physics are summarized. Highlights include demonstrated laser performance exceeding Nova's original design goals, the observation of improved target compressions with temporally shaped laser pulses, and demonstrated lasing at wavelengths shorter than 45 Å.

High-intensity laser beams propagating in a plasma become focused because the index of refraction depends on the relativistic mass of the electron and therefore is a function of the electric field strength through the electron velocity. Around the focus the laser field has such a high density of energy that electrons and ions are emitted owing to the nonlinear force arising from this field. The equations of motion for the electrons and the ions and the Maxwellian equations for the laser and plasma fields are solved under certain approximations. We calculate the maximal energy and the angular distribution of the emitted ions and compare the results with experimental data.

Recent technological developments have resulted in sub 100 ps shutter times of X-ray cameras that are based on the gating of microchannel plates. Moreover, these cameras are reliable enough to be used on large experimental systems. A review is given of the development of gated proximity focused detectors and of the factors affecting their performance.

The effect of long-wavelength irradiation nonuniformities on the performance of singleshell, reactor targets is investigated by means of 2-D numerical simulations. The stages of target collapse, hot-spot formation, ignition, and burn are illustrated. Evidence is shown for the occurrence of the Rayleigh–Taylor instability during target stagnation. It is then shown that the sensitivity of a given family of targets to the nonuniformities of the driving pressure critically depend on the 1–D ignition margin and on the spark convergence ratio of the target. The tolerable levels of nonuniformity as a function of the perturbation mode number are determined, for selected targets, by means of a parametric numerical study.

The possibility of compressing the cryogenic hollow pellet of inertial confinement nuclear fusion with multiple adiabatic shock waves is discussed, on the basis of the estimation of the properties of a high-density deuterium plasma (1024−1027 cm−3, 10−1−104 eV), such as the velocity and the attenuation constant of the adiabatic sound wave, the width of the shock wave, and the surface tension.

It is found that in the course of compression the wavelength of the adiabatic sound wave and the width of the weak shock wave sometimes become comparable to or exceed the fuel shell width of the pellet, and that the surface tension is negative. These results show that it is rather difficult to compress stably the hollow pellet with successive weak shock waves.

State of the art capabilities in soft X-ray lenses, multilayer mirrors, beamsplitters, and synthetically generated holograms are reviewed. Application of these capabilities in recent X-ray laser cavity experiments, and to the development of a soft X-ray interferometer and a high intensity (≥1013 watt/cm2) soft X-ray laser are discussed.

Experimental results are given on high-power ion beams (HPIB) generation in a vacuumspherical focusing diode with self-magnetic insulation, obtained from the nanosecond accelerator PARUS with 0.2-TW power and 60-ns pulse duration for a matched load. When the passive plasma source of the ions was used, the efficiency of the HPIB generationwas measured to be as high as 20% for 700-kV diode voltage and 10-kA/cm2 beam density in the focal plane.

The application of a coaxial plasma opening switch (POS) prior to the diode resultedin a factor-of-1.8 increase in the diode power in comparison with a match operation inthe absence of a POS.

From analytic models of the ablation process in laser-plasma experiments, as well as simulations with Fokker–Planck and Spitzer codes, we have identified a new effect, thermal inertia smoothing. This effect results in a smoother Fokker–Planck temporal and spatial variation of the ablation pressure than that for Spitzer, for the same applied timevarying laser intensity. It is therefore advantageous for incoherent optical smoothing schemes. This is especially true at early times in the laser pulse (≤100 ps).

Radiation-induced conductivity (RIC) is a generalized term for photoconductivity expanded to include nonelectromagnetic radiation. RIC offers several distinct advantages for the detection of high-energy radiation: (i) the speed of response of a detector is determined by a bulk property of the material, the carrier lifetime; (ii) the detector can be directly illuminated by the signal radiation-no dead layer; and (iii) the selection of the detector material and its geometry is very flexible. This paper will discuss the principles of RIC for X rays and neutrons, the fabrication of detectors, and applications. RIC detectors have been fabricated from Si, InP, GaAs, and diamond. Bulk and thin film materials have been used. The carrier lifetime was varied by the introduction of trapping sites in the material. This can be done in the material production process in the case of doping (e.g., Fe in InP) and thin films or produced from radiation damage of a pure crystalline material. Lifetimes as short as a few picoseconds have been observed. A variety of detectors have been tested using pulsed optical, X ray, and neutron sources. Absolute sensitivities and temporal response has been measured and compared to theoretical models of the detector's performance for both X rays and neutrons. Finally, applications of these detectors to inertial confinement fusion measurement will be shown.

The results of high-power ion beam (HPIB) generation and in the magnetically insulated diode (MID) installed on a 3 × 1010-W nanosecond accelerator are given. The possibility of efficient HPIB ballistic focusing with the use of the preformed plasma in the HPIB transport region was demonstrated.

Several new diagnostics (spring pendulum and acoustic probe) were used to measure the plasma ablation pressure during the impact of the HPIB with the target.

The highest degree of HPIB focusing attained during the experiments with spherical geometries of the diode electrodes was equal to 60. The ablation average pressures measured by the spring pendulum gave several kilobars for 8–10 kA/cm2 of HPIB density. The peak pressure measured by acoustic probes attained tens of kilobars for the same HPIB current amplitudes.

To investigate the influence of radiation reabsorption on the level populations of ions in an expanding laser-produced plasma of intermediate density, we start with the system of rate equations for the population densities coupled with the line-radiation transport equation, the dynamical Doppler effect due to the differential macroscopic velocity field included. In a physically motivated approximation, for spatially varying absorption and emission, and general three-dimensional plasma geometry, an integral equation describing the effect of Lyman-a radiation reabsorption on the spatial behavior of the population density of the upper resonance level is derived. Assuming a sufficiently large velocity gradient so that the Doppler-induced frequency shift dominates the linewidth, after asymptotically evaluating the frequency integral involved in the kernel we are led to a simplified integral equation exhibiting the reduction of radiation reabsorption by Doppler decoupling. In particular, in the case of a cylindrical, radially expanding laser plasma we discuss this Fredholm equation for the reabsorption-influenced population density.