Inertial confinement fusion (ICF) has made great progress. In fact several significant scientific firsts have been achieved in the last year. These developments have presented the ICF community with an opportunity to embark on a new phase in ICF research. The key issues of laser fusion are to attain a high absorption of laser light in a plasma, to prevent preheating of fuel during the compression, and to achieve highly efficient implosion by uniform compression of fuel due to the homogeneous deposition of laser energy on the pellet surface. Direct drive and indirect drive have been investigated. The progress in both schemes is remarkable. The neutron yield by the stagnation free compression of the LHART target has attained 1013 which corresponds to a pellet gain of 1/500. The plastic shell target has reached a fuel density as large as 600 times the liquid density which is measured by the Si activation method as well as the D knockon method. A cryogenic foam target is now under investigation.

University research in the UK with high power lasers is carried out at the SERC's Central Laser Facility with a multi-terawatt neodymium glass laser, VULCAN, and a developmental KrF laser, SPRITE. These systems are briefly described together with the design of a new KrF laser to supersede VULCAN. The new laser design, SUPERSPRITE, is based on optical and Raman multiplexing which is being developed with the present SPRITE system. The specification of SUPERSPRITE is for 3.5 kJ in 1 ns and a peak power of 300 TW in short pulses. The new technology is seen as highly cost effective in relation to neodymium glass lasers. A resume of the development of XUV lasers in the UK in collaboration with laboratories overseas is given. The work is based on laser action through recombination in highly ionized ions and recent progress includes collaborative experiments on the GEKKO XII facility in Japan which have demonstrated laser action at the shortest wavelength to date at 45 A in Mg XII. The physics of energy transport in short pulses is fundamental to the extrapolation of recombination lasers to shorter wavelengths and is being studied from a more basic standpoint using both the VULCAN and SPRITE facilities. Some details of this work are given.

A critical test of direct-drive laser-fusion has been conducted with the demonstration of DT compression to densities in the range of 100–200 times liquid density in experiments on the University of Rochester's OMEGA laser facility. The high-density cyrogenic experiments used 351-nm laser pulses with energies of 1500–1800 J and pulse widths in the range of 600–700 ps.

The uniform side-on emission of second harmonic radiation has recently been measured from the corona of a laser irradiated plasma with large electron density gradients. A theoretical model has been developed to study the internal electric fields and double layers in such strongly inhomogeneous plasmas. The analytical model shows immediately a density-independent second harmonic term which reproduces very closely the measured intensity of the second harmonic. A detailed numerical evaluation of the term, for a plasma with a linear density profile (permitting Airy solutions), results in a net intensity with small spatial variation but also with both long and short wavelength periodicities exactly as measured. The observed vanishing of the periodicity, when broad band laser sources are used, can then immediately be explained from integration of the standing-wave like oscillations.

This paper reviews recent developments and achievements in the program of planar foil instability experiments being performed at the AWE HELEN laser. Point projection Xray backlighting, with spectroscopy, is used to measure hydrodynamic mix in radiatively accelerated ablator/foil packages; the mix is identified in the experimental radiograph from the overlap of distinguishable spectral absorption features associated with each of the constituent materials.

The first part of the paper describes the backlighting technique, and briefly summarizes progress made in the past two years, leading to the first results being obtained on a “high mix” Parylene-C ablator/molybdenum payload package. The second part considers the full analysis of one such ‘high mix’ shot (Shot 7772), describing how the spatial distribution of mix has been quantified and considering the various sources of error. Comparisons are made with both one-dimensional and two-dimensional hydrocode simulations. Finally, various improvements and extensions to the experiment and codes are indicated.

The emissivity of the rear of a shocked foil is spectrally and temporally resolved by coupling a transmission grating (1000 I/mm) and an X-UV streak camera (with a low density Csl photocathode), providing a high temporal resolution over a large spectral range. The shock is generated with two techniques: direct illumination of a single Al foil with a 0.26 μm wavelength laser (ablation pressure ≈ 50 Mbars) or by colliding an Al foil with a laser accelerated CH foil (generated pressures greater than 100–200 Mbars). Different thicknesses of Al are used in single foil experiments, and different initial spacing and impacted foil thicknesses are used in double foil experiments. Double foil experiments indicate that targets can be optimized for high pressure generation, and single foil experiments show that there is a radiative heat wave, around 200 eV, due to the heating of the foil by X rays emitted in the ablated region during the laser pulse. Double foil experiments have been compared with 2-D hydrodynamic Lagrangian simulations and single foil experiments have been compared with 1-D hydrodynamic Lagrangian simulations taking into account radiative heat transfer.

The Heavy Ion Fusion Accelerator Research (HIFAR) program of the U.S. Dept. of Energy has for several years concentrated on developing linear induction accelerators as Inertial Fusion (IF) drivers. This accelerator technology is suitable for the IF application because it is readily capable of accelerating short, intense pulses of charged particles with good electrical efficiency. The principal technical difficulty is in injecting and transporting the intense pulses while maintaining the necessary beam quality. The approach used has been to design a system of multiple beams so that not all of the charge has to be confined in a single beam line. The beams are finally brought together in a common focus at the target. This paper will briefly present the status and future plans of the program, and will also briefly review systems study results for HIF.

Focusing processes of rotating and propagating proton beams in a neutral hydrogen gas are studied numerically by using a two-dimensional hybrid code. Processes including beam impact ionization, plasma avalanche and field emission are taken into consideration. The plasma formation time depends on the initial gas density and the beam intensity. When 2-Torr neutral gas is filled initially, enough plasma density is created by the rising part of the beam pulse, so that the main pulse is focused and forms a rotating and propagatingbeam configuration.

In a series of experiments done at the Laboratory for Laser Energetics of the University of Rochester, Kr/Ar- and Ar-filled polymer shell targets were imploded using the 24 beam (351 nm) 2 KJ Omega laser system. We present results from the analysis of the X-ray line spectra recorded on these experiments. In particular, we discuss the Stark broadening of L-shell spectra, its application to plasma diagnostics, and the advantages of recording time-resolved spectra. We also show results from radiation-hydrodynamics modeling of these experiments.

The calculation of the multigroup opacities using several different atomic physics models is the main goal of this work. The atomic data, such as energy levels, bound-electron populations, oscillator strengths and effective charges are worked out by two atomic physics models using the average-atom concept. The result achieves multifrequency opacities. These are weighted with the Planck function or the real radiation field, making up finally the multigroup opacities in the selected number of groups.

Recently, we have developed a one-dimensional radiation-hydrodynamics code called SARA that implicitly solves the multigroup radiation transport equations. A high-order differencing algorithm as well as multifrequency-grey synthetic acceleration techniques are used to obtain a robust algorithm that can be extensively used for radiation energy transport problems and radiative regimes.

The major goal of writing this code has been to explore the performance of the indirectdrive light ion beam capsules. Numerical results show that the efficiency of the energy conversion into soft X rays and the power flux amplification factor are high enough to efficiently compress the fuel capsule for a wide range of ion beam parameters.

The results of the interaction of laser beams integrated by an optical system composed of two arrays of 256 elements each are presented. Optical dark-field shadowgraphy as well as interferograms show significant smoothing effects when compared with experiments performed in the same conditions but without beam integrators.

A numerical analysis is presented of the electrostrictive filamentation of an electromagnetic wave in the presence of a reflected wave. Maxwell's equations are solved in the steadystate simultaneously with one fluid hydrodynamics and a simplified equation of state to obtain a self-consistent solution. The threshold for filamentation is shown to be often below the laser intensity necessary to modify the plasma density profile, however, even weak profile modification substantially affects the filamentation.

Stimulated Brillouin and Raman scattering are of considerable interest because of their importance to basic nonlinear plasma physics phenomena and to laser-driven inertial confinement fusion. Induced scattering can be substantial for high intensity (I), long wavelength (λ) lasers because the instability growth rates depend exponentially on Jλ2, and also for short wavelength, long scalelength (L) laser/plasma interaction because of nearly homogeneous or large convective gain conditions. Experimental results from both KrF and CO2 laser/plasma interaction studies are presented to illustrate important wavelength dependent features of induced scattering such as the nature of the instability (absolute, convective), threshold, spectra, reflectivity and saturation effects. Backscattering characteristics have been measured for solid target plasmas (aluminum, gold) produced by KrF laser pulses focused to intensities <1014 W/cm2 and gas targets (hydrogen, oxygen) by CO2 laser pulses at intensities <1013 W/cm2. Collisional absorption dominates the KrF laser experiments, whereas particle heating and increased Landau damping dominate the CO2 laser experiments. Current theoretical work concerned with nonlinear effects in Langmuir wave localization, wave collapse and particle heating (generating characteristic high temperature electrons) is also presented.

The development of a hydrodynamic instability in laser targets is studied by means of a 2-D numerical code “ATLANT”. During the linear stage, the perturbations grow as:

In the nonlinear stage the growth rate of the Rayleigh-Taylor instability is reduced, and new harmonics are generated. The effect of the nonuniformity of the laser irradiation has been investigated for long-wave and short-wave perturbations. The growth rate of short-wave perturbations may be effectively decreased by means of symmetrical pre-pulses.

Laser-produced plasmas have many properties similar to, or which can be scaled to, those encountered in space, magnetospheric, ionospheric, and astrophysical situations. We describe several such experiments performed with the PHAROS III Nd-laser facility at NRL.

Thermal energy transport in laser-irradiated glass microshells coated with polystyrene/metal layers seems to be dominated by hot spots. These are connected with filaments which are enhanced by hydrodynamic instability of the Rayleigh-Taylor type.

Tritium self-heats at a rate of 97 W/mole because of its β activity. This energy drives preferential sublimation of solid T2 or DT from regions where a layer is thicker and warmer to regions where the layer is thinner and colder. A frozen tritium layer inside an isothermal container approaches isotropy exponentially with a time constant as short as 14.4 minutes. Targets Isotropized by Radioactively Induced Sublimation (IRIS) and sized for an ICF reactor demonstrate high gain and offer real fabrication advantages.

The paper describes different types of plane targets, the method for obtaining metal microballoons from Au, Ag, and Cu with diameters of 600–1200 μm and wall thickness of 5–20 μm, and spherical cascade and cannonball type targets.