When a large piece of space debris forced a change of flight plan for arecent U.S. Space Shuttle mission, the concept that we are trashing space as well as Earth finally attained broad public awareness. Almost a million pieces of debris have been generated by 35 years of spaceflight, and now threaten long-term space missions. The most economical solution to this problem is to cause space debris items to reenter and burn up in the atmosphere. For safe handling of large objects, it is desired to do this on a precomputed trajectory. Due to the number, speed, and spacial distribution of the objects, a highly agile source of mechanical impulse, as well as a quantum leap in detection capability are required. For reasons we will discuss, we believe that the best means of accomplishing these goals is the system we propose here, which uses a ground-based laser system and active beam phase error correcting beam director to provide the impulse, together with a new, computer-intensive, very high-resolution optical detection system to locate objects as small as 1 cm at 500-km range. Illumination of the objects by the repetitively pulsed laser produces a laser-ablation jet that gives the impulse to de-orbit the object. A laser of just 20-kW average power and state-of-the-art detection capabilities could clear near-Earth space below 100-km altitude of all space debris larger than 1 cm but less massive than 100 kg in about 4 years, and all debris in the threatening 1–20-cm size range in about 2 years of continuous operation. The ORION laser would be sited near the Equator at a high altitude location (e.g., the Uhuru site on Kilimanjaro), minimizing turbulence correction, conversion by stimulated Raman scattering, and absorption of the 530-nm wavelength laser beam. ORION is a special case of Laser Impulse Space Propulsion (LISP), studied extensively by Los Alamos and others over the past 4 years.

The science of high pressure (Eliezer et al. 1986; Eliezer & Ricci 1991) is studied experimentally in the laboratory by using static and dynamic techniques. In static experiments the sample is squeezed between pistons or anvils. The conditions in these static experiments are limited by the strength of the construction materials. In the dynamic experiments shock waves are created. Since the passage time of the shock is short in comparison with the disassembly time of shocked sample, one can do shock-wave research for any pressure that can be supplied by a driver, assuming that a proper diagnostic is available. In the scientific literature, the following shock-wave generators are discussed: chemical explosives, nuclear explosions, rail guns, two stage light-gas gun, exploding foils, magnetic compression, and high-power lasers.

Weakly nonlinear stage of the ablative Rayleigh-Taylor instability has been studied by the perturbation theory. Mode coupling of linear growing waves with wave numbers kA and kB drives new excited waves with wave numbers k0 (= kA ± kB, 2kA, 2kB). We have investigated time evolution of the excited waves and found that the ablation effect plays an important role even in the nonlinear stage to reduce amplitude of the excited waves. Differences between an ablation surface and a classical contact surface have been discussed. Dependence of the excited wave amplitude on the wavenumber k0, the ablation velocity va, and the effective gravity g is also investigated.

Cubic barium titanate (BaTiO3) thin films have been prepared in situ, on a low-temperature substrate, Al/SiO2/Si(100), by intense, pulsed ion beam evaporation. We have first proposed a new deposition configuration, backside deposition, which, in comparison with standard frontside deposition, produces very smooth thin films, Rα (mean roughness) ≈ 3 ∼ 9 nm, without any droplets. There is no significant change of the dielectric constant in the frequency range of 10 ∼ 105 Hz. The dielectric constant for the film deposited at the substrate temperature of 200˚C is typically ∼90 at 1 kHz.

The AWE HELEN laser is being used to measure high-pressure Hugoniot data by the impedance match method. Indirect drive is used to generate pressures of up to 10 Mbar in the aluminum reference material. We are aiming to measure shock velocities in our targets to ± 1 %, leading to errors in pressure and particle velocity of the order of ±2%. This requires improvements in target fabrication and characterization, streak camera calibration and data analysis, coupled with investigations into shock planarity and attenuation. Our latest results have accuracies of 2–4% in shock velocity but have identified work that should allow us to achieve our intended level of accuracy. Experiments have been done with copper and chlorinated plastic; our results are compared with theory, and, for copper, with U.S. and Russian gas-gun, explosively or nuclear-driven experiments.

The theory of magnetic field generation due to the interaction of short relativistic laser pulses with underdense plasmas has been developed. The magnetic field is generated due to the inverse Faraday effect occurring witha circularly polarized laser pulse. The spatial distribution of the magnetic field is investigated. It is shown that the magnetic field magnitude depends on the relationship between the laser beam radius and the plasma skin-depth.

Research on multiply-ionized atoms was pioneered in the 1930s and 40s, particularly in Sweden by Edlén and his colleagues working first in M. Siegbahn's laboratory in Uppsala, and then at Lund University. The key instrument was the grazing-incidence grating spectrometer which opened to observation the spectral range 500–5Å (Edlén 1963). The source of the multiply-charged ions was the plasma of a vacuum spark, a pulsed (~1 µs) electric discharge of up to 50 kA between electrodes of the desired element, some 3–5 mm apart. When the spark was enclosed in a ceramic tube (with a side opening to let out the radiation), the breakdown voltage was less, the discharge was more controllable. Furthermore, it was found that the range of species produced was a useful function of current.

The spatial profile, as well as ion-velocity distribution of laser-produced plasmas can be controlled experimentally by varying the time-form of laser pulse. A compression of nearly all produced plasma into a thin monovelocity spherical shell has been observed for the first time. A hydrodynamic numerical simulation shows that the shell generates due to special dynamics of ion ablation and geometry of experiment.

This paper describes the first results of a feasibility study undertaken at CERN to determine whether a laser-produced plasma can be used as a source of intense highly charged heavy ion beams. A variety of important measurements have been made, and the results are encouraging. Furthermore, a beam of highly charged light ions produced by the laser ion source has been accelerated successfully in a radio frequency quadrupole (RFQ) structure.

A shock wave is a discontinuous surface that connects supersonic flow with subsonic flow. After a shock wave, flow velocity is reduced, and pressure and temperature increase; entropy especially increases across a shock wave. Therefore, flow is in nonequilibrium, and irreversible processes occur inside the shock layer. The thickness of a shock wave in neutral gas is of the order of the mean free path of the fluid particle. A shock wave also appears in magnetized plasma. Provided that when the plasma flow is parallel to the magnetic field, a shock wave appears if the governing equation for velocity potential is in hyperbolic type in relation with the Mach number and the Alfvén number. When the flow is perpendicular to the magnetic field, the Maxwell stress, in addition to the pressure, plays a role in the shock wave in plasma. When the plasma temperature is so high, as the plasma becomes collision-free, another type of shock wave appears. In a collision-free shock wave, gyromotions of electrons around the magnetic field lines cause the shock formation instead of collisions in a collision-dominant plasma or neutral gas. Regardless of a collision-dominant or collision-free shock wave, the fluid that passes through the shock wave is heated in addition to being compressed. In inertial confinement fusion, the fuel must be compressed. Really, implosion motion performs fuel compression. A shock wave, appearing in the process of implosion, compresses the fuel. The shock wave, however, heats the fuel more intensively, and it makes it difficult to compress the fuel further because high temperatures invite high pressure. Adiabatic compression of the fuel is the desired result during the implosion, without the formation of a shock wave.

Achieving inertial confinement fusion using a light-ion-beam driver requires continued improvement in understanding ion diode physics. The power delivered to a light-ion beam target is strongly influenced by the evolution of the charge-particle distributions across the ion beam acceleration gap. Our strategy is to determine this evolution from time- and space-resolved measurements of the electric field using Stark-shifted line emission. In addition to diode physics, the unique high-field (∼10 MV/cm, ∼6T) conditions in present experiments offer the possibility to advance basic atomic physics, for example by measuring field ionization rates for tightly bound low-principal-quantum-number levels. In fact, extension of atomic physics into the high-field regime is required for accurate interpretation of diode physics measurements. This paper describes progress in ion diode physics and basic atomic physics, obtained with visible-light atomic spectroscopy measurements in the ∼20 TW Particle Beam Fusion Accelerator II ion diode.

We present the results of calculations for the K-edges of representative transient carbon ion clusters in a dense carbon plasma. The calculations use the recently implemented non-“muffin-tin” scattered-wave method previously used in the molecular and solid-state fields. Based on a simple model for the cluster potentials it is shown that, compared with a single ion calculation, the presence of neighboring ions can significantly alter the K-edge photoionization cross sections, and hence the resulting opacities.

An experimental technique based on optical scattering to detect melting in release of strongly shocked materials is presented. This method is used to study the asymptotic behavior of the free surface of shock-loaded materials. After reflection of a shock wave from a metallic sample free surface, occurrence of a solid to liquid transition will induce a dynamic behavior such as mass ejection and development of instabilities. A study of the mass ejection due to laser-induced shock waves in aluminium, copper, and tin targets is presented. Shock waves of order of hundreds of kilobars to more than one megabar are produced by a Nd:YAG laser system with a wavelength of 1.06 μm, pulse width of 7 ns FWHM focused to spot of 200 μm. The velocities, size, and topological structure of the ejected particles are measured. The radii of the ejecta are in the range 0.5–7 μm.

Recombining plasmas produced by picosecond laser pulses are characterized by measuring ratio of intensities of resonance lines of H- and He-like ions in the plasmas. It is found that the rapidly recombining plasmas produced by picosecond laser pulses are suitable for highgain operation.

This paper presents a set of complementary corpuscular diagnostics applied in experiments for investigation of laser-produced plasma as a source of ions. The measuring possibilities and methods for processing experimental data of a cylindrical electrostatic ion energy analyzer, a Thomson parabola ion analyzer, various types of electrostatic probes, a detector of neutral atom fluxes, as well as methods for visualization of ion emission areas are discussed. Special attention was focused on the ion-induced secondary electron emission problem and its influence on the accuracy of the measurements.