The X-ray emission, especially the K-shell emission, from a neon gas-puff Z-pinch powered by the Qiang Guang-I accelerator, about 1.5 MA in amplitude and 100 ns in rise time, were calculated based on the two-level model and measured with X-ray diodes and an eight-frame X-ray pinhole camera. The simulation results showed that the K-shell yield is highly sensitive to the peak current. The experimental results confirmed that the matching of the Z-pinch load (mass and initial radius) to the current is crucial for getting a higher X-ray yield. Being determined by the imploding time, the pinch current plays a more important role than the current amplitude in K-shell emission. It seems that the preferable imploding time is about 110 ns. The K-shell radiation power with double shells, as a whole, is higher than that using single neon shell. While an implosion of a light (32 µg/cm) and small (20 mm in diameter) neon shell evolves with rather twist and asymmetries, a heavier (41 µg/cm) and bigger (25 mm in diameter) neon shell implodes more symmetrically. The double neon shells, 30 mm and 30 µg/cm for the outer shell, and 15-mm and 10 µg/cm for the inner shell, create almost “perfect” implosions evidenced by the early-time plasma shells with little perturbation and late stagnated pinch liners with a good axial uniformity. It was found that the “Zippering” effect leads to an earlier K-shell emission in the cathode region than that in the anode region, which extends the pulse width of K-shell emission.

Resonant absorption effects for 1.064 µm infrared laser pulse radiations are investigated by using different techniques producing micrometric surface structures with dimensions comparable to the wavelength value. The laser absorption is controlled through measurement of the Cu ion acceleration using time-of-flight approach. Surface treatments include low energy laser etching in air, deposition of microspheres obtained ablating Cu targets in water, pulse laser deposition of microstructures precursor of thin homogeneous film, chemical etching with HNO3 acid, Ar+ ion sputtering and rolling burnishing surface of thin Cu foils. Results indicate that the best resonance effect is obtained with the rolling burnishing, ion sputtering and microsphere deposition processes which enhance the Cu ion energy and the yield emission.

The AURORA KrF laser at Los Alamos became operational in August 1989. AURORA is the first integrated system for demonstrating the capability of a KrF laser to perform target physics experiments for inertial confinement fusion (ICF) and is currently configured as a 5-kJ, 5-ns, 96-beam device. Both laser physics and ICF target physics experiments have been performed over the last year. Of the four major amplifiers in the AURORA laser system, one performed better than expected, one performed about as expected, and two performed below expectations. The causes of the variability in the amplifier performance are now well enough understood that this information can be used to improve the detailed design of the NIKE laser currently under construction at the Naval Research Laboratory. design of the NIKE laser currently under construction at the Naval Research Laboratory. High-dynamic-range pulse shapes have been propagated with minimal distortion through the AURORA amplifier chain, verifying theoretical predictions. Target physics experiments have been performed with intensities greater than 100 TW/cm2, pulse lengths ranging from 2–7 ns, and spot-size diameters from 500–1100 µm. The analysis of this first-generation kJ-class KrF laser target physics facility identified the strengths and weaknesses of KrF lasers for ICF applications. Detailed measurements of amplifier performance led to a better understanding of issues for KrF laser-fusion systems, and design studies for future KrF lasers for ICF applications incorporate improvements based in part on AURORA experience.

Electron-beam sustained discharges can be used in opening and closing switch applications for producing bursts of energy in pulsed power systems. The incorporation of admixtures of attachers with low attachment rate at low values of E/N and high attachment rate at high values of E/N in the gaseous switch dielectric has been proposed to achieve low forward voltage drop in the conduction phase as well as rapid opening when the sustaining e-beam is terminated. This paper presents model calculations on the characteristics and transient behavior of an electron-beam sustained discharge in the high current density regime in N2. The influence of an attacher (N2O), with the property described above, and of the circuit parameters on the discharge is investigated as an illustrative example. The advantage of using such an attacher is demonstrated for the steady state conduction phases and for the opening phase, while the closing process is obstructed by the attacher. Additional possible control mechanisms, such as photodetachment to aid the closing process are discussed.

The charge-state distribution and the energy loss of oxygen ions in a laser-produced hydrogen plasma have been investigated experimentally. The plasma target had a maximum electron density of 5 × 1018 cm−3 and a maximum electron temperature of 13 eV. The mean charge state of the oxygen ions in the hydrogen plasma was measured to be 5.1, which was considerably higher than that in hydrogen gas. The energy loss of oxygen ions in the plasma of a density less than 1 × 1018 cm−3 in the plasma showed a large enhancement compared with that in hydrogen gas. However, the energy loss in the plasma of a density above 1 × 1018 cm−3 showed no enhancement.

This paper discusses the implications of using different fuels, including pure deuterium, deuterium–tritium, deuterium–helium3, and proton–boron11, on safety and environmental compatibility of the fusion reactor, as well as on the driver requirements. Due to present-day technology limitations, it seems likely that the first generation of the fusion reactors will be based on a deuterium–tritium cycle. Such a scheme, however, would pose serious problems, including neutron activation and tritium handling. We show that by developing low-level tritium inertial fusion targets, one may substantially reduce the daily use of tritium in the reactor that may ultimately lead to a reduction in the overall tritium inventory in the power plant. Such reduced tritium targets will still generate sufficient energy to run the power plant economically.

A time-dependent solution for neutral-plasma isothermal expansions into a vacuum in a special-transformation coordinate system is obtained. In this new coordinate system, the special self-similar solutions of it were given by Huang and co-workers (Appl. Phys. Lett. 92, 031501). Combining the time-dependent solution and the quasi-linear increase of the electron density due to the hot-electron recirculation, an analytic model is proposed to reveal the influence of the hot-electron recirculation on the increase of electric field and on the acceleration of ions of different masses and charges.

This paper investigates the non-linear coaxial (or coupled mode) propagation of Laguerre–Gaussian (LG) (in particular L01 mode) and Gaussian electromagnetic (em) beams in a homogeneous plasma characterized by ponderomotive and relativistic non-linearities. The formulation is based on numerical solution of non-linear Schrödinger wave equation under Jeffreys–Wentzel–Kramers–Brillouin approximation, followed by paraxial approach applicable in the vicinity of intensity maximum of the beams. A set of coupled differential equations for spot size (beam width) and phase evolution with space corresponding to coupled mode has been derived and numerically solved to determine the propagation dynamics. Using focusing equation a critical condition describing the self-trapped (i.e., spatial soliton) mode of laser beam propagation in the plasma has been discussed; as a consequence oscillatory focusing/defocusing of the beams in coupled mode propagation have been analyzed and presented graphically. As an important outcome, significant enhancement in the intensity of LG beam is noticed when it is coupled with the Gaussian mode.

An exploding wire system has been experimentally studied by the observation of its plasma dynamics and the electrical energy delivered by the supporting circuit to the metallic wire. Plasma radial expansion has been obtained from visible light streak images, meanwhile electrical energy transfer dynamics was derived from the analysis of voltage and current traces of the exploding wire circuit. In these measurements, a significant portion of the electrical energy has been transferred to the exploding wire circuit during the plasma expansion, and lower limits for the resistivity during the plasma expansion confirm the existence of a central liquid or solid metallic core in addition to the expanding plasma.

Electron acceleration by relativistic electron plasma waves is studied by theory and particle simulations. The maximum acceleration that can be obtained from this process depends on many different factors. This paper presents a study of how these various factors impact on the acceleration mechanism. Although particular reference is made to the laser plasma beatwave concept, the study is equally relevant to the acceleration of particles in the plasma wakefield accelerator and the laser wakefield accelerator.

Recently much attention has been paid to multilayer inertial confinement fusion (ICF) targets, among them the targets with low-density layers. This allows one to get a number of interesting results using the presently existing and future facilities. This concerns the volume absorption of the laser radiation in a porous matter of the density higher than the critical plasma density, and the formation of the radiation absorption region under condition of increasing geometric opacity of the low-density matter. We consider the low-density foams, 3D nets, free-standing “snow-like” layers, and pseudo low-density layers. We use artificial foam as a convenient model to allow easier comparison of the experimental laser shot data and the simulation. The requirements to such layers are also analyzed. The methods of precision control of the low-density targets are discussed.

The paper presents experiments dealing with interaction of Nd-glass laser radiation with single and double planar Al foil targets. An ablatively accelerated thin foil may achieve high velocity which cannot be obtained in any other way (for the mass of the order of 10−7 g). It can be applied to investigate effects of collision between accelerated foil and planar metal target. The accelerated foil fragment may be regarded as a projectile. Craters arising in this way are similar to those obtained in hypervelocity impact (HVI) experiments. An additional comparison can be made with results of laser simulation method (LSM). The aim of our work was to find the scaling laws for the relative volumes of craters for the velocity range up to about 100 km/s. We should also like to compare results of both methods used by us: laser ablative acceleration method (LAAM) and laser simulation method with hypervelocity impact.

This paper deals with a lithium/tin combined target to increase the conversion efficiency of extreme ultraviolet (EUV) of 13.5 nm emission from laser-produced plasma. The bilayer target of glass/lithium (20 nm)/tin (50 nm) exhibits a sharp and strong emission in comparison with a Sn bulk target. The reverse coating of glass/tin/lithium was unstable and EUV could not be observed. By using nano-porous SnO2 and an electrochemical deposition of lithium, nano-structured lithium/tin composite was prepared, and was stable without deliquescence of lithium.

Strong ionization in metal vapors is known to be very readily produced by a variety of pulsed and CW lasers. Particularly well known is ‘resonance’ ionization by pulsed or CW dye lasers operated at the atomic resonance lines (e.g. Na 3s → 3p). We also have experimental results for two other forms of ionization: ‘quasiresonant’ ionization using a CW dye laser (e.g. at the Na 3p → 4d transitions), and ‘two-photon resonance’ ionization using a pulsed dye laser (e.g. at the Na 3s → 4d two-photon resonances). Both new forms are visually characterized by bright ‘white sparks’ and correspond to reasonably high electron densities of ∼1014−1015 cm3 and low electron temperatures of ∼0·1−0·2 eV. The ‘quasiresonant’ ionization is remarkable in that it occurs even with a very low power 1 mW focused CW laser in 10 torr of Na. A variety of interesting atomic and molecular spectroscopic features have been observed and analyzed.

The development of pulsed power technology, particularly for inductive energy storage, promotes the extensive discussions of electrical explosion process in high energy density. This paper presents the electrical-explosion behavior of carbon fibers subjected to about 20 kA, ~5 µs high-density current pulse igniting an intense electron beam accelerator. After electrical explosion, and surface rupture, submicron particles, fibrillar and strip-shaped structures were observed, experimentally supporting the microstructure model (skin-core heterogeneity) of carbon fiber. Interestingly, the start and turn-off of the current were followed by radiation pulses with different intensities. It was found that the radiation was focused on the explosion stage which was characterized by an oscillating current. The instabilities of plasma produced during the explosion process play an important role in the microstructure changes of carbon fibers and the radiation generation.

Total electron emission yield for impact of slow Neq+(q = 2, 4, 6, 8) ions with various kinetic energy under normal incidence on n-type Si has been measured. It is shown that for the same charge state, the total electron yield γ increases linearly as the kinetic energy of projectile at impact increases, up to velocities corresponding to the “classical” threshold. Separation of kinetic electron yield γKE and potential electron yield γPE shows that γPE is proportional to the ion charge state and γKE increases linearly with projectile velocity. Finally, based on “single hole without hopping” hypothesis, the expression of the “CRF” F(q) is given, and the relation between γKE and q is obtained successfully for the first time, which is also a basis for judging whether the “trampoline effect” exists.

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.

Basic characteristics of an ablation plasma produced by an intense, pulsed, ion beam have been evaluated from the measurement of ion-flux density by a biased ion collector. The target mass loss is detected by the measurement of the weight of the target in the comparison before and after the shot. A one-dimensional hydrodynamic model is introduced with the assumption of a high-power, light-ion beam-driven expansion and the following adiabatic expansion into vacuum. With this model, it is possible for us to deduce the temperature and the pressure from the data of the ion flux and the mass loss of the target, respectively. This method is also applicable to other intense pulsed energy sources such as lasers or electron beams.

A fast photo imaging technique has been used to characterize the expansion dynamics of a laser generated silver plasma propagating through background inert gases (He and Ar) at different pressures. The time evolution of the expanding plasma was investigated in the framework of currently available phenomenological models. Mixed-propagation model gives an accurate description of the initial and late plasma expansion stages in Ar when proper input parameters are taken into account. In He, only the initial quasi-linear expansion and shock wave formation were observed along the space available to plasma motion.

The electron-beam-pumped KrF laser installation GARPUN with a 100-J output energy and long 100-ns pulse duration has been used to investigate laser–target interactions in a broad range of laser intensities for small (150 μm) and large (∼1 cm) irradiated spots. For higher intensities (up to 5 × 1012 W/cm2), a conical shock wave was generated in condensed matter by megabar pressure at the ablation front. It propagated with a supersonic velocity in a quasisteady manner together with a conical shock wave inside a target. Evaporated target material moving with a velocity of ∼50 km/s formed an extended plasma corona of ∼5 mm length with an electron temperature of ∼100 eV. Emission spectra of plasma have been investigated in the extreme UV range 120–250 Å. For lower intensities (108–109 W/cm2), planar shock waves in normal density air were produced with initial velocities up to 4 km/s in the forward direction and 7 km/s in the opposite direction toward incident radiation. In rarefied air, the forward shock wave kept velocities constant whereas the backward ones were accelerated up to 30 km/s. Planar compression waves in transparent condensed matter were also demonstrated propagating with sonic velocity.