A computational study of tungsten wire array z pinches on the Z facility at Sandia National Laboratories shows that individual wires form a core–corona structure early in the current pulse. Further analysis indicates that at 1 mm or smaller interwire gap, the expanding and later merging wire plasmas prevent the growth of m = 0 sausage modes. Although a completely uniform shell is not observed in the simulations, the Hussey–Roderick profile—a characteristic of uniform shell implosions—is seen. Differences in shell characteristics between small- and large-diameter wires are observed, possibly explaining performance differences between these two arrangements.

We describe a direct model for simulation of relativistic electrons acceleration with a given electromagnetic field which is determined by wave packet parameters. The multimode time-spatial structure of a focused Nd-laser beam with stochastic phase disturbances of each spectral component is taken into account as a source of random forces. Electron energies of more than 10 MeV are obtained even at moderate flux densities of 1016 W/cm2. The developed numerical code makes it possible to obtain a quantitative energy distribution function in relation to both field intensity and the temporal bell-shape of the laser pulse. The efficient heating of electrons can be triggered in the presence of a counter propagating wave being reflected from the critical plasma area with a different reflection coefficient. The heating mechanism occurs with a delay relative to the beginning of the pulse when the laser fields exceed some threshold amplitudes. The qualitative comparison of simulation results with the experimental data is given as evidence that this mechanism is reasonable.

We present the results of X-ray diagnostics of Z-pinch hot points, formed during fast electrical discharges through exploding Al wires. Experimental data include the pinhole images and X-ray time integrated radiation spectra. These spectra were obtained with high spectral resolution in the range 1.5–2.2 keV, contained the most intensive resonance lines of Al H- and He-like ions. Comparison of the recorded lines width and peak intensities with the corresponding modeled values, enables us to estimate the main hydrodynamical parameters of hot point, such as average temperature and density, being achieved at a moment of its maximum compression. Additionally, on the base of theoretical analysis of the spectral intensities distribution in well-resolved Lyα satellites, the gradient of compression velocities field is concluded. Some features of the investigated lines spectra forming are discussed.

Stimulated Raman forward scattering (SRFS) of an intense short pulse laser in a plasma channel formed by two pre-laser pulses is investigated. The density nonuniformity of a plasma channel increases the focusing of main laser pulse. Main laser pulse excites a plasma wave and two electromagnetic sideband waves. Laser and the sidebands exert an axial ponderomotive force on electrons driving the plasma wave. The nonlinear currents arise at sideband frequencies. The density perturbation due to plasma wave beats with the oscillatory velocity due to pump to drive the sidebands. The normalized growth rate of SRFS increases with the density nonuniformity of a plasma channel. However, in the presence of a deep plasma channel the focusing is ineffective to laser intensity, but the growth rate increases with the intensity of main laser pulse.

Pulsed laser induced damage of optical thin films is, in general, initiated by the absorption of laser radiation by imperfections in the films or at interfaces between film layers and/or the substrate. A heat flow analysis of this process stresses the importance that the thermal conductivity of both the thin film host and that of the substrate play in establishing the laser-induced damage threshold. Unfortunately, recent work, which will be reviewed in this presentation, indicates that the thermal conductivity of thin films can be several orders of magnitude lower than that of the corresponding material in bulk form. This situation arises as a consequence of the film structure resulting principally from the deposition process. The importance of thermal conductivity will be compared to parameters such as absorption mechanisms, film materials, composition, and other variables. Its implication for the ultimate optical strength of materials and the direction in which thin film research and processing should proceed will be highlighted.

This report reviews the scientific activities on high power laser and laser plasma physics at CIAE. A 6-beam KrF excimer laser system (100 J/23 ns/248 nm/1013 W/cm2, 15 min/shot) has been built, the Raman technologies used to upgrade it to 1014 W/cm2 has been studied. A UV femtosecond Ti:sapphire/KrF hybrid laser (50 mJ/220 fs/248 nm/1017 W/cm2) has been developed also, hot electron generation research has been carried out in the fs laser. In the near future, the fs laser will be amplified in six-beam laser system to produce ultra-high intensity to do fundamental researches on Fast Ignition of ICF.

A new and simple type of self-magnetically insulated, vacuum ion diode named “Plasma Focus Diode” has been successfully developed with a large solid angle of irradiation and low divergence angle. The diode has a pair of coaxial cylindrical electrodes similar to a Mather-type plasma focus device. Ion-current density of 1·9 kA/cm2 has been obtained on the anode surface under the experimental conditions of diode voltage ∼1·4 MV, diode current ∼180 kA, and pulse width ∼75 ns. The generated ion beam has been two-dimensionally focused (line focusing) with a focusing radius of ∼0·18 mm, giving a maximum ion current density and beam power density at the axis of ∼0·14 MA/cm2 and ∼0·18 TW/cm2, respectively. The motion of electrons in the gap has been numerically simulated by use of a newly developed particle-in-cell computer simulation code, and good agreement has been obtained between the simulation and the experiment.

Soft X-ray contact microscopy (SXCM) experiments have been performed using the Prague Asterix Iodine Laser System (PALS). Laser wavelength and pulse duration were λ = 1.314 μm and τ (FWHM) = 450 ps, respectively. Pulsed X rays were generated using teflon, gold, and molybdenum targets with laser intensities I ≥ 1014 W/cm2. Experiments have been performed on the nematodes Caenorhabditis elegans. Images were recorded on PMMA photo resists and analyzed using an atomic force microscope operating in contact mode. Our preliminary results indicate the suitability of the SXCM for multicellular specimens.

The calculations of 1014–1015 W/cm2 laser interaction with volume-structured agar-agar and Cu targets were performed. The influence of intrinsic X-ray plasma radiation on the propagation of thermal waves in such targets was investigated. It is shown that the velocity of heat transfer in agar-agar foam targets is increased due to X-ray preheating when a thin Cu layer is added.

Analyses are given for beam generations of three kinds of charged particles: electrons, light ions, and heavy ions. The electron beam oscillates in a dense plasma irradiated by a strong laser light. When the frequency of laser light is high and its intensity is large, the acceleration of oscillating electrons becomes large and the electrons radiate electromagnetic waves. As the reaction, the electrons feel a damping force, whose effect on oscillating electron motion is investigated first. Second, the electron beam induces the strong electromagnetic field by its self-induced electric current density when the electron number density is high. The induced electric field reduces the oscillation motion and deforms the beam.

In the case of a light ion beam, the electrostatic field, induced by the beam charge, as well as the electromagnetic field, induced by the beam current, affects the beam motion. The total energy of the magnetic field surrounding the beam is rather small in comparison with its kinetic energy.

In the case of heavy ion beams the beam charge at the leading edge is much smaller in comparison with the case of light ion beams when the heavy ion beam propagates in the background plasma. Thus, the induced electrostatic and electromagnetic fields do not much affect the beam propagation.

A comparative study of superficial changes on the superalloy Inconel 600, induced by a picosecond Nd:YAG laser operating at 1064, 532, and 266 nm, is presented. All of the laser wavelengths, as well as the used fluences of 2.5 (1064 nm), 4.3 (532 nm), and 0.6 J/cm2 (266 nm) were found to be adequate for inducing surface variations. Quite different surface features were produced depending on the laser wavelength used. The measured surface damage thresholds were 0.25, 0.13 and 0.10 J/cm2 for 1064, 532, and 266 nm, respectively. Drastic differences, in function of the wavelength used, were recorded for the crater depths, as well the appearance of hydrodynamic effects and periodic surface structures. Differences in crater depths were explained via an easier propagation of the first harmonic laser radiation (1064 nm) through the ejected material and plasma compared to a radiation at 532 and 266 nm. Finally, changes in the surface oxygen content caused by ultrashort laser pulses were considered.

We study the problem of the radiation pressure acceleration of ions and the formation of plasma jets, driven by a high-intensity circularly polarized laser beam normally incident on thin plasma targets. We use an Eulerian Vlasov code to solve the one-dimensional relativistic Vlasov-Maxwell equations for both electrons and ions. We consider the case of a high density plasma with n/ncr = 100, where ncr is the critical density. Three cases are studied with different target thicknesses, to investigate the physical processes involved when decreasing the target thickness from several electron skin depths down to the order of one skin depth. The results show a more important acceleration of the ions when the thickness is decreased. Although we observe in all cases a neutral plasma jet ejected from the back of the target, the evolution of the system which leads to the formation of this neutral plasma jet is different in the three cases considered. In each case, this evolution will be studied in details. Also, a leak or ejection of electrons from the back of the target is observed in the thinnest case treated (thickness of the order of the skin depth), before the formation of the neutral plasma jet, a regime called leaky light sail radiation pressure acceleration. The absence of noise in the Eulerian Vlasov code allows an accurate representation of the phase-space structures of the distribution functions.

It is proposed that it is possible to amplify the energy of a pulsed laser beam by imploding it inside a capillary metallic liner. If imploded with megaampere currents by the pinch effect, implosion velocities up to ∼3 × 108 cm/s can be reached, imploding a few cm long liner with an inner radius of 2 × 10−3 cm in about ∼10−10 s. If the liner radius can be imploded by 30-fold, the laser pulse would in the absence of absorption losses into the linear wall be amplified 1000-fold. Because the amplification is through the conversion from longer to shorter wave lengths, the concept offers the prospect of intense short wave length laser pulses in the far ultraviolet and soft X-ray domain. Apart from the direct drive laser beam compression by the pinch effect, an alternative indirect drive through the conversion of the electric pulse power into soft X-rays is possible as well. The limitations of this concept are the absorption losses into the liner wall, and ways to overcome these losses are presented. The most important application of the proposed laser amplification scheme might be for the fast ignition of various inertial confinement fusion schemes. An integrated fast ignition inertial confinement fusion concept using the indirect drive is also presented.

A novel electron acceleration approach with two overlapping linearly polarized laser pulses in vacuum is proposed. By our simulation, the energy and space spreads can reduce greatly comparing with the acceleration with only one laser pulse having doubled peak laser intensity for realistic laser parameters and the average energy gain from our scheme can be doubled for certain pulse lengths, at the same time. Using numerical simulation, analytical criteria for optimal regimes of our acceleration scheme is found.

The use of laboratory experiments as plasma creating sources is a valuable tool for understanding astrophysical observations. Recently plasma created through irradiation by lasers with relativistic intensities has been used to study effects of hot electrons and X-ray pumping on X-ray formation of multiply charged ions spectra. This paper discusses the formation of K-shell Fe spectra recorded from a plasma irradiated by 35 fs pulses with intensities of 1021 W/cm2. Modeling of the spectra suggests three different regions of plasma radiation including a cold ~10 eV region, a mild ~700 eV region, and a hot ~3500 eV region. The influence of hot electrons and X-ray pumping is discussed and a comparison with K-shell Fe spectra from a 1 MA X-pinch experiment is included to highlight the differences due to the shorter time frame of the laser–plasma interaction experiment.

In this paper, we describe the experimental validation of the technique of correction of wavefront aberration in the middle of the laser amplifying chain. This technique allows the correction of the aberrations from the first part of the laser system, and the pre-compensation of the aberrations built in the second part. This approach will allow an effective aberration management in the laser chain, to protect the optical surfaces and optimize performances, and is the only possible approach for multi-petawatt laser system from the technical and economical point of view. This approach is now possible after the introduction of new deformable mirrors with lower static aberrations and higher dynamic than the standard devices.

The analytical evaluation of the capability of Bremsstrahlung highly directional energetic γ-beam to induce photo transmutation of 90Sr (γ,n) 89Sr is presented. Photo transmutation of hazardous nuclear waste of 90Sr, one of the two main sources of heat and radioactivity in spent fuel into valuable nuclear medicine radioisotope of 89Sr is explained. Based on the calculations, a fairly decent fraction of gamma rays in this range are used in transmuting of 90Sr into 89Sr where according to the available experimental data it is shown that by irradiating a 1-cm thick 90Sr sample with lasers of intensity of 1021 W/cm2 and repletion rate of 100 Hz for an hour, the reaction activity would be 1.45 kBq. It is shown that there is not a linear relationship between the growth of the activity and increasing the laser intensity, but there is a dramatic increase in the growth rate especially between 1020and 1021 W/cm2. In this work, the advantage of photonuclear transmutation over the neutron capture transmutation for 90Sr isotope is also discussed.

The Rayleigh-Taylor instability is a key process in many fields of Physics ranging from astrophysics to inertial confinement fusion. It is usually analyzed deriving the linearized fluid equations, but the physics behind the instability is not always clear. Recent works on this instability allow for an very intuitive understanding of the phenomenon and for a straightforward calculation of the linear growth rate. In this Letter, it is shown that the same reasoning allows for a direct derivation of the relativistic expression of the linear growth rate for an incompressible fluid.

Experimental results on the compression of shell targets with aspect ratio A = 150–250 in the “Delfin-1” installation are reported. The absorbed laser energy was 0·3 to 0·5 kJ. The maximum compression was 3·5 × 103, the velocity of target compression at the final stage was 2·6 × 107 cm/s, neutron yield was 106 to 107 D-D neutrons per laser shot. The appearence of plasma corona filamentation correlated with compression stability distruction.

The emission of X-rays from solid tin targets irradiated by low-energy (few mJ) femtosecond laser pulses propagated through air plasma sparks is investigated. The aim is that to better understand the X-ray emission mechanism and to show the possibility to produce proper radiation for spectroscopic and imaging applications with a table-top laser system. The utilization of a controlled ultrashort prepulse is found necessary to optimize the conversion efficiency of laser energy into Lα radiation. The optimum contrast between the main pulse and the controlled prepulse is found about 102. A correlation between the laser contrast value and the laser near-infrared spectra at the exit of the plasma spark is observed.