The differential imaging technique is particularly suitable for the detection of small concentrations of contrasts agents for biological and medical applications in samples using X-ray radiography. In this paper, we present an application of this technique using a laser-plasma soft X-ray source combined with a bent crystal. Using a Fresnel plate as a test object, we were able to obtain spatial resolutions of the order of a few tens of microns. The use of our configuration to perform differential imaging of a test-sample at the L2 edge of Br at 1,596 eV is finally demonstrated.

It was shown (Faenov et al., 2015b) that the energy of femtosecond laser pulses with relativistic intensity approaching to ~1021 W/cm2 is efficiently converted to X-ray radiation and produces exotic states in solid density plasma periphery. We propose and show by one-dimensional two-temperature hydrodynamic modeling, that applying two such unique ultra-bright X-ray sources with intensities above 1017 W/cm2 – allow to generate shock waves with strength of up to some hundreds Mbar, which could give new opportunities for studies of matter in extreme conditions.

We present the results of ab initio, nonperturbative, R-Matrix Floquet calculations of laser-induced continuum structures in helium. We compare our results with recent experimental data and good agreement is found.

Two-photon absorption (TPA) of Au-ion irradiated glasses in the femtosecond regime has been analyzed by an open-aperture Z scan technique. Three types of glasses, namely GIL49, BK7, and Glass B were irradiated by using 1700 keV Au+ ion beams. Samples were post-annealed at 600°C for 5 h. Penetration depth and distribution of Au+ ions having 1700 keV energy within glass substrates were estimated by transport of ions in matter (TRIM) simulations. Detailed calculations with full-damage cascades were performed for each sample, taking into account the chemical composition of glass substrates. TRIM results reveal that there is no significant change in ion range, straggling, and ion distribution with the change in the substrate composition. However, Z scan results showed a difference in TPA coefficients for all three glasses. Extent of crosslinking within each of irradiated sample, owing to its chemical composition, may have affected their TPA coefficients.

Interactions of sub-nanosecond pulses of kJ-class iodine laser “PALS” with low-density foams and acceleration of Al foils by the pressure of the heated foam matter are investigated here, both experimentally and theoretically. X-ray streak camera is used for evaluation of the speed of energy transfer through the porous foam material. The shock-wave arrival on the rear side of the target is monitored by optical streak camera. Accelerated foil velocities, measured by three-frame optical interferometers, and shadowgraphs, reach up to 107 cm/s. The accelerated foil shape is smooth without any signature of small-scale structures present in the incident laser beam. Conversion efficiencies as high as 14% of the laser energy into the kinetic energy of Al foil are derived. Experimental results compare well with our two-dimensional hydrodynamics simulations and with an approximate analytical model.

A new scheme for cone-hollow-assisted fast ignition in inertial fusion is investigated. A hollow is attached to the tip of a conventional gold cone. The transport and heating of the high-current electrons propagating from the cone tip to the compressed fuel core along the hollow is investigated by two-dimensional hybrid simulation. Different hollow geometry sizes are examinized. It is shown that with proper hollow guiding, hot electrons can be collimated between the inner-walls of the hollow by the large interface magnetic fields appearing on the inner surface. When the beam electrons further propagate into the dense region, they are scattered into the gold hollow through collisions with the fuel electrons and ions. The resulting magnetic potential around the hollow then bends beam electrons along the gold hollow to reach the dense core.

Pinched electron beams emit high power microwaves by formation of a virtual cathode. Radiation occurs simultaneously with pinching or slightly thereafter. Observations of strong electrostatic fields and the partitioning of current into reflexing and transmitting populations at the same time that microwaves are emitted indicate virtual cathode formation. Microwaves originate mainly from the virtual cathode side of the anode. A two-dimensional model for the electron flow in the presence of a virtual cathode is presented. The model allows for electron reflexing and velocity distribution spread. Solutions with strong radial flow agree closely with microwave measurements, and result in the microwave frequency scaling linearly with diode current.

A review of recent developments in intense ion beam diagnostics used in the international light ion inertial confinement fusion (ICF) programs will be presented. These developments have occurred in each of the several generic classes of diagnostics, namely, imaging diagnostics, particle spectrograph diagnostics, nuclear activation, and visible spectroscopy. Critical beam parameters measured by the new diagnostics include spatial profile, absolute number, species, anode plasma temperature and density, voltage, current density, and power density. A unique feature of most of these diagnostics is that they are capable of operating in hard (multi-MeV) X-ray (bremsstrahlung) backgrounds of some 109–1011 rad/s. The operating principles of each diagnostic will be summarized in the paper with examples of how the diagnostics may be integrated together to form a complete diagnostic system. The paper will close with a discussion of two new data acquisition systems that have been developed for intense beam diagnostics.

Production of sharply collimated high velocity outflows – plasma jets from massive planar targets by a single laser beam at PALS facility is clarified via numerical simulations. Since only a few experimental data on the intensity distribution in the interaction beam near the focus are available for the PALS facility, the laser beam profile was calculated by a numerical model of the laser system and the interaction optics. The obtained intensity profiles are used as the input for plasma dynamic simulations by our cylindrical two-dimensional fluid code PALE. Jet formation due to laser intensity profile with a minimum on the axis is demonstrated. The outflow collimation improves significantly for heavier elements, even when radiative cooling is omitted. Using an optimized interaction beam profile, a homogeneous jet with a length exceeding its diameter by several times may be reliably generated for applications in laboratory astrophysics and impact ignition studies.

Theoretical treatments of the stopping power are reviewed and problems necessary to extend these treatments to high temperature and high density materials are discussed. Physically important parameters which govern the stopping power properties are indicated. The average equilibrium charge for a gaseous medium is one of the important parameters in the stopping power and the charge-exchange processes involved are discussed. The effective charge is described in terms of a relation between the average equilibrium charge and the effective charge. The atomic energy levels for high density and high temperature matter are also included in the stopping power formula.

Actual calculations of the stopping power are made for Pb ions passing through the HIBLIC-target. Range profiles are estimated for Xe and U ions in an ionized Al target for temperatures T = 0 to T = 1290 eV using the Brueckner, Senbetu & Metzler (1982) theory based on a dielectric response function. Results are compared with those of Northcliffe & Schilling (1970), Ziegler (1980), and Hubert et al. (1980). In order to include dynamic local-field corrections in the dielectric function, a model is proposed similar to a two component plasma.

In this paper, the electrons energy spectrum produced by stochastic acceleration in the interaction of an intense laser pulse with the underdense plasma is described by employing the fully kinetic 1D-3 V particle-in-cell simulation. In this way, two finite laser pulses with the same length 200 fs and with two different rise times 30 and 60 fs are typically selected. It is shown that the maximum energy of electrons in the laser pulse with the short rise time (30 fs) is about eight times greater than the maximum energy of the electrons with the long rise time (60 fs). Furthermore, unlike the pulse with the short rise time, the shape of energy spectrum and the electrons temperature in the long rise time laser pulse are approximately unchanged over the time. These results originated from the fact that in the case of long rise time laser pulse, all electrons are accelerated by the one chaotic mechanism because of the scattered fields generated in the plasma, but in the case of short rise time laser pulse, three different mechanisms accelerate the electrons: first, the stochastic acceleration because of the nonlinear wave breaking via plasma-vacuum boundary effect; second, the stochastic acceleration initiated by the wave breaking; and third, the direct laser acceleration of the released electrons.

For low carbon energy generation, a very large exchange of electricity generators is existentially vital within the next number of years by power stations preferably at considerably low cost than the present installations. When considering the million times higher nuclear energy per reaction than chemical, the usual hydrogen fusion with abundant boron fuel is used for environmentally clean electricity generators. Instead of usually needed ignition temperatures of hundreds of million degrees Celsius, it is possible to use nonthermal ignition pressures from now available CPA laser pulses. In this non-LTE scheme, there is no need for high compression, the medium of hydrogen-boron-11 temperatures is low, and therefore the bremsstrahlung losses practically do not exist. The neutron, created by secondary reactions, elimination device includes tin and is arranged such that the neutrons are brought to nuclear reactions with the tin. We suggest adding the tin that has proven to be particularly advantageous because of its high effective cross section, and the neutron reactions with tin transform the tin nuclei into stable nuclei with a higher atomic weight.

A model of laser interaction with a preformed target plasma is developed for the conditions of so called stimulated Brillouin backscattering (SBS) model experiments and its applicability is demonstrated by various tests. Most of the features can be understood from analytical approximations. A consequence of irradiation by a narrow beam, typical of model experiments, is the stabilization of electron temperature at low values. Another consequence equally unexpected is the SBS threshold dependence on beam radius and the particular power law dependence on plasma density. On the basis of this model the wide scatter of the SBS threshold between model experiments can be explained. It is also demonstrated that, for the conditions of these model experiments, classical Spitzer heat conduction suffices.

The effect of laser intensity distribution along the line focus on the uniformity of the line-shaped plasmas produced is investigated with time-integrated and time-resolved soft X-ray and optical diagnostics. Evident plasma condition nonuniformities along the line focus resulting from nonuniform laser intensity distributions have been observed with a conventional simple line-focusing technique. With a new line-focusing technique producing a uniform laser illumination, a uniform, line-shaped plasma can be obtained. It is also found that nonuniformities under uniform laser illumination occur mostly during laser heating. The line-shaped uniform laser plasma can be used as a large, uniform X-ray source besides its importance in X-ray laser demonstration and amplification. As an application of such line-shaped plasmas as X-ray sources, the no-overcoat 5F X-ray film is calibrated for the first time by a new method in the soft X-ray range from 10–80 A.

Previous experiments at 0.1 TW level have shown that stability and X-ray emission of fast Z-pinch could be significantly improved by imploding an Al vapor jet onto a very thin coaxial wire (Wessel et al., 1992). Here we present the first results of an Al Z-pinch using a similar liner but at mega-ampere level. The pinch is driven by AMBIORIX facility, a 2 TW, 0.5 Ω, 2 MA, and a 50-ns pulse-line generator. We study the effect of an Al wire and its diameter (20–50 μm) on the implosion dynamics, on X-ray yield, on-axis magnetohydrodynamics (MHD) stability, and on Rayleigh–Taylor instability of the column at stagnation. Analysis of an Al jet on Al wire shots demonstrates that X-ray yield due to emission processes in the H- and He-like ionization stages (i.e., the K-shell) is enhanced, relative to the ones with Al jet only. The wire leads also to a better symmetrization of the implosion, and to better reproducibility of the shots. X-ray signals exhibit two similar pulses, 10-ns-wide and separated by 15 ns. To discern spectrally the origin of each pulse, further experiments have been performed with stainless steel wire (25 μm in diameter). Results show that liner and wire radiate simultaneously and contribute to both pulses. Full analysis of a typical Al jet on Al wire shot, using detailed collisional-radiative equilibrium (CRE) model is given in this paper. A sketch of the pinch at stagnation, with a cold dense core embedded in a hot low density corona, reproduces well all features of X-ray emission.

During the propagation of an optically smoothed laser beam through a warm plasma the speckle field pattern and the corresponding speckle intensity distribution are modified in time and along the laser propagation direction. It is shown here that the laser–plasma interaction can change the character of speckle statistics from an initially exponential-type limit law to a Weibull-type law. The Weibull distribution is characterized by a power-law-type behavior in a limited interval of the random variable, which is, in the present case, the speckle intensity. The properties of the speckle distributions are studied using methods of extremal and order statistics. The scattering instability process (here stimulated Brillouin forward scattering) causing the change in speckle statistics has an onset behavior associated with a “critical gain” value, as pointed out in work by Rose and DuBois (1993b). The saturation of the instability process as a function of intensity explains the limited interval of the Weibull-type speckle distribution. The differences in the type of the speckle statistics are analyzed by using “excess over threshold” methods relying on the generalized Pareto distribution, which clearly brings to evidence the transition from an exponential type distribution to the Weibull-type distribution as a function of the instability gain value, that is, from the regime below critical gain to values above the critical gain.

We present a broad study of linear, clustered, noble gas puffs irradiated with the frequency doubled (527 nm) Titan laser at Lawrence Livermore National Laboratory. Pure Ar, Kr, and Xe clustered gas puffs, as well as two mixed-gas puffs consisting of KrAr and XeKrAr gases, make up the targets. Characterization experiments to determine gas-puff density show that varying the experimental parameter gas-delay timing (the delay between gas puff initialization and laser-gas-puff interaction) provides a simple control over the gas-puff density. X-ray emission (>1.4 keV) is studied as a function of gas composition, density, and delay timing. Xe gas puffs produce the strongest peak radiation in the several keV spectral region. The emitted radiation was found to be anisotropic, with smaller X-ray flux observed in the direction perpendicular to both laser beam propagation and polarization directions. The degree of anisotropy is independent of gas target type but increases with photon energy. X-ray spectroscopic measurements estimate plasma parameters and highlight their difference with previous studies. Electron beams with energy in excess of 72 keV are present in the noble gas-puff plasmas and results indicate that Ar plays a key role in their production. A drastic increase in harder X-ray emissions (X-ray flash effect) and multi-MeV electron-beam generation from Xe gas-puff plasma occurred when the laser beam was focused on the front edge of the linear gas puff.

Recent progress in research on Light Ion Beams-Inertial Confinement Fusion (LIB-ICF) at ILE, Osaka University is summarized. We report on pulsed power compression using PEOS, a super high voltage source, on diode physics, on beam trajectory control for focusing, on beam-target interactions and on a conceptual reactor design (Rokko I) in this article.

In this paper, a study on a fusion reactor core is presented in heavy-ion inertial fusion (HIF), including the heavy-ion beam (HIB) transport in a fusion reactor, an HIB interaction with a background gas, the reactor cavity gas dynamics, the reactor gas backflow to the beam lines, and an HIB fusion reactor design. The HIB has remarkable preferable features to release the fusion energy in inertial fusion: in particle accelerators HIBs are generated with a high driver efficiency of about 30–40%, and the HIB ions deposit their energy inside of materials. Therefore, a requirement for the fusion target energy gain is relatively low, that would be ~50 to operate an HIF fusion reactor with a standard energy output of 1 GW of electricity. In a fusion reactor, the HIB charge neutralization is needed for a ballistic HIB transport. Multiple mechanical shutters would be installed at each HIB port at the reactor wall to stop the blast waves and the chamber gas backflow, so that the accelerator final elements would be protected from the reactor gas contaminant. The essential fusion reactor components are discussed in this paper.