For ultrafast material analyses, we constructed the time-resolved X-ray diffraction system utilizing ultrashort X-rays from laser-produced plasma generated by the 12-TW–50-fs laser at the Nuclear Engineering Research Laboratory. Ultrafast transient changes in laser-irradiated GaAs crystals were observed as X-ray diffraction patterns. Experimental results were compared with numerical analyses.

Interaction between energetic electrons and a circularly polarized laser pulse in a relativistic plasma channel is studied. Laser radiation can be resonantly absorbed by electrons executing betatron oscillations in the channel and absorbing angular momentum from the laser. The absorbed angular momentum manifests itself as a strong axial magnetic field (inverse Faraday effect). The magnitude of this magnetic field is calculated and related to the amount of the absorbed energy.

In this article we describe a new ray-trace code. This code is a three-dimensional description of the beam propagation, including the half cavity mirror. It is based on the integration of the ray equation and on the calculation of the intensity along the plasma. It works as a postprocessor of the hydrodynamic/atomic code “EHYBRID,” which calculates the time evolution of the gain, emissivity, electronic density, and the width of the plasma. We present results obtained on different schemes of X-ray laser generation.

A time-compensated monochromator for ultrashort high-order harmonics in the EUV and soft X-ray regions is presented. The system consists of two grazing-incidence toroidal mirrors used, respectively, as collimating and refocusing elements and of two multilayer normal-incidence plane mirrors illuminated in parallel light that rotate along a vertical axis to select the operative wavelength, but remain parallel to guarantee the constant direction of the exit beam. This is performed by simultaneously rotating and translating one of the two mirrors along an axis parallel to the exit direction. The pulse time duration is not altered up to few femtoseconds.

One of the features of ultra high intensity (UHI) short pulse laser–matter interactions is the prospect of creating a cheap, compact source of hard X rays with femtosecond pulse duration. The properties of such Kα sources are studied using analytical and numerical models of hot electron generation and subsequent transport in a range of materials (Reich et al., 2000). First, we find that there is an optimum laser intensity for Kα generation from bulk targets, which scales as Z4.4. Second, we show that efficient hard X-ray pulses with durations below 100 fs can be generated at intensities of ∼1016 W/cm2.

Propagation of an intense laser pulse in a cold electron-ion plasma is considered. Starting with the fully relativistic equations, for pancake-shaped pulses, a one-dimensional nonlinear Schrodinger equation is derived. It is shown, in quasi-stationary stage, both localized and cusp solution exist and relativistic effects cause solitons to move slower as their amplitude increases. These observations indicate particle-like behavior for localized solutions.

We report on an experiment demonstrating the high degree of mutual phase coherence between two white-light continuum pulses independently generated by phase-locked ultrashort laser pulses. We show that these secondary pulses are locked in phase and exhibit surprisingly clear and stable Young's interference fringes when overlapped on a screen in the far field. We discuss the use of such phase-locked continuum pulses in the realization of a new kind of ultrabroad frequency comb for absolute frequency measurements throughout the visible spectrum.

Response of clusters to laser radiation depends on the laser parameters like wavelength, pulse duration, field, and so forth. At moderate laser intensities, I ∼ 1012 W/cm2, using a laser beam of wavelength 1.06 μm and 10-ns pulse duration, we have studied X-ray emission spectra from aluminum clusters of diameter 0.4 μm and gold clusters of 1.25 μm. Aluminum clusters show a different spectra compared to bulk material whereas gold clusters evolve towards bulk gold. Results are analyzed on the basis of cluster dimension, laser wavelength, and pulse duration. At higher laser intensities ≥1018 W/cm2, clusters undergo Coulomb explosion, giving rise to energetic electrons and ions. Here we discuss the possibility of harnessing these energetic particles for heating a small volume of the precompressed DT fuel to ignition condition relevant to fast ignition. Preliminary results are discussed.

A model for nonlocal α particle transport is implemented in a one-dimensional radiation hydrodynamics code and applied for typical directly and indirectly driven ICF target simulations. Ignition criteria are compared for four configurations; spherical, cylindrical, planar with a central hot spot, and another planar configuration with a hot spot on one side. This last planar configuration is then used for fast ignitor studies, since it is able to simulate hot spot formation by direct laser heating and free expansion towards the incoming beam. Ignition requirements as a function of laser intensity and pulse length, taking into account the relationship between intensity, hot electron temperature, and range, are then determined.