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Plasma-based seeded soft-x-ray lasers have the potential to generate high energy and highly coherent short pulse beams. Due to their high density, plasmas created by the interaction of an intense laser with a solid target should store the highest amount of energy density among all plasma amplifiers. Our previous numerical work with a two-dimensional (2D) adaptive mesh refinement hydrodynamic code demonstrated that careful tailoring of plasma shapes leads to a dramatic enhancement of both soft-x-ray laser output energy and pumping efficiency. Benchmarking of our 2D hydrodynamic code in previous experiments demonstrated a high level of confidence, allowing us to perform a full study with the aim of the way for 10-100 μJ seeded soft-x-ray lasers. In this paper, we describe in detail the mechanisms that drive the hydrodynamics of plasma columns. We observed transitions between narrow plasmas, where very strong bidimensional flow prevents them from storing energy, to large plasmas that store a high amount of energy. Millimeter-sized plasmas are outstanding amplifiers, but they have the limitation of transverse lasing. In this paper, we provide a preliminary solution to this problem.

The Hohlraum energetics experimental campaign started in the summer of 2009 on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)]. These experiments showed good coupling of the laser energy into the targets [N. Meezan et al., Phys. Plasmas 17, 056304 (2010)]. They have also demonstrated controlled crossed-beam energy transfer between laser beams as an efficient and robust tool to tune the implosion symmetry of ignition capsules, as predicted by earlier calculations [P. Michel et al., Phys. Rev. Lett. 102, 025004 (2009)]. A new linear model calculating crossed-beam energy transfer between cones of beams on the NIF has been developed. The model has been applied to the subscale Hohlraum targets shot during the National Ignition Campaign in 2009. A good agreement can be found between the calculations and the experiments when the impaired propagation of the laser beams due to backscatter is accounted for. [ABSTRACT FROM AUTHOR]

Observations of a rapid decrease in thermal temperature as a function of depth of solid targets irradiated with a short pulse, ultrahigh-intensity laser are reported. This phenomenon is investigated using the Titan short pulse laser with intensities greater than 1020 W/cm2 interacting with buried layer targets. The longitudinal temperature profile is determined by measuring K-shell spectra from a 0.4 μm copper tracer layer placed at various depths (i.e., 0–1.5 μm) within the 2.4 μm thick target. It is observed that the line ratios (He-like K-shell lines) as a function of temperature require a consideration of at least three parameters to analyze the K-shell spectra: hot electron population, time-dependent plasma conditions, and opacity. Here, the study of the effect of these three parameters on measured spectra in the short pulse high intensity laser-matter interactions using the atomic model FLYCHK [H.-K. Chung et al., High Energy Density Phys. 1, 3 (2005)] is presented. [ABSTRACT FROM AUTHOR]

17–75 keV one- and two-dimensional high-resolution (<10 μm) radiography has been developed using high-intensity short pulse lasers. High energy Kα sources are created by fluorescence from hot electrons interacting in the target material after irradiation by lasers with intensity IL>1017 W/cm2. High-resolution point projection one- and two-dimensional radiography has been achieved using microfoil and microwire targets attached to low-Z substrate materials. The microwire size was 10 μm×10 μm×300 μm on a 300 μm×300 μm×5 μm polystyrene substrate. The radiography experiments were performed using the Titan laser at Lawrence Livermore National Laboratory. The results show that the resolution is dominated by the microwire target size and there is very little degradation from the plasma plume, implying that the high-energy x-ray photons are generated mostly within the microwire volume. There are enough Kα photons created with a 300 J, 1-ω, 40 ps pulse laser from these small volume targets, and that the signal-to-noise ratio is sufficiently high, for single shot radiography experiments. This unique technique will be used on future high energy density experiments at many new high-power laser facilities. [ABSTRACT FROM AUTHOR]

We give an overview of recent experimental results on optical-field-ionization collisional soft X-ray lasers developed at LOA. By focusing a 30-fs, circularly polarized Ti-sapphire laser pulse at an intensity of up to 8×1017 Wcm-2 into a low-density gas cell containing Xe or Kr, we produced a few mm long plasma column for soft X-ray amplifier. Saturated amplification has been achieved on the 4d95d(1S0)­4d95p(1P1) transition at 41.8 nm in Xe8+, and on the 3d94d(1S0)­3d94p(1P1) transition in Kr8+ at 32.8 nm. Under optimum pumping conditions the Xe8+ laser provides about (5±2)×109 photons per pulse whilst the Kr8+ laser delivers up to (2.5±1)×109 photons per shot. The repetition rate of these soft X-ray lasers is 10 Hz. The beam wavefront of the Xe8+ laser has been measured by a Shack­Hartmann soft X-ray wavefront sensor, and the pulse duration by a cross-correlation technique. [ABSTRACT FROM AUTHOR]

Observations of a rapid decrease in thermal temperature as a function of depth of solid targets irradiated with a short pulse, ultrahigh-intensity laser are reported. This phenomenon is investigated using the Titan short pulse laser with intensities greater than 1020 W/cm2 interacting with buried layer targets. The longitudinal temperature profile is determined by measuring K-shell spectra from a 0.4 μm copper tracer layer placed at various depths (i.e., 0–1.5 μm) within the 2.4 μm thick target. It is observed that the line ratios (He-like K-shell lines) as a function of temperature require a consideration of at least three parameters to analyze the K-shell spectra: hot electron population, time-dependent plasma conditions, and opacity. Here, the study of the effect of these three parameters on measured spectra in the short pulse high intensity laser-matter interactions using the atomic model FLYCHK [H.-K. Chung et al., High Energy Density Phys. 1, 3 (2005)] is presented. [ABSTRACT FROM AUTHOR]