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The FIREX-1 project, the goal of which is to demonstrate fuel heating up to 5 keV by fast ignition scheme, has been carried out since 2003 including construction and tuning of LFEX laser and integrated experiments. Implosion and heating experiment of Fast Ignition targets have been performed since 2009 with Gekko-XII and LFEX lasers. A deuterated polystyrene shell target was imploded with the 0.53- μm Gekko-XII, and the 1.053- μm beam of the LFEX laser was injected through a gold cone attached to the shell to generate hot electrons to heat the imploded fuel plasma. Pulse contrast ratio of the LFEX beam was significantly improved. Also a variety of plasma diagnostic instruments were developed to be compatible with harsh environment of intense hard x-rays (γ rays) and electromagnetic pulses due to the intense LFEX beam on the target. Large background signals around the DD neutron signal in time-of-flight record of neutron detector were found to consist of neutrons via (γ,n) reactions and scattered gamma rays. Enhanced neutron yield was confirmed by carefully eliminating such backgrounds. Neutron enhancement up to 3.5 × 107 was observed. Heating efficiency was estimated to be 10–20% assuming a uniform temperature rise model.

The Zama discovery was identified off the coast of Tabasco, Mexico, in the Sureste Basin of the Gulf of Mexico and is hosted in a three‐way closure in the Upper Miocene. This study conducted a detailed detrital zircon (DZ) U–Pb and (U‐Th)/He provenance analyses on samples from sandstone reservoirs in the Zama‐3 and Zama‐2ST1 wells. A total of 22 sandstone samples (11 from each well) were collected for DZ U–Pb and (U‐Th)/He dating from different reservoir zones, testing the hypothesis that different zones were whether originally derived from varied sedimentary source terranes and associated transport pathways to the Zama mini‐basin depositional site. Additional objectives include determination of maximum depositional ages, reconstruction of paleofluvial systems, and exploring the temporal evolution of the drainage region and hinterland tectonics. The DZ U–Pb age spectra from both Zama wells have remarkably homogenous DZ signatures with very similar DZ age modes and modal percentages, displaying dominant Permian/Chiapas Batholith (ca. 35%–45%), Mesoproterozoic/Oaxaquian (ca. 20%–35%), Early Palaeozoic/Acatlán (ca. 8%–20%), and Cenozoic magmatic arc (ca. 15%–25%) age modes, as well as some subsidiary (<5%) early Proterozoic/Archean and Early Cretaceous DZ age components, linked to recycled lower Palaeozoic strata and the Guerrero Terrane and Alisitos arc, respectively. Despite differences in paleocurrent directions, deduced from image logs, there are no systematic differences in DZ spectra, indicating a consistent sediment provenance and no changes in source area. All Zama samples analysed in the study are characterized by abundant syn‐depositional Late Miocene DZ grains, clustering between 8.6 and 10.2 Ma, corroborating a Tortonian (Late Miocene) depositional age, and yield rapid sediment accumulation rates of ca. 200 m in <1.4 Ma (13 m/Myr). Doubled zircon U–Pb and (U‐Th)/He age pairs are indicative of recycling of early Mesozoic rift strata and Paleogene and younger Chiapas basement. These new DZ U–Pb and (U‐Th)/He data have a nearly invariant Tortonian sediment provenance that is similar to the modern Grijalva River flowing generally northward out of the Chiapas highlands. The paleo‐Grijalva drainage, providing sediment to the Late Miocene Zama mini‐basin, was likely drastically larger than the present catchment as it involved 10 Ma plutonic sources that were subsequently downfaulted along the Pacific coast in the latest Miocene. Importantly, DZ U–Pb age components are consistent with Oaxaquia, early Acatlán, and Guerrero/Alisitos signatures and point to sourcing from the Chortis block during its tectonic eastward translation. Such a scenario would allow for a substantially larger Miocene paleo‐drainage that would have encompassed both Chiapas and portions of Chortis. The Miocene tectonic translation of Chortis and erosion of a large and tectonically active hinterland would also reconcile the dramatically larger Middle to Late Miocene sediment supply, funnelling a large influx of sediment into the southern Gulf of Mexico. Rapid Late Miocene sediment accumulation in the salt‐defined Zama mini‐basin must have involved sustained sediment flux via the paleo‐Grijalva drainage and was likely facilitated and focused by continued salt deflation due to sediment loading, as described in Part II. Thus, our work provides new scientific insights into one of the largest hydrocarbon discoveries in Mexico in recent years. [ABSTRACT FROM AUTHOR]

The Late Miocene source terrane tectonic history in the southern Gulf of Mexico Basin, as informed by detrital zircon geothermochronology data, supports a detailed regional palaeogeographic reconstruction from palaeoshoreline to the deepwater Zama minibasin of the Sureste salt basin. Seismic mapping points to a trio of pathways that converge upon two entry points into the Zama minibasin, illuminating how sediment gravity flows transit a complex seascape defined by shallow salt bodies. Consideration of empirical scaling relationships within and between segments of this sediment dispersal system allows for testable predictions of Upper Miocene submarine fan-runout lengths over basin exploration areas. Distances from the reconstructed shelf-margin to the Zama wells vary around 100 km, an increase of 20% over a straight-line distance as flows likely navigated around extant salt stocks, walls and sheets. This 100-km fan length is about 40% of the reconstructed minimum palaeo-river length, within predicted ranges for smaller source-to-sink systems in tectonically active areas (25 to 50%). The estimated fan-runout distance can be extended even further basinwards, considering the contemporaneous passage of the mobile Chortis block along the Tonala shear zone, expanding the Palaeo-Rio Grijalva drainage network during the Tortonian. These Late Miocene deepwater systems linked to the Palaeo-Rio Grijalva differ substantially from onshore Mexico-sourced turbidity flows feeding into the axis of the north-trending Veracruz Trough. Textural data from wells here suggests these systems were less effective at larger grain transport and sorting. Local (intrabasinal) variations are also evident within the Zama minibasin, as well data (image logs and cores) indicate that axially oriented sediment gravity flows involved fewer high-density turbidities, depositing lower net-to-gross sandstones and thicker shales than those flowing transverse to the basin axis from a southeastern basin entry point. These interpretations will guide both local exploitation of these economic resources and could also support future exploration for analogous salt-influenced deepwater reservoir systems in the Sureste basin and globally. [ABSTRACT FROM AUTHOR]

M-band transitions (n = 4 → 3) in gold are responsible for a population of x-rays with energy >1.8 keV in indirect drive inertial fusion. These x-rays can preheat the fuel, cause the ablator–fuel interface to become unstable to Rayleigh–Taylor instabilities, and introduce radiation nonuniformity to the x-ray drive. This work investigates the performance of mid-Z lined Hohlraums for producing an efficient drive spectrum absent of M-band x-rays using the two-dimensional Lagrangian radiation hydrodynamics code h2d. The removal of the M-band transitions is observed in the Cu-lined Hohlraum reducing the total x-ray energy above 1.8 keV to 58% that of the un-lined Hohlraum. Total radiation energy in the Cu-lined Hohlraum is 93% that of the energy in the pure Au Hohlraum for a 1 ns pulse. However, the soft x-ray drive energy (below 1.8 keV) for the lined Hohlraum is 98% that of the pure Au Hohlraum. [ABSTRACT FROM AUTHOR]

The accuracy with which the Thomas–Fermi (TF) model can provide electronic specific heat capacities for use in calculations relevant to fast electron transport in laser-irradiated solids is examined. It is argued that the TF model, since it neglects the quantum shell structure, is likely to be significantly inaccurate for low- and intermediate-Z materials. This argument is supported by examining the results of calculations using more sophisticated methods that account for degeneracy, the quantum shell structure, and other non-ideal corrections. It is further shown that the specific heat capacity curve generated by this more advanced treatment leads to substantial (factor of two) changes in fast electron transport simulations relative to similar modeling based upon the TF model. [ABSTRACT FROM AUTHOR]

Magnetic collimation via resistivity gradients is an innovative approach to electron beam control for the cone-guided fast ignition variant of inertial confinement fusion. This technique uses a resistivity gradient induced magnetic field to collimate the electron beam produced by the high-intensity laser–plasma interaction within a cone-guided fast ignition cone-tip. A variant of the resistive guiding approach, known as the "magnetic switchyard," has been proposed which uses shaped guiding elements to direct the electrons toward the compressed fuel. Here, the 1D radiation-hydrodynamics code HYADES is used to investigate and quantify the gross hydrodynamic motion of these magnetic switchyard guiding elements in conditions relevant to their use in fast ignition. Movement of the layers was assessed for a range of two-layer material combinations. Based upon the results of the simulations, a scaling law is found that enables the relative extent of hydrodynamic motion to be predicted based upon the material properties of the switchyard, thereby enabling optimization of material-combination choice on the basis of reducing hydrodynamic motion. A multi-layered configuration, more representative of an actual switchyard, was also simulated in which an outer Au layer is employed to tamp the motion of the outermost guiding element of the switchyard. [ABSTRACT FROM AUTHOR]

The derivation of the ignition energy for fast ignition inertial confinement fusion is reviewed and one-dimensional simulations are used to produce a revised formula for the ignition energy of an isochoric central hot-spot, which accounts for variation in the radius of the hot-spot rh as well as the density ρ. The required energy may be as low as 1 kJ when ρ r h ≈ 0.36 g c m − 2 , T ≈ 20 keV , and ρ ≥ 700 g c m − 2 . Although there are many physical challenges to creating these conditions, a possible route to producing such a hot-spot is via a bright source of non-thermal soft x-rays. Further one-dimensional simulations are used to study the non-thermal soft x-ray heating of dense DT and it is found to offer the potential to significantly reduce hydrodynamic losses as compared to particle driven fast ignition due to the hotspot being heated supersonically in a layer-by-layer fashion. A sufficiently powerful soft x-ray source would be difficult to produce, but line emission from laser-produced-plasma is the most promising option. [ABSTRACT FROM AUTHOR]

The interaction of ultrahigh power picosecond laser pulses with solid targets is of interest both for benchmarking the results of hybrid particle in cell codes and also for applications in reentrant cone guided fast ignition. We describe the construction of novel targets in which copper/titanium wires are formed into 'nail-like' objects by a process of melting and micromachining so that energy can be reliably coupled to a 24-[micro]m-diameter wire. An extreme-ultraviolet image of the interaction of the Titan laser with such a target is shown. Index Terms--Cone guided fast ignition, extreme ultraviolet imaging, laser-produced electron transport in solids, laser-solid interaction.

The interaction of a high-power laser with a low-density foam target can in some instances result in a significant enhancement in x-ray generation relative to that when the same laser is incident upon a homogenous solid. In this paper, we present x-ray emission studies from foam targets where the density is varied from under-dense to over-dense. The targets are irradiated with the first harmonic of Nd:Glass laser. The laser intensity on the target was approximately 2x1014 W/cm2 with the pulse duration of 500 ps. Mass-matched cellulose triacetate foam targets with densities of 2 mg/cc, 4 mg/cc, 7 mg/cc, and 20 mg/cc were used. The areal density presented by the targets on the laser beam axis was held constant at 0.2 mg/cm2 by varying the target thickness in inverse proportion to the density. The x-ray yield in the spectral range (5-8 keV) and (4.5-16 keV) was found to be enhanced by approximately 2.3 times in foam targets with the density of 2 mg/cc (under-dense) compared with foam targets with the density of 20 mg/cc (over-dense). [ABSTRACT FROM AUTHOR]

Using 3 dimensional numerical simulations, this paper shows that grading the atomic number and thus the resistivity at the interface between an embedded high atomic number guide element and a lower atomic number substrate enhances the growth of a resistive magnetic field. This can lead to a large integrated magnetic flux density, which is fundamental to confining higher energy fast electrons. This results in significant improvements in both magnetic collimation and fast-electrontemperature uniformity across the guiding. The graded interface target provides a method for resistive guiding that is tolerant to laser pointing. [ABSTRACT FROM AUTHOR]

The heating of a solid wire embedded in a solid substrate (of lower Z material) with relativistic electrons generated by ultra-intense laser irradiation is considered. Previously, it has been noted that the initial angular distribution of the fast electrons is a highly important factor in the efficacy of the heating [Robinson et al., Phys. Plasmas 20, 122701 (2013)]. We show that, using 3D numerical simulations, the addition of an inverse conical taper at the front of wire can considerably improve the heating of the wire due to the reduction of angular spread of the fast electrons which is caused by transport through the inverse conical taper [Robinson et al., "Guiding of laser-generated fast electrons by exploiting the resistivity-gradients around a conical guide element," Plasma Phys. Controlled Fusion (to be published)] [ABSTRACT FROM AUTHOR]

The effects of a soy protein diet on hematological, oxidant, and antioxidant levels in brain, liver, and pancreatic tissues in an animal model of simulated weightlessness were investigated in the current study. METHODS: Rats on a regular laboratory pellet diet or on 9.6% soy protein diet were either not suspended (non-HLS) or hind limb suspended (HLS) by their tails for 14 d. Body weights and food and water intakes were monitored and blood samples were analyzed for hematocrit, red blood cell mass, and hemoglobin before and after suspension. Brain, liver and pancreatic tissues were measured for oxidant and antioxidant levels. RESULTS: Body weights of the HLS animals were decreased compared with non-HLS animals (P < 0.05). Hematological variables were not different between the non-HLS and HLS groups. Malondialdehyde (MDA) levels in the brain and liver tissues were lower in the non-HLS soy group than the non-HLS group receiving the regular laboratory diet (P < 0.05). In HLS groups, however, these levels were higher for both diets, but it was only significant (P < 0.05) between the soy non-HLS and the soy HLS group. Basal superoxide dismutase (SOD) levels were not significantly different between the 2 diet groups but were elevated in HLS groups compared with the non-HLS groups (P < 0.05). Glutathione levels in the brains of non-HLS soy group were elevated (P < 0.05) but were not changed after 14 d of suspension. In contrast, glutathione levels in the livers of soy diet group were generally lower in both HLS and non-HLS animals. Malondialdehyde and SOD levels in the pancreatic tissue were not significantly different between groups. No consistent results were found for pancreatic glutathione levels. CONCLUSIONS: Our data suggest that HLS induced a differential tissue-specific oxidative response as determined by MDA, SOD, and glutathione levels. Soy protein in the diet lowered basal peroxide levels but did not affect changes in the peroxide levels induced by HLS. (Supported by a grant from Arkansas Space Grant Consortium.)

An all-optical approach to laser-proton acceleration enhancement is investigated using the simplest of target designs to demonstrate application-relevant levels of energy conversion efficiency between laser and protons. Controlled deposition of laser energy, in the form of a double-pulse temporal envelope, is investigated in combination with thin foil targets in which recirculation of laser-accelerated electrons can lead to optimal conditions for coupling laser drive energy into the proton beam. This approach is shown to deliver a substantial enhancement in the coupling of laser energy to 5-30 MeV protons, compared to single pulse irradiation, reaching a record high 15% conversion efficiency with a temporal separation of 1 ps between the two pulses and a 5 lm-thick Au foil. A 1D simulation code is used to support and explain the origin of the observation of an optimum pulse separation of ~1 ps. [ABSTRACT FROM AUTHOR]

It has been suggested that fast electrons may play a beneficial role in the formation of the ignitor shock in shock ignition owing to the high areal density of the fuel at the time of the ignitor pulse. In this paper, we extend previous studies which have focused on monoenergetic electron sources to populations with extended energy distributions. In good agreement with analytic scalings, we show that strong shocks can be produced with peak pressures of a few hundred Mbar to over 1 Gbar using fast electron intensities of 1-10 PW/cm2 in a uniform deuterium-tritium plasma at 10 g/cm3. However, the length required for shock formation increases with fast electron temperature. As this shock formation distance becomes comparable to the target size, the shock is not able to fully develop, and this implies a limit on the ability of fast electrons to aid shock formation. [ABSTRACT FROM AUTHOR]

Resistively guiding laser-generated fast electron beams in targets consisting of a resistive wire embedded in lower Z material should allow one to rapidly heat the wire to over 100 eV over a substantial distance without strongly heating the surrounding material. On the multi-ps timescale, this can drive hydrodynamic motion in the surrounding material. Thus, ultra-intense laser solid interactions have the potential as a controlled driver of radiation hydrodynamics in solid density material. In this paper, we assess the laser and target parameters needed to achieve such rapid and controlled heating of the embedded wire. [ABSTRACT FROM AUTHOR]