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We have developed conceptual designs of two petawatt-class pulsed-power accelerators: Z 300 and Z 800. The designs are based on an accelerator architecture that is founded on two concepts: single-stage electrical-pulse compression and impedance matching [Phys. Rev. ST Accel. Beams 10, 030401 (2007)]. The prime power source of each machine consists of 90 linear-transformer-driver (LTD) modules. Each module comprises LTD cavities connected electrically in series, each of which is powered by 5-GW LTD bricks connected electrically in parallel. (A brick comprises a single switch and two capacitors in series.) Six water-insulated radial-transmission-line impedance transformers transport the power generated by the modules to a six-level vacuum-insulator stack. The stack serves as the accelerator’s water-vacuum interface. The stack is connected to six conical outer magnetically insulated vacuum transmission lines (MITLs), which are joined in parallel at a 10-cm radius by a triple-post-hole vacuum convolute. The convolute sums the electrical currents at the outputs of the six outer MITLs, and delivers the combined current to a single short inner MITL. The inner MITL transmits the combined current to the accelerator’s physics-package load. Z 300 is 35 m in diameter and stores 48 MJ of electrical energy in its LTD capacitors. The accelerator generates 320 TW of electrical power at the output of the LTD system, and delivers 48 MA in 154 ns to a magnetized-liner inertial-fusion (MagLIF) target [Phys. Plasmas 17, 056303 (2010)]. The peak electrical power at the MagLIF target is 870 TW, which is the highest power throughout the accelerator. Power amplification is accomplished by the centrally located vacuum section, which serves as an intermediate inductive-energy-storage device. The principal goal of Z 300 is to achieve thermonuclear ignition; i.e., a fusion yield that exceeds the energy transmitted by the accelerator to the liner. 2D magnetohydrodynamic (MHD) simulations suggest Z 300 will deliver 4.3 MJ to the liner, and achieve a yield on the order of 18 MJ. Z 800 is 52 m in diameter and stores 130 MJ. This accelerator generates 890 TW at the output of its LTD system, and delivers 65 MA in 113 ns to a MagLIF target. The peak electrical power at the MagLIF liner is 2500 TW. The principal goal of Z 800 is to achieve high-yield thermonuclear fusion; i.e., a yield that exceeds the energy initially stored by the accelerator’s capacitors. 2D MHD simulations suggest Z 800 will deliver 8.0 MJ to the liner, and achieve a yield on the order of 440 MJ. Z 300 and Z 800, or variations of these accelerators, will allow the international high-energy-density-physics community to conduct advanced inertial-confinement-fusion, radiation-physics, material-physics, and laboratory-astrophysics experiments over heretofore-inaccessible parameter regimes.

Several magnetized liner inertial fusion (MagLIF) experiments have been conducted on the Z accelerator at Sandia National Laboratories since late 2013. Measurements of the primary DD (2.45 MeV) neutrons for these experiments suggest that the neutron production is thermonuclear. Primary DD yields up to 3e12 with ion temperatures ∼2-3 keV have been achieved. Measurements of the secondary DT (14 MeV) neutrons indicate that the fuel is significantly magnetized. Measurements of down-scattered neutrons from the beryllium liner suggest ρRliner∼1g cm2. Neutron bang times, estimated from neutron time-of-flight (nTOF) measurements, coincide with peak x-ray production. Plans to improve and expand the Z neutron diagnostic suite include neutron burn-history diagnostics, increased sensitivity and higher precision nTOF detectors, and neutron recoil-based yield and spectral measurements.

A method is described for choosing experimental parameters in studies of high-energy-density (HED) physics relevant to fusion energy, as well as other applications. An important HED issue for magneto-inertial fusion (MIF) is the interaction of metal pusher materials with megagauss (MG) magnetic fields during liner compression of magnetic flux and fusion fuel. The experimental approach described here is to study a stationary conductor when a pulsed current generates MG fields at the surface, instead of studying the inner surface of a moving liner. This places less demand upon the pulsed power system, and significantly improves diagnostic access. Thus the deceptively simple geometry chosen for this work is that of a z pinch composed of a metal cylinder carrying large current. Consideration of well known stability issues for the z pinch shows that for given peak current and rise time from a particular power supply, there is a minimum radius and thus maximum B field that can be created without disruption of the conductor before peak current. The reasons are reviewed why MG levels of magnetic field, as required for MIF, result in high temperatures and plasma formation at the surface of the metal in response to Ohmic heating. The distinction is noted between the liner regime obtained with cylindrical rods, which have a skin depth small compared to the conductor radius, and the exploding thin-wire regime, which has skin depth larger than the wire radius. A means of diagnostic development is described using a small facility (DPM15) built at the University of Nevada, Reno. It is argued that surface plasma temperature measurements in the 10-eV range are feasible based on the intensity of visible light emission.

Two codes have been developed to model solid metal or wire-wound conductors. The calculations are based on the decomposition of the conductors into arrays of thin wires. The first code, EDDY, models cylindrically symmetric conductors with currents in the theta direction. This code accurately models eddy current induction and magnetic diffusion. It was created in order to aid the design of magnetic-field shields in the FRX-L experiment for Magnetized Target Fusion (MTF). EDDY uses fast, accurate elliptic integral subroutines from MATLAB to solve for the time-dependent current flowing through each wire loop and the resultant magnetic field configuration. The second code, INDIV, models arbitrarily shaped conductors with current flow in the z direction. It was designed to model current division in an inductive divider that would inject current into a liner cavity, for magnetic flux and magnetized-plasma compression experiments. An experiment has been performed to test the INDIV code and the inductive division concept. The numerical results compare well with those of the experiment.

In this paper, we explore magnetized liner inertial fusion (MagLIF) [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] using a semi-analytic model [R. D. McBride and S. A. Slutz, Phys. Plasmas 22, 052708 (2015)]. Specifically, we present simulation results from this model that: (a) illustrate the parameter space, energetics, and overall system efficiencies of MagLIF; (b) demonstrate the dependence of radiative loss rates on the radial fraction of the fuel that is preheated; (c) explore some of the recent experimental results of the MagLIF program at Sandia National Laboratories [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]; (d) highlight the experimental challenges presently facing the MagLIF program; and (e) demonstrate how increases to the preheat energy, fuel density, axial magnetic field, and drive current could affect future MagLIF performance.

We report experimental results on the parameters, structure, and evolution of high-Mach-number (M) argon plasma jets formed and launched by a pulsed-power-driven railgun. The nominal initial average jet parameters in the data set analyzed are density \\approx 2 x 10^(16) cm^(-3), electron temperature \\approx 1.4 eV, velocity \\approx 30 km/s, M \\approx 14, ionization fraction \\approx 0.96, diameter \\approx 5 cm, and length \\approx 20 cm. These values approach the range needed by the Plasma Liner Experiment (PLX), which is designed to use merging plasma jets to form imploding spherical plasma liners that can reach peak pressures of 0.1-1 Mbar at stagnation. As these jets propagate a distance of approximately 40 cm, the average density drops by one order of magnitude, which is at the very low end of the 8-160 times drop predicted by ideal hydrodynamic theory of a constant-M jet.

One-dimensional radiation-hydrodynamic simulations are performed to develop insight into the scaling of stagnation pressure with initial conditions of an imploding spherical plasma shell or \"liner.\" Simulations reveal the evolution of high-Mach-number (M), annular, spherical plasma flows during convergence, stagnation, shock formation, and disassembly, and indicate that cm- and {\\mu}s-scale plasmas with peak pressures near 1 Mbar can be generated by liners with initial kinetic energy of several hundred kilo-joules. It is shown that radiation transport and thermal conduction must be included to avoid non-physical plasma temperatures at the origin which artificially limit liner convergence and thus the peak stagnation pressure. Scalings of the stagnated plasma lifetime ({\\tau}stag) and average stagnation pressure (Pstag, the pressure at the origin, averaged over {\\tau}stag) are determined by evaluating a wide range of liner initial conditions. For high-M flows, {\\tau}stag L0/v0, where L0 and v0 are the initial liner thickness and velocity, respectively. Furthermore, for argon liners, Pstag scales approximately as v0^(15/4) over a wide range of initial densities (n0), and as n0^(1/2) over a wide range of v0. The approximate scaling Pstag ~ M 3/2 is also found for a wide range of liner-plasma initial conditions.

Morphological analysis of teeth found at Lida Ajer shows that these belong to Homo sapiens , indicating that modern humans were in Sumatra between 73,000 and 63,000 years ago. Early modern human presence in Sumatra Genetic evidence points to the presence of modern humans in southeast Asia before 60,000 years ago, but actual fossil evidence is scant and circumstantial. Kira Westaway et al . present evidence for a modern human presence in the region between 73,000 and 63,000 years based on three dating methods applied to consolidated breccia rocks in a cave in Sumatra, Indonesia, which had previously yielded human teeth. The findings establish that modern humans were present in the region at around the time of the catastrophic eruption of Toba that took place in Sumatra around 73,000 years ago. Genetic evidence for anatomically modern humans (AMH) out of Africa before 75 thousand years ago (ka) 1 and in island southeast Asia (ISEA) before 60 ka (93–61 ka) 2 predates accepted archaeological records of occupation in the region 3 . Claims that AMH arrived in ISEA before 60 ka (ref. 4 ) have been supported only by equivocal 5 or non-skeletal evidence 6 . AMH evidence from this period is rare and lacks robust chronologies owing to a lack of direct dating applications 7 , poor preservation and/or excavation strategies 8 and questionable taxonomic identifications 9 . Lida Ajer is a Sumatran Pleistocene cave with a rich rainforest fauna associated with fossil human teeth 7 , 10 . The importance of the site is unclear owing to unsupported taxonomic identification of these fossils and uncertainties regarding the age of the deposit, therefore it is rarely considered in models of human dispersal. Here we reinvestigate Lida Ajer to identify the teeth confidently and establish a robust chronology using an integrated dating approach. Using enamel–dentine junction morphology, enamel thickness and comparative morphology, we show that the teeth are unequivocally AMH. Luminescence and uranium-series techniques applied to bone-bearing sediments and speleothems, and coupled uranium-series and electron spin resonance dating of mammalian teeth, place modern humans in Sumatra between 73 and 63 ka. This age is consistent with biostratigraphic estimations 7 , palaeoclimate and sea-level reconstructions, and genetic evidence for a pre-60 ka arrival of AMH into ISEA 2 . Lida Ajer represents, to our knowledge, the earliest evidence of rainforest occupation by AMH, and underscores the importance of reassessing the timing and environmental context of the dispersal of modern humans out of Africa.

BACKGROUND AND AIMS: The knowledge of soil water storage is vital for rational agricultural management, and in soil-plant-water relations. This study was conducted to evaluate the temporal processes of soil water status of a sugarcane field under residue management during the 2011/2012 and 2012/2013 growing seasons in southern Brazil. METHODS: Soil water storage (SWS) and matric potential (Ψ) were monitored in the 0–10 and 10–20 and 40–60 cm layers using time domain reflectometer sensors and tensiometers while precipitation (P) and potential crop evapotranspiration (ET) were obtained using rainguage and daily weather data. RESULTS: There was significant temporal variation of soil water status with soil depths. SWS was lower while matric potential was higher in no mulch treatment than in mulched treatment in both growing seasons. SWS cross-correlated with other variables, however, results were not the same for the different soil depths and treatments. Classical regression of SWS from combinations of log (Ψ), ET and P gave satisfactory results, however state-time analysis was better with higher R²values and incorporated errors. CONCLUSIONS: State-time analysis, combined with state-space could be a useful tool for good predictions of soil water status. Residue mulching influenced soil water status, thus proved to be a sustainable soil management practice.