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The recent discovery of more than a thousand planets outside our Solar System (1,2), together with the significant push to achieve inertially confined fusion in the laboratory (3), has prompted a renewed interest in how dense matter behaves at millions to billions of atmospheres of pressure. The theoretical description of such electron-degenerate matter has matured since the early quantum statistical model of Thomas and Fermi (4-10), and now suggests that new complexities can emerge at pressures where core electrons (not only valence electrons) influence the structure and bonding of matter (11). Recent developments in shock-free dynamic (ramp) compression now allow laboratory access to this dense matter regime. Here we describe ramp-compression measurements for diamond, achieving 3.7-fold compression at a peak pressure of 5 terapascals (equivalent to 50 million atmospheres). These equation-of-state data can now be compared to first-principles density functional calculations (12) and theories long used to describe matter present in the interiors of giant planets, in stars, and in inertial-confinement fusion experiments. Our data also provide new constraints on mass-radius relationships for carbon-rich planets., Mass-radius data for extrasolar planets combined with equation-of-state (EOS) models for constituent materials reveal that matter at pressures of several terapascals is quite common throughout the Universe (1,2,13). At several [...]

Ignition implosions on the National Ignition Facility (NIF) [Lindl et al., Phys. Plasmas 11, 339 (2004)] are driven with a very carefully tailored sequence of four shock waves that must be timed to very high precision in order to keep the fuel on a low adiabat. The first series of precision tuning experiments on NIF have been performed. These experiments use optical diagnostics to directly measure the strength and timing of all four shocks inside the hohlraum-driven, cryogenic deuterium-filled capsule interior. The results of these experiments are presented demonstrating a significant decrease in the fuel adiabat over previously un-tuned implosions. The impact of the improved adiabat on fuel compression is confirmed in related deuterium-tritium (DT) layered capsule implosions by measurement of fuel areal density (ρR), which show the highest fuel compression (ρR ∼ 1.0 g/cm2) measured to date.

An experimental campaign to tune the initial shock compression sequence of capsule implosions on the National Ignition Facility (NIF) was initiated in late 2010. The experiments use a NIF ignition-scale hohlraum and capsule that employs a re-entrant cone to provide optical access to the shocks as they propagate in the liquid deuterium-filled capsule interior. The strength and timing of the shock sequence is diagnosed with velocity interferometry that provides target performance data used to set the pulse shape for ignition capsule implosions that follow. From the start, these measurements yielded significant new information on target performance, leading to improvements in the target design. We describe the results and interpretation of the initial tuning experiments.

The mechanical properties of SiC films grown via [C.sub.60] precursors were determined using atomic force microscopy (AFM). Conventional silicon nitride and diamond-tipped steel AFM cantilevers were employed to determine the film hardness, friction coefficient, and elastic modulus. The hardness is found to be 26 GPa by nanoindentation of the film with a Berkovich diamond tip. The friction coefficient for the silicon nitride tip on the SiC film is about one half to one third that for silicon nitride sliding on a silicon substrate. By combining nanoindentation and AFM measurements an elastic modulus of [approximately]300 GPa is estimated for these SiC films.

Double pulse experiments were done to evaluate optical damage mechanisms in hafnia and silica thin films. The emission of neutral constituents during excitation on BK-7 substrates with time-delayed pairs of 70-ps laser pulses at a wavelength of 1064 nm were monitored and measured. Linear absorption was found to be responsible for energy deposition into the films for silicon dioxide. There wasno clearcut mechanism for hafnium dioxide although linear absorption may have produced the damage.

The two major contributors of roughness to plastic deformation are shown to be surface bands of the basal slip systems and thermal grooves formed on deformation-produced low-angle grain boundaries. The studies have major implications for designing strategies aimed at controlling uniformity of the hydrogen fuel layer in fusion targets.

Soft x-ray absorption near-edge structure (XANES) spectroscopy is used for studying the electronic structure of ultralow density nanoporous chromatin monoliths (aerogels). Thermal treatment has transformed the as-prepared amorphous aerogel into [alpha]-[Cr.sub.2][O.sub.3] nanopowder.

An instrument for the synthesis and analysis of nanoparticles and ultrathin films of Pu and other actinides has been constructed. To facilitate the production of nanoscale specimens of these materials, pulsed laser ablation was chosen for the deposition process. The highly toxic and radioactive nature of these materials created a challenging safety environment that needed to be addressed before any work could begin. Particular attention has been paid in this respect towards our future work with plutonium, though the design structure presented here would work equally well with other nonradioactive toxic or reactive materials. The analytical capabilities of the instrument include in situ photoelectron spectroscopy, low energy electron diffraction, scanning tunneling microscopy, and scanning tunneling spectroscopy. The instrument design and first results will be discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Depth profiles of [sup 1]H and [sup 2]D in rapidly grown KD[sub 2x]H[sub 2(1-x)]PO[sub 4] single crystals are studied by elastic recoil detection analysis. Results show that, under ambient conditions, deuteration in the first ∼500 nm from the sample surface significantly decreases within the first several days after D[sub 2]O surface polishing. This effect is attributed to deuterium–hydrogen exchange. The effective diffusion coefficient of this process is strongly dependent on both the degree of deuteration and the sample growth conditions. Physical mechanisms of D/H exchange are discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Observes the fullerene cage opening on silicon(111) by scanning tunneling microscopy. Correlation between silicon-carbon bonding and fullerene cage opening; Effect of thermal annealing on fullerene clusters; Agglomeration of opened clusters on the surface.

The first hydrodynamic instability growth measurements with three-dimensional (3D) surface-roughness modulations were performed on CH shell spherical implosions at the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)]. The initial capsule outer-surface amplitudes were increased approximately four times, compared with the standard specifications, to increase the signal-to-noise ratio, helping to qualify a technique for measuring small 3D modulations. The instability growth measurements were performed using x-ray through-foil radiography based on time-resolved pinhole imaging. Averaging over 15 similar images significantly increased the signal-to-noise ratio, making possible a comparison with 3D simulations. At a convergence ratio of ${\sim}2.4$, the measured modulation levels were ${\sim}3$ times larger than those simulated based on the growth of the known imposed initial surface modulations. Several hypotheses are discussed, including increased instability growth due to modulations of the oxygen content in the bulk of the capsule. Future experiments will be focused on measurements with standard 3D ‘native-roughness’ capsules as well as with deliberately imposed oxygen modulations. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline diamond (NCD) films with a thickness of ~6 µm and average grain sizes ranging from 60 to 9 nm were deposited on silicon wafers using a hot-filament chemical vapor deposition (HFCVD) process. These samples were then characterized in order to identify correlations between grain size, chemical composition and mechanical properties. The characterization reveals that our films are phase pure and exhibit a relatively smooth surface morphology. The levels of sp 2-bonded carbon and hydrogen impurities are low, showing a systematic variation with the grain size. The hydrogen content increases with decreasing grain size, whereas the sp 2 carbon content decreases with decreasing grain size. The material is weaker than single crystalline diamond, since both stiffness and hardness decrease with the reduction in crystal size. These trends suggest gradual changes in the nature of the grain boundaries, from graphitic in case of 60 nm grain size material to hydrogen terminated sp 3 carbon in 9 nm grain size material. The films exhibit low levels of internal stress and free-standing structures with a length of several centimeters could be fabricated without noticeable bending [Copyright &y& Elsevier]