PBX 9502 TENSILE ANALYSIS

With the recent creation of the PX HE Core Surveillance Database, individual specimen surveillance values can be easily compared to the corresponding individual qualification values to evaluate for trends. A review of the data shows a broad scatter in measured stress-strain values. Using the available HE surveillance database, it is clear that the surveillance measurements from the two Cycle 15 charges fall within the range of qualification stress and strain values recorded previously for PBX 9502 lots and that no apparent stockpile-age related trends are evident in the tensile stress-strain data. As a result of this investigation, some changes are being made to the core surveillance specifications to minimize the effects on tensile data scatter due to temperature and humidity differences and method to method changes. These data analyses do point out the need for a comprehensive understanding of the effect of a number of variables, i.e. formulation and pressing method, density, stockpile age, lot-to-lot variations, temperature, and humidity on the mechanical property behavior of HE composite materials. Too often data have been compared without the relevant details made available to determine if the test conditions were nominally the same or different. These results also point out the critical need to establish useful stress-strain limits for qualification and surveillance testing of HEs

Sympathetic Cooling of Trapped Cd+ Isotopes

We sympathetically cool a trapped 112Cd+ ion by directly Doppler-cooling a 114Cd+ ion in the same trap. This is the first demonstration of optically addressing a single trapped ion being sympathetically cooled by a different species ion. Notably, the experiment uses a single laser source, and does not require strong focusing. This paves the way toward reducing decoherence in an ion trap quantum computer based on Cd+ isotopes.Comment: 4 figure

Cosmological parameters from large scale structure - geometric versus shape information

The matter power spectrum as derived from large scale structure (LSS) surveys contains two important and distinct pieces of information: an overall smooth shape and the imprint of baryon acoustic oscillations (BAO). We investigate the separate impact of these two types of information on cosmological parameter estimation, and show that for the simplest cosmological models, the broad-band shape information currently contained in the SDSS DR7 halo power spectrum (HPS) is by far superseded by geometric information derived from the baryonic features. An immediate corollary is that contrary to popular beliefs, the upper limit on the neutrino mass m_\nu presently derived from LSS combined with cosmic microwave background (CMB) data does not in fact arise from the possible small-scale power suppression due to neutrino free-streaming, if we limit the model framework to minimal LambdaCDM+m_\nu. However, in more complicated models, such as those extended with extra light degrees of freedom and a dark energy equation of state parameter w differing from -1, shape information becomes crucial for the resolution of parameter degeneracies. This conclusion will remain true even when data from the Planck surveyor become available. In the course of our analysis, we introduce a new dewiggling procedure that allows us to extend consistently the use of the SDSS HPS to models with an arbitrary sound horizon at decoupling. All the cases considered here are compatible with the conservative 95%-bounds \sum m_\nu < 1.16 eV, N_eff = 4.8 \pm 2.0.Comment: 18 pages, 4 figures; v2: references added, matches published versio

Magnetism, Critical Fluctuations and Susceptibility Renormalization in Pd

Some of the most popular ways to treat quantum critical materials, that is, materials close to a magnetic instability, are based on the Landau functional. The central quantity of such approaches is the average magnitude of spin fluctuations, which is very difficult to measure experimentally or compute directly from the first principles. We calculate the parameters of the Landau functional for Pd and use these to connect the critical fluctuations beyond the local-density approximation and the band structure.Comment: Replaced with the revised version accepted for publication. References updated, errors corrected, other change

Sympathetic cooling of 9Be+^9Be^+ and 24Mg+^{24}Mg^+ for quantum logic

We demonstrate the cooling of a two species ion crystal consisting of one $^9Be^+$ and one $^{24}Mg^+$ ion. Since the respective cooling transitions of these two species are separated by more than 30 nm, laser manipulation of one ion has negligible effect on the other even when the ions are not individually addressed. As such this is a useful system for re-initializing the motional state in an ion trap quantum computer without affecting the qubit information. Additionally, we have found that the mass difference between ions enables a novel method for detecting and subsequently eliminating the effects of radio frequency (RF) micro-motion.Comment: Submitted to PR

Erbium environment in glass-ceramics investigated by atom probe tomography

Glass-ceramics (considered here as a glassy host containing crystalline or amorphous nanoparticles) are of interest for luminescent properties as they can combine the sturdiness and low cost of a matrix host with particular spectroscopic behavior that would not appear in this host [1]. Ideally, nanoparticles would fully encapsulate luminescent ions to produce engineered spectroscopic properties. This approach is particularly promising for optical fibers. Indeed, silica is the most common glass used to prepare such waveguides. However, it is necessary to overcome some of its characteristics (high phonon energy, low luminesent ions solubility, ...) which may be detrimental to luminescent properties. As silicate systems have a large phase immiscibility domain when they contain divalent metal oxides (such as Mg), one can take advantage of thermal treatments inherent to the MCVD (Modified Chemical Vapor Deposition) process to obtain nanoparticles through phase separation [2]. By modifying Mg concentration, we have observed modifications of luminescent properties of Er3+ ions [3]. However the question arises of the partition of rare-earth ions in nanoparticles. Qualitative partition of erbium ions in nanoparticles was reported thanks to Secondary Ion Mass Spectrometry analyses [4]. However, the spatial resolution is about the particle size. To go further, we take advantages of recent developments in Atom Probe Tomography (APT) which allowed the extension of such studies to glass-ceramics [5]. Partition of erbium ions is clearly observed in nanoparticles smaller than 10 nm (Figure 1). During this presentation, we will discuss this partition and the most probable nearest neighbors and correlate these results with luminescent properties

Variation de la composition de nanoparticules de 1-10 nm obtenues par séparation de phase dans un verre de silice

National audienceLes verres contenant des nanoparticules ont de nombreuses applications industrielles, notamment grâce à leurs excellentes propriétés thermo-mécaniques [1]. Ils présentent aussi un intérêt pour les propriétés optiques. En effet, l'encapsulation d'ions luminescents (ions de terre rare par exemple) dans des nanoparticules entraînent de nouvelles propriétés de luminescence qui n'existeraient pas dans le verre hôte (bande d'émission élargie, efficacité quantique augmentée, etc) [2]. La préparation de tels verres repose sur des mécanismes de nucléation, croissance et de démixtion dont les premières étapes sont encore assez mal connues. Mais l'avènement de nouvelles techniques de caractérisation à l'échelle nanométrique permet d'améliorer notre compréhension de ces phénomènes. Par exemple, une évolution structurelle des nanoparticules à travers des phases cristallines métastables [3] ou une transformation d'un nucléus amorphe vers une nanoparticule cristalline [4] ont été observées. Des changements de composition ont aussi été rapportés pour des particules de taille 1-10 nm dans des alliages [5] et dans des métaux [6]. Dans cette présentation, nous nous intéressons à la composition de nanoparticules amorphes obtenues par séparation de phase dans un verre de silice. De telles études ont été rendues possibles grâce au développement récent de l'APT (Atom Probe Tomography) pour l'analyse des verres [7]. Nous étudions une fibre optique à base de silice préparée par le procédé MCVD (Modified Chemical Vapor Deposition). Les nanoparticules sont obtenues en incorporant du magnésium qui déclenche une séparation de phase grâce aux traitements thermiques inhérents au procédé MCVD [8]. La composition des nanoparticules dans le verre de silice dopée avec Mg, P, Ge et Er est étudiée dans la gamme 1-10 nm. Nous montrons la partition de Mg, P et Er dans ces nanoparticules ainsi qu'une modification de la composition en fonction de la taille des particules

Deterministic delivery of externally cold and precisely positioned single molecular ions

We present the preparation and deterministic delivery of a selectable number of externally cold molecular ions. A laser cooled ensemble of Mg^+ ions subsequently confined in several linear Paul traps inter-connected via a quadrupole guide serves as a cold bath for a single or up to a few hundred molecular ions. Sympathetic cooling embeds the molecular ions in the crystalline structure. MgH^+ ions, that serve as a model system for a large variety of other possible molecular ions, are cooled down close to the Doppler limit and are positioned with an accuracy of one micrometer. After the production process, severely compromising the vacuum conditions, the molecular ion is efficiently transfered into nearly background-free environment. The transfer of a molecular ion between different traps as well as the control of the molecular ions in the traps is demonstrated. Schemes, optimized for the transfer of a specific number of ions, are realized and their efficiencies are evaluated. This versatile source applicable for broad charge-to-mass ratios of externally cold and precisely positioned molecular ions can serve as a container-free target preparation device well suited for diffraction or spectroscopic measurements on individual molecular ions at high repetition rates (kHz).Comment: 11 pages, 8 figure

A direct probe of cosmological power spectra of the peculiar velocity field and the gravitational lensing magnification from photometric redshift surveys

The cosmological peculiar velocity field (deviations from the pure Hubble flow) of matter carries significant information on dark energy, dark matter and the underlying theory of gravity on large scales. Peculiar motions of galaxies introduce systematic deviations between the observed galaxy redshifts z and the corresponding cosmological redshifts z_cos. A novel method for estimating the angular power spectrum of the peculiar velocity field based on observations of galaxy redshifts and apparent magnitudes m (or equivalently fluxes) is presented. This method exploits the fact that a mean relation between z_cos and m of galaxies can be derived from all galaxies in a redshift-magnitude survey. Given a galaxy magnitude, it is shown that the z_cos(m) relation yields its cosmological redshift with a 1-sigma error of sigma_z~0.3 for a survey like Euclid (~10^9 galaxies at z<~2), and can be used to constrain the angular power spectrum of z-z_cos(m) with a high signal-to-noise ratio. At large angular separations corresponding to l<~15, we obtain significant constraints on the power spectrum of the peculiar velocity field. At 15<~l<~60, magnitude shifts in the z_cos(m) relation caused by gravitational lensing magnification dominate, allowing us to probe the line-of-sight integral of the gravitational potential. Effects related to the environmental dependence in the luminosity function can easily be computed and their contamination removed from the estimated power spectra. The amplitude of the combined velocity and lensing power spectra at z~1 can be measured with <~5% accuracy.Comment: 22 pages, 3 figures; added a discussion of systematic errors, accepted for publication in JCA

Calculation of magnetic anisotropy energy in SmCo5

SmCo5 is an important hard magnetic material, due to its large magnetic anisotropy energy (MAE). We have studied the magnetic properties of SmCo5 using density functional theory (DFT) calculations where the Sm f-bands, which are difficult to include in DFT calculations, have been treated within the LDA+U formalism. The large MAE comes mostly from the Sm f-shell anisotropy, stemming from an interplay between the crystal field and the spin-orbit coupling. We found that both are of similar strengths, unlike some other Sm compounds, leading to a partial quenching of the orbital moment (f-states cannot be described as either pure lattice harmonics or pure complex harmonics), an optimal situation for enhanced MAE. A smaller portion of the MAE can be associated with the Co-d band anisotropy, related to the peak in the density of states at the Fermi energy. Our result for the MAE of SmCo5, 21.6 meV/f.u., agrees reasonably with the experimental value of 13-16 meV/f.u., and the calculated magnetic moment (including the orbital component) of 9.4 mu_B agrees with the experimental value of 8.9 mu_B.Comment: Submitted to Phys. Rev.