bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron correlation within the relativistic no-pair approximation
Authors: Almoukhalalati Adel , Knecht Stefan , Jensen Hans Jørgen Aa. , Dyall Kenneth G. , Saue Trond
Published: August 2016

This paper addresses the definition of correlation energy within 4-component relativistic atomic and molecular calculations. In the nonrelativistic domain the correlation energy is defined as the difference between the exact eigenvalue of the electronic Hamiltonian and the Hartree-Fock energy. In practice, what is reported is the basis set correlation energy, where the “exact” value is provided by a full Configuration Interaction (CI) calculation with some specified one-particle basis. The extension of this definition to the relativistic domain is not straightforward since the corresponding electronic Hamiltonian, the Dirac-Coulomb Hamiltonian, has no bound solutions. Present-day relativistic calculations are carried out within the no-pair approximation, where the Dirac-Coulomb Hamiltonian is embedded by projectors eliminating the troublesome negative-energy solutions. Hartree-Fock calculations are carried out with the implicit use of such projectors and only positive-energy orbitals are retained at the correlated level, meaning that the Hartree-Fock projectors are frozen at the correlated level. We argue that the projection operators should be optimized also at the correlated level and that this is possible by full Multiconfigurational Self-Consistent Field (MCSCF) calculations, that is, MCSCF calculations using a no-pair full CI expansion, but including orbital relaxation from the negative-energy orbitals. We show by variational perturbation theory that the MCSCF correlation energy is a pure MP2-like correlation expression, whereas the corresponding CI correlation energy contains an additional relaxation term. We explore numerically our theoretical analysis by carrying out variational and perturbative calculations on the two-electron rare gas atoms with specially tailored basis sets. In particular, we show that the correlation energy obtained by the suggested MCSCF procedure is smaller than the no-pair full CI correlation energy, in accordance with the underlying minmax principle and our theoretical analysis. We also show that the relativistic correlation energy, obtained from no-pair full MCSCF calculations, scales at worst as X−2 with respect to the cardinal number X of our correlation-consistent basis sets optimized for the two-electron atoms. This is better than the X−1 scaling suggested by previous studies, but worse than the X−3 scaling observed in the nonrelativistic domain. The well-known 1/Z- expansion in nonrelativistic atomic theory follows from coordinate scaling. We point out that coordinate scaling for consistency should be accompanied by velocity scaling. In the nonrelativistic domain this comes about automatically, whereas in the relativistic domain an explicit scaling of the speed of light is required. This in turn explains why the relativistic correlation energy to the lowest order is not independent of nuclear charge, in contrast to nonrelativistic theory.
High resolution x-ray Thomson scattering measurements from cryogenic hydrogen jets using the linac coherent light source
Authors: Fletcher L. B. , Zastrau U. , Galtier E. , Gamboa E. J. , Goede S. , Schumaker W. , Ravasio A. , Gauthier M. , MacDonald M. J. , Chen Z. , Granados E. , Lee H. J. , Fry A. , Kim J. B. , Roedel C. , Mishra R. , Pelka A. , Kraus D. , Barbrel B. , Döppner T. , Glenzer S. H.
Published: August 2016

We present the first spectrally resolved measurements of x-rays scattered from cryogenic hydrogen jets in the single photon counting limit. The 120 Hz capabilities of the LCLS, together with a novel hydrogen jet design [J. B. Kim et al., Rev. Sci. Instrum. (these proceedings)], allow for the ability to record a near background free spectrum. Such high-dynamic-range x-ray scattering measurements enable a platform to study ultra-fast, laser-driven, heating dynamics of hydrogen plasmas. This measurement has been achieved using two highly annealed pyrolytic graphite crystal spectrometers to spectrally resolve 5.5 keV x-rays elastically and inelastically scattered from cryogenic hydrogen and focused on Cornell-SLAC pixel array detectors [S. Herrmann et al., Nucl. Instrum. Methods Phys. Res., Sect. A 718, 550 (2013)].
Spectral survey of helium lines in a linear plasma device for use in HELIOS imaging
Authors: Ray H. B. , Biewer T. M. , Fehling D. T. , Isler R. C. , Unterberg E. A.
Published: August 2016

Fast visible cameras and a filterscope are used to examine the visible light emission from Oak Ridge National Laboratory’s Proto-MPEX. The filterscope has been configured to perform helium line ratio measurements using emission lines at 667.9, 728.1, and 706.5 nm. The measured lines should be mathematically inverted and the ratios compared to a collisional radiative model (CRM) to determine Te and ne. Increasing the number of measurement chords through the plasma improves the inversion calculation and subsequent Te and ne localization. For the filterscope, one spatial chord measurement requires three photomultiplier tubes (PMTs) connected to pellicle beam splitters. Multiple, fast visible cameras with narrowband filters are an alternate technique for performing these measurements with superior spatial resolution. Each camera contains millions of pixels; each pixel is analogous to one filterscope PMT. The data can then be inverted and the ratios compared to the CRM to determine 2-dimensional “images” of Te and ne in the plasma. An assessment is made in this paper of the candidate He I emission lines for an imaging technique.
Low oxidation state aluminum-containing cluster anions: Cp∗AlnH−, n = 1–3
Authors: Zhang Xinxing , Ganteför Gerd , Eichhorn Bryan , Mayo Dennis , Sawyer William H. , Gill Ann F. , Kandalam Anil K. , Schnöckel Hansgeorg , Bowen Kit
Published: August 2016

Three new, low oxidation state, aluminum-containing cluster anions, Cp*AlnH−, n = 1–3, were prepared via reactions between aluminum hydride cluster anions, AlnHm−, and Cp*H ligands. These were characterized by mass spectrometry, anion photoelectron spectroscopy, and density functional theory based calculations. Agreement between the experimentally and theoretically determined vertical detachment energies and adiabatic detachment energies validated the computed geometrical structures. Reactions between aluminum hydride cluster anions and ligands provide a new avenue for discovering low oxidation state, ligated aluminum clusters.
Recommended Correlations for the Surface Tension of Aliphatic, Carboxylic, and Polyfunctional Organic Acids
Authors: Mulero A. , Cachadiña I. , Sanjuán E. L.
Published: August 2016

In previous papers, we have proposed specific correlations to reproduce the surface tension values for several sets of fluids and for wide ranges of temperatures. In this paper, we focus our attention on organic fatty (aliphatic, carboxylic, and polyfunctional) acids. We have taken into account the available data and values in the DIPPR and DETHERM databases and also Wohlfarth and Wohlfarth’s (1997) book. In some cases we have also considered new data published elsewhere. All the data and values have been carefully filtered and subsequently fitted with the use of the model currently implemented in NIST’s REFPROP program, calculating two or four adjustable coefficients for each fluid. As a result, we propose recommended correlations for 99 acids, providing mean absolute percentage deviations below 1.6% in all cases.
Fast island phase identification for tearing mode feedback control on J-TEXT tokamak
Authors: Rao B. , Li D. , Hu F. R. , Ding Y. H. , Hu Q. M. , Jin H.
Published: August 2016

A new method to control the tearing mode (TM) in tokamaks has been proposed [Q. Hu and Q. Yu, Nucl. Fusion 56, 034001 (5pp.) (2016)], according to which, the external resonant magnetic perturbation needs to be applied in certain magnetic island phase regions. Therefore, it is very important to identify the helical phase of magnetic islands in real time. The TM in tokamak plasmas is normally rotating and carries magnetic oscillations, which are known as Mirnov oscillations and can be detected by Mirnov probes. When the O-point or X-point of the magnetic island passes through the probe, the signal will experience a zero-crossing. A poloidal Mirnov probe array and a corresponding island phase identification method are presented. A field-programmable gate array is used to provide the magnetic island helical phase in real time by using multichannel zero crossing detection. This system has been developed on the J-TEXT tokamak and works well. This paper introduces the establishment of the fast magnetic island phase identifying system.
Flash characteristics of plasma induced by hypervelocity impact
Authors: Zhang Kai , Long Renrong , Zhang Qingming , Xue Yijiang , Ju Yuanyuan
Published: August 2016

Using a two-stage light gas gun, a series of hypervelocity impact experiments was conducted in which 6.4-mm-diameter spherical 2024-aluminum projectiles impact 23-mm-thick targets made of the same material at velocities of 5.0, 5.6, and 6.3 km/s. Both an optical pyrometer composed of six photomultiplier tubes and a spectrograph were used to measure the flash of the plasma during hypervelocity impact. Experimental results show that, at a projectile velocity of 6.3 km/s, the strong flash lasted about 10 μs and reached a temperature of 4300 K. Based on the known emission lines of AL I, spectral methods can provide the plasma electron temperature. An electron-temperature comparison between experiment and theoretical calculation indicates that single ionization and secondary ionization are the two main ionizing modes at velocities 5.0–6.3 km/s.
In situ wavelength calibration of the edge CXS spectrometers on JET
Authors: Delabie E. , Hawkes N. , Biewer T. M. , O’Mullane M. G. ,   JET Contributors
Published: August 2016

A method for obtaining an accurate wavelength calibration over the entire focal plane of the JET edge CXS spectrometers is presented that uses a combination of the fringe pattern created with a Fabry–Pérot etalon and a neon lamp for cross calibration. The accuracy achieved is 0.03 Å, which is the same range of uncertainty as when neglecting population effects on the rest wavelength of the CX line. For the edge CXS diagnostic, this corresponds to a flow velocity of 4.5 km/s in the toroidal direction or 1.9 km/s in the poloidal direction.
Onion-peeling inversion of stellarator images
Authors: Hammond K. C. , Diaz-Pacheco R. R. , Kornbluth Y. , Volpe F. A. , Wei Y.
Published: August 2016

An onion-peeling technique is developed for inferring the emissivity profile of a stellarator plasma from a two-dimensional image acquired through a CCD or CMOS camera. Each pixel in the image is treated as an integral of emission along a particular line-of-sight. Additionally, the flux surfaces in the plasma are partitioned into discrete layers, each of which is assumed to have uniform emissivity. If the topology of the flux surfaces is known, this construction permits the development of a system of linear equations that can be solved for the emissivity of each layer. We present initial results of this method applied to wide-angle visible images of the Columbia Neutral Torus (CNT) stellarator plasma.
Design of the polar neutron-imaging aperture for use at the National Ignition Facility
Authors: Fatherley V. E. , Barker D. A. , Fittinghoff D. N. , Hibbard R. L. , Martinez J. I. , Merrill F. E. , Oertel J. A. , Schmidt D. W. , Volegov P. L. , Wilde C. H.
Published: August 2016

The installation of a neutron imaging diagnostic with a polar view at the National Ignition Facility (NIF) required design of a new aperture, an extended pinhole array (PHA). This PHA is different from the pinhole array for the existing equatorial system due to significant changes in the alignment and recording systems. The complex set of component requirements, as well as significant space constraints in its intended location, makes the design of this aperture challenging. In addition, lessons learned from development of prior apertures mandate careful aperture metrology prior to first use. This paper discusses the PHA requirements, constraints, and the final design. The PHA design is complex due to size constraints, machining precision, assembly tolerances, and design requirements. When fully assembled, the aperture is a 15 mm × 15 mm × 200 mm tungsten and gold assembly. The PHA body is made from 2 layers of tungsten and 11 layers of gold. The gold layers include 4 layers containing penumbral openings, 4 layers containing pinholes and 3 spacer layers. In total, there are 64 individual, triangular pinholes with a field of view (FOV) of 200 μm and 6 penumbral apertures. Each pinhole is pointed to a slightly different location in the target plane, making the effective FOV of this PHA a 700 μm square in the target plane. The large FOV of the PHA reduces the alignment requirements both for the PHA and the target, allowing for alignment with a laser tracking system at NIF.
Unsteady fluid flow in a slightly curved pipe: A comparative study of a matched asymptotic expansions solution with a single analytical solution
Authors: Messaris Gerasimos A. T. , Hadjinicolaou Maria , Karahalios George T.
Published: August 2016

The present work is motivated by the fact that blood flow in the aorta and the main arteries is governed by large finite values of the Womersley number α and for such values of α there is not any analytical solution in the literature. The existing numerical solutions, although accurate, give limited information about the factors that affect the flow, whereas an analytical approach has an advantage in that it can provide physical insight to the flow mechanism. Having this in mind, we seek analytical solution to the equations of the fluid flow driven by a sinusoidal pressure gradient in a slightly curved pipe of circular cross section when the Womersley number varies from small finite to infinite values. Initially the equations of motion are expanded in terms of the curvature ratio δ and the resulting linearized equations are solved analytically in two ways. In the first, we match the solution for the main core to that for the Stokes boundary layer. This solution is valid for very large values of α. In the second, we derive a straightforward single solution valid to the entire flow region and for 8 ≤ α < ∞, a range which includes the values of α that refer to the physiological flows. Each solution contains expressions for the axial velocity, the stream function, and the wall stresses and is compared to the analogous forms presented in other studies. The two solutions give identical results to each other regarding the axial flow but differ in the secondary flow and the circumferential wall stress, due to the approximations employed in the matched asymptotic expansion process. The results on the stream function from the second solution are in agreement with analogous results from other numerical solutions. The second solution predicts that the atherosclerotic plaques may develop in any location around the cross section of the aortic wall unlike to the prescribed locations predicted by the first solution. In addition, it gives circumferential wall stresses augmented by approximately 100% with respect to the matched asymptotic expansions, a factor that may contribute jointly with other pathological factors to the faster aging of the arterial system and the possible malfunction of the aorta.
Upper wide-angle viewing system for ITER
Authors: Lasnier C. J. , McLean A. G. , Gattuso A. , O’Neill R. , Smiley M. , Vasquez J. , Feder R. , Smith M. , Stratton B. , Johnson D. , Verlaan A. L. , Heijmans J. A. C.
Published: August 2016

The Upper Wide Angle Viewing System (UWAVS) will be installed on five upper ports of ITER. This paper shows major requirements, gives an overview of the preliminary design with reasons for some design choices, examines self-emitted IR light from UWAVS optics and its effect on accuracy, and shows calculations of signal-to-noise ratios for the two-color temperature output as a function of integration time and divertor temperature. Accurate temperature output requires correction for vacuum window absorption vs. wavelength and for self-emitted IR, which requires good measurement of the temperature of the optical components. The anticipated signal-to-noise ratio using presently available IR cameras is adequate for the required 500 Hz frame rate.
Realization of highly efficient hexagonal boron nitride neutron detectors
Authors: Maity A. , Doan T. C. , Li J. , Lin J. Y. , Jiang H. X.
Published: August 2016

We report the achievement of highly efficient 10B enriched hexagonal boron nitride (h-10BN) direct conversion neutron detectors. These detectors were realized from freestanding 4-in. diameter h-10BN wafers 43 μm in thickness obtained from epitaxy growth and subsequent mechanical separation from sapphire substrates. Both sides of the film were subjected to ohmic contact deposition to form a simple vertical “photoconductor-type” detector. Transport measurements revealed excellent vertical transport properties including high electrical resistivity (>1013 Ω cm) and mobility-lifetime (μτ) products. A much larger μτ product for holes compared to that of electrons along the c-axis of h-BN was observed, implying that holes (electrons) behave like majority (minority) carriers in undoped h-BN. Exposure to thermal neutrons from a californium-252 (252Cf) source moderated by a high density polyethylene moderator reveals that 43 μm h-10BN detectors possess 51.4% detection efficiency at a bias voltage of 400 V, which is the highest reported efficiency for any semiconductor-based neutron detector. The results point to the possibility of obtaining highly efficient, compact solid-state neutron detectors with high gamma rejection and low manufacturing and maintenance costs.
Linear and nonlinear dust ion acoustic solitary waves in a quantum dusty electron-positron-ion plasma
Authors: Emadi E. , Zahed H.
Published: August 2016

The behavior of linear and nonlinear dust ion acoustic (DIA) solitary waves in an unmagnetized quantum dusty plasma, including inertialess electrons and positrons, ions, and mobile negative dust grains, are studied. Reductive perturbation and Sagdeev pseudopotential methods are employed for small and large amplitude DIA solitary waves, respectively. A minimum value of the Mach number obtained for the existence of solitary waves using the analytical expression of the Sagdeev potential. It is observed that the variation on the values of the plasma parameters such as different values of Mach number M, ion to electron Fermi temperature ratio σ, and quantum diffraction parameter H can lead to the creation of compressive solitary waves.
Calibration of a time-resolved hard-x-ray detector using radioactive sources
Authors: Stoeckl C. , Theobald W. , Regan S. P. , Romanofsky M. H.
Published: August 2016

A four-channel, time-resolved, hard x-ray detector (HXRD) has been operating at the Laboratory for Laser Energetics for more than a decade. The slope temperature of the hot-electron population in direct-drive inertial confinement fusion experiments is inferred by recording the hard x-ray radiation generated in the interaction of the electrons with the target. Measuring the energy deposited by hot electrons requires an absolute calibration of the hard x-ray detector. A novel method to obtain an absolute calibration of the HXRD using single photons from radioactive sources was developed, which uses a thermoelectrically cooled, low-noise, charge-sensitive amplifier.
Monolayers of hard rods on planar substrates. I. Equilibrium
Authors: Oettel M. , Klopotek M. , Dixit M. , Empting E. , Schilling T. , Hansen–Goos H.
Published: August 2016

The equilibrium properties of hard rod monolayers are investigated in a lattice model (where position and orientation of a rod are restricted to discrete values) as well as in an off-lattice model featuring spherocylinders with continuous positional and orientational degrees of freedom. Both models are treated using density functional theory and Monte Carlo simulations. Upon increasing the density of rods in the monolayer, there is a continuous ordering of the rods along the monolayer normal (“standing up” transition). The continuous transition also persists in the case of an external potential which favors flat-lying rods in the monolayer. This behavior is found in both the lattice and the continuum models. For the lattice model, we find very good agreement between the results from the specific DFT used (lattice fundamental measure theory) and simulations. The properties of lattice fundamental measure theory are further illustrated by the phase diagrams of bulk hard rods in two and three dimensions.
Effects of alpha-proton drift velocity on alpha particle firehose instability
Authors: Seough Jungjoon , Nariyuki Yasuhiro
Published: August 2016

In situ measurements have shown that the less-abundant alpha particles are characterized by temperature anisotropy which could drive the anisotropy-driven kinetic instabilities in the solar wind. In the collisionless plasma, the differential alpha-proton flow velocity Vd=Vα−Vp usually has a non-zero value of the order of the local Alfvén velocity. The presence of such differential flow may affect the properties of dispersion relations for anisotropy-driven instabilities. Based upon linear Vlasov dispersion theory in a homogeneous plasma, the present study investigates the effects of the alpha-proton drift velocity on the parallel and oblique firehose instabilities driven by an excessive parallel temperature anisotropy of alpha particles, where the parallel and oblique represent directions of fluctuation propagation relative to the background magnetic field. It is found that for oblique firehose mode as well as parallel mode, the dispersion properties are affected by the presence of the alpha-proton drift velocity, which in turn results in the increase of the maximum growth rates as Vd increases and consequently leads to the modification of the marginal stability conditions in the parameter space (β∥α,T⊥α/T∥α). We discuss the relevance of our results to the measured temperature anisotropy of alpha particles in the solar wind context.
Radiating electron source generation in ultraintense laser-foil interactions
Authors: Capdessus R. , King M. , McKenna P.
Published: August 2016

A radiating electron source is shown to be created by a laser pulse (with intensity of 1023 W/cm2 and duration equal to 30 fs) interacting with a near-critical density plasma. It is shown that the back radiation reaction resulting from high energy synchrotron radiation tends to counteract the action of the ponderomotive force. This enhances the collective dynamics of the radiating electrons in the highest field areas, resulting in the production of a compact radiation source (containing 80% of the synchrotron radiation emission), with an energy on the order of tens of MeV over the laser pulse duration. These phenomena are investigated using a QED-particle-in-cell code, and compared with a kinetic model accounting for the radiation reaction force in the electron distribution function. The results shed new light on electron-photon sources at ultra-high laser intensities and could be tested on future laser facilities.
A phase contrast imaging–interferometer system for detection of multiscale electron density fluctuations on DIII-D
Authors: Davis E. M. , Rost J. C. , Porkolab M. , Marinoni A. , Van Zeeland M. A.
Published: August 2016

Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI–interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz <f < 5 MHz and 0 cm-1 ≤k ≤ 20 cm-1), allowing simultaneous measurement of ion- and electron-scale instabilities. Further, correlating our interferometer’s measurements with those from DIII-D’s pre-existing, toroidally separated interferometer allows core-localized, low-n MHD studies that may otherwise be inaccessible via external magnetic measurements. The combined diagnostic’s small port requirements and minimal access restrictions make it well-suited to the harsh neutron environments and limited port space expected in next-step devices.
Effective of the q-deformed pseudoscalar magnetic field on the charge carriers in graphene
Authors: Eshghi M. , Mehraban H.
Published: August 2016

In this paper, we have obtained exact analytical solutions of the time-independent Dirac-Weyl equation for the charge carriers with q-deformed pseudoscalar magnetic barrier (PMB) in graphene by using the ansatz method. We have also found a solution that describes the left propagating wave function to calculation of the reflection and transmission coefficients using the Riemann’s equation. This allows us to conclude about the Dirac-Weyl equation with PMB and to understand quantum behavior of the Dirac fermions. Finally, some of the numerical results are shown, too.
Local and global solutions of Chern-Simons gauged O(3) sigma equations in one space dimension
Authors: Huh Hyungjin , Jin Guanghui
Published: August 2016

We study an initial value problem of the Chern-Simons gauged O(3) sigma model in one space dimension. The global existence of solutions to the model is proved for high regularity initial data. Moreover we study low regularity local well-posedness, observing null forms of the system and applying bilinear estimates for wave-Sobolev space Hs, θ. As a by-product, a finite energy global solution is constructed.
Existence and uniqueness of small energy weak solution to multi-dimensional compressible Navier-Stokes equations with large external potential force
Authors: Cheung Ka Luen , Suen Anthony
Published: August 2016

We study the 3-D compressible Navier-Stokes equations with an external potential force and a general non-decreasing pressure. We prove the global-in-time existence of weak solutions with small-energy initial data and with densities being non-negative and essentially bounded. A solution may have large oscillations and contain vacuum states. No smallness assumption is made on the external force nor the initial perturbation in L∞ for density. Initial velocity u0 is taken to be bounded in Lq for some q > 6 and no further regularity assumption is imposed on u0. Finally, we discuss the uniqueness of weak solutions.
Three new extreme ultraviolet spectrometers on NSTX-U for impurity monitoring
Authors: Weller M. E. , Beiersdorfer P. , Soukhanovskii V. A. , Magee E. W. , Scotti F.
Published: August 2016

Three extreme ultraviolet (EUV) spectrometers have been mounted on the National Spherical Torus Experiment–Upgrade (NSTX-U). All three are flat-field grazing-incidence spectrometers and are dubbed X-ray and Extreme Ultraviolet Spectrometer (XEUS, 8–70 Å), Long-Wavelength Extreme Ultraviolet Spectrometer (LoWEUS, 190–440 Å), and Metal Monitor and Lithium Spectrometer Assembly (MonaLisa, 50–220 Å). XEUS and LoWEUS were previously implemented on NSTX to monitor impurities from low- to high-Z sources and to study impurity transport while MonaLisa is new and provides the system increased spectral coverage. The spectrometers will also be a critical diagnostic on the planned laser blow-off system for NSTX-U, which will be used for impurity edge and core ion transport studies, edge-transport code development, and benchmarking atomic physics codes.
Hanle effect as a magnetic diagnostic for field-reversed configuration plasmas
Authors: Gupta Deepak K.
Published: August 2016

Hanle effect is presented as a low magnetic-field diagnostic for field-reversed configuration (FRC) plasmas. The non-perturbative technique is capable of measuring not only magnetic-field profile and direction but also field-null position and its shape. Conditions and configurations for the measurement are discussed. The technique is applicable to other low magnetic-field laboratory plasmas, e.g., magnetic-cusps, where measurements of low field are desirable, and it may also be extended to measure the two-dimensional vector magnetic-field.
2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)
Authors: Yang Xiaoyi , Xiao Chijie , Chen Yihang , Xu Tianchao , Lin Chen , Wang Long , Xu Min , Yu Yi
Published: August 2016

Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (Bp) and radial electric field (Er) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D Bp profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.
Mixing model with multi-particle interactions for Lagrangian simulations of turbulent mixing
Authors: Watanabe T. , Nagata K.
Published: August 2016

We report on the numerical study of the mixing volume model (MVM) for molecular diffusion in Lagrangian simulations of turbulent mixing problems. The MVM is based on the multi-particle interaction in a finite volume (mixing volume). A priori test of the MVM, based on the direct numerical simulations of planar jets, is conducted in the turbulent region and the interfacial layer between the turbulent and non-turbulent fluids. The results show that the MVM predicts well the mean effects of the molecular diffusion under various numerical and flow parameters. The number of the mixing particles should be large for predicting a value of the molecular diffusion term positively correlated to the exact value. The size of the mixing volume relative to the Kolmogorov scale η is important in the performance of the MVM. The scalar transfer across the turbulent/non-turbulent interface is well captured by the MVM especially with the small mixing volume. Furthermore, the MVM with multiple mixing particles is tested in the hybrid implicit large-eddy-simulation/Lagrangian-particle-simulation (LES–LPS) of the planar jet with the characteristic length of the mixing volume of O(100η). Despite the large mixing volume, the MVM works well and decays the scalar variance in a rate close to the reference LES. The statistics in the LPS are very robust to the number of the particles used in the simulations and the computational grid size of the LES. Both in the turbulent core region and the intermittent region, the LPS predicts a scalar field well correlated to the LES.
Single orientation graphene synthesized on iridium thin films grown by molecular beam epitaxy
Authors: Dangwal Pandey A. , Krausert K. , Franz D. , Grånäs E. , Shayduk R. , Müller P. , Keller T. F. , Noei H. , Vonk V. , Stierle A.
Published: August 2016

Heteroepitaxial iridium thin films were deposited on (0001) sapphire substrates by means of molecular beam epitaxy, and subsequently, one monolayer of graphene was synthesized by chemical vapor deposition. The influence of the growth parameters on the quality of the Ir films, as well as of graphene, was investigated systematically by means of low energy electron diffraction, x-ray reflectivity, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Our study reveals (111) oriented iridium films with high crystalline quality and extremely low surface roughness, on which the formation of large-area epitaxial graphene is achieved. The presence of defects, like dislocations, twins, and 30° rotated domains in the iridium films is also discussed. The coverage of graphene was found to be influenced by the presence of 30° rotated domains in the Ir films. Low iridium deposition rates suppress these rotated domains and an almost complete coverage of graphene was obtained. This synthesis route yields inexpensive, air-stable, and large-area graphene with a well-defined orientation, making it accessible to a wider community of researchers for numerous experiments or applications, including those which use destructive analysis techniques or irreversible processes. Moreover, this approach can be used to tune the structural quality of graphene, allowing a systematic study of the influence of defects in various processes like intercalation below graphene.
Nanoscale patterns produced by self-sputtering of solid surfaces: The effect of ion implantation
Authors: Bradley R. Mark , Hofsäss Hans
Published: August 2016

A theory of the effect that ion implantation has on the patterns produced by ion bombardment of solid surfaces is introduced. For simplicity, the case of self-sputtering of an elemental material is studied. We find that implantation of self-ions has a destabilizing effect along the projected beam direction for angles of incidence θ that exceed a critical value. In the transverse direction, ion implantation has a stabilizing influence for all θ.
Response of MDOF strongly nonlinear systems to fractional Gaussian noises
Authors: Deng Mao-Lin , Zhu Wei-Qiu
Published: August 2016

In the present paper, multi-degree-of-freedom strongly nonlinear systems are modeled as quasi-Hamiltonian systems and the stochastic averaging method for quasi-Hamiltonian systems (including quasi-non-integrable, completely integrable and non-resonant, completely integrable and resonant, partially integrable and non-resonant, and partially integrable and resonant Hamiltonian systems) driven by fractional Gaussian noise is introduced. The averaged fractional stochastic differential equations (SDEs) are derived. The simulation results for some examples show that the averaged SDEs can be used to predict the response of the original systems and the simulation time for the averaged SDEs is less than that for the original systems.
Nonlocal nonlinear Schrödinger equation and its discrete version: Soliton solutions and gauge equivalence
Authors: Ma Li-Yuan , Zhu Zuo-Nong
Published: August 2016

In this paper, we try to understand the geometry for a nonlocal nonlinear Schrödinger equation (nonlocal NLS) and its discrete version introduced by Ablowitz and Musslimani, Phys. Rev. Lett. 110, 064105 (2013); Phys. Rev. E 90, 042912 (2014). We show that, under the gauge transformations, the nonlocal focusing NLS and the nonlocal defocusing NLS are, respectively, gauge equivalent to a Heisenberg-like equation and a modified Heisenberg-like equation, and their discrete versions are, respectively, gauge equivalent to a discrete Heisenberg-like equation and a discrete modified Heisenberg-like equation. Although the geometry related to the nonlocal NLS and its discrete version is not very clear, from the gauge equivalence, we can see that the properties between the nonlocal NLS and its discrete version and NLS and discrete NLS have significant difference. By constructing the Darboux transformation for discrete nonlocal NLS equations including the cases of focusing and defocusing, we derive their discrete soliton solutions, which differ from the ones obtained by using the inverse scattering transformation.
Nonlinear differential algorithm to compute all the zeros of a generic polynomial
Authors: Calogero Francesco
Published: August 2016

A simple algorithm to compute all the zeros of a generic polynomial is proposed.
Quantum mechanical expansion of variance of a particle in a weakly non-uniform electric and magnetic field
Authors: Chan Poh Kam , Oikawa Shun-ichi , Kosaka Wataru
Published: August 2016

We have solved the Heisenberg equation of motion for the time evolution of the position and momentum operators for a non-relativistic spinless charged particle in the presence of a weakly non-uniform electric and magnetic field. It is shown that the drift velocity operator obtained in this study agrees with the classical counterpart, and that, using the time dependent operators, the variances in position and momentum grow with time. The expansion rate of variance in position and momentum are dependent on the magnetic gradient scale length, however, independent of the electric gradient scale length. In the presence of a weakly non-uniform electric and magnetic field, the theoretical expansion rates of variance expansion are in good agreement with the numerical analysis. It is analytically shown that the variance in position reaches the square of the interparticle separation, which is the characteristic time much shorter than the proton collision time of plasma fusion. After this time, the wavefunctions of the neighboring particles would overlap, as a result, the conventional classical analysis may lose its validity. The broad distribution of individual particle in space means that their Coulomb interactions with other particles become weaker than that expected in classical mechanics.
Low-frequency surface waves on semi-bounded magnetized quantum plasma
Authors: Moradi Afshin
Published: August 2016

The propagation of low-frequency electrostatic surface waves on the interface between a vacuum and an electron-ion quantum plasma is studied in the direction perpendicular to an external static magnetic field which is parallel to the interface. A new dispersion equation is derived by employing both the quantum magnetohydrodynamic and Poisson equations. It is shown that the dispersion equations for forward and backward-going surface waves are different from each other.
Optical Tamm states in one-dimensional superconducting photonic crystal
Authors: El Abouti O. , El Boudouti E. H. , El Hassouani Y. , Noual A. , Djafari-Rouhani B.
Published: August 2016

In this study, we investigate localized and resonant optical waves associated with a semi-infinite superlattice made out of superconductor-dielectric bilayers and terminated with a cap layer. Both transverse electric and transverse magnetic waves are considered. These surface modes are analogous to the so-called Tamm states associated with electronic states found at the surface of materials. The surface guided modes induced by the cap layer strongly depend on whether the superlattice ends with a superconductor or a dielectric layer, the thickness of the surface layer, the temperature of the superconductor layer as well as on the polarization of the waves. Different kinds of surface modes are found and their properties examined. These structures can be used to realize the highly sensitive photonic crystal sensors.
Volume nanograting formation in laser-silica interaction as a result of the 1D plasma-resonance ionization instability
Authors: Gildenburg V. B. , Pavlichenko I. A.
Published: August 2016

The initial stage of the small-scale ionization-induced instability developing inside the fused silica volume exposed to the femtosecond laser pulse is studied as a possible initial cause of the self-organized nanograting formation. We have calculated the spatial spectra of the instability with the electron-hole diffusion taken into account for the first time and have found that it results in the formation of some hybrid (diffusion-wave) 1D structure with the spatial period determined as the geometrical mean of the laser wavelength and characteristic diffusion length of the process considered. Near the threshold of the instability, this period occurs to be approximately equal to the laser half-wavelength in the silica, close to the one experimentally observed.
Study on the heat flux reconstruction with the infrared thermography for the divertor target plates in the KSTAR tokamak
Authors: Kang C. S. , Lee H. H. , Oh S. , Lee S. G. , Wi H. M. , Kim Y. S. , Kim H. S.
Published: August 2016

An infrared (IR) thermography is the preferred diagnostic that can quantify heat flux by measuring the surface temperature distributions of the divertor plates. The IR thermography is successfully instrumented on Korea Superconducting Tokamak Advanced Research (KSTAR). In this study, finite volume method is considered to solve the heat conduction equations. 1D-, 2D-, and 3D models are developed and compared with various calculation algorithms, such as Duhamel’s theorem and THEODOR. These comparisons show good agreement. In order to acquire more efficient and reliable calculation results, we consider two numerical analysis schemes, influence of temperature on thermal properties and image stabilization. Recently, this reconstruction code is successfully applied to the KSTAR IR thermography.
Two-dimensional ZnO ultrathin nanosheets decorated with Au nanoparticles for effective photocatalysis
Authors: Hu Jin , You Ning , Yu Zhe , Zhou Gang , Xu Xiaoyong
Published: August 2016

Two-dimensional (2D) materials, especially the inorganic 2D nanosheets (NSs), are of particular interest due to their unique structural and electronic properties, which are favorable for photoelectronic applications such as photocatalysis. Here, we design and fabricate the ultrathin 2D ZnO NSs decorated with Au nanoparticles (AuNPs), though molecular modelling 2D hydrothermal growth and followed by surface modification are used as an effective photocatalyst for photocatalytic organic dye degradation and hydrogen production. The ultrathin 2D nature enables ultrahigh atom ratio near surface to proliferate the active sites, and the Au plasmon plays a promoting role in the visible-light absorption and photogenerated charge separation, thus integrating the synergistic benefits to boost the redox reactions at catalyst/electrolyte interface. The AuNPs-decorated ZnO NSs yield the impressive photocatalytic activities such as the dye degradation rate constant of 7.69 × 10−2 min−1 and the hydrogen production rate of 350 μmol h−1 g−1.
The Richtmyer-Meshkov instability of a “V” shaped air/helium interface subjected to a weak shock
Authors: Zhai Zhigang , Dong Ping , Si Ting , Luo Xisheng
Published: August 2016

The Richtmyer-Meshkov instability of a “V” shaped air/helium gaseous interface subjected to a weak shock wave is experimentally studied. A soap film technique is adopted to create a “V” shaped interface with accurate initial conditions. Five kinds of air/helium “V” shaped interfaces with different vertex angles (60°, 90°, 120°, 140°, and 160°), i.e., different amplitude-wavelength ratios, are formed to highlight the effects of initial conditions, especially the initial amplitude, on the flow characteristics. The interface morphologies identified by the high-speed schlieren photography show that a spike is generated from the vertex after the shock impact, and grows constantly with time accompanied by the occurrence of the phase reversal. As the vertex angle increases, vortices generated on the interface become less noticeable, and the spike develops less pronouncedly. The linear growth rate of the interface mixing width of a heavy/light interface configuration after compression phase is estimated by a linear model and a revised linear model, and the latter is proven to be more effective for the interface with high initial amplitudes. It is found for the first time in a heavy/light interface configuration that the linear growth rate of interface width is a non-monotonous function of the initial perturbation amplitude-wavelength ratio. In the nonlinear stage, it is confirmed that the width growth rate of interface with high initial amplitudes can be well predicted by a model proposed by Dimonte and Ramaprabhu [“Simulations and model of the nonlinear Richtmyer-Meshkov instability,” Phys. Fluids 22, 014104 (2010)].
Harmonic plasma waves excitation and structure evolution of intense ion beams in background plasmas
Authors: Hu Zhang-Hu , Wang You-Nian
Published: August 2016

The long-term dynamic evolutions of intense ion beams in plasmas have been investigated with two-dimensional electromagnetic particle simulations, taking into account the effect of the two-stream instability between beam ions and plasma electrons. Depending on the initial beam radial density profile and velocity distribution, ring structures may be formed in the beam edge regions. At the later stage of beam-plasma interactions, the ion beams are strongly modulated by the two-stream instability and multiple density spikes are formed in the longitudinal direction. The formation of these density spikes is shown to result from the excitation of harmonic plasma waves when the instability gets saturated. Comparisons between the beam cases with initial flat-top and Gaussian radial density profiles are made, and a higher instability growth rate is observed for the flat-top profile case.
Screening effects due to carrier doping on valley relaxation in transition metal dichalcogenide monolayers
Authors: Konabe Satoru
Published: August 2016

This work theoretically investigated the mechanism of valley polarization relaxation in monolayers of transition metal dichalcogenides, focusing on the exchange interactions between electrons and holes. In particular, we elucidated the effects of screening resulting from carrier doping on valley depolarization dynamics. The results show that the valley relaxation time is highly dependent on the extent of carrier doping. In addition, a finite degree of doping is predicted to induce additional valley relaxation temperature dependence at low temperatures, an effect that is absent at zero doping. Our calculation results suggest the possibility of increasing the valley relaxation time by tuning carrier doping, which could present a means of manipulating the valley degrees of freedom.
Wireless actuation of bulk acoustic modes in micromechanical resonators
Authors: Mateen Farrukh , Brown Benjamin , Erramilli Shyamsunder , Mohanty Pritiraj
Published: August 2016

We report wireless actuation of a Lamb wave micromechanical resonator from a distance of over 1 m with an efficiency of over 15%. Wireless actuation of conventional micromechanical resonators can have broad impact in a number of applications from wireless communication and implantable biomedical devices to distributed sensor networks.
Ab initio study of electronic and magnetic properties in Ni-doped WS2 monolayer
Authors: Luo Min , Hao Shen Yu , Ling Yin Tai
Published: August 2016

The magnetic properties of Ni-doped WS2 monolayer are investigated using first-principles method. The results indicate that both one-Ni-doped and the nearest two-Ni-doped systems are magnetic. The p-d hybridization between the Ni atom and its neighboring S atoms results in the ferromagnetic interaction of the Ni-doped WS2 monolayer. The antiferromagnetic coupling is observed with increasing Ni-Ni distance which can be explained by two-impurity Haldane-Anderson model using quantum Monte Carlo method. Our studies show that the nearest two Ni-doped WS2 monolayers to be candidates for two-dimensional transition-metal nanosheets. Moreover, we discussed the differences in the formation energy between W-rich and S-rich conditions. Our results also predict that it would be easier to incorporate Ni atoms into a S-rich WS2 monolayer in the experiment.