bluuebunny/crossref_metadata_2025 huggingface dataset:
Gamma bang time analysis at OMEGA
Authors: McEvoy A. M. , Herrmann H. W. , Horsfield C. J. , Young C. S. , Miller E. K. , Mack J. M. , Kim Y. , Stoeffl W. , Rubery M. , Evans S. , Sedillo T. , Ali Z. A.
Published: October 2010

Absolute bang time measurements with the gas Cherenkov detector (GCD) and gamma reaction history (GRH) diagnostic have been performed to high precision at the OMEGA laser facility at the University of Rochester with bang time values for the two diagnostics agreeing to within 5 ps on average. X-ray timing measurements of laser-target coupling were used to calibrate a facility-generated laser timing fiducial with rms spreads in the measured coupling times of 9 ps for both GCD and GRH. Increased fusion yields at the National Ignition Facility (NIF) will allow for improved measurement precision with the GRH easily exceeding NIF system design requirements.
Analysis of the ITER low field side reflectometer transmission line system
Authors: Hanson G. R. , Wilgen J. B. , Bigelow T. S. , Diem S. J. , Biewer T. M.
Published: October 2010

A critical issue in the design of the ITER low field side reflectometer is the transmission line (TL) system. A TL connects each launcher to a diagnostic instrument. Each TL will typically consist of ∼42 m of corrugated waveguide and up to ten miter bends. Important issues for the performance of the TL system are mode conversion and reflections. Minimizing these issues are critical to minimizing standing waves and phase errors. The performance of TL system is analyzed and recommendations are given.
High-throughput accurate-wavelength lens-based visible spectrometer
Authors: Bell Ronald E. , Scotti Filippo
Published: October 2010

A scanning visible spectrometer has been prototyped to complement fixed-wavelength transmission grating spectrometers for charge exchange recombination spectroscopy. Fast f/1.8 200 mm commercial lenses are used with a large 2160 mm−1 grating for high throughput. A stepping-motor controlled sine drive positions the grating, which is mounted on a precision rotary table. A high-resolution optical encoder on the grating stage allows the grating angle to be measured with an absolute accuracy of 0.075 arc sec, corresponding to a wavelength error ≤0.005 Å. At this precision, changes in grating groove density due to thermal expansion and variations in the refractive index of air are important. An automated calibration procedure determines all the relevant spectrometer parameters to high accuracy. Changes in bulk grating temperature, atmospheric temperature, and pressure are monitored between the time of calibration and the time of measurement to ensure a persistent wavelength calibration.
Development of multi-channel electron spectrometer
Authors: Iwawaki T. , Habara H. , Tanimoto T. , Nakanii N. , Shimada K. , Yabuuchi T. , Kondo K. , Tanaka K. A.
Published: October 2010

In order to obtain the angular dependent electron energy distributions, we developed a multichannel electron spectrometer (MCESM) with high energy and angular resolutions. The MCESM consists of seven small electron spectrometers set in every 5° on the basement, each of which detection range is up to 25 MeV. In the experiment, we successfully obtained electron spectra from imploded cone-shell target as well as gold plane target irradiated by ultraintense (300 J/5 ps) laser beam.
Exponential and polynomial stability of an elastic Bresse system with two locally distributed feedbacks
Authors: Wehbe Ali , Youssef Wael
Published: October 2010

In this paper, we study the energy decay rate for the elastic Bresse system in one-dimensional bounded domain. The physical system consists of three wave equations. The two wave equations about the rotation angle and the longitudinal displacement are damped by two locally distributed feedbacks at the neighborhood of the boundary. Then indirect damping is applied to the equation for the transverse displacement of the beam through the coupling terms. We will establish the exponential stability for this system in the case of the same speed of propagation in the equation for the vertical displacement and the equation for the rotation angle of the system. When the wave speeds are different, nonexponential decay rate is proved and a polynomial-type decay rate is obtained. The frequency domain method and the multiplier technique are applied.
Thermal conductivity and Seebeck coefficients of icosahedral boron arsenide films on silicon carbide
Authors: Gong Y. , Zhang Y. , Dudley M. , Zhang Y. , Edgar J. H. , Heard P. J. , Kuball M.
Published: October 2010

The thermal conductivity of icosahedral boron arsenide (B12As2) films grown on (0001) 6H–SiC substrates by chemical vapor deposition was studied by the 3ω technique. The room temperature thermal conductivity decreased from 27.0 to 15.3 W/m K as the growth temperature was decreased from 1450 to 1275 °C. This is mainly attributed to the differences in the impurity concentration and microstructure, determined from secondary ion mass spectrometry and high resolution transmission electron microscopy, respectively. Callaway’s theory was applied to calculate the temperature-dependent thermal conductivity, and the results are in good agreement with the experimental data. Seebeck coefficients were determined as 107 μV/K and 136 μV/K for samples grown at 1350 °C with AsH3/B2H6 flow ratio equals to 1:1 and 3:5, respectively.
Spatially resolvable optical emission spectrometer for analyzing density uniformity of semiconductor process plasma
Authors: Oh Changhoon , Ryoo Hoonchul , Lee Hyungwoo , Kim Se-Yeon , Yi Hun-Jung , Hahn Jae W.
Published: October 2010

We proposed a spatially resolved optical emission spectrometer (SROES) for analyzing the uniformity of plasma density for semiconductor processes. To enhance the spatial resolution of the SROES, we constructed a SROES system using a series of lenses, apertures, and pinholes. We calculated the spatial resolution of the SROES for the variation of pinhole size, and our calculated results were in good agreement with the measured spatial variation of the constructed SROES. The performance of the SROES was also verified by detecting the correlation between the distribution of a fluorine radical in inductively coupled plasma etch process and the etch rate of a SiO2 film on a silicon wafer.
Fully transparent InGaZnO thin film transistors using indium tin oxide/graphene multilayer as source/drain electrodes
Authors: Seo David , Jeon Sanghun , Seo Sunae , Song Ihun , Kim Changjung , Park Sungho , Harris James S. , Chung U.-In
Published: October 2010

Demonstration of a transparent InGaZnO thin film transistor using a graphene composite as the transparent source/drain electrode is presented. Graphene growth was confirmed by Raman spectroscopy, showing all associated peaks at 1350, 1580, and 2700 cm−1. The graphene composite showed a sheet resistance reduction of 15% while losing only 1.2% transparency when compared to the reference indium-tin oxide only electrode. Device characteristics of the composite device were on similar levels to those of the reference indium-tin oxide only device reaching a peak saturation mobility of nearly 30 cm2 v−1 s−1 indicating that graphene integration did not degrade InGaZnO transistor performance.
Electrolytes in a nanometer slab-confinement: Ion-specific structure and solvation forces
Authors: Kalcher Immanuel , Schulz Julius C. F. , Dzubiella Joachim
Published: October 2010

We study the liquid structure and solvation forces of dense monovalent electrolytes (LiCl, NaCl, CsCl, and NaI) in a nanometer slab-confinement by explicit-water molecular dynamics (MD) simulations, implicit-water Monte Carlo (MC) simulations, and modified Poisson–Boltzmann (PB) theories. In order to consistently coarse-grain and to account for specific hydration effects in the implicit methods, realistic ion-ion and ion-surface pair potentials have been derived from infinite-dilution MD simulations. The electrolyte structure calculated from MC simulations is in good agreement with the corresponding MD simulations, thereby validating the coarse-graining approach. The agreement improves if a realistic, MD-derived dielectric constant is employed, which partially corrects for (water-mediated) many-body effects. Further analysis of the ionic structure and solvation pressure demonstrates that nonlocal extensions to PB (NPB) perform well for a wide parameter range when compared to MC simulations, whereas all local extensions mostly fail. A Barker–Henderson mapping of the ions onto a charged, asymmetric, and nonadditive binary hard-sphere mixture shows that the strength of structural correlations is strongly related to the magnitude and sign of the salt-specific nonadditivity. Furthermore, a grand canonical NPB analysis shows that the Donnan effect is dominated by steric correlations, whereas solvation forces and overcharging effects are mainly governed by ion-surface interactions. However, steric corrections to solvation forces are strongly repulsive for high concentrations and low surface charges, while overcharging can also be triggered by steric interactions in strongly correlated systems. Generally, we find that ion-surface and ion-ion correlations are strongly coupled and that coarse-grained methods should include both, the latter nonlocally and nonadditive (as given by our specific ionic diameters), when studying electrolytes in highly inhomogeneous situations.
The first measurements of soft x-ray flux from ignition scale Hohlraums at the National Ignition Facility using DANTE (invited)
Authors: Kline J. L. , Widmann K. , Warrick A. , Olson R. E. , Thomas C. A. , Moore A. S. , Suter L. J. , Landen O. , Callahan D. , Azevedo S. , Liebman J. , Glenzer S. H. , Conder A. , Dixit S. N. , Torres P. , Tran V. , Dewald E. L. , Kamperschroer J. , Atherton L. J. , Beeler R. , Berzins L. , Celeste J. , Haynam C. , Hsing W. , Larson D. , MacGowan B. J. , Hinkel D. , Kalantar D. , Kauffman R. , Kilkenny J. , Meezan N. , Rosen M. D. , Schneider M. , Williams E. A. , Vernon S. , Wallace R. J. , Van Wonterghem B. , Young B. K.
Published: October 2010

The first 96 and 192 beam vacuum Hohlraum target experiments have been fielded at the National Ignition Facility demonstrating radiation temperatures up to 340 eV and fluxes of 20 TW/sr as viewed by DANTE representing an ∼20 times flux increase over NOVA/Omega scale Hohlraums. The vacuum Hohlraums were irradiated with 2 ns square laser pulses with energies between 150 and 635 kJ. They produced nearly Planckian spectra with about 30±10% more flux than predicted by the preshot radiation hydrodynamic simulations. To validate these results, careful verification of all component calibrations, cable deconvolution, and software analysis routines has been conducted. In addition, a half Hohlraum experiment was conducted using a single 2 ns long axial quad with an irradiance of ∼2×1015 W/cm2 for comparison with NIF Early Light experiments completed in 2004. We have also completed a conversion efficiency test using a 128-beam nearly uniformly illuminated gold sphere with intensities kept low (at 1×1014 W/cm2 over 5 ns) to avoid sensitivity to modeling uncertainties for nonlocal heat conduction and nonlinear absorption mechanisms, to compare with similar intensity, 3 ns OMEGA sphere results. The 2004 and 2009 NIF half-Hohlraums agreed to 10% in flux, but more importantly, the 2006 OMEGA Au Sphere, the 2009 NIF Au sphere, and the calculated Au conversion efficiency agree to ±5% in flux, which is estimated to be the absolute calibration accuracy of the DANTEs. Hence we conclude that the 30±10% higher than expected radiation fluxes from the 96 and 192 beam vacuum Hohlraums are attributable to differences in physics of the larger Hohlraums.
Deuterium velocity and temperature measurements on the DIII-D tokamak
Authors: Grierson B. A. , Burrell K. H. , Solomon W. M. , Pablant N. A.
Published: October 2010

Newly installed diagnostic capabilities on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 46, 6114 (2002)] enable the measurement of main ion (deuterium) velocity and temperature by charge exchange recombination spectroscopy. The uncertainty in atomic physics corrections for determining the velocity is overcome by exploiting the geometrical dependence of the apparent velocity on the viewing angle with respect to the neutral beam.
Electron cyclotron emission diagnostics on KSTAR tokamak
Authors: Jeong S. H. , Lee K. D. , Kogi Y. , Kawahata K. , Nagayama Y. , Mase A. , Kwon M.
Published: October 2010

A new electron cyclotron emission (ECE) diagnostics system was installed for the Second Korea Superconducting Tokamak Advanced Research (KSTAR) campaign. The new ECE system consists of an ECE collecting optics system, an overmode circular corrugated waveguide system, and 48 channel heterodyne radiometer with the frequency range of 110–162 GHz. During the 2 T operation of the KSTAR tokamak, the electron temperatures as well as its radial profiles at the high field side were measured and sawtooth phenomena were also observed. We also discuss the effect of a window on in situ calibration.
Note: Electrical resolution during conductive atomic force microscopy measurements under different environmental conditions and contact forces
Authors: Lanza M. , Porti M. , Nafría M. , Aymerich X. , Whittaker E. , Hamilton B.
Published: October 2010

Conductive atomic force microscopy experiments on gate dielectrics in air, nitrogen, and UHV have been compared to evaluate the impact of the environment on topography and electrical measurements. In current images, an increase of the lateral resolution and a reduction of the conductivity were observed in N2 and, especially, in UHV (where current depends also on the contact force). Both effects were related to the reduction/elimination of the water layer between the tip and the sample in N2/UHV. Therefore, since current measurements are very sensitive to environmental conditions, these factors must be taken into consideration when comparisons between several experiments are performed.
Development of a time-resolved soft x-ray spectrometer for laser produced plasma experiments
Authors: Cone K. V. , Dunn J. , Schneider M. B. , Baldis H. A. , Brown G. V. , Emig J. , James D. L. , May M. J. , Park J. , Shepherd R. , Widmann K.
Published: October 2010

A 2400 lines/mm variable-spaced grating spectrometer has been used to measure soft x-ray emission (8–22 Å) from laser-produced plasma experiments at Lawrence Livermore National Laboratory’s Compact Multipulse Terrawatt (COMET) Laser Facility. The spectrometer was coupled to a Kentech x-ray streak camera to study the temporal evolution of soft x rays emitted from the back of the Mylar and the copper foils irradiated at 1015 W/cm2. The instrument demonstrated a resolving power of ∼120 at 19 Å with a time resolution of 31 ps. The time-resolved copper emission spectrum was consistent with a photodiode monitoring the laser temporal pulse shape and indicated that the soft x-ray emission follows the laser heating of the target. The time and spectral resolutions of this diagnostic make it useful for studies of high temperature plasmas.
Laser printed micron-scale free standing laminate composites: Process and properties
Authors: Birnbaum A. J. , Auyeung R. C. , Wahl K. J. , Zalalutidnov M. , Laracuente A. R. , Piqué A.
Published: October 2010

Micron-scale free standing structures were generated via the laser decal transfer process using high viscosity Ag nanoinks without the use of any sacrificial or release layers. Both cantilevered (34×10×0.46 μm3) and doubly suspended beams (38×5×0.46 μm3) were fabricated. Laminate composites were then generated by selectively coating the underside of these structures with silicon using a focused ion beam deposition technique. The static responses of the composite structures were characterized via fitting nanoindentation induced beam deflections with a derived closed-form solution yielding Young’s modulii of the Ag and Si layers as EAg≈40 GPa and ESi≈16 GPa, respectively. The dynamic response of these structures was also characterized via laser vibrometry revealing quality factors of approximately 400 and 800 for cantilevers and microbridges, respectively. Several techniques (static and dynamic) to ascertain the residual stress state of these structures were also employed revealing an average residual stress, σ0≈89 MPa.
The nonlocal dielectric function in the random phase approximation for n-type delta-doped quantum wells in GaAs
Authors: Rodríguez-Coppola H. , Gaggero-Sager L. M. , Mora-Ramos M. E. , Pérez-Álvarez R.
Published: October 2010

The nonlocal dielectric function, calculated using the random phase approximation (RPA) is obtained for a delta-doped quantum well of Si in GaAs. The formal analysis can be performed by considering the response function in the RPA and/or further approximations. The behavior of the real and imaginary parts of the dielectric function is studied for different values of three basic parameters of the system: the energy of an exciting signal, the in-plane linear momentum, and the distance from the doping plane as a function of the concentration of electrons in the doping plane. The results are obtained varying the concentration of electrons in the doping plane from n2D=3×1012 to 7×1012 cm−2. They show a natural change in the intensity of the dielectric response as long as the concentration changes from n2D=6×1012 to 7×1012 cm−2, in agreement with recent experimental results for the mobility of electric carriers.
Multimode photoacoustic method for the evaluation of mechanical properties of heteroepitaxial diamond layers
Authors: Shen Zhonghua H. , Lomonosov Alexey M. , Hess Peter , Fischer Martin , Gsell Stefan , Schreck Matthias
Published: October 2010

A multimode photoacoustic method was developed for evaluating acoustically thick anisotropic layers, using surface acoustic waves. Such layers support multiple acoustic modes. This complicates the reverse problem, but on the other hand, makes it possible to extract more materials properties. Several mechanical properties of a layer-substrate system, consisting of a 110 μm thick heteroepitaxial chemical vapor deposited diamond layer on Ir/YSZ (yttria-stabilized zirconia)/Si(001), were evaluated, based on two surface acoustic modes. A dispersive and a nondispersive mode measured in two different crystallographic directions were employed to evaluate the three elastic stiffness coefficients C11, C12, C44, and the mass density of the diamond layer. It is demonstrated that accurate elastic moduli can be determined without special sample preparation, employing the layered system as obtained from the heteroepitaxial diamond growth process.
Event recognition using signal spectrograms in long pulse experiments
Authors: González J. , Ruiz M. , Vega J. , Barrera E. , Arcas G. , López J. M.
Published: October 2010

As discharge duration increases, real-time complex analysis of the signal becomes more important. In this context, data acquisition and processing systems must provide models for designing experiments which use event oriented plasma control. One example of advanced data analysis is signal classification. The off-line statistical analysis of a large number of discharges provides information to develop algorithms for the determination of the plasma parameters from measurements of magnetohydrodinamic waves, for example, to detect density fluctuations induced by the Alfvén cascades using morphological patterns. The need to apply different algorithms to the signals and to address different processing algorithms using the previous results necessitates the use of an event-based experiment. The Intelligent Test and Measurement System platform is an example of architecture designed to implement distributed data acquisition and real-time processing systems. The processing algorithm sequence is modeled using an event-based paradigm. The adaptive capacity of this model is based on the logic defined by the use of state machines in SCXML. The Intelligent Test and Measurement System platform mixes a local multiprocessing model with a distributed deployment of services based on Jini.
Development of KSTAR Thomson scattering system
Authors: Lee J. H. , Oh S. T. , Wi H. M.
Published: October 2010

To measure the electron temperature (Te) and electron density (ne) profiles in the Korean Superconducting Tokamak Advanced Research (KSTAR) device for the KSTAR third campaign (September 2010), we designed and installed a Thomson scattering system. The KSTAR Thomson scattering system is designed as a tangential Thomson scattering system and utilizes the N-, L-, and B-ports. The N-port is designed for the collection optics with a cassette system, the L-port is the laser input port, and the B-port is the location of the beam dump. In this paper, we will describe the final design of the KSTAR Thomson scattering system.
Vacuum ultraviolet impurity spectroscopy on the Alcator C-Mod tokamak
Authors: Reinke M. L. , Beiersdorfer P. , Howard N. T. , Magee E. W. , Podpaly Y. , Rice J. E. , Terry J. L.
Published: October 2010

Vacuum ultraviolet spectroscopy is used on the Alcator C-Mod tokamak to study the physics of impurity transport and provide feedback on impurity levels to assist experimental operations. Sputtering from C-Mod’s all metal (Mo+W) plasma facing components and ion cyclotron range of frequency antenna and vessel structures (sources for Ti, Fe, Cu, and Ni), the use of boronization for plasma surface conditioning and Ar, Ne, or N2 gas seeding combine to provide a wealth of spectroscopic data from low-Z to high-Z. Recently, a laser blow-off impurity injector has been added, employing CaF2 to study core and edge impurity transport. One of the primary tools used to monitor the impurities is a 2.2 m Rowland circle spectrometer utilizing a Reticon array fiber coupled to a microchannel plate. With a 600 lines/mm grating the 80<λ<1050 Å range can be scanned, although only 40–100 Å can be observed for a single discharge. Recently, a flat-field grating spectrometer was installed which utilizes a varied line spacing grating to image the spectrum to a soft x-ray sensitive Princeton Instruments charge-coupled device camera. Using a 2400 lines/mm grating, the 10<λ<70 Å range can be scanned with 5–6 nm observed for a single discharge. A variety of results from recent experiments are shown that highlight the capability to track a wide range of impurities.
Ab initio calculations of optical absorption spectra: Solution of the Bethe–Salpeter equation within density matrix perturbation theory
Authors: Rocca Dario , Lu Deyu , Galli Giulia
Published: October 2010

We describe an ab initio approach to compute the optical absorption spectra of molecules and solids, which is suitable for the study of large systems and gives access to spectra within a wide energy range. In this approach, the quantum Liouville equation is solved iteratively within first order perturbation theory, with a Hamiltonian containing a static self-energy operator. This procedure is equivalent to solving the statically screened Bethe–Salpeter equation. Explicit calculations of single particle excited states and inversion of dielectric matrices are avoided using techniques based on density functional perturbation theory. In this way, full absorption spectra may be obtained with a computational workload comparable to ground state Hartree–Fock calculations. We present results for small molecules, for the spectra of a 1 nm Si cluster in a wide energy range (20 eV), and for a dipeptide exhibiting charge transfer excitations.
DNA capture into a nanopore: Interplay of diffusion and electrohydrodynamics
Authors: Grosberg Alexander Y. , Rabin Yitzhak
Published: October 2010

We present a detailed analysis of the process of voltage driven capture of DNA molecules by nanopores. We show that ionic current generates a nonuniform electric field that acts on both the DNA and on its counterions and that the response of DNA to the electric field is affected by its electroosmotic coupling to the mobile counterions. We calculate the voltage and molecular mass dependence of the radius of capture and of the capture rate in the diffusion limited regime. We argue that electroosmotic flow through the DNA coil is suppressed in the vicinity of the pore and present a tentative estimate of the capture rate in the barrier limited regime.
The ITER core imaging x-ray spectrometer: X-ray calorimeter performance
Authors: Beiersdorfer P. , Brown G. V. , Clementson J. , Dunn J. , Morris K. , Wang E. , Kelley R. L. , Kilbourne C. A. , Porter F. S. , Bitter M. , Feder R. , Hill K. W. , Johnson D. , Barnsley R.
Published: October 2010

We describe the anticipated performance of an x-ray microcalorimeter instrument on ITER. As part of the core imaging x-ray spectrometer, the instrument will augment the imaging crystal spectrometers by providing a survey of the concentration of heavy ion plasma impurities in the core and possibly ion temperature values from the emission lines of different elemental ions located at various radial positions.
Molecular quantum control landscapes in von Neumann time-frequency phase space
Authors: Ruetzel Stefan , Stolzenberger Christoph , Fechner Susanne , Dimler Frank , Brixner Tobias , Tannor David J.
Published: October 2010

Recently we introduced the von Neumann representation as a joint time-frequency description for femtosecond laser pulses and suggested its use as a basis for pulse shaping experiments. Here we use the von Neumann basis to represent multidimensional molecular control landscapes, providing insight into the molecular dynamics. We present three kinds of time-frequency phase space scanning procedures based on the von Neumann formalism: variation of intensity, time-frequency phase space position, and/or the relative phase of single subpulses. The shaped pulses produced are characterized via Fourier-transform spectral interferometry. Quantum control is demonstrated on the laser dye IR140 elucidating a time-frequency pump-dump mechanism.
Design of a new high repetition rate Nd:YAG Thomson scattering system for Heliotron J
Authors: Minami Takashi , Kobayashi Shinji , Mizuuchi Touru , Yashiro Hiroaki , Takeuchi Masaki , Ohshima Shinsuke , Yamamoto Satoshi , Okada Hiroyuki , Nagasaki Kazunobu , Nakamura Yuji , Hanatani Kiyoshi , Konoshima Shigeru , Sano Fumimichi
Published: October 2010

A new high repetition rate Nd:YAG Thomson scattering system has been designed for the Heliotron J helical device. The main purpose of installing the new Thomson scattering system is an investigation of an improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma. The system has 25 spatial points with ∼10 mm resolution. Two high repetition Nd:YAG lasers (>550 mJ at 50 Hz) realize the measurement of the time evolution of the plasma profile with 10 ms time interval. Scattered light is collected with a large concave mirror (D=800 mm, f/2.25) with a solid angle of ∼100 msr. The laser beam is injected from obliquely downward to upward, and obliquely backscattered light is detected (scattering angle is 20°). Model simulation of the polychromator shows the measurable electron temperature and density range are from10 eV to 10 keV, >5×1018 m−3 within 3% error for the temperature measurement, respectively.
First results of the resistive bolometers on KSTAR
Authors: Seo Dongcheol , Peterson B. J. , Lee Seung Hun
Published: October 2010

The resistive bolometers have been successfully installed in the midplane of L-port in Korea Superconducting Tokamak Advanced Research (KSTAR) device. The spatial and temporal resolutions, 4.5 cm and ∼1 kHz, respectively, enable us to measure the radial profile of the total radiated power from magnetically confined plasma at a high temperature through radiation and neutral particles. The radiated power was measured at all shots. Even at low plasma current, the bolometer signal was detectable. The electron cyclotron resonance heating (ECH) has been used in tokamak for ECH assisted start-up and plasma control by local heating and current drive. The detectors of resistive bolometer, near the antenna of ECH, are affected by electron cyclotron wave. The tomographic reconstruction, using the Phillips–Tikhonov regularization method, will be carried out for a major radial profile of the radiation emissivity of the circular cross-section plasma.
Scanning tunneling microscopy/spectroscopy study of atomic and electronic structures of In2O on InAs and In0.53Ga0.47As(001)-(4×2) surfaces
Authors: Shen Jian , Chagarov Evgueni A. , Feldwinn Darby L. , Melitz Wilhelm , Santagata Nancy M. , Kummel Andrew C. , Droopad Ravi , Passlack Matthias
Published: October 2010

Interfacial bonding geometry and electronic structures of In2O on InAs and In0.53Ga0.47As(001)-(4×2) have been investigated by scanning tunneling microscopy/scanning tunneling spectroscopy (STM/STS). STM images show that the In2O forms an ordered monolayer on both InAs and InGaAs surfaces. In2O deposition on the InAs(001)-(4×2) surface does not displace any surface atoms during both room temperature deposition and postdeposition annealing. Oxygen atoms from In2O molecules bond with trough In/Ga atoms on the surface to form a new layer of O–In/Ga bonds, which restore many of the strained trough In/Ga atoms into more bulklike tetrahedral sp3 bonding environments. STS reveals that for both p-type and n-type clean In0.53Ga0.47As(001)-(4×2) surfaces, the Fermi level resides near the valence band maximum (VBM); however, after In2O deposition and postdeposition annealings, the Fermi level position is close to the VBM for p-type samples and close to the conduction band minimum for n-type samples. This result indicates that In2O bonding eliminates surface states within the bandgap and forms an unpinned interface when bonding with In0.53Ga0.47As/InP(001)-(4×2). Density function theory is used to confirm the experimental finding.
Spin-state splittings, highest-occupied-molecular-orbital and lowest-unoccupied-molecular-orbital energies, and chemical hardness
Authors: Johnson Erin R. , Yang Weitao , Davidson Ernest R.
Published: October 2010

It is known that the exact density functional must give ground-state energies that are piecewise linear as a function of electron number. In this work we prove that this is also true for the lowest-energy excited states of different spin or spatial symmetry. This has three important consequences for chemical applications: the ground state of a molecule must correspond to the state with the maximum highest-occupied-molecular-orbital energy, minimum lowest-unoccupied-molecular-orbital energy, and maximum chemical hardness. The beryllium, carbon, and vanadium atoms, as well as the CH2 and C3H3 molecules are considered as illustrative examples. Our result also directly and rigorously connects the ionization potential and electron affinity to the stability of spin states.
Artificial magnetotactic motion control of Tetrahymena pyriformis using ferromagnetic nanoparticles: A tool for fabrication of microbiorobots
Authors: Kim Dal Hyung , Cheang U. Kei , Kőhidai László , Byun Doyoung , Kim Min Jun
Published: October 2010

We induce artificial magnetotaxis in Tetrahymena pyriformis, a eukaryotic ciliate, using ferro-magnetic nanoparticles and an external time-varying magnetic field. Magnetizing internalized iron oxide particles (magnetite), allows control of the swimming direction of an individual cell using two sets of electromagnets. Real-time feedback control was performed with a vision tracking system, which demonstrated controllability of a single cell. Since the endogenous motility of the cell is combined in one system with artificial magnetotaxis, the motion of artificially magnetotactic T. pyriformis is finely controllable. Thus, artificially magnetotactic T. pyriformis is a promising candidate microrobot for microassembly and transport in microfluidic environments.
Conformational and rheological properties of semiflexible polymers in shear flow
Authors: Winkler Roland G.
Published: October 2010

A theoretical description is provided for the nonequilibrium conformational and dynamical properties of a polymer in shear flow. Using a mean-field semiflexible chain model, which accounts for hydrodynamic interactions within the preaveraging approximation, analytical expressions are derived for the dependence of the deformation, orientation, and relaxation times on polymer persistence length and shear rate. Moreover, the rheological properties of a dilute polymer solution are discussed. The model yields shear thinning at large Weissenberg numbers. The analytical results are compared with fluorescence microscopy measurements of individual DNA molecules, which yield qualitative and partial quantitative agreement.
Green tensors for Debye–Büche–Brinkman equations generalized for axisymmetric medium
Authors: Cichocki Bogdan , Ekiel-Jeżewska Maria L.
Published: October 2010

A fluid flow through a nonisotropic porous medium with an axial symmetry is considered. The Green tensors for the corresponding nonisotropic Debye–Büche–Brinkman equations are calculated in terms of single integrals. Short-distance and far-field limiting behavior is discussed. The exact solution for the Green tensors is found explicitly in the limiting case of an infinite shielding length along the symmetry axis of the system.
Microstructural, optical, and electrical characterization of semipolar (112¯2) gallium nitride grown by epitaxial lateral overgrowth
Authors: Zhu Tongtong , Johnston Carol F. , Kappers Menno J. , Oliver Rachel A.
Published: October 2010

Semipolar (112¯2) gallium nitride (GaN) films have been grown on m-plane (11¯00) sapphire by epitaxial lateral overgrowth. Transmission electron microscopy (TEM) studies show that the inclination of the [0001] axis at 32° from the film surface combined with the high [0001] growth rate under the reactor conditions used, allowed a low defect density (LDD) wing growing along [0001] to partially overgrow the highly defective window region and the other wing, resulting in a coalescence boundary, at which stacking faults and dislocations appear to terminate. Low temperature cathodoluminescence (CL) was performed to correlate the optical properties with the different stages of the growth process. It is found that emission from the LDD wing is dominated by near band edge recombination, whereas an emission band at 3.42 eV related to basal plane stacking faults and a broad band from 3.15–3.38 eV possibly related to emission from prismatic stacking faults and partial dislocations were observed in the window region. Scanning capacitance microscopy (SCM) studies showed that almost the entire film is unintentionally n-doped. By correlating the spatial variation in the unintentional doping to the overgrowth process, different impurity incorporation rates between the (112¯2) and (0001) facets have been observed. Dislocations of a or a+c type were found to bend over toward the growth direction in the LDD wing by TEM appear to be nonradiative by cross-sectional CL and SCM studies have revealed that they also impact the local electrical properties.
Model for localized buildup and thinning of metal due to electromigration
Authors: Flinn P. A. , Doan J. C.
Published: October 2010

We present a model to account for the highly localized buildup and thinning of metal that has been observed during electromigration testing. It assumes variations in mobility along the line, rather than complete blockage. Using reasonable estimates for the parameters needed, it is possible to obtain a quantitative fit to previously observed data.
A study of J-coupling spectroscopy using the Earth’s field nuclear magnetic resonance inside a laboratory
Authors: Liao Shu-Hsien , Chen Ming-Jye , Yang Hong-Chang , Lee Shin-Yi , Chen Hsin-Hsien , Horng Herng-Er , Yang Shieh-Yueh
Published: October 2010

In this paper, an instrumentation of the Earth’s field nuclear magnetic resonance (EFNMR) inside a laboratory is presented. A lock-in analysis (LIA) technique was proposed to enhance the signal-to-noise ratio (SNR). A SNR of 137.8 was achieved in a single measurement for 9 ml tap water, and the LIA technique significantly enhanced the SNR to 188 after a 10-average in a noisy laboratory environment. The proton-phosphorus coupling in trimethyl phosphate ((CH3O)3PO) with J-coupling J[H,F]=(10.99±0.013) Hz has been demonstrated. The LIA technique improves the SNR, and a 2.6-fold improvement in SNR over that of the frequency-adjusted averaging is achieved. To reduce the noise in EFNMR, it was suggested that the LIA technique and the first order gradient shim be used to achieve a subhertz linewidth.
Haptic controlled three-axis MEMS gripper system
Authors: Vijayasai Ashwin P. , Sivakumar Ganapathy , Mulsow Matthew , Lacouture Shelby , Holness Alex , Dallas Tim E.
Published: October 2010

In this work, we describe the development and testing of a three degree of freedom meso/micromanipulation system for handling micro-objects, including biological cells and microbeads. Three-axis control is obtained using stepper motors coupled to micromanipulators. The test specimen is placed on a linear X-stage, which is coupled to one stepper motor. The remaining two stepper motors are coupled to the Y and Z axes of a micromanipulator. The stepper motor-micromanipulator arrangement in the Y and Z axes has a minimum step resolution of ∼0.4 μm with a total travel of 12 mm and the stepper motor-X stage arrangement has a minimum resolution of ∼0.3 μm with a total travel of 10 mm. Mechanical backlash error is ∼0.8 μm for ∼750 μm of travel. A MEMS microgripper from Femtotools™ acts as an end-effector in the shaft end of the micromanipulator. The gripping ranges of the grippers used are 0–100 μm (for FT-G100) and 0–60 μm (for FT-G60). As the gripping action is performed, the force sense circuit of FT-G100 measures the handling force. This force feedback is integrated to a commercially available three degree of freedom haptic device (Novint Falcon) allowing the user to receive tactile feedback during the microscale handling. Both mesoscale and microscale controls are important, as mesoscale control is required for the travel motion of the test object whereas microscale control is required for the gripping action. The haptic device is used to control the position of the microgripper, control the actuation of the microgripper, and provide force feedback. A LABVIEW program was developed to interlink communication and control among hardware used in the system. Micro-objects such as SF-9 cells and polystyrene beads (∼45 μm) are handled and handling forces of ∼50 μN were experienced.
Pulsed magnetic field excitation sensitivity of match-type electric blasting caps
Authors: Parson Jonathan , Dickens James , Walter John , Neuber Andreas A.
Published: October 2010

This paper presents a study on energy deposition and electromagnetic compatibility of match-type electroexplosive devices (EEDs), which recently have found more usage in pulsed power environments with high electromagnetic interference (EMI) background. The sensitivity of these devices makes them dangerous to intended and unintended radiation produced by devices commonly used in pulsed power environments. Match-type EEDs have been found to be susceptible to such low levels of energy (7–8 mJ) that safe operation of these EEDs is vital when in use near devices that produce high levels of pulsed EMI. The scope of this paper is to provide an investigation that incorporates results of similar studies to provide detonation characteristics of these EEDs. The three topics included in this study are sensitivity testing, modeling of the thermodynamic heat propagation, and electromagnetic compatibility from pulsed electromagnetic radiation. The thermodynamic joule heating of the primary explosive has been modeled by a solution to the 1D heat equation. A simple pulsed generator, Marx generator with an inductive load, was used for the electromagnetic compatibility assessment of the coupled field between the pulse generator and shorted EED. The results of the electromagnetic compatibility assessment relate the resistive, inductive, and capacitive components of the pulse generator to the area of the shorted EED.
Grain size and strain effects on the optical and electrical properties of hafnium oxide nanocrystalline thin films
Authors: Kamala Bharathi K. , Kalidindi N. R. , Ramana C. V.
Published: October 2010

Nanocrystalline hafnium oxide (HfO2) thin films with an average crystal size ∼5–50 nm have been produced under controlled temperature and pressure and their structural, optical and electrical properties have been evaluated. Structural investigations indicate that the monoclinic HfO2 nanocrystals are highly oriented along the (1¯11) direction. The lattice expansion increases with a reduction in size while minimum strain energy occurs at maximum lattice expansion. The strain factor increases linearly from 2.4% to 4% with increasing HfO2 crystal dimensions from 10 to 40 nm. The optical absorption measurements indicate that the band gap (Eg) changes are not very significant with size reduction. The interband absorption corresponding to O 2p→Hf 5d transitions dominate the optical absorption edge at E∼6.25 eV; Eg varied in the range 5.42–5.60 eV for a variation in crystal dimension in the range 10–40 nm. Room temperature electrical conductivity increases from 1.08×10−3 to 1.7×10−3 (Ω cm)−1 with increasing size from 10 to 40 nm. The frequency dispersion of the electrical resistivity reveals the hopping conduction mechanism. The functional relationship derived between geometric and electronic structure for HfO2 suggest that tuning properties for desired applications can be achieved by controlling the grain size and, hence, the strain at the nanoscale dimensions.

At the request of the authors, this article is being retracted effective 31 May 2011.
Time-dependent scattering theory for charged Dirac fields on a Reissner–Nordström black hole
Authors: Thierry Daudé
Published: October 2010

In this paper, we prove a complete time-dependent scattering theory for charged (massive or not) Dirac fields outside a Reissner–Nordström black hole. We shall take the point of view of observers static at infinity, well described by the Schwarzschild system of coordinates. For such observers, the exterior of a Reissner–Nordström black hole is a smooth manifold having two distinct asymptotic regions: the horizon and spacelike infinity. We first simplify the later analysis using the spherical symmetry of the Reissner–Nordström black hole and we reduce the initial 3+1 dimensional evolution equation of hyperbolic type into a 1+1 dimensional one. Then, we establish various propagation estimates for such fields in the same spirit as in the works by Dereziński and Gérard [Scattering Theory of Classical and Quantum N-Particle Systems (Springer-Verlag, Berlin, 1997)]. We construct the asymptotic velocity operators P± and we show that their spectra are equal to σ(P+)={−1}∪[0,1] and σ(P−)=[−1,0]∪{1}. This information points out the very distinct behaviors of Dirac fields near the two asymptotic regions of the black hole. As a consequence of this construction, we prove the existence and asymptotic completeness of (Dollard modified at infinity) wave operators.
Relativistic expansion of electron-positron-photon plasma droplets and photon emission
Authors: Yaresko R. , Mustafa Munshi G. , Kämpfer B.
Published: October 2010

The expansion dynamics of hot electron-positron-photon plasma droplets is dealt with within relativistic hydrodynamics. Such droplets, envisaged to be created in future experiments by irradiating thin foils with counterpropagating ultraintense laser beams, are sources of flashes of gamma radiation. Warm electron-positron plasma droplets may be identified and characterized by a broadened 511 keV line.
Photoluminescence of Frank-type defects on the basal plane in 4H–SiC epilayers
Authors: Kamata Isaho , Zhang Xuan , Tsuchida Hidekazu
Published: October 2010

Frank-type defects on the basal plane in thick 4H–SiC epitaxial layers have been characterized by photoluminescence (PL) spectroscopy and a PL imaging microscopy. The PL emission wavelength of the three kinds of Frank-type defects were determined at ∼424, 457, and 488 nm at room temperature, respectively. The high-resolution PL imaging of the defects was obtained, and the PL emission at the Frank partial dislocations was confirmed in the near infrared region (>700 nm). Correspondence between the optical properties and the microscopic structures of the defects was clarified.
Interacting and noninteracting dipole systems in ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer
Authors: Martin Bjoern , Kuehn Markus , Kliem Herbert
Published: October 2010

Ultrathin films of poly(vinylidene fluoride-trifluoroethylene) copolymers are prepared by a Langmuir–Blodgett technique. These films show ferroelectric properties like hysteresis loops of the polarization and butterfly curves of the ac capacitance versus the applied field. Small signal measurements exhibit a power law of the dielectric permittivity in the frequency domain as well as a power law for the depolarization current in the time domain, respectively. This behavior can be explained by a distribution of relaxation times in the dipole system. From these measurements alone it cannot clearly be distinguished whether this distribution results from the interaction between the dipoles or if the dipoles relax independently from each other with individual relaxation times. To this aim the field reversal experiment which is sensitive to the coupling of dipole systems is introduced. As final result we get that the small signal nonswitching relaxational response resulting in the dielectric permittivity is coupled to the large signal ferroelectric behavior resulting in the hysteresis loops.
Thermal effects on spin-torque-driven switching in high-tunneling-magnetoresistance magnetic tunnel junctions
Authors: Aurélio D. , Torres L. , Finocchio G.
Published: October 2010

This paper presents a micromagnetic study of the spin-transfer torque induced, thermally assisted switching, in magnetic tunnel junctions. Having performed numerous repeated simulations, we confirm that temperature fluctuations facilitate reversal processes. In particular, different averaging procedures were employed in order to separate pure thermal effects from other contributions. The results indicate that the finite temperature introduces well-defined pre and postswitching oscillation modes and thus, the “incubation delay” is not observed for the simulated device. Detailed analysis of the preswitching oscillations, for both the antiparallel to parallel and parallel to antiparallel transitions, reveals that the oscillations in the center of the sample are the dominating mode. The excitation of these central modes is the main mechanism leading to earlier switching, especially at current densities below the critical ones computed at T=0 K.
Analysis of plasma instabilities and verification of the BOUT code for the Large Plasma Device
Authors: Popovich P. , Umansky M. V. , Carter T. A. , Friedman B.
Published: October 2010

The properties of linear instabilities in the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] are studied both through analytic calculations and solving numerically a system of linearized collisional plasma fluid equations using the three-dimensional fluid code BOUT [M. Umansky et al., Contrib. Plasma Phys. 180, 887 (2009)], which has been successfully modified to treat cylindrical geometry. Instability drive from plasma pressure gradients and flows is considered, focusing on resistive drift waves and the Kelvin–Helmholtz and rotational interchange instabilities. A general linear dispersion relation for partially ionized collisional plasmas including these modes is derived and analyzed. For Large Plasma Device relevant profiles including strongly driven flows, it is found that all three modes can have comparable growth rates and frequencies. Detailed comparison with solutions of the analytic dispersion relation demonstrates that BOUT accurately reproduces all characteristics of linear modes in this system.