Scanning Hall probe microscopy of a diluted magnetic semiconductor

NASA Astrophysics Data System (ADS)

Kweon, Seongsoo; Samarth, Nitin; de Lozanne, Alex

2009-05-01

We have measured the micromagnetic properties of a diluted magnetic semiconductor as a function of temperature and applied field with a scanning Hall probe microscope built in our laboratory. The design philosophy for this microscope and some details are described. The samples analyzed in this work are Ga0.94Mn0.06As films grown by molecular beam epitaxy. We find that the magnetic domains are 2-4 μm wide and fairly stable with temperature. Magnetic clusters are observed above TC, which we ascribe to MnAs defects too small and sparse to be detected by a superconducting quantum interference device magnetometer.

An interchangeable scanning Hall probe/scanning SQUID microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Chiu-Chun; Lin, Hui-Ting; Wu, Sing-Lin

2014-08-15

We have constructed a scanning probe microscope for magnetic imaging, which can function as a scanning Hall probe microscope (SHPM) and as a scanning SQUID microscope (SSM). The scanning scheme, applicable to SHPM and SSM, consists of a mechanical positioning (sub) micron-XY stage and a flexible direct contact to the sample without a feedback control system for the Z-axis. With the interchangeable capability of operating two distinct scanning modes, our microscope can incorporate the advantageous functionalities of the SHPM and SSM with large scan range up to millimeter, high spatial resolution (⩽4 μm), and high field sensitivity in a widemore » range of temperature (4.2 K-300 K) and magnetic field (10{sup −7} T-1 T). To demonstrate the capabilities of the system, we present magnetic images scanned with SHPM and SSM, including a RbFeB magnet and a nickel grid pattern at room temperature, surface magnetic domain structures of a La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin film at 77 K, and superconducting vortices in a striped niobium film at 4.2 K.« less

Hall-Effect Measurements Probing the Degree of Charge-Carrier Delocalization in Solution-Processed Crystalline Molecular Semiconductors

NASA Astrophysics Data System (ADS)

Chang, Jui-Fen; Sakanoue, Tomo; Olivier, Yoann; Uemura, Takafumi; Dufourg-Madec, Marie-Beatrice; Yeates, Stephen G.; Cornil, Jérôme; Takeya, Jun; Troisi, Alessandro; Sirringhaus, Henning

2011-08-01

Intramolecular structure and intermolecular packing in crystalline molecular semiconductors should have profound effects on the charge-carrier wave function, but simple drift mobility measurements are not very sensitive to this. Here we show that differences in the Hall resistance of two soluble pentacene derivatives can be explained with different degrees of carrier delocalization being limited by thermal lattice fluctuations. A combination of Hall measurements, optical spectroscopy, and theoretical simulations provides a powerful probe of structure-property relationships at a molecular level.

Assessment of bilayer silicene to probe as quantum spin and valley Hall effect

NASA Astrophysics Data System (ADS)

Rehman, Majeed Ur; Qiao, Zhenhua

2018-02-01

Silicene takes precedence over graphene due to its buckling type structure and strong spin orbit coupling. Motivated by these properties, we study the silicene bilayer in the presence of applied perpendicular electric field and intrinsic spin orbit coupling to probe as quantum spin/valley Hall effect. Using analytical approach, we calculate the spin Chern-number of bilayer silicene and then compare it with monolayer silicene. We reveal that bilayer silicene hosts double spin Chern-number as compared to single layer silicene and therefore accordingly has twice as many edge states in contrast to single layer silicene. In addition, we investigate the combined effect of intrinsic spin orbit coupling and the external electric field, we find that bilayer silicene, likewise single layer silicene, goes through a phase transitions from a quantum spin Hall state to a quantum valley Hall state when the strength of the applied electric field exceeds the intrinsic spin orbit coupling strength. We believe that the results and outcomes obtained for bilayer silicene are experimentally more accessible as compared to bilayer graphene, because of strong SO coupling in bilayer silicene.

Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA 300M Hall Thruster

NASA Technical Reports Server (NTRS)

Herman, Daniel A; Shastry, Rohit; Huang, Wensheng; Soulas, George C.; KamHawi, Hani

2012-01-01

In order to aid in the design of high-power Hall thrusters and provide experimental validation for existing modeling efforts, plasma potential and Langmuir probe measurements were performed in the near-field plume of the NASA 300M Hall thruster. A probe array consisting of a Faraday probe, Langmuir probe, and emissive probe was used to interrogate the plume from approximately 0.1 - 2.0 DT,m downstream of the thruster exit plane at four operating conditions: 300 V, 400 V, and 500 V at 20 kW as well as 300 V at 10 kW. Results show that the acceleration zone and high-temperature region were contained within 0.3 DT,m from the exit plane at all operating conditions. Isothermal lines were shown to strongly follow magnetic field lines in the nearfield, with maximum temperatures ranging from 19 - 27 eV. The electron temperature spatial distribution created large drops in measured floating potentials in front of the magnetic pole surfaces where the plasma density was small, which suggests strong sheaths at these surfaces. The data taken have provided valuable information for future design and modeling validation, and complements ongoing internal measurement efforts on the NASA 300 M.

Exploring 4D quantum Hall physics with a 2D topological charge pump

NASA Astrophysics Data System (ADS)

Lohse, Michael; Schweizer, Christian; Price, Hannah M.; Zilberberg, Oded; Bloch, Immanuel

2018-01-01

The discovery of topological states of matter has greatly improved our understanding of phase transitions in physical systems. Instead of being described by local order parameters, topological phases are described by global topological invariants and are therefore robust against perturbations. A prominent example is the two-dimensional (2D) integer quantum Hall effect: it is characterized by the first Chern number, which manifests in the quantized Hall response that is induced by an external electric field. Generalizing the quantum Hall effect to four-dimensional (4D) systems leads to the appearance of an additional quantized Hall response, but one that is nonlinear and described by a 4D topological invariant—the second Chern number. Here we report the observation of a bulk response with intrinsic 4D topology and demonstrate its quantization by measuring the associated second Chern number. By implementing a 2D topological charge pump using ultracold bosonic atoms in an angled optical superlattice, we realize a dynamical version of the 4D integer quantum Hall effect. Using a small cloud of atoms as a local probe, we fully characterize the nonlinear response of the system via in situ imaging and site-resolved band mapping. Our findings pave the way to experimentally probing higher-dimensional quantum Hall systems, in which additional strongly correlated topological phases, exotic collective excitations and boundary phenomena such as isolated Weyl fermions are predicted.

Exploring 4D quantum Hall physics with a 2D topological charge pump.

PubMed

Lohse, Michael; Schweizer, Christian; Price, Hannah M; Zilberberg, Oded; Bloch, Immanuel

2018-01-03

The discovery of topological states of matter has greatly improved our understanding of phase transitions in physical systems. Instead of being described by local order parameters, topological phases are described by global topological invariants and are therefore robust against perturbations. A prominent example is the two-dimensional (2D) integer quantum Hall effect: it is characterized by the first Chern number, which manifests in the quantized Hall response that is induced by an external electric field. Generalizing the quantum Hall effect to four-dimensional (4D) systems leads to the appearance of an additional quantized Hall response, but one that is nonlinear and described by a 4D topological invariant-the second Chern number. Here we report the observation of a bulk response with intrinsic 4D topology and demonstrate its quantization by measuring the associated second Chern number. By implementing a 2D topological charge pump using ultracold bosonic atoms in an angled optical superlattice, we realize a dynamical version of the 4D integer quantum Hall effect. Using a small cloud of atoms as a local probe, we fully characterize the nonlinear response of the system via in situ imaging and site-resolved band mapping. Our findings pave the way to experimentally probing higher-dimensional quantum Hall systems, in which additional strongly correlated topological phases, exotic collective excitations and boundary phenomena such as isolated Weyl fermions are predicted.

Plasma Perturbations in High-Speed Probing of Hall Thruster Discharge Chambers: Quantification and Mitigation

NASA Technical Reports Server (NTRS)

Jorns, Benjamin A.; Goebel, Dan M.; Hofer, Richard R.

2015-01-01

An experimental investigation is presented to quantify the effect of high-speed probing on the plasma parameters inside the discharge chamber of a 6-kW Hall thruster. Understanding the nature of these perturbations is of significant interest given the importance of accurate plasma measurements for characterizing thruster operation. An array of diagnostics including a high-speed camera and embedded wall probes is employed to examine in real time the changes in electron temperature and plasma potential induced by inserting a high-speed reciprocating Langmuir probe into the discharge chamber. It is found that the perturbations onset when the scanning probe is downstream of the electron temperature peak, and that along channel centerline, the perturbations are best characterized as a downstream shift of plasma parameters by 15-20% the length of the discharge chamber. A parametric study is performed to investigate techniques to mitigate the observed probe perturbations including varying probe speed, probe location, and operating conditions. It is found that the perturbations largely disappear when the thruster is operated at low power and low discharge voltage. The results of this mitigation study are discussed in the context of recommended methods for generating unperturbed measurements of the discharge chamber plasma.

A Preliminary Investigation of Hall Thruster Technology

NASA Technical Reports Server (NTRS)

Gallimore, Alec D.

1997-01-01

A three-year, NASA/BMDO-sponsored experimental program to conduct performance and plume plasma property measurements on two Russian Stationary Plasma Thrusters (SPTs) has been completed. The program utilized experimental facilitates at the University of Michigan's Plasmadynamics and Electric Propulsion Laboratory (PEPL). The main features of the proposed effort were as follows: We Characterized Hall thruster [and arcjet] performance by measuring ion exhaust velocity with probes at various thruster conditions. Used a variety of probe diagnostics in the thruster plume to measure plasma properties and flow properties including T(sub e) and n(sub e), ion current density and ion energy distribution, and electric fields by mapping plasma potential. Used emission spectroscopy to identify species within the plume and to measure electron temperatures.

What do you measure when you measure the Hall effect?

NASA Astrophysics Data System (ADS)

Koon, D. W.; Knickerbocker, C. J.

1993-02-01

A formalism for calculating the sensitivity of Hall measurements to local inhomogeneities of the sample material or the magnetic field is developed. This Hall weighting function g(x,y) is calculated for various placements of current and voltage probes on square and circular laminar samples. Unlike the resistivity weighting function, it is nonnegative throughout the entire sample, provided all probes lie at the edge of the sample. Singularities arise in the Hall weighting function near the current and voltage probes except in the case where these probes are located at the corners of a square. Implications of the results for cross, clover, and bridge samples, and the implications of our results for metal-insulator transition and quantum Hall studies are discussed.

Plume Characteristics of the BHT-HD-600 Hall Thruster (Preprint)

DTIC Science & Technology

2006-07-01

Hall thruster on spacecraft, a number of plume properties have been measured. These include current density using a Faraday probe, ion energy distribution using a retarding potential analyzer, and ion species fractions using an E x B probe. The BHT-HD-600 Hall thruster is a nominally 600 W xenon Hall thruster developed by Busek Co. Inc. for the U.S. Air Force Research Laboratory. Plume characterization of Hall thrusters is required to fully understand the impacts of thruster operation on spacecraft. Much of these plume data are

Optimum Design Rules for CMOS Hall Sensors

PubMed Central

Crescentini, Marco; Biondi, Michele; Romani, Aldo; Tartagni, Marco; Sangiorgi, Enrico

2017-01-01

This manuscript analyzes the effects of design parameters, such as aspect ratio, doping concentration and bias, on the performance of a general CMOS Hall sensor, with insight on current-related sensitivity, power consumption, and bandwidth. The article focuses on rectangular-shaped Hall probes since this is the most general geometry leading to shape-independent results. The devices are analyzed by means of 3D-TCAD simulations embedding galvanomagnetic transport model, which takes into account the Lorentz force acting on carriers due to a magnetic field. Simulation results define a set of trade-offs and design rules that can be used by electronic designers to conceive their own Hall probes. PMID:28375191

Optimum Design Rules for CMOS Hall Sensors.

PubMed

Crescentini, Marco; Biondi, Michele; Romani, Aldo; Tartagni, Marco; Sangiorgi, Enrico

2017-04-04

This manuscript analyzes the effects of design parameters, such as aspect ratio, doping concentration and bias, on the performance of a general CMOS Hall sensor, with insight on current-related sensitivity, power consumption, and bandwidth. The article focuses on rectangular-shaped Hall probes since this is the most general geometry leading to shape-independent results. The devices are analyzed by means of 3D-TCAD simulations embedding galvanomagnetic transport model, which takes into account the Lorentz force acting on carriers due to a magnetic field. Simulation results define a set of trade-offs and design rules that can be used by electronic designers to conceive their own Hall probes.

Imaging ac losses in superconducting films via scanning Hall probe microscopy

NASA Astrophysics Data System (ADS)

Dinner, Rafael B.; Moler, Kathryn A.; Feldmann, D. Matthew; Beasley, M. R.

2007-04-01

Various local probes have been applied to understanding current flow through superconducting films, which are often surprisingly inhomogeneous. Here, we show that magnetic imaging allows quantitative reconstruction of both current density J and electric field E resolved in time and space in a film carrying subcritical ac current. Current reconstruction entails inversion of the Biot-Savart law, while electric fields are reconstructed using Faraday’s law. We describe the corresponding numerical procedures, largely adapting existing work to the case of a strip carrying ac current, but including other methods of obtaining the complete electric field from the inductive portion determined by Faraday’s law. We also delineate the physical requirements behind the mathematical transformations. We then apply the procedures to images of a strip of YBa2Cu3O7-δ carrying an ac current at 400Hz . Our scanning Hall probe microscope produces a time series of magnetic images of the strip with 1μm spatial resolution and 25μs time resolution. Combining the reconstructed J and E , we obtain a complete characterization including local critical current density, E-J curves, and power losses. This analysis has a range of applications from fundamental studies of vortex dynamics to practical coated conductor development.

Remote Diagnostic Measurements of Hall Thruster Plumes

DTIC Science & Technology

2009-08-14

This paper describes measurements of Hall thruster plumes that characterize ion energy distributions and charge state fractions using remotely...charge state. Next, energy and charge state measurements are described from testing of a 200 W Hall thruster at AFIT. Measurements showed variation in...position. Finally, ExB probe charge state measurements are presented from a 6-kW laboratory Hall thruster operated at low discharge voltage levels at AFRL

Characterizing the performance of eddy current probes using photoinductive field-mapping

NASA Astrophysics Data System (ADS)

Moulder, John C.; Nakagawa, Norio

1992-12-01

We present a new method for characterizing the performance of eddy current probes by mapping their electromagnetic fields. The technique is based on the photoinductive effect, the change in the impedance of an eddy current probe induced by laser heating of the material under the probe. The instrument we developed maps a probe's electric field distribution by scanning an infrared laser beam over a thin film of gold lying underneath the probe. Measurements of both photoinductive signals and flaw signals for a series of similar probes demonstrates that the impedance change caused by an electrical-discharge-machined notch or a fatigue crack is proportional to the strength of the photoinductive signal. Thus, photoinductive measurements can supplant the use of artifact standards to calibrate eddy current probes.

Real-space imaging of fractional quantum Hall liquids

NASA Astrophysics Data System (ADS)

Hayakawa, Junichiro; Muraki, Koji; Yusa, Go

2013-01-01

Electrons in semiconductors usually behave like a gas--as independent particles. However, when confined to two dimensions under a perpendicular magnetic field at low temperatures, they condense into an incompressible quantum liquid. This phenomenon, known as the fractional quantum Hall (FQH) effect, is a quantum-mechanical manifestation of the macroscopic behaviour of correlated electrons that arises when the Landau-level filling factor is a rational fraction. However, the diverse microscopic interactions responsible for its emergence have been hidden by its universality and macroscopic nature. Here, we report real-space imaging of FQH liquids, achieved with polarization-sensitive scanning optical microscopy using trions (charged excitons) as a local probe for electron spin polarization. When the FQH ground state is spin-polarized, the triplet/singlet intensity map exhibits a spatial pattern that mirrors the intrinsic disorder potential, which is interpreted as a mapping of compressible and incompressible electron liquids. In contrast, when FQH ground states with different spin polarization coexist, domain structures with spontaneous quasi-long-range order emerge, which can be reproduced remarkably well from the disorder patterns using a two-dimensional random-field Ising model. Our results constitute the first reported real-space observation of quantum liquids in a class of broken symmetry state known as the quantum Hall ferromagnet.

Probing the thermal Hall effect using miniature capacitive strontium titanate thermometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tinsman, Colin; Li, Gang; Asaba, Tomoya

2016-06-27

The thermal Hall effect is the thermal analog of the electrical Hall effect. Rarely observed in normal metals, thermal Hall signals have been argued to be a key property for a number of strongly correlated materials, such as high temperature superconductors, correlated topological insulators, and quantum magnets. The observation of the thermal Hall effect requires precise measurement of temperature in intense magnetic fields. Particularly at low temperature, resistive thermometers have a strong dependence on field, which makes them unsuitable for this purpose. We have created capacitive thermometers which instead measure the dielectric constant of strontium titanate (SrTiO{sub 3}). SrTiO{sub 3}more » approaches a ferroelectric transition, causing its dielectric constant to increase by a few orders of magnitude at low temperature. As a result, these thermometers are very sensitive at low temperature while having very little dependence on the applied magnetic field, making them ideal for thermal Hall measurements. We demonstrate this method by making measurements of the thermal Hall effect in Bismuth in magnetic fields of up to 10 T.« less

Langmuir Probe Measurements Within the Discharge Channel of the 20-kW NASA-300M and NASA-300MS Hall Thrusters

NASA Technical Reports Server (NTRS)

Shastry, Rohit; Huang, Wensheng; Haag, Thomas W.; Kamhawi, Hani

2013-01-01

NASA is presently developing a high-power, high-efficiency, long-lifetime Hall thruster for the Solar Electric Propulsion Technology Demonstration Mission. In support of this task, studies have been performed on the 20-kW NASA-300M Hall thruster to aid in the overall design process. The ability to incorporate magnetic shielding into a high-power Hall thruster was also investigated with the NASA- 300MS, a modified version of the NASA-300M. The inclusion of magnetic shielding would allow the thruster to push existing state-of-the-art technology in regards to service lifetime, one of the goals of the Technology Demonstration Mission. Langmuir probe measurements were taken within the discharge channels of both thrusters in order to characterize differences at higher power levels, as well as validate ongoing modeling efforts using the axisymmetric code Hall2De. Flush-mounted Langmuir probes were also used within the channel of the NASA-300MS to verify that magnetic shielding was successfully applied. Measurements taken from 300 V, 10 kW to 600 V, 20 kW have shown plasma potentials near anode potential and electron temperatures of 4 to 12 eV at the walls near the thruster exit plane of the NASA-300MS, verifying magnetic shielding and validating the design process at this power level. Channel centerline measurements on the NASA-300M from 300 V, 10 kW to 500 V, 20 kW show the electron temperature peak at approximately 0.1 to 0.2 channel lengths upstream of the exit plane, with magnitudes increasing with discharge voltage. The acceleration profiles appear to be centered about the exit plane with a width of approximately 0.3 to 0.4 channel lengths. Channel centerline measurements on the NASA-300MS were found to be more challenging due to additional probe heating. Ionization and acceleration zones appeared to move downstream on the NASA-300MS compared to the NASA-300M, as expected based on the shift in peak radial magnetic field. Additional measurements or alternative

Note: Fiber optic transport probe for Hall measurements under light and magnetic field at low temperatures: Case study of a two dimensional electron gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhadauria, P. P. S.; Gupta, Anurag; Kumar, Pramod

2015-05-15

A fiber optic based probe is designed and developed for electrical transport measurements in presence of quasi-monochromatic (360–800 nm) light, varying temperature (T = 1.8–300 K), and magnetic field (B = 0–7 T). The probe is tested for the resistivity and Hall measurements performed on a LaAlO{sub 3}–SrTiO{sub 3} heterointerface system with a conducting two dimensional electron gas.

Plasma Properties in the Plume of a Hall Thruster Cluster

DTIC Science & Technology

2003-06-04

The Hall thruster cluster is an attractive propulsion approach for spacecraft requiring very high-power electric propulsion systems. This article...probes in the plume of a low-power, four-engine Hall thruster cluster. Simple analytical formulas are introduced that allow these quantities to be

Probing bulk physics in the 5/2 fractional quantum Hall effect using the Corbino geometry

NASA Astrophysics Data System (ADS)

Schmidt, Benjamin; Bennaceur, Keyan; Bilodeau, Simon; Gaucher, Samuel; Lilly, Michael; Reno, John; Pfeiffer, Loren; West, Ken; Reulet, Bertrand; Gervais, Guillaume

We present two- and four-point Corbino geometry transport measurements in the second Landau level in GaAs/AlGaAs heterostructures. By avoiding edge transport, we are able to directly probe the physics of the bulk quasiparticles in fractional quantum Hall (FQH) states including 5/2. Our highest-quality sample shows stripe and bubble phases in high Landau levels, and most importantly well-resolved FQH minima in the second Landau level. We report Arrhenius-type fits to the activated conductance, and find that σ0 agrees well with theory and existing Hall geometry data in the first Landau level, but not in the second Landau level. We will discuss the advantages the Corbino geometry could bring to various experiments designed to detect the non-Abelian entropy at 5/2, and our progress towards realizing those schemes. The results of these experiments could complement interferometry and other edge-based measurements by providing direct evidence for non-Abelian behaviour of the bulk quasiparticles. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL8500.

Atom probe trajectory mapping using experimental tip shape measurements.

PubMed

Haley, D; Petersen, T; Ringer, S P; Smith, G D W

2011-11-01

Atom probe tomography is an accurate analytical and imaging technique which can reconstruct the complex structure and composition of a specimen in three dimensions. Despite providing locally high spatial resolution, atom probe tomography suffers from global distortions due to a complex projection function between the specimen and detector which is different for each experiment and can change during a single run. To aid characterization of this projection function, this work demonstrates a method for the reverse projection of ions from an arbitrary projection surface in 3D space back to an atom probe tomography specimen surface. Experimental data from transmission electron microscopy tilt tomography are combined with point cloud surface reconstruction algorithms and finite element modelling to generate a mapping back to the original tip surface in a physically and experimentally motivated manner. As a case study, aluminium tips are imaged using transmission electron microscopy before and after atom probe tomography, and the specimen profiles used as input in surface reconstruction methods. This reconstruction method is a general procedure that can be used to generate mappings between a selected surface and a known tip shape using numerical solutions to the electrostatic equation, with quantitative solutions to the projection problem readily achievable in tens of minutes on a contemporary workstation. © 2011 The Authors Journal of Microscopy © 2011 Royal Microscopical Society.

Mapping Rotational Wavepacket Dynamics with Chirped Probe Pulses

NASA Astrophysics Data System (ADS)

Romanov, Dmitri; Odhner, Johanan; Levis, Robert

2014-05-01

We develop an analytical model description of the strong-field pump-probe polarization spectroscopy of rotational transients in molecular gases in a situation when the probe pulse is considerably chirped: the frequency modulation over the pulse duration is comparable with the carrier frequency. In this scenario, a femtosecond pump laser pulse prepares a rotational wavepacket in a gas-phase sample at room temperature. The rotational revivals of the wavepacket are then mapped onto a chirped broadband probe pulse derived from a laser filament. The slow-varying envelope approximation being inapplicable, an alternative approach is proposed which is capable of incorporating the substantial chirp and the related temporal dispersion of refractive indices. Analytical expressions are obtained for the probe signal modulation over the interaction region and for the resulting heterodyned transient birefringence spectra. Dependencies of the outputs on the probe pulse parameters reveal the trade-offs and the ways to optimize the temporal-spectral imaging. The results are in good agreement with the experiments on snapshot imaging of rotational revival patterns in nitrogen gas. We gratefully acknowledge financial support through AFOSR MURI Grant No. FA9550-10-1-0561.

Remnant Geometric Hall Response in a Quantum Quench.

PubMed

Wilson, Justin H; Song, Justin C W; Refael, Gil

2016-12-02

Out-of-equilibrium systems can host phenomena that transcend the usual restrictions of equilibrium systems. Here, we unveil how out-of-equilibrium states, prepared via a quantum quench in a two-band system, can exhibit a nonzero Hall-type current-a remnant Hall response-even when the instantaneous Hamiltonian is time reversal symmetric (in contrast to equilibrium Hall currents). Interestingly, the remnant Hall response arises from the coherent dynamics of the wave function that retain a remnant of its quantum geometry postquench, and can be traced to processes beyond linear response. Quenches in two-band Dirac systems are natural venues for realizing remnant Hall currents, which exist when either mirror or time-reversal symmetry are broken (before or after the quench). Its long time persistence, sensitivity to symmetry breaking, and decoherence-type relaxation processes allow it to be used as a sensitive diagnostic of the complex out-of-equilibrium dynamics readily controlled and probed in cold-atomic optical lattice experiments.

Mapping alternating current electroosmotic flow at the dielectrophoresis crossover frequency of a colloidal probe.

PubMed

Wang, Jingyu; Wei, Ming-Tzo; Cohen, Joel A; Ou-Yang, H Daniel

2013-07-01

AC electroosmotic (ACEO) flow above the gap between coplanar electrodes is mapped by the measurement of Stokes forces on an optically trapped polystyrene colloidal particle. E²-dependent forces on the probe particle are selected by amplitude modulation (AM) of the ACEO electric field (E) and lock-in detection at twice the AM frequency. E²-dependent DEP of the probe is eliminated by driving the ACEO at the probe's DEP crossover frequency. The location-independent DEP crossover frequency is determined, in a separate experiment, as the limiting frequency of zero horizontal force as the probe is moved toward the midpoint between the electrodes. The ACEO velocity field, uncoupled from probe DEP effects, was mapped in the region 1-9 μm above a 28 μm gap between the electrodes. By use of variously sized probes, each at its DEP crossover frequency, the frequency dependence of the ACEO flow was determined at a point 3 μm above the electrode gap and 4 μm from an electrode tip. At this location the ACEO flow was maximal at ∼117 kHz for a low salt solution. This optical trapping method, by eliminating DEP forces on the probe, provides unambiguous mapping of the ACEO velocity field. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasmon Geometric Phase and Plasmon Hall Shift

NASA Astrophysics Data System (ADS)

Shi, Li-kun; Song, Justin C. W.

2018-04-01

The collective plasmonic modes of a metal comprise a simple pattern of oscillating charge density that yields enhanced light-matter interaction. Here we unveil that beneath this familiar facade plasmons possess a hidden internal structure that fundamentally alters its dynamics. In particular, we find that metals with nonzero Hall conductivity host plasmons with an intricate current density configuration that sharply departs from that of ordinary zero Hall conductivity metals. This nontrivial internal structure dramatically enriches the dynamics of plasmon propagation, enabling plasmon wave packets to acquire geometric phases as they scatter. At boundaries, these phases accumulate allowing plasmon waves that reflect off to experience a nonreciprocal parallel shift. This plasmon Hall shift, tunable by Hall conductivity as well as plasmon wavelength, displaces the incident and reflected plasmon trajectories and can be readily probed by near-field photonics techniques. Anomalous plasmon geometric phases dramatically enrich the nanophotonics toolbox, and yield radical new means for directing plasmonic beams.

Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA-457Mv2 Hall Thruster

NASA Technical Reports Server (NTRS)

Shastry, Rohit; Huang, Wensheng; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

2012-01-01

In order to further the design of future high-power Hall thrusters and provide experimental validation for ongoing modeling efforts, plasma potential and Langmuir probe measurements were performed on the 50-kW NASA-457Mv2. An electrostatic probe array comprised of a near-field Faraday probe, single Langmuir probe, and emissive probe was used to interrogate the near-field plume from approximately 0.1 - 2.0 mean thruster diameters downstream of the thruster exit plane at the following operating conditions: 300 V, 400 V and 500 V at 30 kW and 500 V at 50 kW. Results have shown that the acceleration zone is limited to within 0.4 mean thruster diameters of the exit plane while the high-temperature region is limited to 0.25 mean thruster diameters from the exit plane at all four operating conditions. Maximum plasma potentials in the near-field at 300 and 400 V were approximately 50 V with respect to cathode potential, while maximum electron temperatures varied from 24 - 32 eV, depending on operating condition. Isothermal lines at all operating conditions were found to strongly resemble the magnetic field topology in the high-temperature regions. This distribution was found to create regions of high temperature and low density near the magnetic poles, indicating strong, thick sheath formation along these surfaces. The data taken from this study are considered valuable for future design as well as modeling validation.

Spacecraft Interactions Studies with a 1 Kw Class Closed-Drift Hall Thruster

DTIC Science & Technology

1998-01-31

Closed Drift Hall thruster plume with spacecraft surfaces and systems. Two basic interaction modes were investigated: (1) the influence of the plume...Spectrometer (MBMS) capable of discerning both the mass and energy of Hall thruster plume species, and the ion acoustic wave probe to measure the drift velocity of the plume plasma.

Trajectory Design for the Microwave Anisotropy Probe (MAP)

NASA Technical Reports Server (NTRS)

Newman, Lauri Kraft; Rohrbaugh, David; Bauer, Frank H. (Technical Monitor)

2001-01-01

The Microwave Anisotropy, Probe (MAP) is a Medium Class Explorers (MIDEX) Mission produced in partnership between Goddard Space Flight Center (GSFC) and Princeton University. The goal of the MAP mission is to produce an accurate fill-sky, map of the cosmic microwave background temperature fluctuations (anisotropy). The mission orbit is a Lissajous orbit about the L(sub 2) Sun-Earth Lagrange point. The trajectory design for MAP is complex, having many requirements that must be met including shadow avoidance, sun angle constraints, Lissqjous size and shape characteristics, and limited Delta-V budget. In order to find a trajectory that met the design requirements for the entire 4-year mission lifetime goal, GSFC Flight Dynamics engineers performed many analyses, the results of which are presented herein. The paper discusses the preliminary trade-offs to establish a baseline trajectory, analysis to establish the nominal daily trajectory, and the launch window determination to widen the opportunity from instantaneous to several minutes for each launch date.

Moiré assisted fractional quantum Hall state spectroscopy

DOE PAGES

Wu, Fengcheng; MacDonald, A. H.

2016-12-14

Intra-Landau level excitations in the fractional quantum Hall regime are not accessible via optical absorption measurements. Here we point out that optical probes are enabled by the periodic potentials produced by a moire pattern. Our observation is motivated by the recent observations of fractional quantum Hall incompressible states in moire-patterned graphene on a hexagonal boron nitride substrate, and is theoretically based on f-sum rule considerations supplemented by a perturbative analysis of the influence of the moire potential on many-body states.

Critical current density measurement of striated multifilament-coated conductors using a scanning Hall probe microscope

NASA Astrophysics Data System (ADS)

Li, Xiao-Fen; Kochat, Mehdi; Majkic, Goran; Selvamanickam, Venkat

2016-08-01

In this paper the authors succeeded in measuring the critical current density ({J}{{c}}) of multifilament-coated conductors (CCs) with thin filaments as low as 0.25 mm using the scanning hall probe microscope (SHPM) technique. A new iterative method of data analysis is developed to make the calculation of {J}{{c}} for thin filaments possible, even without a very small scan distance. The authors also discussed in detail the advantage and limitation of the iterative method using both simulation and experiment results. The results of the new method correspond well with the traditional fast Fourier transform method where this is still applicable. However, the new method is applicable for the filamentized CCs in much wider measurement conditions such as with thin filament and a large scan distance, thus overcoming the barrier for application of the SHPM technique on {J}{{c}} measurement of long filamentized CCs with narrow filaments.

Mapped DNA probes from Ioblolly pine can be used for restriction fragment length polymorphism mapping in other conifers

Treesearch

M.R. Ahuja; M.E. Devey; A.T. Groover; K.D. Jermstad; D.B Neale

1994-01-01

A high-density genetic map based on restriction fragment length polymorphisms (RFLPs) is being constructed for loblolly pine (Pinus taeda L.). Consequently, a large number of DNA probes from loblolly pine are potentially available for use in other species. We have used some of these DNA probes to detect RFLPs in 12 conifers and an angiosperm....

The Microwave Anisotropy Probe (MAP) Mission

NASA Technical Reports Server (NTRS)

Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.; Bauer, Frank H. (Technical Monitor)

2002-01-01

The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an inertial reference unit, two star trackers, a digital sun sensor, twelve coarse sun sensors, three reaction wheel assemblies, and a propulsion system. This paper presents an overview of the design of the attitude control system to carry out this mission and presents some early flight experience.

The Microwave Anisotropy Probe (MAP) Mission

NASA Technical Reports Server (NTRS)

Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.; Ericsson, Aprille J.; Bauer, Frank H. (Technical Monitor)

2002-01-01

The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an Inertial Reference Unit, two Autonomous Star Trackers, a Digital Sun Sensor, twelve Coarse Sun Sensors, three Reaction Wheel Assemblies, and a propulsion system. This paper describes the design of the attitude control system that carries out this mission and presents some early flight experience.

Uprobe: a genome-wide universal probe resource for comparative physical mapping in vertebrates.

PubMed

Kellner, Wendy A; Sullivan, Robert T; Carlson, Brian H; Thomas, James W

2005-01-01

Interspecies comparisons are important for deciphering the functional content and evolution of genomes. The expansive array of >70 public vertebrate genomic bacterial artificial chromosome (BAC) libraries can provide a means of comparative mapping, sequencing, and functional analysis of targeted chromosomal segments that is independent and complementary to whole-genome sequencing. However, at the present time, no complementary resource exists for the efficient targeted physical mapping of the majority of these BAC libraries. Universal overgo-hybridization probes, designed from regions of sequenced genomes that are highly conserved between species, have been demonstrated to be an effective resource for the isolation of orthologous regions from multiple BAC libraries in parallel. Here we report the application of the universal probe design principal across entire genomes, and the subsequent creation of a complementary probe resource, Uprobe, for screening vertebrate BAC libraries. Uprobe currently consists of whole-genome sets of universal overgo-hybridization probes designed for screening mammalian or avian/reptilian libraries. Retrospective analysis, experimental validation of the probe design process on a panel of representative BAC libraries, and estimates of probe coverage across the genome indicate that the majority of all eutherian and avian/reptilian genes or regions of interest can be isolated using Uprobe. Future implementation of the universal probe design strategy will be used to create an expanded number of whole-genome probe sets that will encompass all vertebrate genomes.

Far-Field Plume Measurements of a Nested-Channel Hall-Effect Thruster (PREPRINT)

DTIC Science & Technology

2010-12-13

nude Faraday probe, retarding potential analyzer, and ExB probe. Data from these probes were used to calculate utilization efficiencies from existing...USA Far-field plume measurements were performed on the X2 nested-channel Hall-effect thruster using an ar- ray of diagnostics, including a nude Faraday...mode to nested-channel mode by utilizing a traditional array of far-field diagnostics, which include a nude Faraday probe, retarding potential analyzer

A Filtering Method to Reveal Crystalline Patterns from Atom Probe Microscopy Desorption Maps

DTIC Science & Technology

2016-03-26

Gault, S.P. Ringer, J.M. Cairney, Atom probe crystallography : characterization of grain boundary orientation relationships in nanocrystalline...J.M. Cairney, Atom probe crystallography : atomic- scale 3-D orientation mapping, Scr. Mater. 66 (11) (2012) 907. L. Yao /MethodsX 3 (2016) 268–273 273

Mapping the CMB with the Wilkinson Microwave Anisotropy Probe

NASA Technical Reports Server (NTRS)

Hinshaw, Gary

2007-01-01

The data from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite provide detailed full-sky maps of the cosmic microwave background temperature anisotropy and new full-sky maps of the polarization. Together, the data provide a wealth of cosmological information, including the age of the universe, the epoch when the first stars formed, and the overall composition of baryonic matter, dark matter, and dark energy. The results also provide constraints on the period of inflationary expansion in the very first moments of time. These and other aspects of the mission results will be discussed and commented on.

Nondestructive hall coefficient measurements using ACPD techniques

NASA Astrophysics Data System (ADS)

Velicheti, Dheeraj; Nagy, Peter B.; Hassan, Waled

2018-04-01

Hall coefficient measurements offer great opportunities as well as major challenges for nondestructive materials characterization. The Hall effect is produced by the magnetic Lorentz force acting on moving charge carriers in the presence of an applied magnetic field. The magnetic perturbation gives rise to a Hall current that is normal to the conduction current but does not directly perturb the electric potential distribution. Therefore, Hall coefficient measurements usually exploit the so-called transverse galvanomagnetic potential drop effect that arises when the Hall current is intercepted by the boundaries of the specimen and thereby produce a measurable potential drop. In contrast, no Hall potential is produced in a large plate in the presence of a uniform normal field at quasi-static low frequencies. In other words, conventional Hall coefficient measurements are inherently destructive since they require cutting the material under tests. This study investigated the feasibility of using alternating current potential drop (ACPD) techniques for nondestructive Hall coefficient measurements in plates. Specifically, the directional four-point square-electrode configuration is investigated with superimposed external magnetic field. Two methods are suggested to make Hall coefficient measurements in large plates without destructive machining. At low frequencies, constraining the bias magnetic field can replace constraining the dimensions of the specimen, which is inherently destructive. For example, when a cylindrical permanent magnet is used to provide the bias magnetic field, the peak Hall voltage is produced when the diameter of the magnet is equal to the diagonal of the square ACPD probe. Although this method is less effective than cutting the specimen to a finite size, the loss of sensitivity is less than one order of magnitude even at very low frequencies. In contrast, at sufficiently high inspection frequencies the magnetic field of the Hall current induces a

The Maneuverable Atmospheric Probe (MAP), a Remotely Piloted Vehicle.

DTIC Science & Technology

1982-05-01

9 lb. MAP vehicle and major- components .................................... 10 2. Endevco Pitot tube airspeed indicator mounted below front...28 8. Cascaded PIXE impactors, housing cylinder and wing pod front end cup with aerosol inlet plastic tubing ........................... 30 9...turbulence sensors, a Pitot tube , two air temperature sensors, and a yaw gust probe. Located at each wing tip are sensors that contain encapsulated

Photonic topological boundary pumping as a probe of 4D quantum Hall physics

NASA Astrophysics Data System (ADS)

Zilberberg, Oded; Huang, Sheng; Guglielmon, Jonathan; Wang, Mohan; Chen, Kevin P.; Kraus, Yaacov E.; Rechtsman, Mikael C.

2018-01-01

When a two-dimensional (2D) electron gas is placed in a perpendicular magnetic field, its in-plane transverse conductance becomes quantized; this is known as the quantum Hall effect. It arises from the non-trivial topology of the electronic band structure of the system, where an integer topological invariant (the first Chern number) leads to quantized Hall conductance. It has been shown theoretically that the quantum Hall effect can be generalized to four spatial dimensions, but so far this has not been realized experimentally because experimental systems are limited to three spatial dimensions. Here we use tunable 2D arrays of photonic waveguides to realize a dynamically generated four-dimensional (4D) quantum Hall system experimentally. The inter-waveguide separation in the array is constructed in such a way that the propagation of light through the device samples over momenta in two additional synthetic dimensions, thus realizing a 2D topological pump. As a result, the band structure has 4D topological invariants (known as second Chern numbers) that support a quantized bulk Hall response with 4D symmetry. In a finite-sized system, the 4D topological bulk response is carried by localized edge modes that cross the sample when the synthetic momenta are modulated. We observe this crossing directly through photon pumping of our system from edge to edge and corner to corner. These crossings are equivalent to charge pumping across a 4D system from one three-dimensional hypersurface to the spatially opposite one and from one 2D hyperedge to another. Our results provide a platform for the study of higher-dimensional topological physics.

Photonic topological boundary pumping as a probe of 4D quantum Hall physics.

PubMed

Zilberberg, Oded; Huang, Sheng; Guglielmon, Jonathan; Wang, Mohan; Chen, Kevin P; Kraus, Yaacov E; Rechtsman, Mikael C

2018-01-03

When a two-dimensional (2D) electron gas is placed in a perpendicular magnetic field, its in-plane transverse conductance becomes quantized; this is known as the quantum Hall effect. It arises from the non-trivial topology of the electronic band structure of the system, where an integer topological invariant (the first Chern number) leads to quantized Hall conductance. It has been shown theoretically that the quantum Hall effect can be generalized to four spatial dimensions, but so far this has not been realized experimentally because experimental systems are limited to three spatial dimensions. Here we use tunable 2D arrays of photonic waveguides to realize a dynamically generated four-dimensional (4D) quantum Hall system experimentally. The inter-waveguide separation in the array is constructed in such a way that the propagation of light through the device samples over momenta in two additional synthetic dimensions, thus realizing a 2D topological pump. As a result, the band structure has 4D topological invariants (known as second Chern numbers) that support a quantized bulk Hall response with 4D symmetry. In a finite-sized system, the 4D topological bulk response is carried by localized edge modes that cross the sample when the synthetic momenta are modulated. We observe this crossing directly through photon pumping of our system from edge to edge and corner to corner. These crossings are equivalent to charge pumping across a 4D system from one three-dimensional hypersurface to the spatially opposite one and from one 2D hyperedge to another. Our results provide a platform for the study of higher-dimensional topological physics.

Measuring the Hall weighting function for square and cloverleaf geometries

NASA Astrophysics Data System (ADS)

Scherschligt, Julia K.; Koon, Daniel W.

2000-02-01

We have directly measured the Hall weighting function—the sensitivity of a four-wire Hall measurement to the position of macroscopic inhomogeneities in Hall angle—for both a square shaped and a cloverleaf specimen. Comparison with the measured resistivity weighting function for a square geometry [D. W. Koon and W. K. Chan, Rev. Sci. Instrum. 69, 12 (1998)] proves that the two measurements sample the same specimen differently. For Hall measurements on both a square and a cloverleaf, the function is nonnegative with its maximum in the center and its minimum of zero at the edges of the square. Converting a square into a cloverleaf is shown to dramatically focus the measurement process onto a much smaller portion of the specimen. While our results agree qualitatively with theory, details are washed out, owing to the finite size of the magnetic probe used.

Probing quantum Hall states with single-electron transistors at high magnetic fields

NASA Astrophysics Data System (ADS)

Gustafsson, Martin; Yankowitz, Matthew; Forsythe, Carlos; Zhu, Xiaoyang; Dean, Cory

The sequence of fractional quantum Hall states in graphene is not yet fully understood, largely due to disorder-induced limitations of conventional transport studies. Measurements of magnetotransport in other 2D crystals are further complicated by the difficulties in making ohmic contact to the materials. On the other hand, bulk electronic compressibility can provide clear signatures of the integer and fractional quantum Hall effects, does not require ohmic contact, and can be localized to regions of low disorder. The single-electron transistor (SET) is a suitable tool for such experiments due to its small size and high charge sensitivity, which allow electric fields penetrating the 2D electron system to be detected locally and with high fidelity. Here we report studies of exfoliated 2D van der Waals materials fully encapsulated in flakes of hexagonal boron nitride. SETs are fabricated lithographically on top of the encapsulation, yielding a structure which lends itself to experiments at high electric and magnetic fields. We demonstrate the method on monolayer graphene, where we observe fractional quantum Hall states at all filling factors ν = n / 3 up to n = 17 and extract their associated energy gaps for magnetic fields up to 31 tesla.

Magnetic Field Tailored Annular Hall Thruster with Anode Layer

NASA Astrophysics Data System (ADS)

Lee, Seunghun; Kim, Holak; Kim, Junbum; Lim, Youbong; Choe, Wonho; Korea Institute of Materials Science Collaboration

2016-09-01

Plasma propulsion system is one of the key components for advanced missions of satellites as well as deep space exploration. A typical plasma propulsion system is Hall effect thruster that uses crossed electric and magnetic fields to ionize a propellant gas and to accelerate the ionized gas to generate momentum. In Hall thruster plasmas, magnetic field configuration is important due to the fact that electron confinement in the electromagnetic fields affects both plasma and ion beam characteristics as well as thruster performance parameters including thrust, specific impulse, power efficiency, and life time. In this work, development of an anode layer Hall thruster (TAL) with magnetic field tailoring has been attempted. The TAL is possible to keep discharge in 1 to 2 kilovolts of anode voltage, which is useful to obtain high specific impulse. The magnetic field tailoring is used to minimize undesirable heat dissipation and secondary electron emission from the wall surrounding the plasma. We will report 3 W and 200 W thrusters performances measured by a pendulum thrust stand according to the magnetic field configuration. Also, the measured result will be compared with the plasma diagnostics conducted by an angular Faraday probe, a retarding potential analyzer, and a ExB probe.

Mu2e Solenoid Field Mapping System Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feher, Sandor; DeLurgio, Patrick M.; Elementi, Luciano

The Mu2e experiment at Fermilab plans to search for charged-lepton flavor violation by looking for neutrino-less muon to electron conversion in the field of the nucleus. A complex solenoid system and precise knowledge of its magnetic field play a major role in the experimental approach Mu2e has chosen. It is essential to map the solenoid field up to 10 -4 accuracy. This article describes the design of the Field Mapping System Mu2e will use to measure the magnetic field. Two different mechanical mapper systems, a survey based position determination of the in-house calibrated 3D Hall probes, a motion control system,more » and a data acquisition and readout system are presented.« less

Mu2e Solenoid Field Mapping System Design

DOE PAGES

Feher, Sandor; DeLurgio, Patrick M.; Elementi, Luciano; ...

2018-01-11

The Mu2e experiment at Fermilab plans to search for charged-lepton flavor violation by looking for neutrino-less muon to electron conversion in the field of the nucleus. A complex solenoid system and precise knowledge of its magnetic field play a major role in the experimental approach Mu2e has chosen. It is essential to map the solenoid field up to 10 -4 accuracy. This article describes the design of the Field Mapping System Mu2e will use to measure the magnetic field. Two different mechanical mapper systems, a survey based position determination of the in-house calibrated 3D Hall probes, a motion control system,more » and a data acquisition and readout system are presented.« less

MIP-MAP: High-Throughput Mapping of Caenorhabditis elegans Temperature-Sensitive Mutants via Molecular Inversion Probes

PubMed Central

Mok, Calvin A.; Au, Vinci; Thompson, Owen A.; Edgley, Mark L.; Gevirtzman, Louis; Yochem, John; Lowry, Joshua; Memar, Nadin; Wallenfang, Matthew R.; Rasoloson, Dominique; Bowerman, Bruce; Schnabel, Ralf; Seydoux, Geraldine; Moerman, Donald G.; Waterston, Robert H.

2017-01-01

Mutants remain a powerful means for dissecting gene function in model organisms such as Caenorhabditis elegans. Massively parallel sequencing has simplified the detection of variants after mutagenesis but determining precisely which change is responsible for phenotypic perturbation remains a key step. Genetic mapping paradigms in C. elegans rely on bulk segregant populations produced by crosses with the problematic Hawaiian wild isolate and an excess of redundant information from whole-genome sequencing (WGS). To increase the repertoire of available mutants and to simplify identification of the causal change, we performed WGS on 173 temperature-sensitive (TS) lethal mutants and devised a novel mapping method. The mapping method uses molecular inversion probes (MIP-MAP) in a targeted sequencing approach to genetic mapping, and replaces the Hawaiian strain with a Million Mutation Project strain with high genomic and phenotypic similarity to the laboratory wild-type strain N2. We validated MIP-MAP on a subset of the TS mutants using a competitive selection approach to produce TS candidate mapping intervals with a mean size < 3 Mb. MIP-MAP successfully uses a non-Hawaiian mapping strain and multiplexed libraries are sequenced at a fraction of the cost of WGS mapping approaches. Our mapping results suggest that the collection of TS mutants contains a diverse library of TS alleles for genes essential to development and reproduction. MIP-MAP is a robust method to genetically map mutations in both viable and essential genes and should be adaptable to other organisms. It may also simplify tracking of individual genotypes within population mixtures. PMID:28827289

Molecular cytogenetic mapping of 24 CEPH YACs and 24 gene-specific large insert probes to chromosome 17.

PubMed

Bärlund, M; Nupponen, N N; Karhu, R; Tanner, M M; Paavola, P; Kallioniemi, O P; Kallioniemi, A

1998-01-01

Defining boundaries of chromosomal rearrangements at the molecular level would benefit from landmarks that link the cytogenetic map to physical, genetic, and transcript maps, as well as from large-insert FISH probes for such loci to detect numerical and structural rearrangements in metaphase or interphase cells. Here, we determined the locations of 24 genetically mapped CEPH-Mega YACs along the FLpter scale (fractional length from p-telomere) by quantitative fluorescence in situ hybridization analysis. This generated a set of cytogenetically mapped probes for chromosome 17 with an average spacing of about 5 cM. We then developed large-insert YAC, BAC, PAC, or P1 clones to the following 24 known genes, and determined refined map locations along the same FLpter scale: pter-TP53-TOP3-cen-TNFAIP1-ERBB2-TOP2A- BRCA1-TCF11-NME1-HLF-ZNF147/CL N80-BCL5/MPO/SFRS1-TBX2-PECAM1-DDX5/ PRKCA-ICAM2-GH1/PRKAR1A-GRB2-CDK3 /FKHL13-qter. Taken together, these 48 cytogenetically mapped large-insert probes provide tools for the molecular analysis of chromosome 17 rearrangements, such as mapping amplification, deletion, and translocation breakpoints in this chromosome, in cancer and other diseases.

New developments in ground probing radar for Earth resource mapping and planetology

NASA Astrophysics Data System (ADS)

Cattermole, P. J.; Junkin, G.; Finkelstein, M. I.; Kingsley, S. P.

1992-07-01

Ground probing radar is a well established technique for locating buried objects and has found application in resource mapping. The development of this technology for the Mars exploration programme has lead to lightweight systems with potential applications for investigating shallow geological structures on Earth, Mars and Venus. Recent advances in ground probing radar technology for planetary exploration include the development of single-antenna systems with improved beam focussing into the ground and a move to lower frequencies which considerably extends the depth penetration in dry ground. These systems are designed for mobility and could form the basis of autonomous mapping systems for terrestrial exploration. Such systems would be particularly valuable for water resource surveying in arid and semi-arid regions, where there is a need to have lightweight instrumentation that can be moved into sometimes inhospitable terrain.

High-order multipole radiation from quantum Hall states in Dirac materials

NASA Astrophysics Data System (ADS)

Gullans, Michael J.; Taylor, Jacob M.; Imamoǧlu, Ataç; Ghaemi, Pouyan; Hafezi, Mohammad

2017-06-01

We investigate the optical response of strongly disordered quantum Hall states in two-dimensional Dirac materials and find qualitatively different effects in the radiation properties of the bulk versus the edge. We show that the far-field radiation from the edge is characterized by large multipole moments (>50 ) due to the efficient transfer of angular momentum from the electrons into the scattered light. The maximum multipole transition moment is a direct measure of the coherence length of the edge states. Accessing these multipole transitions would provide new tools for optical spectroscopy and control of quantum Hall edge states. On the other hand, the far-field radiation from the bulk appears as random dipole emission with spectral properties that vary with the local disorder potential. We determine the conditions under which this bulk radiation can be used to image the disorder landscape. Such optical measurements can probe submicron-length scales over large areas and provide complementary information to scanning probe techniques. Spatially resolving this bulk radiation would serve as a novel probe of the percolation transition near half filling.

Field Mapping System for Solenoid Magnet

NASA Astrophysics Data System (ADS)

Park, K. H.; Jung, Y. K.; Kim, D. E.; Lee, H. G.; Park, S. J.; Chung, C. W.; Kang, B. K.

2007-01-01

A three-dimensional Hall probe mapping system for measuring the solenoid magnet of PLS photo-cathode RF e-gun has been developed. It can map the solenoid field either in Cartesian or in cylindrical coordinate system with a measurement reproducibility better than 5 × 10-5 T. The system has three axis motors: one for the azimuthal direction and the other two for the x and z direction. This architecture makes the measuring system simple in fabrication. The magnetic center was calculated using the measured axial component of magnetic field Bz in Cartesian coordinate system because the accuracy of magnetic axis measurement could be improved significantly by using Bz, instead of the radial component of magnetic field Br. This paper describes the measurement system and summarizes the measurement results for the solenoid magnetic of PLS photo-cathode RF e-gun.

Interplay between snake and quantum edge states in a graphene Hall bar with a pn-junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milovanović, S. P., E-mail: slavisa.milovanovic@uantwerpen.be; Peeters, F. M., E-mail: francois.peeters@uantwerpen.be; Ramezani Masir, M., E-mail: mrmphys@gmail.com

2014-09-22

The magneto- and Hall resistance of a locally gated cross shaped graphene Hall bar is calculated. The edge of the top gate is placed diagonally across the center of the Hall cross. Four-probe resistance is calculated using the Landauer-Büttiker formalism, while the transmission coefficients are obtained using the non-equilibrium Green's function approach. The interplay between transport due to edge channels and snake states is investigated. When two edge channels are occupied, we predict oscillations in the Hall and the bend resistance as function of the magnetic field, which are a consequence of quantum interference between the occupied snake states.

MIP-MAP: High-Throughput Mapping of Caenorhabditis elegans Temperature-Sensitive Mutants via Molecular Inversion Probes.

PubMed

Mok, Calvin A; Au, Vinci; Thompson, Owen A; Edgley, Mark L; Gevirtzman, Louis; Yochem, John; Lowry, Joshua; Memar, Nadin; Wallenfang, Matthew R; Rasoloson, Dominique; Bowerman, Bruce; Schnabel, Ralf; Seydoux, Geraldine; Moerman, Donald G; Waterston, Robert H

2017-10-01

Mutants remain a powerful means for dissecting gene function in model organisms such as Caenorhabditis elegans Massively parallel sequencing has simplified the detection of variants after mutagenesis but determining precisely which change is responsible for phenotypic perturbation remains a key step. Genetic mapping paradigms in C . elegans rely on bulk segregant populations produced by crosses with the problematic Hawaiian wild isolate and an excess of redundant information from whole-genome sequencing (WGS). To increase the repertoire of available mutants and to simplify identification of the causal change, we performed WGS on 173 temperature-sensitive (TS) lethal mutants and devised a novel mapping method. The mapping method uses molecular inversion probes (MIP-MAP) in a targeted sequencing approach to genetic mapping, and replaces the Hawaiian strain with a Million Mutation Project strain with high genomic and phenotypic similarity to the laboratory wild-type strain N2 We validated MIP-MAP on a subset of the TS mutants using a competitive selection approach to produce TS candidate mapping intervals with a mean size < 3 Mb. MIP-MAP successfully uses a non-Hawaiian mapping strain and multiplexed libraries are sequenced at a fraction of the cost of WGS mapping approaches. Our mapping results suggest that the collection of TS mutants contains a diverse library of TS alleles for genes essential to development and reproduction. MIP-MAP is a robust method to genetically map mutations in both viable and essential genes and should be adaptable to other organisms. It may also simplify tracking of individual genotypes within population mixtures. Copyright © 2017 by the Genetics Society of America.

Evidence of Collisionless Shocks in a Hall Thruster Plume

DTIC Science & Technology

2003-04-25

Triple Langmuir probes and emissive probes are used to measure the electron number density, electron temperature, and plasma potential downstream of a low-power Hall thruster . The results show a high density plasma core with elevated electron temperature and plasma potential along the thruster centerline. These properties are believed to be due to collisionless shocks formed as a result of the ion/ion acoustic instability. A simple model is presented that shows the existence of a collisionless shock to be consistent with the observed phenomena.

NHS-Esters As Versatile Reactivity-Based Probes for Mapping Proteome-Wide Ligandable Hotspots.

PubMed

Ward, Carl C; Kleinman, Jordan I; Nomura, Daniel K

2017-06-16

Most of the proteome is considered undruggable, oftentimes hindering translational efforts for drug discovery. Identifying previously unknown druggable hotspots in proteins would enable strategies for pharmacologically interrogating these sites with small molecules. Activity-based protein profiling (ABPP) has arisen as a powerful chemoproteomic strategy that uses reactivity-based chemical probes to map reactive, functional, and ligandable hotspots in complex proteomes, which has enabled inhibitor discovery against various therapeutic protein targets. Here, we report an alkyne-functionalized N-hydroxysuccinimide-ester (NHS-ester) as a versatile reactivity-based probe for mapping the reactivity of a wide range of nucleophilic ligandable hotspots, including lysines, serines, threonines, and tyrosines, encompassing active sites, allosteric sites, post-translational modification sites, protein interaction sites, and previously uncharacterized potential binding sites. Surprisingly, we also show that fragment-based NHS-ester ligands can be made to confer selectivity for specific lysine hotspots on specific targets including Dpyd, Aldh2, and Gstt1. We thus put forth NHS-esters as promising reactivity-based probes and chemical scaffolds for covalent ligand discovery.

A new method for mapping the three-dimensional atomic distribution within nanoparticles by atom probe tomography (APT).

PubMed

Kim, Se-Ho; Kang, Phil Woong; Park, O Ok; Seol, Jae-Bok; Ahn, Jae-Pyoung; Lee, Ji Yeong; Choi, Pyuck-Pa

2018-07-01

We present a new method of preparing needle-shaped specimens for atom probe tomography from freestanding Pd and C-supported Pt nanoparticles. The method consists of two steps, namely electrophoresis of nanoparticles on a flat Cu substrate followed by electrodeposition of a Ni film acting as an embedding matrix for the nanoparticles. Atom probe specimen preparation can be subsequently carried out by means of focused-ion-beam milling. Using this approach, we have been able to perform correlative atom probe tomography and transmission electron microscopy analyses on both nanoparticle systems. Reliable mass spectra and three-dimensional atom maps could be obtained for Pd nanoparticle specimens. In contrast, atom probe samples prepared from C-supported Pt nanoparticles showed uneven field evaporation and hence artifacts in the reconstructed atom maps. Our developed method is a viable means of mapping the three-dimensional atomic distribution within nanoparticles and is expected to contribute to an improved understanding of the structure-composition-property relationships of various nanoparticle systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Nanobits, Nembranes and Micro Four-Point Probes: Customizable Tools for insitu Manipulation and Characterisation of Nanostructures

NASA Astrophysics Data System (ADS)

Boggild, Peter; Hjorth Petersen, Dirch; Sardan Sukas, Ozlem; Dam, Henrik Friis; Lei, Anders; Booth, Timothy; Molhave, Kristian; Eicchorn, Volkmar

2010-03-01

We present a range of highly adaptable microtools for direct interaction with nanoscale structures; (i) semiautomatic pick-and-place assembly of multiwalled carbon nanotubes onto cantilevers for high-aspect ratio scanning probe microscopy, using electrothermal microgrippers inside a SEM. Topology optimisation was used to calculate the optimal gripper shape defined by the boundary conditions, resulting in 10-100 times better performance. By instead pre-defining detachable tips using electron beam lithography, free-form scanning probe tips (Nanobits) can be mounted in virtually any position on a cantilever; (ii) scanning micro four point probes allow fast, non- destructive mapping of local electrical properties (sheet resistance and Hall mobility) and hysteresis effects of graphene sheets; (iii) sub 100 nm freestanding devices with wires, heaters, actuators, sensors, resonators and probes were defined in a 100 nm thin membrane with focused ion beam milling. By patterning generic membrane templates (Nembranes) the fabrication time of a TEM compatible NEMS device is effectively reduced to less around 20 minutes.

Application of Monte-Carlo Analyses for the Microwave Anisotropy Probe (MAP) Mission

NASA Technical Reports Server (NTRS)

Mesarch, Michael A.; Rohrbaugh, David; Schiff, Conrad; Bauer, Frank H. (Technical Monitor)

2001-01-01

The Microwave Anisotropy Probe (MAP) is the third launch in the National Aeronautics and Space Administration's (NASA's) a Medium Class Explorers (MIDEX) program. MAP will measure, in greater detail, the cosmic microwave background radiation from an orbit about the Sun-Earth-Moon L2 Lagrangian point. Maneuvers will be required to transition MAP from it's initial highly elliptical orbit to a lunar encounter which will provide the remaining energy to send MAP out to a lissajous orbit about L2. Monte-Carlo analysis methods were used to evaluate the potential maneuver error sources and determine their effect of the fixed MAP propellant budget. This paper will discuss the results of the analyses on three separate phases of the MAP mission - recovering from launch vehicle errors, responding to phasing loop maneuver errors, and evaluating the effect of maneuver execution errors and orbit determination errors on stationkeeping maneuvers at L2.

Feasibility of a GNSS-Probe for Creating Digital Maps of High Accuracy and Integrity

NASA Astrophysics Data System (ADS)

Vartziotis, Dimitris; Poulis, Alkis; Minogiannis, Alexandros; Siozos, Panayiotis; Goudas, Iraklis; Samson, Jaron; Tossaint, Michel

The “ROADSCANNER” project addresses the need for increased accuracy and integrity Digital Maps (DM) utilizing the latest developments in GNSS, in order to provide the required datasets for novel applications, such as navigation based Safety Applications, Advanced Driver Assistance Systems (ADAS) and Digital Automotive Simulations. The activity covered in the current paper is the feasibility study, preliminary tests, initial product design and development plan for an EGNOS enabled vehicle probe. The vehicle probe will be used for generating high accuracy, high integrity and ADAS compatible digital maps of roads, employing a multiple passes methodology supported by sophisticated refinement algorithms. Furthermore, the vehicle probe will be equipped with pavement scanning and other data fusion equipment, in order to produce 3D road surface models compatible with standards of road-tire simulation applications. The project was assigned to NIKI Ltd under the 1st Call for Ideas in the frame of the ESA - Greece Task Force.

Highly sensitive mode mapping of whispering-gallery modes by scanning thermocouple-probe microscopy.

PubMed

Klein, Angela E; Schmidt, Carsten; Liebsch, Mattes; Janunts, Norik; Dobynde, Mikhail; Tünnermann, Andreas; Pertsch, Thomas

2014-03-01

We propose a method for mapping optical near-fields with the help of a thermocouple scanning-probe microscope tip. As the tip scans the sample surface, its apex is heated by light absorption, generating a thermovoltage. The thermovoltage map represents the intensity distribution of light at the sample surface. The measurement technique has been employed to map optical whispering-gallery modes in fused silica microdisk resonators operating at near-infrared wavelengths. The method could potentially be employed for near-field imaging of a variety of systems in the near-infrared and visible spectral range.

Data Validation for Earth Probe-Total Ozone Mapping Spectrometer

NASA Technical Reports Server (NTRS)

Stanford, John L.

1995-01-01

This presentation represents the final report for the NASA grant project. The goal of this project was to provide scientific analysis to aid in validation fo data sets used in detection of long term global trends of total ozone. Ozone data from the Earth Probe Total Ozone Mapping Spectrometer instrument was compared for validation purposes with features in previous TOMS data. Atmospheric dynamic concepts were used in the analysis. The publications sponsored by the grant are listed along with abstracts.

The Microwave Anisotropy Probe (MAP) Attitude Control System

NASA Technical Reports Server (NTRS)

Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.; Ericsson, Aprille J.; Bauer, Frank H. (Technical Monitor)

2002-01-01

The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an Inertial Reference Unit, two Autonomous Star Trackers, a Digital Sun Sensor, twelve Coarse Sun Sensors, three Reaction Wheel Assemblies, and a propulsion system. This paper describes the design of the attitude control system that carries out this mission and presents some early flight experience.

Stationkeeping Approach for the Microwave Anisotropy Probe (MAP)

NASA Technical Reports Server (NTRS)

Rohrbaugh, Dave; Schiff, Conrad

2002-01-01

The Microwave Anisotropy Probe was successfully launched on June 30, 2001 and placed into a Lissajous orbit about the L2 Sun-Earth-Moon libration point. However, the L2 libration point is unstable which necessitates occasional stationkeeping maneuvers in order to maintain the spacecraft s Lissajous orbit. Analyses were performed in order to develop a feasible L2 stationkeeping strategy for the MAP mission. The resulting strategy meets the allotted fuel budget, allowing for enough fuel to handle additional he1 taxes, while meeting the attitude requirements for the maneuvers. Results from the first two stationkeeping maneuvers are included.

Ion Current Density Study of the NASA-300M and NASA-457Mv2 Hall Thrusters

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

2012-01-01

NASA Glenn Research Center is developing a Hall thruster in the 15-50 kW range to support future NASA missions. As a part of the process, the performance and plume characteristics of the NASA-300M, a 20-kW Hall thruster, and the NASA-457Mv2, a 50-kW Hall thruster, were evaluated. The collected data will be used to improve the fidelity of the JPL modeling tool, Hall2De, which will then be used to aid the design of the 15-50 kW Hall thruster. This paper gives a detailed overview of the Faraday probe portion of the plume characterization study. The Faraday probe in this study is a near-field probe swept radially at many axial locations downstream of the thruster exit plane. Threshold-based integration limits with threshold values of 1/e, 1/e2, and 1/e3 times the local peak current density are tried for the purpose of ion current integration and divergence angle calculation. The NASA-300M is operated at 7 conditions and the NASA-457Mv2 at 14 conditions. These conditions span discharge voltages of 200 to 500 V and discharge power of 10 to 50 kW. The ion current density profiles of the near-field plume originating from the discharge channel are discovered to strongly resemble Gaussian distributions. A novel analysis approach involving a form of ray tracing is used to determine an effective point of origin for the near-field plume. In the process of performing this analysis, definitive evidence is discovered that showed the near-field plume is bending towards the thruster centerline.

Ion Current Density Study of the NASA-300M and NASA-457Mv2 Hall Thrusters

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

2012-01-01

NASA Glenn Research Center is developing a Hall thruster in the 15-50 kW range to support future NASA missions. As a part of the process, the performance and plume characteristics of the NASA-300M, a 20-kW Hall thruster, and the NASA-457Mv2, a 50-kW Hall thruster, were evaluated. The collected data will be used to improve the fidelity of the JPL modeling tool, Hall2De, which will then be used to aid the design of the 15-50 kW Hall thruster. This paper gives a detailed overview of the Faraday probe portion of the plume characterization study. The Faraday probe in this study is a near-field probe swept radially at many axial locations downstream of the thruster exit plane. Threshold-based integration limits with threshold values of 1/e, 1/e(sup 2), and 1/e(sup 3) times the local peak current density are tried for the purpose of ion current integration and divergence angle calculation. The NASA-300M is operated at 7 conditions and the NASA-457Mv2 at 14 conditions. These conditions span discharge voltages of 200 to 500 V and discharge power of 10 to 50 kW. The ion current density profiles of the near-field plume originating from the discharge channel are discovered to strongly resemble Gaussian distributions. A novel analysis approach involving a form of ray tracing is used to determine an effective point of origin for the near-field plume. In the process of performing this analysis, definitive evidence is discovered that showed the near-field plume is bending towards the thruster centerline.

Quantitatively Mapping Cellular Viscosity with Detailed Organelle Information via a Designed PET Fluorescent Probe

PubMed Central

Liu, Tianyu; Liu, Xiaogang; Spring, David R.; Qian, Xuhong; Cui, Jingnan; Xu, Zhaochao

2014-01-01

Viscosity is a fundamental physical parameter that influences diffusion in biological processes. The distribution of intracellular viscosity is highly heterogeneous, and it is challenging to obtain a full map of cellular viscosity with detailed organelle information. In this work, we report 1 as the first fluorescent viscosity probe which is able to quantitatively map cellular viscosity with detailed organelle information based on the PET mechanism. This probe exhibited a significant ratiometric fluorescence intensity enhancement as solvent viscosity increases. The emission intensity increase was attributed to combined effects of the inhibition of PET due to restricted conformational access (favorable for FRET, but not for PET), and the decreased PET efficiency caused by viscosity-dependent twisted intramolecular charge transfer (TICT). A full map of subcellular viscosity was successfully constructed via fluorescent ratiometric detection and fluorescence lifetime imaging; it was found that lysosomal regions in a cell possess the highest viscosity, followed by mitochondrial regions. PMID:24957323

Crossover to the anomalous quantum regime in the extrinsic spin Hall effect of graphene

NASA Astrophysics Data System (ADS)

Ferreira, Aires; Milletari, Mirco

Recent reports of spin-orbit coupling enhancement in chemically modified graphene have opened doors to studies of the spin Hall effect with massless chiral fermions. Here, we theoretically investigate the interaction and impurity density dependence of the extrinsic spin Hall effect in spin-orbit coupled graphene. We present a nonperturbative quantum diagrammatic calculation of the spin Hall response function in the strong-coupling regime that incorporates skew scattering and anomalous impurity density-independent contributions on equal footing. The spin Hall conductivity dependence on Fermi energy and electron-impurity interaction strength reveals the existence of experimentally accessible regions where anomalous quantum processes dominate. Our findings suggest that spin-orbit-coupled graphene is an ideal model system for probing the competition between semiclassical and bona fide quantum scattering mechanisms underlying the spin Hall effect. A.F. gratefully acknowledges the financial support of the Royal Society (U.K.).

A holographic model for the fractional quantum Hall effect

NASA Astrophysics Data System (ADS)

Lippert, Matthew; Meyer, René; Taliotis, Anastasios

2015-01-01

Experimental data for fractional quantum Hall systems can to a large extent be explained by assuming the existence of a Γ0(2) modular symmetry group commuting with the renormalization group flow and hence mapping different phases of two-dimensional electron gases into each other. Based on this insight, we construct a phenomenological holographic model which captures many features of the fractional quantum Hall effect. Using an -invariant Einstein-Maxwell-axio-dilaton theory capturing the important modular transformation properties of quantum Hall physics, we find dyonic diatonic black hole solutions which are gapped and have a Hall conductivity equal to the filling fraction, as expected for quantum Hall states. We also provide several technical results on the general behavior of the gauge field fluctuations around these dyonic dilatonic black hole solutions: we specify a sufficient criterion for IR normalizability of the fluctuations, demonstrate the preservation of the gap under the action, and prove that the singularity of the fluctuation problem in the presence of a magnetic field is an accessory singularity. We finish with a preliminary investigation of the possible IR scaling solutions of our model and some speculations on how they could be important for the observed universality of quantum Hall transitions.

Nonlocal Polarization Feedback in a Fractional Quantum Hall Ferromagnet.

PubMed

Hennel, Szymon; Braem, Beat A; Baer, Stephan; Tiemann, Lars; Sohi, Pirouz; Wehrli, Dominik; Hofmann, Andrea; Reichl, Christian; Wegscheider, Werner; Rössler, Clemens; Ihn, Thomas; Ensslin, Klaus; Rudner, Mark S; Rosenow, Bernd

2016-04-01

In a quantum Hall ferromagnet, the spin polarization of the two-dimensional electron system can be dynamically transferred to nuclear spins in its vicinity through the hyperfine interaction. The resulting nuclear field typically acts back locally, modifying the local electronic Zeeman energy. Here we report a nonlocal effect arising from the interplay between nuclear polarization and the spatial structure of electronic domains in a ν=2/3 fractional quantum Hall state. In our experiments, we use a quantum point contact to locally control and probe the domain structure of different spin configurations emerging at the spin phase transition. Feedback between nuclear and electronic degrees of freedom gives rise to memristive behavior, where electronic transport through the quantum point contact depends on the history of current flow. We propose a model for this effect which suggests a novel route to studying edge states in fractional quantum Hall systems and may account for so-far unexplained oscillatory electronic-transport features observed in previous studies.

Automated High-Temperature Hall-Effect Apparatus

NASA Technical Reports Server (NTRS)

Parker, James B.; Zoltan, Leslie D.

1992-01-01

Automated apparatus takes Hall-effect measurements of specimens of thermoelectric materials at temperatures from ambient to 1,200 K using computer control to obtain better resolution of data and more data points about three times as fast as before. Four-probe electrical-resistance measurements taken in 12 electrical and 2 magnetic orientations to characterize specimens at each temperature. Computer acquires data, and controls apparatus via three feedback loops: one for temperature, one for magnetic field, and one for electrical-potential data.

Anode power deposition in a MPD thruster with a magnetically annulled Hall parameter anode

NASA Technical Reports Server (NTRS)

Gallimore, Alec D.; Kelly, Arnold J.; Jahn, Robert G.

1992-01-01

Results from previous studies indicate that the anode fall increases monotonically with the electron Hall parameter. In an attempt to reduce the anode fall by decreasing the local electron Hall parameter, a proof-of-concept test was performed in which an array of 36 permanent magnets were imbedded within the anode of a high power quasi-steady MPD thruster to decrease the local azimuthal component of the induced magnetic field. The modified thruster was operated at power levels between 150 kW and 4 MW with Ar and He propellants. Terminal voltage, triple probe, floating probe, and magnetic probe measurements were made to characterize the performance of the thruster with new anode. Incorporation of the modified anode resulted in a reduction of the anode fall by up to 15 V with Ar and 20 V with He, which corresponded to decreased anode power fractions of 40 and 45 percent with Ar and He, respectively.

Electrical control of the anomalous valley Hall effect in antiferrovalley bilayers

NASA Astrophysics Data System (ADS)

Tong, Wen-Yi; Duan, Chun-Gang

2017-08-01

In analogy to all-electric spintronics, all-electric valleytronics, i.e., valley manipulation via electric means, becomes an exciting new frontier as it may bring revolutions in the field of data storage with ultra-high speed and ultra-low power consumption. The existence of the anomalous valley Hall effect in ferrovalley materials demonstrates the possibility of electrical detection for valley polarization. However, in previously proposed valley-polarized monolayers, the anomalous valley Hall effect is controlled by external magnetic fields. Here, through elaborate structural design, we propose the antiferrovally bilayer as an ideal candidate for realizing all-electric valleytronic devices. Using the minimal k.p model, we show that the energy degeneracy between valley indexes in such system can be lifted by electric approaches. Subsequently, the anomalous valley Hall effect strongly depends on the electric field as well. Taking the bilayer VSe2 as an example, all-electric tuning and detecting of anomalous valley Hall effect is confirmed by density-functional theory calculations, indicating that the valley information in such antiferrovalley bilayer can be reversed by an electric field perpendicular to the plane of the system and easily probed through the sign of the Hall voltage.

Automated clustering of probe molecules from solvent mapping of protein surfaces: new algorithms applied to hot-spot mapping and structure-based drug design

NASA Astrophysics Data System (ADS)

Lerner, Michael G.; Meagher, Kristin L.; Carlson, Heather A.

2008-10-01

Use of solvent mapping, based on multiple-copy minimization (MCM) techniques, is common in structure-based drug discovery. The minima of small-molecule probes define locations for complementary interactions within a binding pocket. Here, we present improved methods for MCM. In particular, a Jarvis-Patrick (JP) method is outlined for grouping the final locations of minimized probes into physical clusters. This algorithm has been tested through a study of protein-protein interfaces, showing the process to be robust, deterministic, and fast in the mapping of protein "hot spots." Improvements in the initial placement of probe molecules are also described. A final application to HIV-1 protease shows how our automated technique can be used to partition data too complicated to analyze by hand. These new automated methods may be easily and quickly extended to other protein systems, and our clustering methodology may be readily incorporated into other clustering packages.

G. Stanley Hall, Child Study, and the American Public.

PubMed

Young, Jacy L

2016-01-01

In the final decades of the 19th century psychologist Granville Stanley Hall was among the most prominent pedagogical experts in the nation. The author explores Hall's carefully crafted persona as an educational expert, and his engagements with the American public, from 1880 to 1900, arguably the height of his influence. Drawing from accounts of Hall's lecture circuit in the popular press, a map of his talks across the nation is constructed to assess the geographic scope of his influence. These talks to educators on the psychology underlying childhood and pedagogy, and his views and research on child life more generally, were regularly discussed in newspapers and popular periodicals. The venues in which Hall's ideas were disseminated, discussed, and in some cases, dismissed are described. His efforts to mobilize popular support for, and assistance with, his research endeavors in child study are also discussed. Such efforts were controversial both within the burgeoning field of psychology and among the public. Through his various involvements in pedagogy, and concerted efforts to engage with the American public, Hall helped establish psychology's relevance to parenting and educational practices.

Final report: Mapping Interactions in Hybrid Systems with Active Scanning Probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berezovsky, Jesse

2017-09-29

This project aimed to study and map interactions between components of hybrid nanodevices using a novel scanning probe approach. To enable this work, we initially constructed a flexible experimental apparatus allowing for simultaneous scanning probe and confocal optical microscopy measurements. This setup was first used for all-optical measurements of nanostructures, with the focus then shifting to hybrid devices in which single coherent electron spins are coupled to micron-scale ferromagnetic elements, which may prove useful for addressing single spins, enhanced sensing, or spin-wave-mediated coupling of spins for quantum information applications. A significant breakthrough was the realization that it is not necessarymore » to fabricate a magnetic structure on a scanning probe – instead a ferromagnetic vortex core can act as an integrated, solid state, scanning probe. The core of the vortex produces a very strong, localized fringe field which can be used analogously to an MFM tip. Unlike a traditional MFM tip, however, the vortex core is scanned within an integrated device (eliminating drift), and can be moved on vastly faster timescales. This approach allows the detailed investigation of interactions between single spins and complex driven ferromagnetic dynamics.« less

Open-Source Automated Mapping Four-Point Probe.

PubMed

Chandra, Handy; Allen, Spencer W; Oberloier, Shane W; Bihari, Nupur; Gwamuri, Jephias; Pearce, Joshua M

2017-01-26

Scientists have begun using self-replicating rapid prototyper (RepRap) 3-D printers to manufacture open source digital designs of scientific equipment. This approach is refined here to develop a novel instrument capable of performing automated large-area four-point probe measurements. The designs for conversion of a RepRap 3-D printer to a 2-D open source four-point probe (OS4PP) measurement device are detailed for the mechanical and electrical systems. Free and open source software and firmware are developed to operate the tool. The OS4PP was validated against a wide range of discrete resistors and indium tin oxide (ITO) samples of different thicknesses both pre- and post-annealing. The OS4PP was then compared to two commercial proprietary systems. Results of resistors from 10 to 1 MΩ show errors of less than 1% for the OS4PP. The 3-D mapping of sheet resistance of ITO samples successfully demonstrated the automated capability to measure non-uniformities in large-area samples. The results indicate that all measured values are within the same order of magnitude when compared to two proprietary measurement systems. In conclusion, the OS4PP system, which costs less than 70% of manual proprietary systems, is comparable electrically while offering automated 100 micron positional accuracy for measuring sheet resistance over larger areas.

Open-Source Automated Mapping Four-Point Probe

PubMed Central

Chandra, Handy; Allen, Spencer W.; Oberloier, Shane W.; Bihari, Nupur; Gwamuri, Jephias; Pearce, Joshua M.

2017-01-01

Scientists have begun using self-replicating rapid prototyper (RepRap) 3-D printers to manufacture open source digital designs of scientific equipment. This approach is refined here to develop a novel instrument capable of performing automated large-area four-point probe measurements. The designs for conversion of a RepRap 3-D printer to a 2-D open source four-point probe (OS4PP) measurement device are detailed for the mechanical and electrical systems. Free and open source software and firmware are developed to operate the tool. The OS4PP was validated against a wide range of discrete resistors and indium tin oxide (ITO) samples of different thicknesses both pre- and post-annealing. The OS4PP was then compared to two commercial proprietary systems. Results of resistors from 10 to 1 MΩ show errors of less than 1% for the OS4PP. The 3-D mapping of sheet resistance of ITO samples successfully demonstrated the automated capability to measure non-uniformities in large-area samples. The results indicate that all measured values are within the same order of magnitude when compared to two proprietary measurement systems. In conclusion, the OS4PP system, which costs less than 70% of manual proprietary systems, is comparable electrically while offering automated 100 micron positional accuracy for measuring sheet resistance over larger areas. PMID:28772471

Tunneling Spectroscopy of Quantum Hall States in Bilayer Graphene

NASA Astrophysics Data System (ADS)

Wang, Ke; Harzheim, Achim; Watanabe, Kenji; Taniguchi, Takashi; Kim, Philip

In the quantum Hall (QH) regime, ballistic conducting paths along the physical edges of a sample appear, leading to quantized Hall conductance and vanishing longitudinal magnetoconductance. These QH edge states are often described as ballistic compressible strips separated by insulating incompressible strips, the spatial profiles of which can be crucial in understanding the stability and emergence of interaction driven QH states. In this work, we present tunneling transport between two QH edge states in bilayer graphene. Employing locally gated device structure, we guide and control the separation between the QH edge states in bilayer graphene. Using resonant Landau level tunneling as a spectroscopy tool, we measure the energy gap in bilayer graphene as a function of displacement field and probe the emergence and evolution of incompressible strips.

Pulsed eddy current differential probe to detect the defects in a stainless steel pipe

NASA Astrophysics Data System (ADS)

Angani, C. S.; Park, D. G.; Kim, C. G.; Leela, P.; Kishore, M.; Cheong, Y. M.

2011-04-01

Pulsed eddy current (PEC) is an electromagnetic nondestructive technique widely used to detect and quantify the flaws in conducting materials. In the present study a differential Hall-sensor probe which is used in the PEC system has been fabricated for the detection of defects in stainless steel pipelines. The differential probe has an exciting coil with two Hall-sensors. A stainless steel test sample with electrical discharge machining (EDM) notches under different depths of 1-5 mm was made and the sample was laminated by plastic insulation having uniform thickness to simulate the pipelines in nuclear power plants (NPPs). The driving coil in the probe is excited by a rectangular current pulse and the resultant response, which is the difference of the two Hall-sensors, has been detected as the PEC probe signal. The discriminating time domain features of the detected pulse such as peak value and time to zero are used to interpret the experimental results with the defects in the test sample. A feature extraction technique such as spectral power density has been devised to infer the PEC response.

Propulsion Instruments for Small Hall Thruster Integration

NASA Technical Reports Server (NTRS)

Johnson, Lee K.; Conroy, David G.; Spanjers, Greg G.; Bromaghim, Daron R.

2001-01-01

Planning and development are underway for the propulsion instrumentation necessary for the next AFRL electric propulsion flight project, which includes both a small Hall thruster and a micro-PPT. These instruments characterize the environment induced by the thruster and the associated data constitute part of a 'user's manual' for these thrusters. Several instruments probe the back-flow region of the thruster plume, and the data are intended for comparison with detailed numerical models in this region. Specifically, an ion probe is under development to determine the energy and species distributions, and a Langmuir probe will be employed to characterize the electron density and temperature. Other instruments directly measure the effects of thruster operation on spacecraft thermal control surfaces, optical surfaces, and solar arrays. Specifically, radiometric, photometric, and solar-cell-based sensors are under development. Prototype test data for most sensors should be available, together with details of the instrumentation subsystem and spacecraft interface.

Mapping the CMB with the Wilkinson Microwave Anisotropy Probe

NASA Technical Reports Server (NTRS)

Hinshaw, Gary F.

2007-01-01

The data from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite provide detailed full-sky maps of the cosmic microwave background temperature anisotropy and new full-sky maps of the polarization. Together, the data provide a wealth of cosmological information, including the age of the universe, the epoch when the first stars formed, and the overall composition of baryonic matter, dark matter, and dark energy. The results also provide constraints on the period of inflationary expansion in the very first moments of time. These and other aspects of the mission results will be discussed and commented on. WMAP, part of NASA's Explorers program, was launched on June 30,200 1. The WMAP satellite was produced in a partnership between the Goddard Space Flight Center and Princeton University. The WMAP team also includes researchers at the Johns Hopkins University; the Canadian Institute of Theoretical Astrophysics; University of Texas; University of Chicago; Brown University; University of British Columbia; and University of California, Los Angeles.

The impact of finite-area inhomogeneities on resistive and Hall measurement

NASA Astrophysics Data System (ADS)

Koon, Daniel

2013-03-01

I derive an iterative expression for the electric potential in an otherwise homogeneous thin specimen as the result of a finite-area inhomogeneity in either the direct conductance, the Hall conductance, or both. This expression extends to the finite-area regime the calculation of the effect of such inhomogeneities on the measurement error in the sheet resistance and Hall sheet resistance. I then test these results on the exactly-solvable case of a circular inhomogeneity equally distant from the four electrodes of either a square four-point-probe array on an infinitely large conducting specimen or a circular van der Pauw specimen with symmetrically-placed electrodes.

Topological phase transitions and quantum Hall effect in the graphene family

NASA Astrophysics Data System (ADS)

Ledwith, P.; Kort-Kamp, W. J. M.; Dalvit, D. A. R.

2018-04-01

Monolayer staggered materials of the graphene family present intrinsic spin-orbit coupling and can be driven through several topological phase transitions using external circularly polarized lasers and static electric or magnetic fields. We show how topological features arising from photoinduced phase transitions and the magnetic-field-induced quantum Hall effect coexist in these materials and simultaneously impact their Hall conductivity through their corresponding charge Chern numbers. We also show that the spectral response of the longitudinal conductivity contains signatures of the various phase-transition boundaries, that the transverse conductivity encodes information about the topology of the band structure, and that both present resonant peaks which can be unequivocally associated with one of the four inequivalent Dirac cones present in these materials. This complex optoelectronic response can be probed with straightforward Faraday rotation experiments, allowing the study of the crossroads between quantum Hall physics, spintronics, and valleytronics.

Study of the Accelerating Channel Wall Property Influence on the Hall Thruster Discharge Characteristics

DTIC Science & Technology

2004-11-01

Hall thruster characteristics there was prepared Hall thruster model of the SPT-100 type for these experiments and there were manufactured the required discharge chamber parts (rings) made of the Russian BN-SiO2 (borosil) ceramics and of the Russian AIN-BN (ABN) and Western ABN ceramics having secondary electron emission yield (SEEY) different from that one for borosil. These parts were replaceable during experiments. Thruster model was equipped by set of the near wall probes mounted at external discharge chamber wall. There was made characterization

Orbit Determination Support for the Microwave Anisotropy Probe (MAP)

NASA Technical Reports Server (NTRS)

Bauer, Frank (Technical Monitor); Truong, Son H.; Cuevas, Osvaldo O.; Slojkowski, Steven

2003-01-01

NASA's Microwave Anisotropy Probe (MAP) was launched from the Cape Canaveral Air Force Station Complex 17 aboard a Delta II 7425-10 expendable launch vehicle on June 30, 2001. The spacecraft received a nominal direct insertion by the Delta expendable launch vehicle into a 185-km circular orbit with a 28.7deg inclination. MAP was then maneuvered into a sequence of phasing loops designed to set up a lunar swingby (gravity-assisted acceleration) of the spacecraft onto a transfer trajectory to a lissajous orbit about the Earth-Sun L2 Lagrange point, about 1.5 million km from Earth. Because of its complex orbital characteristics, the mission provided a unique challenge for orbit determination (OD) support in many orbital regimes. This paper summarizes the premission trajectory covariance error analysis, as well as actual OD results. The use and impact of the various tracking stations, systems, and measurements will be also discussed. Important lessons learned from the MAP OD support team will be presented. There will be a discussion of the challenges presented to OD support including the effects of delta-Vs at apogee as well as perigee, and the impact of the spacecraft attitude mode on the OD accuracy and covariance analysis.

Observation of the Zero Hall Plateau in a Quantum Anomalous Hall Insulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Yang; Feng, Xiao; Ou, Yunbo

We report experimental investigations on the quantum phase transition between the two opposite Hall plateaus of a quantum anomalous Hall insulator. We observe a well-defined plateau with zero Hall conductivity over a range of magnetic field around coercivity when the magnetization reverses. The features of the zero Hall plateau are shown to be closely related to that of the quantum anomalous Hall effect, but its temperature evolution exhibits a significant difference from the network model for a conventional quantum Hall plateau transition. We propose that the chiral edge states residing at the magnetic domain boundaries, which are unique to amore » quantum anomalous Hall insulator, are responsible for the novel features of the zero Hall plateau.« less

Multifunctional semiconductor micro-Hall devices for magnetic, electric, and photo-detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbertson, A. M.; Cohen, L. F.; Sadeghi, Hatef

2015-12-07

We report the real-space voltage response of InSb/AlInSb micro-Hall devices to local photo-excitation, electric, and magnetic fields at room temperature using scanning probe microscopy. We show that the ultrafast generation of localised photocarriers results in conductance perturbations analogous to those produced by local electric fields. Experimental results are in good agreement with tight-binding transport calculations in the diffusive regime. The magnetic, photo, and charge sensitivity of a 2 μm wide probe are evaluated at a 10 μA bias current in the Johnson noise limit (valid at measurement frequencies > 10 kHz) to be, respectively, 500 nT/√Hz; 20 pW/√Hz (λ = 635 nm) comparable to commercial photoconductive detectors;more » and 0.05 e/√Hz comparable to that of single electron transistors. These results demonstrate the remarkably versatile sensing attributes of simple semiconductor micro-Hall devices that can be applied to a host of imaging and sensing applications.« less

Towards Thermal Reading of Magnetic States in Hall Crosses

NASA Astrophysics Data System (ADS)

Xu, Y.; Petit-Watelot, S.; Polewczyk, V.; Parent, G.; Montaigne, F.; Wegrowe, J.-E.; Mangin, S.; Lacroix, D.; Hehn, M.; Lacour, D.

2018-03-01

The 3 ω method is a standard way to measure the thermal conductivity of thin films. In this study, we apply the method to read the magnetic state of a perpendicularly magnetized CoTb ferrimagnetic Hall cross using a thermal excitation. In order to generate the thermal excitation, an oscillating current at an ω frequency is applied to the Hall cross using different geometries. The magnetic signals oscillating at ω , 2 ω , and 3 ω are probed using a lock-in technique. From the analysis of the power dependence, we can attribute the 3 ω response to the temperature oscillation and the 2 ω to the temperature-gradient oscillation. Finally, the frequency dependence of the magnetic signals can be understood by considering the heat diffusion in a two-dimensional model.

Anomalous Hall resistance in bilayer quantum Hall systems

NASA Astrophysics Data System (ADS)

Ezawa, Z. F.; Suzuki, S.; Tsitsishvili, G.

2007-07-01

We present a microscopic theory of the Hall current in the bilayer quantum Hall system on the basis of noncommutative geometry. By analyzing the Heisenberg equation of motion and the continuity equation of charge, we demonstrate the emergence of the phase current in a system where the interlayer phase coherence develops spontaneously. The phase current arranges itself to minimize the total energy of the system, as it induces certain anomalous behaviors in the Hall current in the counterflow geometry and also in the drag experiment. They explain the recent experimental data for anomalous Hall resistances due to Kellogg [Phys. Rev. Lett. 88, 126804 (2002); 93, 036801 (2004)] and Tutuc [Phys. Rev. Lett. 93, 036802 (2004)] at ν=1 .

5. View of Community Hall, first floor interior, entrance hall ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. View of Community Hall, first floor interior, entrance hall on east side of building, facing southeast. Ticket booth center foreground, stairway to auditorium right foreground. - Community Hall, Rainier Avenue & View Drive, Port Gamble, Kitsap County, WA

Mapping the Heavens: Probing Cosmology with Large Surveys

ScienceCinema

Frieman, Joshua [Fermilab

2017-12-09

This talk will provide an overview of recent and on-going sky surveys, focusing on their implications for cosmology. I will place particular emphasis on the Sloan Digital Sky Survey, the most ambitious mapping of the Universe yet undertaken, showing a virtual fly-through of the survey that reveals the large-scale structure of the galaxy distribution. Recent measurements of this large-scale structure, in combination with observations of the cosmic microwave background, have provided independent evidence for a Universe dominated by dark matter and dark energy as well as insights into how galaxies and larger-scale structures formed. Future planned surveys will build on these foundations to probe the history of the cosmic expansion--and thereby the dark energy--with greater precision.

The Oxford Probe: an open access five-hole probe for aerodynamic measurements

NASA Astrophysics Data System (ADS)

Hall, B. F.; Povey, T.

2017-03-01

The Oxford Probe is an open access five-hole probe designed for experimental aerodynamic measurements. The open access probe can be manufactured by the end user via additive manufacturing (metal or plastic). The probe geometry, drawings, calibration maps, and software are available under a creative commons license. The purpose is to widen access to aerodynamic measurement techniques in education and research environments. There are many situations in which the open access probe will allow results of comparable accuracy to a well-calibrated commercial probe. We discuss the applications and limitations of the probe, and compare the calibration maps for 16 probes manufactured in different materials and at different scales, but with the same geometrical design.

Intrinsic spin and momentum relaxation in organic single-crystalline semiconductors probed by ESR and Hall measurements

NASA Astrophysics Data System (ADS)

Tsurumi, Junto; Häusermann, Roger; Watanabe, Shun; Mitsui, Chikahiko; Okamoto, Toshihiro; Matsui, Hiroyuki; Takeya, Jun

Spin and charge momentum relaxation mechanism has been argued among organic semiconductors with various methods, devices, and materials. However, little is known in organic single-crystalline semiconductors because it has been hard to obtain an ideal organic crystal with an excellent crystallinity and controllability required for accurate measurements. By using more than 1-inch sized single crystals which are fabricated via contentious edge-casting method developed by our group, we have successfully demonstrated a simultaneous determination of spin and momentum relaxation time for gate-induced charges of 3,11-didecyldinaphtho[2,3- d:2',3'- d']benzo[1,2- b:4,5- b']dithiophene, by combining electron spin resonance (ESR) and Hall effect measurements. The obtained temperature dependences of spin and momentum relaxation times are in good agreement in terms of power law with a factor of approximately -2. It is concluded that Elliott-Yafet spin relaxation mechanism can be dominant at room temperature regime (200 - 300 K). Probing characteristic time scales such as spin-lattice, spin-spin, and momentum relaxation times, demonstrated in the present work, would be a powerful tool to elucidate fundamental spin and charge transport mechanisms. We acknowledge the New Energy and Industrial Technology Developing Organization (NEDO) for financial support.

Topological phase transitions and quantum Hall effect in the graphene family

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ledwith, Patrick John; Kort-Kamp, Wilton Junior de Melo; Dalvit, Diego Alejandro Roberto

Monolayer staggered materials of the graphene family present intrinsic spin-orbit coupling and can be driven through several topological phase transitions using external circularly polarized lasers and static electric or magnetic fields. We show how topological features arising from photoinduced phase transitions and the magnetic-field-induced quantum Hall effect coexist in these materials and simultaneously impact their Hall conductivity through their corresponding charge Chern numbers. We also show that the spectral response of the longitudinal conductivity contains signatures of the various phase-transition boundaries, that the transverse conductivity encodes information about the topology of the band structure, and that both present resonant peaksmore » which can be unequivocally associated with one of the four inequivalent Dirac cones present in these materials. As a result, this complex optoelectronic response can be probed with straightforward Faraday rotation experiments, allowing the study of the crossroads between quantum Hall physics, spintronics, and valleytronics.« less

Topological phase transitions and quantum Hall effect in the graphene family

DOE PAGES

Ledwith, Patrick John; Kort-Kamp, Wilton Junior de Melo; Dalvit, Diego Alejandro Roberto

2018-04-15

Monolayer staggered materials of the graphene family present intrinsic spin-orbit coupling and can be driven through several topological phase transitions using external circularly polarized lasers and static electric or magnetic fields. We show how topological features arising from photoinduced phase transitions and the magnetic-field-induced quantum Hall effect coexist in these materials and simultaneously impact their Hall conductivity through their corresponding charge Chern numbers. We also show that the spectral response of the longitudinal conductivity contains signatures of the various phase-transition boundaries, that the transverse conductivity encodes information about the topology of the band structure, and that both present resonant peaksmore » which can be unequivocally associated with one of the four inequivalent Dirac cones present in these materials. As a result, this complex optoelectronic response can be probed with straightforward Faraday rotation experiments, allowing the study of the crossroads between quantum Hall physics, spintronics, and valleytronics.« less

Ion Species Fractions in the Far-Field Plume of a High-Specific Impulse Hall Thruster

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Gallimore, Alec D.

2003-01-01

An ExB probe was used to measure the ion species fractions of Xe(+), Xe(2+), and Xe(3+) in the far-field plume of the NASA-173Mv2 laboratory-model Hall thruster. The thruster was operated at a constant xenon flow rate of 10 milligrams per second and discharge voltages of 300 to 900 V. The ExB probe was placed two meters downstream of the thruster exit plane on the thruster centerline. At a discharge voltage of 300 V, the species fractions of Xe(2+) and Xe(3+) were lower, but still consistent with, previous Hall thruster studies using other mass analyzers. Over discharge voltages of 300 to 900 V, the Xe(2+) species fractions increased from 0.04 to 0.12 and the Xe(3+) species fraction increased from 0.01 to 0.02.

Higher (odd) dimensional quantum Hall effect and extended dimensional hierarchy

NASA Astrophysics Data System (ADS)

Hasebe, Kazuki

2017-07-01

We demonstrate dimensional ladder of higher dimensional quantum Hall effects by exploiting quantum Hall effects on arbitrary odd dimensional spheres. Non-relativistic and relativistic Landau models are analyzed on S 2 k - 1 in the SO (2 k - 1) monopole background. The total sub-band degeneracy of the odd dimensional lowest Landau level is shown to be equal to the winding number from the base-manifold S 2 k - 1 to the one-dimension higher SO (2 k) gauge group. Based on the chiral Hopf maps, we clarify the underlying quantum Nambu geometry for odd dimensional quantum Hall effect and the resulting quantum geometry is naturally embedded also in one-dimension higher quantum geometry. An origin of such dimensional ladder connecting even and odd dimensional quantum Hall effects is illuminated from a viewpoint of the spectral flow of Atiyah-Patodi-Singer index theorem in differential topology. We also present a BF topological field theory as an effective field theory in which membranes with different dimensions undergo non-trivial linking in odd dimensional space. Finally, an extended version of the dimensional hierarchy for higher dimensional quantum Hall liquids is proposed, and its relationship to quantum anomaly and D-brane physics is discussed.

Advanced concentration analysis of atom probe tomography data: Local proximity histograms and pseudo-2D concentration maps.

PubMed

Felfer, Peter; Cairney, Julie

2018-06-01

Analysing the distribution of selected chemical elements with respect to interfaces is one of the most common tasks in data mining in atom probe tomography. This can be represented by 1D concentration profiles, 2D concentration maps or proximity histograms, which represent concentration, density etc. of selected species as a function of the distance from a reference surface/interface. These are some of the most useful tools for the analysis of solute distributions in atom probe data. In this paper, we present extensions to the proximity histogram in the form of 'local' proximity histograms, calculated for selected parts of a surface, and pseudo-2D concentration maps, which are 2D concentration maps calculated on non-flat surfaces. This way, local concentration changes at interfaces or and other structures can be assessed more effectively. Copyright © 2018 Elsevier B.V. All rights reserved.

Robert B. Laughlin and the Fractional Quantum Hall Effect

Science.gov Websites

dropdown arrow Site Map A-Z Index Menu Synopsis Robert B. Laughlin and the Fractional Quantum Hall Effect Tsui discovered the effect. In 1983, Laughlin, then at the Lawrence Livermore National Laboratory , provided the theoretical explanation of the effect in terms of fractionally charged particles. It was a

In-Situ Measurement of Hall Thruster Erosion Using a Fiber Optic Regression Probe

NASA Technical Reports Server (NTRS)

Polzink, Kurt A.; Korman, Valentin

2008-01-01

One potential life-limiting mechanism in a Hall thruster is the erosion of the ceramic material comprising the discharge channel. This is especially true for missions that require long thrusting periods and can be problematic for lifetime qualification, especially when attempting to qualify a thruster by analysis rather than a test lasting the full duration of the mission. In addition to lifetime, several analytical and numerical models include electrode erosion as a mechanism contributing to enhanced transport properties. However, there is still a great deal of dispute over the importance of erosion to transport in Hall thrusters. The capability to perform an in-situ measurement of discharge channel erosion is useful in addressing both the lifetime and transport concerns. An in-situ measurement would allow for real-time data regarding the erosion rates at different operating points, providing a quick method for empirically anchoring any analysis geared towards lifetime qualification. Erosion rate data over a thruster's operating envelope would also be useful in the modeling of the detailed physics inside the discharge chamber. A recent fundamental sensor development effort has led to a novel regression, erosion, and ablation sensor technology (REAST). The REAST sensor allows for measurement of real-time surface erosion rates at a discrete surface location. The sensor was tested using a linear Hall thruster geometry, which served as a means of producing plasma erosion of a ceramic discharge chamber. The mass flow rate, discharge voltage, and applied magnetic field strength could be varied, allowing for erosion measurements over a broad thruster operating envelope. Results are presented demonstrating the ability of the REAST sensor to capture not only the insulator erosion rates but also changes in these rates as a function of the discharge parameters.

Comparison of Hall Thruster Plume Expansion Model with Experimental Data

DTIC Science & Technology

2006-05-23

focus of this study, is a hybrid particle- in-cell ( PIC ) model that tracks particles along an unstructured tetrahedral mesh. * Research Engineer...measurements of the ion current density profile, ion energy distributions, and ion species fraction distributions using a nude Faraday probe, retarding...Vol.37 No.1. 6 Oh, D. and Hastings, D., “Three Dimensional PIC -DSMC Simulations of Hall Thruster Plumes and Analysis for Realistic Spacecraft

On-chip microwave circulators using quantum Hall plasmonics

NASA Astrophysics Data System (ADS)

Mahoney, Alice; Colless, James; Pauka, Sebastian; Hornibrook, John; Doherty, Andrew; Reilly, David; Peeters, Lucas; Fox, Eli; Goldhaber-Gordon, David; Kou, Xuefeng; Pan, Lei; Wang, Kang; Watson, John; Gardner, Geoffrey; Manfra, Michael

Circulators are directional circuit elements integral to technologies including radar systems, microwave communication transceivers and the readout of quantum information devices. Their non-reciprocity commonly arises from the interference of microwaves over the centimetre-scale of the signal wavelength in the presence of bulky magnetic media that breaks time-reversal symmetry. We present a completely passive on-chip microwave circulator with size 1/1000th the wavelength by exploiting the chiral, `slow-light' response of a GaAs/AlGaAs 2-dimensional electron gas in the quantum Hall regime. Further, by implementing this circulator design on a thin film of a magnetic topological insulator (Cr0.12(Bi0.26Sb0.62)2Te3), we show that similar non-reciprocity can be achieved at zero magnetic field. This additional mode of operation serves as a non-invasive probe of edge states in the quantum anomalous Hall effect, while also extending the possibility for integration with superconducting devices.

Mapping the plasmon response of Ag nanoislands on graphite at 100 nm resolution with scanning probe energy loss spectroscopy

NASA Astrophysics Data System (ADS)

Murphy, Shane; Bauer, Karl; Sloan, Peter A.; Lawton, James J.; Tang, Lin; Palmer, Richard E.

2015-12-01

We demonstrate plasmon mapping of Ag nanostructures on graphite using scanning probe energy loss spectroscopy (SPELS) with a spatial resolution of 100 nm. In SPELS, an STM tip is used as a localized source of field-emitted electrons to probe the sample surface. The energy loss spectrum of the backscattered electrons is measured to provide a chemical signature of the surface under the tip. We acquire three images simultaneously with SPELS: i) constant-current field-emission images, which provide topographical information; ii) backscattered electron images, which display material contrast; and iii) SPELS images, where material-dependent features such as plasmons are mapped.

In-Situ Measurement of Hall Thruster Erosion Using a Fiber Optic Regression Probe

NASA Technical Reports Server (NTRS)

Polzin, Kurt; Korman, Valentin

2009-01-01

One potential life-limiting mechanism in a Hall thruster is the erosion of the ceramic material comprising the discharge channel. This is especially true for missions that require long thrusting periods and can be problematic for lifetime qualification, especially when attempting to qualify a thruster by analysis rather than a test lasting the full duration of the mission. In addition to lifetime, several analytical and numerical models include electrode erosion as a mechanism contributing to enhanced transport properties. However, there is still a great deal of dispute over the importance of erosion to transport in Hall thrusters. The capability to perform an in-situ measurement of discharge channel erosion is useful in addressing both the lifetime and transport concerns. An in-situ measurement would allow for real-time data regarding the erosion rates at different operating points, providing a quick method for empirically anchoring any analysis geared towards lifetime qualification. Erosion rate data over a thruster s operating envelope would also be useful in the modeling of the detailed physics inside the discharge chamber. There are many different sensors and techniques that have been employed to quantify discharge channel erosion in Hall thrusters. Snapshots of the wear pattern can be obtained at regular shutdown intervals using laser profilometry. Many non-intrusive techniques of varying complexity and sensitivity have been employed to detect the time-varying presence of erosion products in the thruster plume. These include the use quartz crystal microbalances, emission spectroscopy, laser induced flourescence, and cavity ring-down spectroscopy. While these techniques can provide a very accurate picture of the level of eroded material in the thruster plume, it is more difficult to use them to determine the location from which the material was eroded. Furthermore, none of the methods cited provide a true in-situ measure of erosion at the channel surface while

Concert hall acoustics

NASA Astrophysics Data System (ADS)

Schroeder, Manfred

2004-05-01

I will review some work at Bell Laboratories on artificial reverberation and concert hall acoustics including Philharmonic Hall (Lincoln Center for the Performing Arts, New York). I will also touch on sound diffusion by number-theoretic surfaces and the measurement of reverberation time using the music as played in the hall as a ``test'' signal.

Performance of a Permanent-Magnet Cylindrical Hall-Effect Thruster

NASA Technical Reports Server (NTRS)

Polzin, K. A.; Sooby, E. S.; Kimberlin, A. C.; Raites, Y.; Merino, E.; Fisch, N. J.

2009-01-01

The performance of a low-power cylindrical Hall thruster, which more readily lends itself to miniaturization and low-power operation than a conventional (annular) Hall thruster, was measured using a planar plasma probe and a thrust stand. The field in the cylindrical thruster was produced using permanent magnets, promising a power reduction over previous cylindrical thruster iterations that employed electromagnets to generate the required magnetic field topology. Two sets of ring-shaped permanent magnets are used, and two different field configurations can be produced by reorienting the poles of one magnet relative to the other. A plasma probe measuring ion flux in the plume is used to estimate the current utilization for the two magnetic topologies. The measurements indicate that electron transport is impeded much more effectively in one configuration, implying higher thrust efficiency. Thruster performance measurements on this configuration were obtained over a power range of 70-350 W and with the cathode orifice located at three different axial positions relative to the thruster exit plane. The thrust levels over this power range were 1.25-6.5 mN, with anode efficiencies and specific impulses spanning 4-21% and 400-1950 s, respectively. The anode efficiency of the permanent-magnet thruster compares favorable with the efficiency of the electromagnet thruster when the power consumed by the electromagnets is taken into account.

Evaluation of ion collection area in Faraday probes.

PubMed

Brown, Daniel L; Gallimore, Alec D

2010-06-01

A Faraday probe with three concentric rings was designed and fabricated to assess the effect of gap width and collector diameter in a systematic study of the diagnostic ion collection area. The nested Faraday probe consisted of two concentric collector rings and an outer guard ring, which enabled simultaneous current density measurements on the inner and outer collectors. Two versions of the outer collector were fabricated to create gaps of 0.5 and 1.5 mm between the rings. Distribution of current density in the plume of a low-power Hall thruster ion source was measured in azimuthal sweeps at constant radius from 8 to 20 thruster diameters downstream of the exit plane with variation in facility background pressure. A new analytical technique is proposed to account for ions collected in the gap between the Faraday probe collector and guard ring. This method is shown to exhibit excellent agreement between all nested Faraday probe configurations, and to reduce the magnitude of integrated ion beam current to levels consistent with Hall thruster performance analyses. The technique is further studied by varying the guard ring bias potential with a fixed collector bias potential, thereby controlling ion collection in the gap. Results are in agreement with predictions based on the proposed analytical technique. The method is applied to a past study comparing the measured ion current density profiles of two Faraday probe designs. These findings provide new insight into the nature of ion collection in Faraday probe diagnostics, and lead to improved accuracy with a significant reduction in measurement uncertainty.

Mode transition of a Hall thruster discharge plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hara, Kentaro, E-mail: kenhara@umich.edu; Sekerak, Michael J., E-mail: msekerak@umich.edu; Boyd, Iain D.

2014-05-28

A Hall thruster is a cross-field plasma device used for spacecraft propulsion. An important unresolved issue in the development of Hall thrusters concerns the effect of discharge oscillations in the range of 10–30 kHz on their performance. The use of a high speed Langmuir probe system and ultra-fast imaging of the discharge plasma of a Hall thruster suggests that the discharge oscillation mode, often called the breathing mode, is strongly correlated to an axial global ionization mode. Stabilization of the global oscillation mode is achieved as the magnetic field is increased and azimuthally rotating spokes are observed. A hybrid-direct kinetic simulationmore » that takes into account the transport of electronically excited atoms is used to model the discharge plasma of a Hall thruster. The predicted mode transition agrees with experiments in terms of the mean discharge current, the amplitude of discharge current oscillation, and the breathing mode frequency. It is observed that the stabilization of the global oscillation mode is associated with reduced electron transport that suppresses the ionization process inside the channel. As the Joule heating balances the other loss terms including the effects of wall loss and inelastic collisions, the ionization oscillation is damped, and the discharge oscillation stabilizes. A wide range of the stable operation is supported by the formation of a space charge saturated sheath that stabilizes the electron axial drift and balances the Joule heating as the magnetic field increases. Finally, it is indicated from the numerical results that there is a strong correlation between the emitted light intensity and the discharge current.« less

A Comprehensive Investigation of Facility Effects on the Testing of High-Power Monolithic and Clustered Hall Thruster Systems

DTIC Science & Technology

2004-09-02

path for developing high-power EP systems is somewhat certain given NASA’s recent success with its 70+ kW NASA-457M Hall thruster , it is clear that...current density distribution, and summarize findings from cold- and hot-flow pressure map data of our vacuum chamber for a number of Hall thruster mass flow rates.

Comparison of Hall Thruster Plume Expansion Model with Experimental Data (Preprint)

DTIC Science & Technology

2006-07-01

Cartesian mesh. AQUILA, the focus of this study, is a hybrid PIC model that tracks particles along an unstructured tetrahedral mesh. COLISEUM is capable...measurements of the ion current density profile, ion energy distributions, and ion species fraction distributions using a nude Faraday probe...Spacecraft and Rockets, Vol.37 No.1. 6 Oh, D. and Hastings, D., “Three Dimensional PIC -DSMC Simulations of Hall Thruster Plumes and Analysis for

Electrical impedance map (EIM) for margin assessment during robot-assisted laparoscopic prostatectomy (RALP) using a microendoscopic probe

NASA Astrophysics Data System (ADS)

Mahara, Aditya; Khan, Shadab; Schned, Alan R.; Hyams, Elias S.; Halter, Ryan J.

2015-03-01

Positive surgical margins (PSMs) found following prostate cancer surgery are a significant risk factor for post-operative disease recurrence. Noxious adjuvant radiation and chemical-based therapies are typically offered to men with PSMs. Unfortunately, no real-time intraoperative technology is currently available to guide surgeons to regions of suspicion during the initial prostatectomy where immediate surgical excisions could be used to reduce the chance of PSMs. A microendoscopic electrical impedance sensing probe was developed with the intention of providing real-time feedback regarding margin status to surgeons during robot-assisted laparoscopic prostatectomy (RALP) procedures. A radially configured 17-electrode microendoscopic probe was designed, constructed, and initially evaluated through use of gelatin-based phantoms and an ex vivo human prostate specimen. Impedance measurements are recorded at 10 frequencies (10 kHz - 100 kHz) using a high-speed FPGA-based electrical impedance tomography (EIT) system. Tetrapolar impedances are recorded from a number of different electrode configurations strategically chosen to sense tissue in a pre-defined sector underlying the probe face. A circular electrical impedance map (EIM) with several color-coded pie-shaped sectors is created to represent the impedance values of the probed tissue. Gelatin phantom experiments show an obvious distinction in the impedance maps between high and low impedance regions. Similarly, the EIM generated from the ex vivo prostate case shows distinguishing features between cancerous and benign regions. Based on successful development of this probe and these promising initial results, EIMs of additional prostate specimens are being collected to further evaluate this approach for intraoperative surgical margin assessment during RALP procedures.

Focal overlap gating in velocity map imaging to achieve high signal-to-noise ratio in photo-ion pump-probe experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shivaram, Niranjan; Champenois, Elio G.; Cryan, James P.

We demonstrate a technique in velocity map imaging (VMI) that allows spatial gating of the laser focal overlap region in time resolved pump-probe experiments. This significantly enhances signal-to-noise ratio by eliminating background signal arising outside the region of spatial overlap of pump and probe beams. This enhancement is achieved by tilting the laser beams with respect to the surface of the VMI electrodes which creates a gradient in flight time for particles born at different points along the beam. By suitably pulsing our microchannel plate detector, we can select particles born only where the laser beams overlap. Furthermore, this spatialmore » gating in velocity map imaging can benefit nearly all photo-ion pump-probe VMI experiments especially when extreme-ultraviolet light or X-rays are involved which produce large background signals on their own.« less

Focal overlap gating in velocity map imaging to achieve high signal-to-noise ratio in photo-ion pump-probe experiments

DOE PAGES

Shivaram, Niranjan; Champenois, Elio G.; Cryan, James P.; ...

2016-12-19

We demonstrate a technique in velocity map imaging (VMI) that allows spatial gating of the laser focal overlap region in time resolved pump-probe experiments. This significantly enhances signal-to-noise ratio by eliminating background signal arising outside the region of spatial overlap of pump and probe beams. This enhancement is achieved by tilting the laser beams with respect to the surface of the VMI electrodes which creates a gradient in flight time for particles born at different points along the beam. By suitably pulsing our microchannel plate detector, we can select particles born only where the laser beams overlap. Furthermore, this spatialmore » gating in velocity map imaging can benefit nearly all photo-ion pump-probe VMI experiments especially when extreme-ultraviolet light or X-rays are involved which produce large background signals on their own.« less

Performance and Environmental Test Results of the High Voltage Hall Accelerator Engineering Development Unit

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Haag, Thomas; Huang, Wensheng; Shastry, Rohit; Pinero, Luis; Peterson, Todd; Mathers, Alex

2012-01-01

NASA Science Mission Directorate's In-Space Propulsion Technology Program is sponsoring the development of a 3.5 kW-class engineering development unit Hall thruster for implementation in NASA science and exploration missions. NASA Glenn and Aerojet are developing a high fidelity high voltage Hall accelerator that can achieve specific impulse magnitudes greater than 2,700 seconds and xenon throughput capability in excess of 300 kilograms. Performance, plume mappings, thermal characterization, and vibration tests of the high voltage Hall accelerator engineering development unit have been performed. Performance test results indicated that at 3.9 kW the thruster achieved a total thrust efficiency and specific impulse of 58%, and 2,700 sec, respectively. Thermal characterization tests indicated that the thruster component temperatures were within the prescribed material maximum operating temperature limits during full power thruster operation. Finally, thruster vibration tests indicated that the thruster survived the 3-axes qualification full-level random vibration test series. Pre and post-vibration test performance mappings indicated almost identical thruster performance. Finally, an update on the development progress of a power processing unit and a xenon feed system is provided.

Complementary Density Measurements for the 200W Busek Hall Thruster (PREPRINT)

DTIC Science & Technology

2006-07-12

Hall thruster are presented. Both a Faraday probe and microwave interferometry system are used to examine the density distribution of the thruster plasma at regular spatial intervals. Both experiments are performed in situ under the same conditions. The resulting density distributions obtained from both experiments are presented. Advantages and uncertainties of both methods are presented, as well as how comparison between the two data sets can account for the uncertainties of each method

Rotating plasma structures in the cross-field discharge of Hall thrusters

NASA Astrophysics Data System (ADS)

Mazouffre, Stephane; Grimaud, Lou; Tsikata, Sedina; Matyash, Konstantin

2016-09-01

Rotating plasma structures, also termed rotating spokes, are observed in various types of low-pressure discharges with crossed electric and magnetic field configurations, such as Penning sources, magnetron discharges, negative ion sources and Hall thrusters. Such structures correspond to large-scale high-density plasma blocks that rotate in the E×B drift direction with a typical frequency on the order of a few kHz. Although such structures have been extensively studied in many communities, the mechanism at their origin and their role in electron transport across the magnetic field remain unknown. Here, we will present insights into the nature of spokes, gained from a combination of experiments and advanced particle-in-cell numerical simulations that aim at better understanding the physics and the impact of rotating plasma structures in the ExB discharge of the Hall thruster. As rotating spokes appear in the ionization region of such thrusters, and are therefore difficult to probe with diagnostics, experiments have been performed with a wall-less Hall thruster. In this configuration, the entire plasma discharge is pushed outside the dielectric cavity, through which the gas is injected, using the combination of specific magnetic field topology with appropriate anode geometry.

Discharge Oscillations in a Permanent Magnet Cylindrical Hall-Effect Thruster

NASA Technical Reports Server (NTRS)

Polzin, K. A.; Sooby, E. S.; Raitses, Y.; Merino, E.; Fisch, N. J.

2009-01-01

Measurements of the discharge current in a cylindrical Hall thruster are presented to quantify plasma oscillations and instabilities without introducing an intrusive probe into the plasma. The time-varying component of the discharge current is measured using a current monitor that possesses a wide frequency bandwidth and the signal is Fourier transformed to yield the frequency spectra present, allowing for the identification of plasma oscillations. The data show that the discharge current oscillations become generally greater in amplitude and complexity as the voltage is increased, and are reduced in severity with increasing flow rate. The breathing mode ionization instability is identified, with frequency as a function of discharge voltage not increasing with discharge voltage as has been observed in some traditional Hall thruster geometries, but instead following a scaling similar to a large-amplitude, nonlinear oscillation mode recently predicted in for annular Hall thrusters. A transition from lower amplitude oscillations to large relative fluctuations in the oscillating discharge current is observed at low flow rates and is suppressed as the mass flow rate is increased. A second set of peaks in the frequency spectra are observed at the highest propellant flow rate tested. Possible mechanisms that might give rise to these peaks include ionization instabilities and interactions between various oscillatory modes.

Topological Hall and Spin Hall Effects in Disordered Skyrmionic Textures

NASA Astrophysics Data System (ADS)

Ndiaye, Papa Birame; Akosa, Collins; Manchon, Aurelien; Spintronics Theory Group Team

We carry out a throughout study of the topological Hall and topological spin Hall effects in disordered skyrmionic systems: the dimensionless (spin) Hall angles are evaluated across the energy band structure in the multiprobe Landauer-Büttiker formalism and their link to the effective magnetic field emerging from the real space topology of the spin texture is highlighted. We discuss these results for an optimal skyrmion size and for various sizes of the sample and found that the adiabatic approximation still holds for large skyrmions as well as for few atomic size-nanoskyrmions. Finally, we test the robustness of the topological signals against disorder strength and show that topological Hall effect is highly sensitive to momentum scattering. This work was supported by the King Abdullah University of Science and Technology (KAUST) through the Award No OSR-CRG URF/1/1693-01 from the Office of Sponsored Research (OSR).

Optical probing of quantum Hall effect of composite fermions and of the liquid-insulator transition

NASA Astrophysics Data System (ADS)

Rossella, F.; Bellani, V.; Dionigi, F.; Amado, M.; Diez, E.; Kowalik, K.; Biasiol, G.; Sorba, L.

2011-12-01

In the photoluminescence spectra of a two-dimensional electron gas in the fractional quantum Hall regime we observe the states at filling factors ν = 4/5, 5/7, 4/11 and 3/8 as clear minima in the intensity or area emission peak. The first three states are described as interacting composite fermions in fractional quantum Hall regime. The minimum in the intensity at ν = 3/8, which is not explained within this picture, can be an evidence of a suppression of the screening of the Coulomb interaction among the effective quasi-particles involved in this intriguing state. The magnetic field energy dispersion at very low temperatures is also discussed. At low field the emission follows a Landau dispersion with a screened magneto-Coulomb contribution. At intermediate fields the hidden symmetry manifests. At high field above ν = 1/3 the electrons correlate into an insulating phase, and the optical emission behaviour at the liquid-insulator transition is coherent with a charge ordering driven by Coulomb correlations.

Facility Focus: Residence Halls.

ERIC Educational Resources Information Center

College Planning & Management, 2002

2002-01-01

Describes residence halls seeking to meet needs beyond traditional mass housing for the 18- to 22-year-old students: Whittemore Hall at the Tuck School of Business at Dartmouth College (for older students); Small Group Housing at Washington University (grouping students with common interests); and the renovation of the residence hall at Boston's…

Astronaut Hall of Fame

NASA Image and Video Library

2018-04-21

Scott D. Altman, second from left, is inducted into the Astronaut Hall of Fame (AHOF) during a ceremony inside the Space Shuttle Atlantis attraction at NASA's Kennedy Space Center Visitor Complex in Florida. At far left, Hall of Famer Curt Brown, board chairman, Astronaut Scholarship Foundation (ASF), inducts Altman into the Hall of Fame Class of 2018. At right is Hall of Famer John Grunsfeld, who spoke on Altman's behalf during the ceremony. At far right is Thomas D. Jones, Ph.D., who also was inducted into the AHOF Class of 2018. Inductees into the Hall of Fame are selected by a committee of Hall of Fame astronauts, former NASA officials, flight directors, historians and journalists. The process is administered by the Astronaut Scholarship Foundation. To be eligible, an astronaut must have made his or her first flight at least 17 years before the induction. Candidates must be a U.S. citizen and a NASA-trained commander, pilot or mission specialist who has orbited the earth at least once. Including Altman and Jones, 97 astronauts have been inducted into the AHOF.

Astronaut Hall of Fame

NASA Image and Video Library

2018-04-21

Thomas D. Jones, Ph.D., in the center, is inducted into the Astronaut Hall of Fame (AHOF) during a ceremony inside the Space Shuttle Atlantis attraction at NASA’s Kennedy Space Center Visitor Complex in Florida. At left, Hall of Famer Curt Brown, board chairman, Astronaut Scholarship Foundation (ASF), inducts Jones into the Hall of Fame Class of 2018. At right is Hall of Famer Storey Musgrave, who spoke on Jones behalf during the ceremony. Also inducted was retired astronaut Scott D. Altman. Inductees into the Hall of Fame are selected by a committee of Hall of Fame astronauts, former NASA officials, flight directors, historians and journalists. The process is administered by the Astronaut Scholarship Foundation. To be eligible, an astronaut must have made his or her first flight at least 17 years before the induction. Candidates must be a U.S. citizen and a NASA-trained commander, pilot or mission specialist who has orbited the earth at least once. Including Altman and Jones, 97 astronauts have been inducted into the AHOF.

NASA's 2004 Hall Thruster Program

NASA Technical Reports Server (NTRS)

Jacobson, David T.; Manzella, David H.; Hofer, Richard R.; Peterson, Peter Y.

2004-01-01

An overview of NASA's Hall thruster research and development tasks conducted during fiscal year 2004 is presented. These tasks focus on: raising the technology readiness level of high power Hall thrusters, developing a moderate-power/ moderate specific impulse Hall thruster, demonstrating high-power/high specific impulse Hall thruster operation, and addressing the fundamental technical challenges of emerging Hall thruster concepts. Programmatic background information, technical accomplishments and out year plans for each program element performed under the sponsorship of the In-Space Transportation Program, Project Prometheus, and the Energetics Project are provided.

Quasiparticle-mediated spin Hall effect in a superconductor.

PubMed

Wakamura, T; Akaike, H; Omori, Y; Niimi, Y; Takahashi, S; Fujimaki, A; Maekawa, S; Otani, Y

2015-07-01

In some materials the competition between superconductivity and magnetism brings about a variety of unique phenomena such as the coexistence of superconductivity and magnetism in heavy-fermion superconductors or spin-triplet supercurrent in ferromagnetic Josephson junctions. Recent observations of spin-charge separation in a lateral spin valve with a superconductor evidence that these remarkable properties are applicable to spintronics, although there are still few works exploring this possibility. Here, we report the experimental observation of the quasiparticle-mediated spin Hall effect in a superconductor, NbN. This compound exhibits the inverse spin Hall (ISH) effect even below the superconducting transition temperature. Surprisingly, the ISH signal increases by more than 2,000 times compared with that in the normal state with a decrease of the injected spin current. The effect disappears when the distance between the voltage probes becomes larger than the charge imbalance length, corroborating that the huge ISH signals measured are mediated by quasiparticles.

Experimental and Numerical Examination of a Hall Thruster Plume (Preprint)

DTIC Science & Technology

2007-07-31

Hall thruster has been characterized through measurements from various plasma electrostatic probes. Ion current flux, plasma potential, plasma density, and electron temperatures were measured from the near-field plume to 60 cm downstream of the exit plane. These experimentally derived measurements were compared to numerical simulations run with the plasma plume code DRACO. A major goal of this study was to determine the fidelity of the DRACO numerical simulation. The effect of background pressure on the thruster plume was also examined using ion current flux measurements

Excitation correlation photoluminescence in the presence of Shockley-Read-Hall recombination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borgwardt, M., E-mail: mario.borgwardt@helmholtz-berlin.de; Sippel, P.; Eichberger, R.

Excitation correlation photoluminescence (ECPL) measurements are often analyzed in the approximation of a cross correlation of charge carrier populations generated by the two delayed pulses. In semiconductors, this approach is valid for a linear non-radiative recombination path, but not for a non-linear recombination rate as in the general Shockley-Read-Hall recombination scenario. Here, the evolution of the ECPL signal was studied for deep trap recombination following Shockley-Read-Hall statistics. Analytic solutions can be obtained for a fast minority trapping regime and steady state recombination. For the steady state case, our results show that the quadratic radiative term plays only a minor role,more » and that the shape of the measured signal is mostly determined by the non-linearity of the recombination itself. We find that measurements with unbalanced intense pump and probe pulses can directly provide information about the dominant non-radiative recombination mechanism. The signal traces follow the charge carrier concentrations, despite the complex origins of the signal, thus showing that ECPL can be applied to study charge carrier dynamics in semiconductors without requiring elaborate calculations. The model is compared with measurements on a reference sample with alternating layers of InGaAs/InAlAs that were additionally cross-checked with time resolved optical pump terahertz probe measurements and found to be in excellent agreement.« less

Spin pumping and inverse spin Hall effects—Insights for future spin-orbitronics (invited)

DOE PAGES

Zhang, Wei; Jungfleisch, Matthias B.; Jiang, Wanjun; ...

2015-03-13

Quantification of spin-charge interconversion has become increasingly important in the fast-developing field of spin-orbitronics. Pure spin current generated by spin pumping acts a sensitive probe for many bulk and interface spin-orbit effects, which has been indispensable for the discovery of many promising new spin-orbit materials. Here, we apply spin pumping and inverse spin Hall effect experiments, as a useful metrology, and study spin-orbit effects in a variety of metals and metal interfaces. We also quantify the spin Hall effects in Ir and W using the conventional bilayer structures, and discuss the self-induced voltage in a single layer of ferromagnetic permalloy.more » Finally, we extend our discussions to multilayer structures and quantitatively reveal the spin current flow in two consecutive normal metal layers.« less

Geologic map of the White Hall quadrangle, Frederick County, Virginia, and Berkeley County, West Virginia

USGS Publications Warehouse

Doctor, Daniel H.; Orndorff, Randall C.; Parker, Ronald A.; Weary, David J.; Repetski, John E.

2010-01-01

The White Hall 7.5-minute quadrangle is located within the Valley and Ridge province of northern Virginia and the eastern panhandle of West Virginia. The quadrangle is one of several being mapped to investigate the geologic framework and groundwater resources of Frederick County, Va., as well as other areas in the northern Shenandoah Valley of Virginia and West Virginia. All exposed bedrock outcrops are clastic and carbonate strata of Paleozoic age ranging from Middle Cambrian to Late Devonian. Surficial materials include unconsolidated alluvium, colluvium, and terrace deposits of Quaternary age, and local paleo-terrace deposits possibly of Tertiary age. The quadrangle lies across the northeast plunge of the Great North Mountain anticlinorium and includes several other regional folds. The North Mountain fault zone cuts through the eastern part of the quadrangle; it is a series of thrust faults generally oriented northeast-southwest that separate the Silurian and Devonian clastic rocks from the Cambrian and Ordovician carbonate rocks and shales. Karst development in the quadrangle occurs in all of the carbonate rocks. Springs occur mainly near or on faults. Sinkholes occur within all of the carbonate rock units, especially where the rocks have undergone locally intensified deformation through folding, faulting, or some combination.

Unconventional topological Hall effect in skyrmion crystals caused by the topology of the lattice

NASA Astrophysics Data System (ADS)

Göbel, Börge; Mook, Alexander; Henk, Jürgen; Mertig, Ingrid

2017-03-01

The hallmark of a skyrmion crystal (SkX) is the topological Hall effect (THE). In this article we predict and explain an unconventional behavior of the topological Hall conductivity in SkXs. In simple terms, the spin texture of the skyrmions causes an inhomogeneous emergent magnetic field whose associated Lorentz force acts on the electrons. By making the emergent field homogeneous, the THE is mapped onto the quantum Hall effect (QHE). Consequently, each electronic band of the SkX is assigned to a Landau level. This correspondence of THE and QHE allows us to explain the unconventional behavior of the THE of electrons in SkXs. For example, a skyrmion crystal on a triangular lattice exhibits a quantized topological Hall conductivity with steps of 2 .e2/h below and with steps of 1 .e2/h above the van Hove singularity. On top of this, the conductivity shows a prominent sign change at the van Hove singularity. These unconventional features are deeply connected to the topology of the structural lattice.

Gate-controlled tunneling of quantum Hall edge states in bilayer graphene

NASA Astrophysics Data System (ADS)

Zhu, Jun; Li, Jing; Wen, Hua

Controlled tunneling of integer and fractional quantum Hall edge states provides a powerful tool to probe the physics of 1D systems and exotic particle statistics. Experiments in GaAs 2DEGs employ either a quantum point contact or a line junction tunnel barrier. It is generally difficult to independently control the filling factors νL and νR on the two sides of the barrier. Here we show that in bilayer graphene both νL and νR as well as their Landau level structures can be independently controlled using a dual-split-gate structure. In addition, the height of the line-junction tunnel barrier implemented in our experiments is tunable via a 5th gate. By measuring the tunneling resistance across the junction RT we examine the equilibration of the edge states in a variety of νL/νR scenarios and under different barrier heights. Edge states from both sides are fully mixed in the case of a low barrier. As the barrier height increases, we observe plateaus in RT that correspond to sequential complete backscattering of edge states. Gate-controlled manipulation of edge states offers a new angle to the exploration of quantum Hall magnetism and fractional quantum Hall effect in bilayer graphene.

g8: Physics with Linearly-Polarized Photons in Hall B of JLab

NASA Astrophysics Data System (ADS)

Cole, Philip L.

2001-11-01

The set of experiments forming the g8 run in Hall B took place this past summer (6/4/01-8/13/01) in Hall B of Jefferson Lab. These experiments make use of a beam of linearly-polarized photons produced through coherent bremsstrahlung and represent the first time such a probe has been employed at Jefferson Lab. Several new and upgraded Hall-B beamline devices were commissioned prior to the production running of g8. The scientific purpose of g8 is to improve the understanding of the underlying symmetry of the quark degrees of freedom in the nucleon, the nature of the parity exchange between the incident photon and the target nucleon, and the mechanism of associated strangeness production in electromagnetic reactions. With the high-quality beam of the tagged and collimated linearly-polarized photons and the nearly complete angular coverage of the Hall-B spectrometer, we will extract the differential cross sections and polarization observables for the photoproduction of vector mesons and kaons at photon energies ranging between 1.9 and 2.1 GeV. We collected over 1.2 trillion triggers. After data cuts, we expect to have 500 times the world's data set on rhos and omegas produced via a beam of linearly-polarized photons. A report on the results of the commissioning of the beamline devices and the progress of the analysis of the g8 run will be presented.

Power Dependence of the Electron Mobility Profile in a Hall Thruster

NASA Technical Reports Server (NTRS)

Jorns, Benjamin A.; Hofery, Richard H.; Mikellides, Ioannis G.

2014-01-01

The electron mobility profile is estimated in a 4.5 kW commercial Hall thruster as a function of discharge power. Internal measurements of plasma potential and electron temperature are made in the thruster channel with a high-speed translating probe. These measurements are presented for a range of throttling conditions from 150 - 400 V and 0.6 - 4.5 kW. The fluid-based solver, Hall2De, is used in conjunction with these internal plasma parameters to estimate the anomalous collision frequency profile at fixed voltage, 300 V, and three power levels. It is found that the anomalous collision frequency profile does not change significantly upstream of the location of the magnetic field peak but that the extent and magnitude of the anomalous collision frequency downstream of the magnetic peak does change with thruster power. These results are discussed in the context of developing phenomenological models for how the collision frequency profile depends on thruster operating conditions.

Hall Plateaus at magic angles in ultraquantum Bismuth

NASA Astrophysics Data System (ADS)

Benoît, Fauqué.

2009-03-01

The behaviour of a three-dimensional electron gas in the presence of a magnetic field strong enough to put all carriers in the first Landau level (i.e. beyond the quantum limit) is a longstanding question of theoretical condensed matter physics [1]. This issue has been recently explored by two high-field experiments on elemental semi-metal Bismuth. In a first study of transport coefficients (which are dominated by hole-like carriers), the Nernst coefficient presented three unexpected maxima that are concomitant with quasi-plateaux in the Hall coefficient [2]. In a second series of experiments, torque magnetometry (which mainly probes the three Dirac valley electron pockets) detected a field-induced phase transition [3]. The full understanding of the electron and hole behaviours above the quantum limit of pure Bi is therefore still under debate. In this talk, we will present our measurement of the Hall resistivity and torque magnetometry with magnetic field up to 31 T and rotating in the trigonal-bisectrix plane [4]. The Hall response is dominated by the hole pockets according to its sign as well as the period and the angular dependence of its quantum oscillations. In the vicinity of the quantum limit, it presents additional anomalies which are the fingerprints of the electron pockets. We found that for particular orientations of the magnetic field (namely ``magic angles''), the Hall response becomes field-independent within the experimental resolution around 20T. This drastic dependence of the plateaux on the field orientation provides strong constraints for theoretical scenarios. [4pt] [1] Bertrand I. Halperin, Japanese Journal of Applied Physics, 26, Supplement 26-3 (1987).[0pt] [2] Kamran Behnia, Luis Balicas, Yakov Kopelevich, Science, 317, 1729 (2008).[0pt] [3] Lu Li, J. G. Checkelsky, Y. S. Hor, C. Uher, A. F. Hebard, R. J. Cava, and N. P. Ong , Science, 321, 5888 (2008).[0pt] [4] Benoît Fauqu'e, Luis Balicas, Ilya Sheikin, Jean Paul Issi and Kamran Behnia

Probing and mapping electrode surfaces in solid oxide fuel cells.

PubMed

Blinn, Kevin S; Li, Xiaxi; Liu, Mingfei; Bottomley, Lawrence A; Liu, Meilin

2012-09-20

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen (1-7). The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion(2). Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation(8-12). It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition(8, 10, 13, 14) ("coking") and sulfur poisoning(11, 15) and the manner in which surface modifications stave off this degradation(16). The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

PubMed Central

Blinn, Kevin S.; Li, Xiaxi; Liu, Mingfei; Bottomley, Lawrence A.; Liu, Meilin

2012-01-01

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM

A dual-modal magnetic nanoparticle probe for preoperative and intraoperative mapping of sentinel lymph nodes by magnetic resonance and near infrared fluorescence imaging

PubMed Central

Zhou, Zhengyang; Chen, Hongwei; Lipowska, Malgorzata; Wang, Liya; Yu, Qiqi; Yang, Xiaofeng; Tiwari, Diana; Yang, Lily; Mao, Hui

2016-01-01

The ability to reliably detect sentinel lymph nodes for sentinel lymph node biopsy and lymphadenectomy is important in clinical management of patients with metastatic cancers. However, the traditional sentinel lymph node mapping with visible dyes is limited by the penetration depth of light and fast clearance of the dyes. On the other hand, sentinel lymph node mapping with radionucleotide technique has intrinsically low spatial resolution and does not provide anatomic details in the sentinel lymph node mapping procedure. This work reports the development of a dual modality imaging probe with magnetic resonance and near infrared imaging capabilities for sentinel lymph node mapping using magnetic iron oxide nanoparticles (10 nm core size) conjugated with a near infrared molecule with emission at 830 nm. Accumulation of magnetic iron oxide nanoparticles in sentinel lymph nodes leads to strong T2 weighted magnetic resonance imaging contrast that can be potentially used for preoperative localization of sentinel lymph nodes, while conjugated near infrared molecules provide optical imaging tracking of lymph nodes with a high signal to background ratio. The new magnetic nanoparticle based dual imaging probe exhibits a significant longer lymph node retention time. Near infrared signals from nanoparticle conjugated near infrared dyes last up to 60 min in sentinel lymph node compared to that of 25 min for the free near infrared dyes in a mouse model. Furthermore, axillary lymph nodes, in addition to sentinel lymph nodes, can be also visualized with this probe, given its slow clearance and sufficient sensitivity. Therefore, this new dual modality imaging probe with the tissue penetration and sensitive detection of sentinel lymph nodes can be applied for preoperative survey of lymph nodes with magnetic resonance imaging and allows intraoperative sentinel lymph node mapping using near infrared optical devices. PMID:23812946

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheehan, J. P.; Raitses, Yevgeny; Hershkowitz, Noah

Here, this article provides recommended methods for building, operating, and taking plasma potential measurements from electron-emitting probes in electric propulsion devices, including Hall thrusters, gridded ion engines, and others. The two major techniques, the floating point technique and the inflection point technique, are described in detail as well as calibration and error-reduction methods. The major heating methods are described as well as the various considerations for emissive probe construction. Lastly, special considerations for electric propulsion plasmas are addressed, including high-energy densities, ion flows, magnetic fields, and potential fluctuations. Recommendations for probe design and operation are provided.

Recommended Practice for Use of Emissive Probes in Electric Propulsion Testing

DOE PAGES

Sheehan, J. P.; Raitses, Yevgeny; Hershkowitz, Noah; ...

2016-11-03

Here, this article provides recommended methods for building, operating, and taking plasma potential measurements from electron-emitting probes in electric propulsion devices, including Hall thrusters, gridded ion engines, and others. The two major techniques, the floating point technique and the inflection point technique, are described in detail as well as calibration and error-reduction methods. The major heating methods are described as well as the various considerations for emissive probe construction. Lastly, special considerations for electric propulsion plasmas are addressed, including high-energy densities, ion flows, magnetic fields, and potential fluctuations. Recommendations for probe design and operation are provided.

Astronaut Hall of Fame

NASA Image and Video Library

2018-04-21

Inside the Space Shuttle Atlantis attraction at NASA’s Kennedy Space Center Visitor Complex in Florida, two space explorers, Scott D. Altman, second from left, and Thomas D. Jones, Ph.D., far right, are inducted into the U.S. Astronaut Hall of Fame Class of 2018. At far left is Hall of Famer Curt Brown, board chairman, Astronaut Scholarship Foundation, who inducted Altman and Jones into the AHOF. Second from right is Hall of Famer John Grunsfeld, who spoke on behalf of Altman during the ceremony. Inductees into the Hall of Fame are selected by a committee of Hall of Fame astronauts, former NASA officials, flight directors, historians and journalists. The process is administered by the Astronaut Scholarship Foundation. To be eligible, an astronaut must have made his or her first flight at least 17 years before the induction. Candidates must be a U.S. citizen and a NASA-trained commander, pilot or mission specialist who has orbited the earth at least once. Including Altman and Jones, 97 astronauts have been inducted into the AHOF.

Recent Results From Internal and Very-Near-Field Plasma Diagnostics of a High Specific Impulse Hall Thruster

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Gallimore, Alec D.; Jacobson, David (Technical Monitor)

2003-01-01

Floating potential and ion current density measurements were taken on the laboratory model NASA-173Mv2 in order to improve understanding of the physical processes affecting Hall thruster performance at high specific impulse. Floating potential was measured on discharge chamber centerline over axial positions spanning 10 mm from the anode to 100 mm downstream of the exit plane. Ion current density was mapped radially up to 300 mm from thruster centerline over axial positions in the very-near-field (10 to 250 mm from the exit plane). All data were collected using a planar probe in conjunction with a high-speed translation stage to minimize probe-induced thruster perturbations. Measurements of floating potential at a xenon flow rate of 10 mg/s have shown that the acceleration layer moved upstream 3 1 mm when the voltage increased from 300 to 600 V. The length of the acceleration layer was 14 2 mm and was approximately constant with voltage and magnetic field. Ion current density measurements indicated the annular ion beam crossed the thruster centerline 163 mm downstream of the exit plane. Radial integration of the ion current density at the cathode plane provided an estimate of the ion current fraction. At 500 V and 5 mg/s, the ion current fraction was calculated as 0.77.

Sprayable enzyme-activatable fluorescent probes: kinetic mapping using dynamic fluorescence imaging can help detecting tiny cancer foci (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kobayashi, Hisataka

2017-02-01

Optical fluorescence-guided imaging is increasingly used to guide surgery and endoscopic procedures. Sprayable enzyme-activatable probes are particularly useful because of high target-to-background ratios that increase sensitivity for tiny cancer foci. However, green fluorescent activatable probes suffers from interference from autofluorescence found in biological tissue. Dynamic imaging followed by the kinetic analysis could be detected local enzyme activity and used to differentiate specific fluorescence arising from an activated probe in a tumor from autofluorescence in background tissues especially when low concentrations of the dye are applied to detect tiny cancer foci. Serial fluorescence imaging was performed using various concentrations of γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) which was sprayed on the peritoneal surface with tiny implants of SHIN3-dsRed ovarian cancer tumors. Temporal differences in signal between specific green fluorescence in cancer foci and non-specific autofluorescence in background tissue was measured and processed into three kinetic maps reflecting maximum fluorescence signal (MF), wash-in rate (WIR), and area under the curve (AUC), respectively. Especially at lower concentrations, kinetic maps derived from dynamic fluorescence imaging were clearly superior to unprocessed images for detection small cancer foci.

Effects of macroscopic inhomogeneities on resistive and Hall measurements on crosses, cloverleafs, and bars

NASA Astrophysics Data System (ADS)

Koon, D. W.; Knickerbocker, C. J.

1996-12-01

The effect of macroscopic inhomogeneities on resistivity and Hall angle measurements is studied by calculating weighting functions (the relative effect of perturbations in a local transport property on the measured global average for the object) for cross, cloverleaf, and bar-shaped geometries. The ``sweet spot,'' the region in the center of the object that the measurement effectively samples, is smaller for crosses and cloverleafs than for the circles and squares already studied, and smaller for the cloverleaf than for the corresponding cross. Resistivity measurements for crosses and cloverleafs suffer from singularities and negative weighting, which can be eliminated by averaging two independent resistance measurements, as done in the van der Pauw technique. Resistivity and Hall measurements made on sufficiently narrow bars are shown to effectively sample only the region directly between the voltage probes.

NASA's Hall Thruster Program 2002

NASA Technical Reports Server (NTRS)

Jankovsky, Robert S.; Jacobson, David T.; Pinero, Luis R.; Manzella, David H.; Hofer, Richard R.; Peterson, Peter Y.

2002-01-01

The NASA Hall thruster program currently supports a number of tasks related to high power thruster development for a number of customers including the Energetics Program (formerly called the Space-based Program), the Space Solar Power Program, and the In-space Propulsion Program. In program year 2002, two tasks were central to the NASA Hall thruster program: 1) the development of a laboratory Hall thruster capable of providing high thrust at high power-, and 2) investigations into operation of Hall thrusters at high specific impulse. In addition to these two primary thruster development activities, there are a number of other on-going activities supported by the NASA Hall thruster program. These additional activities are related to issues such as high-power power processor architecture, thruster lifetime, and spacecraft integration.

Not your grandfather's concert hall

NASA Astrophysics Data System (ADS)

Cooper, Russell; Malenka, Richard; Griffith, Charles; Friedlander, Steven

2004-05-01

The opening of Judy and Arthur Zankel Hall on 12 September 2003, restores Andrew Carnegie's original 1891 concept of having three outstanding auditoriums of different sizes under one roof, and creates a 21st-century venue for music performance and education. With concerts ranging from early music to avant-garde multimedia productions, from jazz to world music, and from solo recitals to chamber music, Zankel Hall expands the breadth and depth of Carnegie Hall's offerings. It allows for the integration of programming across three halls with minifestivals tailored both to the size and strengths of each hall and to the artists and music to be performed. The new flexible space also provides Carnegie Hall with an education center equipped with advanced communications technology. This paper discusses the unique program planned for this facility and how the architects, theatre consultants, and acousticians developed a design that fulfilled the client's expectations and coordinated the construction of the facility under the floor of the main Isaac Stern Auditorium without having to cancel a single performance.

Interior and Exterior Laser-Induced Fluorescence and Plasma Potential Measurements on a Laboratory Hall Thruster (Postprint)

DTIC Science & Technology

1999-06-01

Hall thruster is provided by a 1 mm axial slot in the insulator outer wall. Axial ion velocity profiles for four discharge voltages (100 V, 160 V, 200 V, 250 V) are measured as are radial velocity profiles in the near field plume. Internal neutral xenon axial velocity profiles are also measured at these conditions. For comparison, the plume plasma potential profile is measured with an emissive probe. These probe based potential measurements extend from 50 mm outside the plume to the near anode region for all but the highest discharge voltage condition. For each condition,

Development of internal magnetic probe for current density profile measurement in Versatile Experiment Spherical Torus

NASA Astrophysics Data System (ADS)

Yang, J.; Lee, J. W.; Jung, B. K.; Chung, K. J.; Hwang, Y. S.

2014-11-01

An internal magnetic probe using Hall sensors to measure a current density profile directly with perturbation of less than 10% to the plasma current is successfully operated for the first time in Versatile Experiment Spherical Torus (VEST). An appropriate Hall sensor is chosen to produce sufficient signals for VEST magnetic field while maintaining the small size of 10 mm in outer diameter. Temperature around the Hall sensor in a typical VEST plasma is regulated by blown air of 2 bars. First measurement of 60 kA VEST ohmic discharge shows a reasonable agreement with the total plasma current measured by Rogowski coil in VEST.

Sensitivity of resistive and Hall measurements to local inhomogeneities: Finite-field, intensity, and area corrections

NASA Astrophysics Data System (ADS)

Koon, Daniel W.; Wang, Fei; Petersen, Dirch Hjorth; Hansen, Ole

2014-10-01

We derive exact, analytic expressions for the sensitivity of sheet resistance and Hall sheet resistance measurements to local inhomogeneities for the cases of nonzero magnetic fields, strong perturbations, and perturbations over a finite area, extending our earlier results on weak perturbations. We express these sensitivities for conductance tensor components and for other charge transport quantities. Both resistive and Hall sensitivities, for a van der Pauw specimen in a finite magnetic field, are a superposition of the zero-field sensitivities to both sheet resistance and Hall sheet resistance. Strong perturbations produce a nonlinear correction term that depends on the strength of the inhomogeneity. Solution of the specific case of a finite-sized circular inhomogeneity coaxial with a circular specimen suggests a first-order correction for the general case. Our results are confirmed by computer simulations on both a linear four-point probe array on a large circular disc and a van der Pauw square geometry. Furthermore, the results also agree well with Náhlík et al. published experimental results for physical holes in a circular copper foil disc.

Hall-plot of the phase diagram for Ba(Fe1-xCox)2As2

NASA Astrophysics Data System (ADS)

Iida, Kazumasa; Grinenko, Vadim; Kurth, Fritz; Ichinose, Ataru; Tsukada, Ichiro; Ahrens, Eike; Pukenas, Aurimas; Chekhonin, Paul; Skrotzki, Werner; Teresiak, Angelika; Hühne, Ruben; Aswartham, Saicharan; Wurmehl, Sabine; Mönch, Ingolf; Erbe, Manuela; Hänisch, Jens; Holzapfel, Bernhard; Drechsler, Stefan-Ludwig; Efremov, Dmitri V.

2016-06-01

The Hall effect is a powerful tool for investigating carrier type and density. For single-band materials, the Hall coefficient is traditionally expressed simply by , where e is the charge of the carrier, and n is the concentration. However, it is well known that in the critical region near a quantum phase transition, as it was demonstrated for cuprates and heavy fermions, the Hall coefficient exhibits strong temperature and doping dependencies, which can not be described by such a simple expression, and the interpretation of the Hall coefficient for Fe-based superconductors is also problematic. Here, we investigate thin films of Ba(Fe1-xCox)2As2 with compressive and tensile in-plane strain in a wide range of Co doping. Such in-plane strain changes the band structure of the compounds, resulting in various shifts of the whole phase diagram as a function of Co doping. We show that the resultant phase diagrams for different strain states can be mapped onto a single phase diagram with the Hall number. This universal plot is attributed to the critical fluctuations in multiband systems near the antiferromagnetic transition, which may suggest a direct link between magnetic and superconducting properties in the BaFe2As2 system.

Magnetic measurements of the 12-pole trim magnets for the 200 MeV compact synchrotron XLS at the National Synchrotron Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnaswamy, J.; Kalsi, S.; Hsieh, H.

1991-01-01

Magnetic measurements performed on the 12-pole trim magnets is described including Hall probe measurements to verify symmetry of the field and, rotating coil measurements to map the multipoles. The rotating coil measurements were carried out using a HP Dynamic Signal Analyzer. Excited as a quadrupole the dominant error multipole is the 20th pole and excited as a sextrupole the dominant error multipole is the 18th pole. Reasonable agreement was found between the Hall probe measurements and the rotating coil measurements. 2 refs., 5 figs.

NASA's Hall Thruster Program

NASA Technical Reports Server (NTRS)

Jankovsky, Robert S.; Jacobson, David T.; Rawlin, Vincent K.; Mason, Lee S.; Mantenieks, Maris A.; Manzella, David H.; Hofer, Richard R.; Peterson, Peter Y.

2001-01-01

NASA's Hall thruster program has base research and focused development efforts in support of the Advanced Space Transportation Program, Space-Based Program, and various other programs. The objective of the base research is to gain an improved understanding of the physical processes and engineering constraints of Hall thrusters to enable development of advanced Hall thruster designs. Specific technical questions that are current priorities of the base effort are: (1) How does thruster life vary with operating point? (2) How can thruster lifetime and wear rate be most efficiently evaluated? (3) What are the practical limitations for discharge voltage as it pertains to high specific impulse operation (high discharge voltage) and high thrust operation (low discharge voltage)? (4) What are the practical limits for extending Hall thrusters to very high input powers? and (5) What can be done during thruster design to reduce cost and integration concerns? The objective of the focused development effort is to develop a 50 kW-class Hall propulsion system, with a milestone of a 50 kW engineering model thruster/system by the end of program year 2006. Specific program wear 2001 efforts, along with the corporate and academic participation, are described.

Micro-Hall devices for magnetic, electric and photo-detection

NASA Astrophysics Data System (ADS)

Gilbertson, A.; Sadeghi, H.; Panchal, V.; Kazakova, O.; Lambert, C. J.; Solin, S. A.; Cohen, L. F.

Multifunctional mesoscopic sensors capable of detecting local magnetic (B) , electric (E) , and optical fields can greatly facilitate image capture in nano-arrays that address a multitude of disciplines. The use of micro-Hall devices as B-field sensors and, more recently as E-field sensors is well established. Here we report the real-space voltage response of InSb/AlInSb micro-Hall devices to not only local E-, and B-fields but also to photo-excitation using scanning probe microscopy. We show that the ultrafast generation of localised photocarriers results in conductance perturbations analogous to those produced by local E-fields. Our experimental results are in good agreement with tight-binding transport calculations in the diffusive regime. At room temperature, samples exhibit a magnetic sensitivity of >500 nT/ √Hz, an optical noise equivalent power of >20 pW/ √Hz (λ = 635 nm) comparable to commercial photoconductive detectors, and charge sensitivity of >0.04 e/ √Hz comparable to that of single electron transistors. Work done while on sabbatical from Washington University. Co-founder of PixelEXX, a start-up whose focus is imaging nano-arrays.

DNA Probe Pooling for Rapid Delineation of Chromosomal Breakpoints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Chun-Mei; Kwan, Johnson; Baumgartner, Adolf

2009-01-30

Structural chromosome aberrations are hallmarks of many human genetic diseases. The precise mapping of translocation breakpoints in tumors is important for identification of genes with altered levels of expression, prediction of tumor progression, therapy response, or length of disease-free survival as well as the preparation of probes for detection of tumor cells in peripheral blood. Similarly, in vitro fertilization (IVF) and preimplantation genetic diagnosis (PGD) for carriers of balanced, reciprocal translocations benefit from accurate breakpoint maps in the preparation of patient-specific DNA probes followed by a selection of normal or balanced oocytes or embryos. We expedited the process of breakpointmore » mapping and preparation of case-specific probes by utilizing physically mapped bacterial artificial chromosome (BAC) clones. Historically, breakpoint mapping is based on the definition of the smallest interval between proximal and distal probes. Thus, many of the DNA probes prepared for multi-clone and multi-color mapping experiments do not generate additional information. Our pooling protocol described here with examples from thyroid cancer research and PGD accelerates the delineation of translocation breakpoints without sacrificing resolution. The turnaround time from clone selection to mapping results using tumor or IVF patient samples can be as short as three to four days.« less

Mapping energetics of atom probe evaporation events through first principles calculations.

PubMed

Peralta, Joaquín; Broderick, Scott R; Rajan, Krishna

2013-09-01

The purpose of this work is to use atomistic modeling to determine accurate inputs into the atom probe tomography (APT) reconstruction process. One of these inputs is evaporation field; however, a challenge occurs because single ions and dimers have different evaporation fields. We have calculated the evaporation field of Al and Sc ions and Al-Al and Al-Sc dimers from an L1₂-Al₃Sc surface using ab initio calculations and with a high electric field applied to the surface. The evaporation field is defined as the electric field at which the energy barrier size is calculated as zero, corresponding to the minimum field that atoms from the surface can break their bonds and evaporate from the surface. The evaporation field of the surface atoms are ranked from least to greatest as: Al-Al dimer, Al ion, Sc ion, and Al-Sc dimer. The first principles results were compared with experimental data in the form of an ion evaporation map, which maps multi-ion evaporations. From the ion evaporation map of L1₂-Al₃Sc, we extract relative evaporation fields and identify that an Al-Al dimer has a lower evaporation field than an Al-Sc dimer. Additionally, comparatively an Al-Al surface dimer is more likely to evaporate as a dimer, while an Al-Sc surface dimer is more likely to evaporate as single ions. These conclusions from the experiment agree with the ab initio calculations, validating the use of this approach for modeling APT energetics. Copyright © 2013 Elsevier B.V. All rights reserved.

Pump-probe Kelvin-probe force microscopy: Principle of operation and resolution limits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murawski, J.; Graupner, T.; Milde, P., E-mail: peter.milde@tu-dresden.de

Knowledge on surface potential dynamics is crucial for understanding the performance of modern-type nanoscale devices. We describe an electrical pump-probe approach in Kelvin-probe force microscopy that enables a quantitative measurement of dynamic surface potentials at nanosecond-time and nanometer-length scales. Also, we investigate the performance of pump-probe Kelvin-probe force microscopy with respect to the relevant experimental parameters. We exemplify a measurement on an organic field effect transistor that verifies the undisturbed functionality of our pump-probe approach in terms of simultaneous and quantitative mapping of topographic and electronic information at a high lateral and temporal resolution.

Spin Hall effects

NASA Astrophysics Data System (ADS)

Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

2015-10-01

Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

Scanned gate microscopy of inter-edge channel scattering in the quantum Hall regime

NASA Astrophysics Data System (ADS)

Woodside, Michael T.; Vale, Chris; McEuen, Paul L.; Kadow, C.; Maranowski, K. D.; Gossard, A. C.

2000-03-01

Novel scanned probe techniques have recently been used to study in detail the microscopic properties of 2D electron gases in the quantum Hall regime [1]. We report local measurements of the scattering between edge states in a quantum Hall conductor with non-equilibrium edge state populations. Using an atomic force microscope (AFM) tip as a local gate to perturb the edge states, we find that the scattering is dominated by individual, microscopic scattering sites, which we directly image and characterise. The dependence of the scattering on the AFM tip voltage reveals that it involves tunneling both through quasi-bound impurity states and through disorder-induced weak links between the edge states. [1] S. H. Tessmer et al., Nature 392, 51 (1998); K. L. McCormick et al., Phys. Rev. B 59, 4654 (1999); A. Yacoby et al., Solid State Comm. 111, 1 (1999).

Tunneling Anomalous and Spin Hall Effects.

PubMed

Matos-Abiague, A; Fabian, J

2015-07-31

We predict, theoretically, the existence of the anomalous Hall effect when a tunneling current flows through a tunnel junction in which only one of the electrodes is magnetic. The interfacial spin-orbit coupling present in the barrier region induces a spin-dependent momentum filtering in the directions perpendicular to the tunneling current, resulting in a skew tunneling even in the absence of impurities. This produces an anomalous Hall conductance and spin Hall currents in the nonmagnetic electrode when a bias voltage is applied across the tunneling heterojunction. If the barrier is composed of a noncentrosymmetric material, the anomalous Hall conductance and spin Hall currents become anisotropic with respect to both the magnetization and crystallographic directions, allowing us to separate this interfacial phenomenon from the bulk anomalous and spin Hall contributions. The proposed effect should be useful for proving and quantifying the interfacial spin-orbit fields in metallic and metal-semiconductor systems.

Synchronization of spin-transfer torque oscillators by spin pumping, inverse spin Hall, and spin Hall effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elyasi, Mehrdad; Bhatia, Charanjit S.; Yang, Hyunsoo, E-mail: eleyang@nus.edu.sg

2015-02-14

We have proposed a method to synchronize multiple spin-transfer torque oscillators based on spin pumping, inverse spin Hall, and spin Hall effects. The proposed oscillator system consists of a series of nano-magnets in junction with a normal metal with high spin-orbit coupling, and an accumulative feedback loop. We conduct simulations to demonstrate the effect of modulated charge currents in the normal metal due to spin pumping from each nano-magnet. We show that the interplay between the spin Hall effect and inverse spin Hall effect results in synchronization of the nano-magnets.

Time-Synchronized Continuous Wave Laser Induced Fluorescence Velocity Measurements of a 600 Watt Hall Thruster

DTIC Science & Technology

2015-07-01

channel and near- field plume region of a 600 W Hall thruster operating on xenon. Results show significant fluctuations in LIF signal intensity... LIF signal intensity (corre- lated with the density of the probed excited metastable state) in time during the discharge current cycle, with the peak...fluorescence ( LIF ).1 LIF provides the opportunity to investigate plasma sources non-intrusively with higher spatial resolution (typically < 1 mm) than

Reversible electrochemical modification of the surface of a semiconductor by an atomic-force microscope probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozhukhov, A. S., E-mail: antonkozhukhov@yandex.ru; Sheglov, D. V.; Latyshev, A. V.

A technique for reversible surface modification with an atomic-force-microscope (AFM) probe is suggested. In this method, no significant mechanical or topographic changes occur upon a local variation in the surface potential of a sample under the AFM probe. The method allows a controlled relative change in the ohmic resistance of a channel in a Hall bridge within the range 20–25%.

Development Status of the Helicon Hall Thruster

DTIC Science & Technology

2009-09-15

Hall thruster , the Helicon Hall Thruster , is presented. The Helicon Hall Thruster combines the efficient ionization mechanism of a helicon source with the favorable plasma acceleration properties of a Hall thruster . Conventional Hall thrusters rely on direct current electron bombardment to ionize the flow in order to generate thrust. Electron bombardment typically results in an ionization cost that can be on the order of ten times the ionization potential, leading to reduced efficiency, particularly at low

A non-invasive Hall current distribution measurement system for Hall Effect thrusters

NASA Astrophysics Data System (ADS)

Mullins, Carl Raymond

A direct, accurate method to measure thrust produced by a Hall Effect thruster on orbit does not currently exist. The ability to calculate produced thrust will enable timely and precise maneuvering of spacecraft---a capability particularly important to satellite formation flying. The means to determine thrust directly is achievable by remotely measuring the magnetic field of the thruster and solving the inverse magnetostatic problem for the Hall current density distribution. For this thesis, the magnetic field was measured by employing an array of eight tunneling magnetoresistive (TMR) sensors capable of milligauss sensitivity when placed in a high background field. The array was positioned outside the channel of a 1.5 kW Colorado State University Hall thruster equipped with a center-mounted electride cathode. In this location, the static magnetic field is approximately 30 Gauss, which is within the linear operating range of the TMR sensors. Furthermore, the induced field at this distance is greater than tens of milligauss, which is within the sensitivity range of the TMR sensors. Due to the nature of the inverse problem, the induced-field measurements do not provide the Hall current density by a simple inversion; however, a Tikhonov regularization of the induced field along with a non-negativity constraint and a zero boundary condition provides current density distributions. Our system measures the sensor outputs at 2 MHz allowing the determination of the Hall current density distribution as a function of time. These data are shown in contour plots in sequential frames. The measured ratios between the average Hall current and the discharge current ranged from 0.1 to 10 over a range of operating conditions from 1.3 kW to 2.2 kW. The temporal inverse solution at 2.0 kW exhibited a breathing mode of 37 kHz, which was in agreement with temporal measurements of the discharge current.

Hall viscosity of hierarchical quantum Hall states

NASA Astrophysics Data System (ADS)

Fremling, M.; Hansson, T. H.; Suorsa, J.

2014-03-01

Using methods based on conformal field theory, we construct model wave functions on a torus with arbitrary flat metric for all chiral states in the abelian quantum Hall hierarchy. These functions have no variational parameters, and they transform under the modular group in the same way as the multicomponent generalizations of the Laughlin wave functions. Assuming the absence of Berry phases upon adiabatic variations of the modular parameter τ, we calculate the quantum Hall viscosity and find it to be in agreement with the formula, given by Read, which relates the viscosity to the average orbital spin of the electrons. For the filling factor ν =2/5 Jain state, which is at the second level in the hierarchy, we compare our model wave function with the numerically obtained ground state of the Coulomb interaction Hamiltonian in the lowest Landau level, and find very good agreement in a large region of the complex τ plane. For the same example, we also numerically compute the Hall viscosity and find good agreement with the analytical result for both the model wave function and the numerically obtained Coulomb wave function. We argue that this supports the notion of a generalized plasma analogy that would ensure that wave functions obtained using the conformal field theory methods do not acquire Berry phases upon adiabatic evolution.

Astronaut Hall of Fame

NASA Image and Video Library

2018-04-21

Kelvin Manning, associate director of NASA's Kennedy Space Center in Florida, welcomes guests to the 2018 U.S. Astronaut Hall of Fame (AHOF) Induction inside the Space Shuttle Atlantis attraction at the Kennedy Space Center Visitor Complex (KSCVC). Two veteran space explorers were inducted into the Hall of Fame Class of 2018. They are Scott D. Altman and Thomas D. Jones, Ph.D. Inductees into the Hall of Fame are selected by a committee of Hall of Fame astronauts, former NASA officials, flight directors, historians and journalists. The process is administered by the Astronaut Scholarship Foundation. To be eligible, an astronaut must have made his or her first flight at least 17 years before the induction. Candidates must be a U.S. citizen and a NASA-trained commander, pilot or mission specialist who has orbited the earth at least once. Including Altman and Jones, 97 astronauts have been inducted into the AHOF.

Astronaut Hall of Fame

NASA Image and Video Library

2018-04-21

Former astronauts and space explorers Scott D. Altman, at left, and Thomas D. Jones, Ph.D., are inducted into the U.S. Astronaut Hall of Fame Class of 2018 during a ceremony inside the Space Shuttle Atlantis attraction at NASA’s Kennedy Space Center Visitor Complex in Florida. They unveiled their plaques, which will be placed in Hall of Fame at the visitor complex. At far right is Master of Ceremonies, John Zarella, former CNN space correspondent. Inductees into the Hall of Fame are selected by a committee of Hall of Fame astronauts, former NASA officials, flight directors, historians and journalists. The process is administered by the Astronaut Scholarship Foundation. To be eligible, an astronaut must have made his or her first flight at least 17 years before the induction. Candidates must be a U.S. citizen and a NASA-trained commander, pilot or mission specialist who has orbited the earth at least once. Including Altman and Jones, 97 astronauts have been inducted into the AHOF.

Astronaut Hall of Fame

NASA Image and Video Library

2018-04-21

Former astronauts and space explorers Scott D. Altman, at left, and Thomas D. Jones, Ph.D., are inducted into the U.S. Astronaut Hall of Fame Class of 2018 during a ceremony inside the Space Shuttle Atlantis attraction at NASA’s Kennedy Space Center Visitor Complex in Florida. They unveiled their plaques, which will be placed in the Hall of Fame at the visitor complex. At far right is Master of Ceremonies, John Zarella, former CNN space correspondent. Inductees into the Hall of Fame are selected by a committee of Hall of Fame astronauts, former NASA officials, flight directors, historians and journalists. The process is administered by the Astronaut Scholarship Foundation. To be eligible, an astronaut must have made his or her first flight at least 17 years before the induction. Candidates must be a U.S. citizen and a NASA-trained commander, pilot or mission specialist who has orbited the earth at least once. Including Altman and Jones, 97 astronauts have been inducted into the AHOF.

Probing the geometry of the Laughlin state

DOE PAGES

Johri, Sonika; Papic, Z.; Schmitteckert, P.; ...

2016-02-05

It has recently been pointed out that phases of matter with intrinsic topological order, like the fractional quantum Hall states, have an extra dynamical degree of freedom that corresponds to quantum geometry. Here we perform extensive numerical studies of the geometric degree of freedom for the simplest example of fractional quantumHall states—the filling v = 1/3 Laughlin state.We perturb the system by a smooth, spatially dependent metric deformation and measure the response of the Hall fluid, finding it to be proportional to the Gaussian curvature of the metric. Further, we generalize the concept of coherent states to formulate the bulkmore » off-diagonal long range order for the Laughlin state, and compute the deformations of the metric in the vicinity of the edge of the system. We introduce a ‘pair amplitude’ operator and show that it can be used to numerically determine the intrinsic metric of the Laughlin state. Furthermore, these various probes are applied to several experimentally relevant settings that can expose the quantum geometry of the Laughlin state, in particular to systems with mass anisotropy and in the presence of an electric field gradient.« less

External electric field driven modification of the anomalous and spin Hall conductivities in Fe thin films on MgO(001)

NASA Astrophysics Data System (ADS)

Pradipto, Abdul-Muizz; Akiyama, Toru; Ito, Tomonori; Nakamura, Kohji

2018-01-01

The effects of applying external electric fields to the anomalous and spin Hall conductivities in Fe thin-film models with different layer thicknesses on MgO(001) are investigated by using first-principles calculations. We observe that, for the considered systems, the application of positive electric field associated with the accumulation of negative charges on the Fe side generally decreases (increases) the anomalous (spin) Hall conductivities. The mapping of the Hall conductivities within the two-dimensional Brillouin zone shows that the electric-field-induced modifications are related to the modification of the band structures of the atoms at the interface with the MgO substrate. In particular, the external electric field affects the Hall conductivities via the modifications of the dx z,dy z orbitals, in which the application of positive electric field pushes the minority-spin states of the dx z,dy z bands closer to the Fermi level. Better agreement with the anomalous Hall conductivity for bulk Fe and a more realistic scenario for the electric field modification of Hall conductivities are obtained by using the thicker layers of Fe on MgO (Fe3/MgO and Fe5/MgO).

ExB Measurements of a 200 W Xenon Hall Thruster (Preprint)

DTIC Science & Technology

2007-08-28

Hall thruster Busek BHT-200 plume were measured using an ExB probe under a variety of thruster operating conditions and background pressures. The thruster was operated at several operating conditions by varying the anode potential of the thruster from 200 V to 325 V in 25 V increments. Measurements of the ion species fractions were made 90 from thruster centerline 60 cm downstream of the exit plane. At reduced discharge voltages, the species fractions of multiply-charged xenon ions were lower, while at increased discharge voltages, Xe+2 and Xe+3 showed an increase in their

Edge physics of the quantum spin Hall insulator from a quantum dot excited by optical absorption.

PubMed

Vasseur, Romain; Moore, Joel E

2014-04-11

The gapless edge modes of the quantum spin Hall insulator form a helical liquid in which the direction of motion along the edge is determined by the spin orientation of the electrons. In order to probe the Luttinger liquid physics of these edge states and their interaction with a magnetic (Kondo) impurity, we consider a setup where the helical liquid is tunnel coupled to a semiconductor quantum dot that is excited by optical absorption, thereby inducing an effective quantum quench of the tunneling. At low energy, the absorption spectrum is dominated by a power-law singularity. The corresponding exponent is directly related to the interaction strength (Luttinger parameter) and can be computed exactly using boundary conformal field theory thanks to the unique nature of the quantum spin Hall edge.

Ion behavior in low-power magnetically shielded and unshielded Hall thrusters

NASA Astrophysics Data System (ADS)

Grimaud, L.; Mazouffre, S.

2017-05-01

Magnetically shielded Hall thrusters achieve a longer lifespan than traditional Hall thrusters by reducing wall erosion. The lower erosion rate is attributed to a reduction of the high energy ion population impacting the walls. To investigate this phenomenon, the ion velocity distribution functions are measured with laser induced fluorescence at several points of interest in the magnetically shielded ISCT200-MS and the unshielded ISCT200-US Hall thrusters. The center of the discharge channel is probed to highlight the difference in plasma positioning between the shielded and unshielded thrusters. Erosion phenomena are investigated by taking measurements of the ion velocity distribution near the inner and outer wall as well as above the magnetic poles where some erosion is observed. The resulting distribution functions show a displacement of the acceleration region from inside the channel in the unshielded thruster to downstream of the exit plane in the ISCT200-MS. Near the walls, the unshielded thruster displays both a higher relative ion density as well as a significant fraction of the ions with velocities toward the walls compared to the shielded thruster. Higher proportions of high velocity ions are also observed. Those results are in accordance with the reduced erosion observed. Both shielded and unshielded thrusters have large populations of ions impacting the magnetic poles. The mechanism through which those ions are accelerated toward the magnetic poles has so far not been explained.

Hall effect of copper nitride thin films

NASA Astrophysics Data System (ADS)

Yue, G. H.; Liu, J. Z.; Li, M.; Yuan, X. M.; Yan, P. X.; Liu, J. L.

2005-08-01

The Hall effect of copper nitride (Cu3N) thin films was investigated in our work. Cu3N films were deposited on glass substrates by radio-frequency (RF) magnetron sputtering at different temperatures using pure copper as the sputtering target. The Hall coefficients of the films are demonstrated to be dependent on the deposition gas flow rate and the measuring temperature. Both the Hall coefficient and resistance of the Cu3N films increase with the nitrogen gas flow rate at room temperature, while the Hall mobility and the carrier density of the films decrease. As the temperature changed from 100 K to 300 K, the Hall coefficient and the resistivity of the films decreased, while the carrier density increased and Hall mobility shows no great change. The energy band gap of the Cu3N films deduced from the curve of the common logarithm of the Hall coefficient against 1/T is 1.17-1.31 eV.

Semiclassical theory of Hall viscosity

NASA Astrophysics Data System (ADS)

Biswas, Rudro

2014-03-01

Hall viscosity is an intriguing stress response in quantum Hall systems and is predicted to be observable via the conductivity in an inhomogeneous electric field. This has been studied extensively using a range of techniques, such as adiabatic transport, effective field theories, and Kubo formulae. All of these are, however, agnostic as to the distinction between strongly correlated quantum Hall states and non-interacting ones, where the effect arises due to the fundamental non-commuting nature of velocities and orbit positions in a magnetic field. In this talk I shall develop the semiclassical theory of quantized cyclotron orbits drifting in an applied inhomogeneous electric field and use it to provide a clear physical picture of how single particle properties in a magnetic field contribute to the Hall viscosity-dependence of the conductivity.

Faster Hall-Effect Current-Measuring Circuit

NASA Technical Reports Server (NTRS)

Sullender, Craig C.; Johnson, Daniel D.; Walker, Daniel D.

1993-01-01

Current-measuring circuit operates on Hall-effect-sensing and magnetic-field-nulling principles similar to those described in article, "Nulling Hall-Effect Current-Measuring Circuit" (LEW-15023), but simpler and responds faster. Designed without feedback loop, and analog pulse-width-modulated output indicates measured current. Circuit measures current at frequency higher than bandwidth of its Hall-effect sensor.

Interfacial scattering effect on anisotropic magnetoresistance and anomalous Hall effect in Ta/Fe multilayers

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Zhang, Junwei; Zhao, Yuelei; Wen, Yan; Li, Peng; Zhang, Senfu; He, Xin; Zhang, Junli; Zhang, Xixiang

2018-05-01

The effect of interfacial scattering on anisotropic magnetoresistance (AMR) and anomalous Hall effect (AHE) was studied in the (Ta12/n/Fe36/n) n multilayers, where the numbers give the thickness in nanometer and n is an integer from 1 to 12. The multilayer structure has been confirmed by the XRR spectra and STEM images of cross-sections. The magneto-transport properties were measured by four-point probe method in Hall bar shaped samples in the temperature range of 5 - 300 K. The AMR increases with n, which could be ascribed to the interfacial spin-orbit scattering. At 5 K, the longitudinal resistivity (ρxx) increases by 6.4 times and the anomalous Hall resistivity (ρAHE) increases by 49.4 times from n =1 to n =12, indicative of the interfacial scattering effect. The skew-scattering, side-jump and intrinsic contributions to the AHE were separated successfully. As n increases from 1 to 12, the intrinsic contribution decreases because of the decaying crystallinity or finite size effect and the intrinsic contribution dominated the AHE for all samples. The side jump changes from negative to positive because the interfacial scattering and intralayer scattering in Fe layers both contribute to side jump in the AHE but with opposite sign.

Jefferson Lab Experimental Hall C

NASA Astrophysics Data System (ADS)

Carlini, Roger D.

1996-10-01

Jefferson Lab's Hall C went into initial operation in November 1995. The hall has a short orbit spectrometer (SOS) for short-lived particles such as pions and kaons and a high-momentum spectrometer (HMS) usually used for electrons. The SOS can also be used for protons. The HMS can range to 7 GeV/c. Both the SOS and HMS have typical resolutions of (10-3). Experiments for this hall range from measuring the neutron electric form factor, to color transparency, to creating strange nuclei. This paper will present the optical capabilities of the spectrometers, the parameters of the detection systems, and the overall beam line characteristics of the hall as determined from the results from the recent physics experiments along with the upcoming experimental schedule. Additional information is available at URL http://www.cebaf.gov/hallc.html.

Observation of a superfluid Hall effect

PubMed Central

Jiménez-García, Karina; Williams, Ross A.; Beeler, Matthew C.; Perry, Abigail R.; Phillips, William D.; Spielman, Ian B.

2012-01-01

Measurement techniques based upon the Hall effect are invaluable tools in condensed-matter physics. When an electric current flows perpendicular to a magnetic field, a Hall voltage develops in the direction transverse to both the current and the field. In semiconductors, this behavior is routinely used to measure the density and charge of the current carriers (electrons in conduction bands or holes in valence bands)—internal properties of the system that are not accessible from measurements of the conventional resistance. For strongly interacting electron systems, whose behavior can be very different from the free electron gas, the Hall effect’s sensitivity to internal properties makes it a powerful tool; indeed, the quantum Hall effects are named after the tool by which they are most distinctly measured instead of the physics from which the phenomena originate. Here we report the first observation of a Hall effect in an ultracold gas of neutral atoms, revealed by measuring a Bose–Einstein condensate’s transport properties perpendicular to a synthetic magnetic field. Our observations in this vortex-free superfluid are in good agreement with hydrodynamic predictions, demonstrating that the system’s global irrotationality influences this superfluid Hall signal. PMID:22699494

Single electron probes of fractional quantum hall states

NASA Astrophysics Data System (ADS)

Venkatachalam, Vivek

When electrons are confined to a two dimensional layer with a perpendicular applied magnetic field, such that the ratio of electrons to flux quanta (nu) is a small integer or simple rational value, these electrons condense into remarkable new phases of matter that are strikingly different from the metallic electron gas that exists in the absence of a magnetic field. These phases, called integer or fractional quantum Hall (IQH or FQH) states, appear to be conventional insulators in their bulk, but behave as a dissipationless metal along their edge. Furthermore, electrical measurements of such a system are largely insensitive to the detailed geometry of how the system is contacted or even how large the system is... only the order in which contacts are made appears to matter. This insensitivity to local geometry has since appeared in a number of other two and three dimensional systems, earning them the classification of "topological insulators" and prompting an enormous experimental and theoretical effort to understand their properties and perhaps manipulate these properties to create robust quantum information processors. The focus of this thesis will be two experiments designed to elucidate remarkable properties of the metallic edge and insulating bulk of certain FQH systems. To study such systems, we can use mesoscopic devices known as single electron transistors (SETs). These devices operate by watching single electrons hop into and out of a confining box and into a nearby wire (for measurement). If it is initially unfavorable for an electron to leave the box, it can be made favorable by bringing another charge nearby, modifying the energy of the confined electron and pushing it out of the box and into the nearby wire. In this way, the SET can measure nearby charges. Alternatively, we can heat up the nearby wire to make it easier for electrons to enter and leave the box. In this way, the SET is a sensitive thermometer. First, by operating the SET as an

Pressure Anisotropy Probe for the Terrestrial Reconnection Experiment (TREX)

NASA Astrophysics Data System (ADS)

Myers, Rachel; Egedal, Jan; Olson, Joseph; Greess, Samuel; Clark, Michael; Nonn, Paul; Wallace, John; Forest, Cary

2016-10-01

The Terrestrial Reconnection Experiment (TREX) at the Wisconsin Plasma Astrophysics Laboratory (WiPAL) studies magnetic reconnection primarily in the collisionless regime. In this regime, electron pressure anisotropy is expected to develop, deviating from traditional Hall reconnection dynamics and driving formation of large-scale current layers. In order to measure the anisotropy, a multi-tip electromagnetic probe similar to the M-probe described by Shadman, consisting of 32 Langmuir probe tips and two magnetic coils, has been constructed. Each tip is biased to a different potential, simultaneously measuring discrete parts of the full I-V characteristic. Pulsing the coil then locally increases the magnetic field, creating a magnetic mirror force to reflect electrons with large values of v⊥ / v . The change in electron velocity modifies the I-V characteristics and can be used to infer p∥ /p⊥ . Analysis with the new probe will be presented. DOE Grant DE-SC0010463, University of Wisconsin-Madison University Fellowship.

High Power Hall Thrusters

NASA Technical Reports Server (NTRS)

Jankovsky, Robert; Tverdokhlebov, Sergery; Manzella, David

1999-01-01

The development of Hall thrusters with powers ranging from tens of kilowatts to in excess of one hundred kilowatts is considered based on renewed interest in high power. high thrust electric propulsion applications. An approach to develop such thrusters based on previous experience is discussed. It is shown that the previous experimental data taken with thrusters of 10 kW input power and less can be used. Potential mass savings due to the design of high power Hall thrusters are discussed. Both xenon and alternate thruster propellant are considered, as are technological issues that will challenge the design of high power Hall thrusters. Finally, the implications of such a development effort with regard to ground testing and spacecraft intecrati'on issues are discussed.

Dyon proliferation in interacting quantum spin Hall edges

NASA Astrophysics Data System (ADS)

Lee, Shu-Ping; Maciejko, Joseph

We show that a quantum spin Hall system with intra-edge multiparticle backscattering and inter-edge exchange interactions exhibits a modular invariant zero-temperature phase diagram. We establish this through mapping to a classical 2D Coulomb gas with electrically and magnetically charged particles; strong coupling phases in the quantum edge problem correspond to the proliferation of various dyons in the Coulomb gas. Distinct dyon proliferated phases can be accessed by tuning the edge Luttinger parameters, for example using a split gate geometry. This research was supported by NSERC Grant #RGPIN-2014-4608, the Canada Research Chair Program (CRC) and the Canadian Institute for Advanced Research (CIFAR).

Pump-probe differencing technique for cavity-enhanced, noise-canceling saturation laser spectroscopy.

PubMed

de Vine, Glenn; McClelland, David E; Gray, Malcolm B; Close, John D

2005-05-15

We present an experimental technique that permits mechanical-noise-free, cavity-enhanced frequency measurements of an atomic transition and its hyperfine structure. We employ the 532-nm frequency-doubled output from a Nd:YAG laser and an iodine vapor cell. The cell is placed in a folded ring cavity (FRC) with counterpropagating pump and probe beams. The FRC is locked with the Pound-Drever-Hall technique. Mechanical noise is rejected by differencing the pump and probe signals. In addition, this differenced error signal provides a sensitive measure of differential nonlinearity within the FRC.

On Floating Potential of Emissive Probes in a Partially-Magnetized Plasma

NASA Astrophysics Data System (ADS)

Raitses, Yevgeny; Kraus, Brian

2016-10-01

We compare measurements of plasma potential in a cross-field Penning discharge from two probes: swept biased Langmuir probe and floating emissive probe. The plasma potential was deduced from the first derivative of the Langmuir probe characteristic. In previous studies, the emissive and swept biased probes were placed at the channel exit of a Hall thruster (HT). Measurements showed that the emissive probe floats below the plasma potential, in agreement with conventional theories. However, recent measurements in the Penning discharge indicate a floating potential of a strongly-emitting hot probe above the plasma potential. In both probe applications, xenon plasmas have magnetized electrons and non-magnetized ions with similar plasma densities (1010 - 1011 cm-3) . Though their electron temperatures differ by an order of magnitude (Penning 5 eV, HT 50 eV), this difference cannot explain the difference in measurement values of the hot floating potential because both temperatures are much higher than the emitting wire. In this work, we investigate how the ion velocity and other plasma parameters affect this discrepancy between probe measurements of the plasma potential. This work was supported by DOE contract DE-AC02-09CH11466.

Beam Diagnostics of the Compton Scattering Chamber in Jefferson Lab's Hall C

NASA Astrophysics Data System (ADS)

Faulkner, Adam; I&C Group Collaboration

2013-10-01

Upcoming experimental runs in Hall C will utilize Compton scattering, involving the construction and installation of a rectangular beam enclosure. Conventional cylindrical stripline-style Beam Position Monitors (BPMs) are not appropriate due to their form factor; therefore to facilitate measurement of position, button-style BPMs are being considered due to the ease of placement within the new beam enclosure. Button BPM experience is limited at JLAB, so preliminary measurements are needed to characterize the field response, and guide the development of appropriate algorithms for the Analog to Digital receiver systems. -field mapping is performed using a Goubau Line (G-Line), which employs a surface wave to mimic the electron beam, helping to avoid problems associated with vacuum systems. Potential algorithms include simplistic 1/r modeling (-field mapping), look-up-tables, as well as a potential third order power series fit. In addition, the use of neural networks specifically the multi-layer Perceptron will be examined. The models, sensor field maps, and utility of the neural network will be presented. Next steps include: modification of the control algorithm, as well as to run an in-situ test of the four Button electrodes inside of a mock beam enclosure. The analysis of the field response using Matlab suggests the button BPMs are accurate to within 10 mm, and may be successful for beam diagnostics in Hall C. More testing is necessary to ascertain the limitations of the new electrodes. The National Science Foundation, Old Dominion University, The Department of Energy, and Jefferson Lab.

The Hall effect in star formation

NASA Astrophysics Data System (ADS)

Braiding, C. R.; Wardle, M.

2012-05-01

Magnetic fields play an important role in star formation by regulating the removal of angular momentum from collapsing molecular cloud cores. Hall diffusion is known to be important to the magnetic field behaviour at many of the intermediate densities and field strengths encountered during the gravitational collapse of molecular cloud cores into protostars, and yet its role in the star formation process is not well studied. We present a semianalytic self-similar model of the collapse of rotating isothermal molecular cloud cores with both Hall and ambipolar diffusion, and similarity solutions that demonstrate the profound influence of the Hall effect on the dynamics of collapse. The solutions show that the size and sign of the Hall parameter can change the size of the protostellar disc by up to an order of magnitude and the protostellar accretion rate by 50 per cent when the ratio of the Hall to ambipolar diffusivities is varied between -0.5 ≤ηH/ηA≤ 0.2. These changes depend upon the orientation of the magnetic field with respect to the axis of rotation and create a preferred handedness to the solutions that could be observed in protostellar cores using next-generation instruments such as ALMA. Hall diffusion also determines the strength and position of the shocks that bound the pseudo and rotationally supported discs, and can introduce subshocks that further slow accretion on to the protostar. In cores that are not initially rotating (not examined here), Hall diffusion can even induce rotation, which could give rise to disc formation and resolve the magnetic braking catastrophe. The Hall effect clearly influences the dynamics of gravitational collapse and its role in controlling the magnetic braking and radial diffusion of the field merits further exploration in numerical simulations of star formation.

Flux and Hall states in ABJM with dynamical flavors

NASA Astrophysics Data System (ADS)

Bea, Yago; Jokela, Niko; Lippert, Matthew; Ramallo, Alfonso V.; Zoakos, Dimitrios

2015-03-01

We study the physics of probe D6-branes with quantized internal worldvolume flux in the ABJM background with unquenched massless flavors. This flux breaks parity in the (2+1)-dimensional gauge theory and allows quantum Hall states. Parity breaking is also explicitly demonstrated via the helicity dependence of the meson spectrum. We obtain general expressions for the conductivities, both in the gapped Minkowski embeddings and in the compressible black hole ones. These conductivities depend on the flux and contain a contribution from the dynamical flavors which can be regarded as an effect of intrinsic disorder due to quantum fluctuations of the fundamentals. We present an explicit, analytic family of supersymmetric solutions with nonzero charge density, electric, and magnetic fields.

Preliminary Results of Performance Measurements on a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

NASA Technical Reports Server (NTRS)

Polzin, K. A.; Raitses, Y.; Merino, E.; Fisch, N. J.

2008-01-01

The performance of a low-power cylindrical Hall thruster, which more readily lends itself to miniaturization and low-power operation than a conventional (annular) Hall thruster, was measured using a planar plasma probe and a thrust stand. The field in the cylindrical thruster was produced using permanent magnets, promising a power reduction over previous cylindrical thruster iterations that employed electromagnets to generate the required magnetic field topology. Two sets of ring-shaped permanent magnets are used, and two different field configurations can be produced by reorienting the poles of one magnet relative to the other. A plasma probe measuring ion flux in the plume is used to estimate the current utilization for the two magnetic configurations. The measurements indicate that electron transport is impeded much more effectively in one configuration, implying a higher thrust efficiency. Preliminary thruster performance measurements on this configuration were obtained over a power range of 100-250 W. The thrust levels over this power range were 3.5-6.5 mN, with anode efficiencies and specific impulses spanning 14-19% and 875- 1425 s, respectively. The magnetic field in the thruster was lower for the thrust measurements than the plasma probe measurements due to heating and weakening of the permanent magnets, reducing the maximum field strength from 2 kG to roughly 750-800 G. The discharge current levels observed during thrust stand testing were anomalously high compared to those levels measured in previous experiments with this thruster.

Non-invasive Hall current distribution measurement in a Hall effect thruster

NASA Astrophysics Data System (ADS)

Mullins, Carl R.; Farnell, Casey C.; Farnell, Cody C.; Martinez, Rafael A.; Liu, David; Branam, Richard D.; Williams, John D.

2017-01-01

A means is presented to determine the Hall current density distribution in a closed drift thruster by remotely measuring the magnetic field and solving the inverse problem for the current density. The magnetic field was measured by employing an array of eight tunneling magnetoresistive (TMR) sensors capable of milligauss sensitivity when placed in a high background field. The array was positioned just outside the thruster channel on a 1.5 kW Hall thruster equipped with a center-mounted hollow cathode. In the sensor array location, the static magnetic field is approximately 30 G, which is within the linear operating range of the TMR sensors. Furthermore, the induced field at this distance is approximately tens of milligauss, which is within the sensitivity range of the TMR sensors. Because of the nature of the inverse problem, the induced-field measurements do not provide the Hall current density by a simple inversion; however, a Tikhonov regularization of the induced field does provide the current density distributions. These distributions are shown as a function of time in contour plots. The measured ratios between the average Hall current and the average discharge current ranged from 6.1 to 7.3 over a range of operating conditions from 1.3 kW to 2.2 kW. The temporal inverse solution at 1.5 kW exhibited a breathing mode frequency of 24 kHz, which was in agreement with temporal measurements of the discharge current.

Non-invasive Hall current distribution measurement in a Hall effect thruster.

PubMed

Mullins, Carl R; Farnell, Casey C; Farnell, Cody C; Martinez, Rafael A; Liu, David; Branam, Richard D; Williams, John D

2017-01-01

A means is presented to determine the Hall current density distribution in a closed drift thruster by remotely measuring the magnetic field and solving the inverse problem for the current density. The magnetic field was measured by employing an array of eight tunneling magnetoresistive (TMR) sensors capable of milligauss sensitivity when placed in a high background field. The array was positioned just outside the thruster channel on a 1.5 kW Hall thruster equipped with a center-mounted hollow cathode. In the sensor array location, the static magnetic field is approximately 30 G, which is within the linear operating range of the TMR sensors. Furthermore, the induced field at this distance is approximately tens of milligauss, which is within the sensitivity range of the TMR sensors. Because of the nature of the inverse problem, the induced-field measurements do not provide the Hall current density by a simple inversion; however, a Tikhonov regularization of the induced field does provide the current density distributions. These distributions are shown as a function of time in contour plots. The measured ratios between the average Hall current and the average discharge current ranged from 6.1 to 7.3 over a range of operating conditions from 1.3 kW to 2.2 kW. The temporal inverse solution at 1.5 kW exhibited a breathing mode frequency of 24 kHz, which was in agreement with temporal measurements of the discharge current.

Star Formation and the Hall Effect

NASA Astrophysics Data System (ADS)

Braiding, Catherine

2011-10-01

Magnetic fields play an important role in star formation by regulating the removal of angular momentum from collapsing molecular cloud cores. Hall diffusion is known to be important to the magnetic field behaviour at many of the intermediate densities and field strengths encountered during the gravitational collapse of molecular cloud cores into protostars, and yet its role in the star formation process is not well-studied. This thesis describes a semianalytic self-similar model of the collapse of rotating isothermal molecular cloud cores with both Hall and ambipolar diffusion, presenting similarity solutions that demonstrate that the Hall effect has a profound influence on the dynamics of collapse. ... Hall diffusion also determines the strength of the magnetic diffusion and centrifugal shocks that bound the pseudo and rotationally-supported discs, and can introduce subshocks that further slow accretion onto the protostar. In cores that are not initially rotating Hall diffusion can even induce rotation, which could give rise to disc formation and resolve the magnetic braking catastrophe. The Hall effect clearly influences the dynamics of gravitational collapse and its role in controlling the magnetic braking and radial diffusion of the field would be worth exploring in future numerical simulations of star formation.

Facility Effect Characterization Test of NASA's HERMeS Hall Thruster

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Kamhawi, Hani; Haag, Thomas W.; Ortega, Alejandro Lopez; Mikellides, Ioannis G.

2016-01-01

A test to characterize the effect of varying background pressure on NASA's 12.5-kW Hall Effect Rocket with Magnetic Shielding had being completed. This thruster is the baseline propulsion system for the Solar Electric Propulsion Technology Demonstration Mission (SEP TDM). Potential differences in thruster performance and oscillation characteristics when in ground facilities versus on-orbit are considered a primary risk for the propulsion system of the Asteroid Redirect Robotic Mission, which is a candidate for SEP TDM. The first primary objective of this test was to demonstrate that the tools being developed to predict the zero-background-pressure behavior of the thruster can provide self-consistent results. The second primary objective of this test was to provide data for refining a physics-based model of the thruster plume that will be used in spacecraft interaction studies. Diagnostics deployed included a thrust stand, Faraday probe, Langmuir probe, retarding potential analyzer, Wien filter spectrometer, and high-speed camera. From the data, a physics-based plume model was refined. Comparisons of empirical data to modeling results are shown.

Reduced Spin Hall Effects from Magnetic Proximity.

DOE PAGES

Zhang, Wei; Jungfleisch, Matthias B.; Jiang, Wanjun; ...

2015-03-26

We investigate temperature-dependent spin pumping and inverse spin Hall effects in thin Pt and Pd in contact with Permalloy. Our experiments show a decrease of the spin Hall effect with decreasing temperature, which is attributed to a temperature-dependent proximity effect. The spin Hall angle decreases from 0.086 at room temperature to 0.042 at 10 K for Pt and is nearly negligible at 10 K for Pd. By first-principle calculations, we show that the spin Hall conductivity indeed reduces by increasing the proximity-induced spin magnetic moments for both Pt and Pd. This work highlights the important role of proximity-induced magnetic orderingmore » to spin Hall phenomena in Pt and Pd.« less

Residence Hall Seating That Works.

ERIC Educational Resources Information Center

Wiens, Janet

2003-01-01

Describes the seating chosen for residence halls at the Massachusetts Institute of Technology and the University of New England. The seating required depends on ergonomics, aesthetics, durability, cost, and code requirements. In addition, residence halls must have a range of seating types to accommodate various uses. (SLD)

75 FR 22770 - Gary E. Hall and Rita Hall; Notice of Availability of Environmental Assessment

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-30

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 13652-000-Montana] Gary E. Hall and Rita Hall; Notice of Availability of Environmental Assessment April 22, 2010. In accordance with the National Environmental Policy Act of 1969, as amended, and the Federal Energy Regulatory...

Charge carrier coherence and Hall effect in organic semiconductors

DOE PAGES

Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

2016-03-30

Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force actingmore » on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Lastly, our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.« less

Charge carrier coherence and Hall effect in organic semiconductors.

PubMed

Yi, H T; Gartstein, Y N; Podzorov, V

2016-03-30

Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.

Charge carrier coherence and Hall effect in organic semiconductors

PubMed Central

Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

2016-01-01

Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor. PMID:27025354

Laurance David Hall.

PubMed

Coxon, Bruce

2011-01-01

An account is given of the life, scientific contributions, and passing of Laurance David Hall (1938-2009), including his early history and education at the University of Bristol, UK, and the synthesis and NMR spectroscopy of carbohydrates and other natural products during ∼20 years of research and teaching at the University of British Columbia in Vancouver, Canada. Lists of graduate students, post-doctoral fellows, and sabbatical visitors are provided for this period. Following a generous endowment by Dr. Herchel Smith, Professor Hall built a new Department of Medicinal Chemistry at Cambridge University, UK, and greatly expanded his researches into the technology and applications of magnetic resonance imaging (MRI) and zero quantum NMR. MRI technology was applied both to medical problems such as the characterization of cartilage degeneration in knee joints, the measurement of ventricular function, lipid localization in animal models of atherosclerosis, paramagnetic metal complexes of polysaccharides as contrast agents, and studies of many other anatomical features, but also to several aspects of materials analysis, including food analyses, process control, and the elucidation of such physical phenomena as the flow of liquids through porous media, defects in concrete, and the visualization of fungal damage to wood. Professor Hall's many publications, patents, lectures, and honors and awards are described, and also his successful effort to keep the Asilomar facility in Pacific Grove, California as the alternating venue for the annual Experimental NMR Conference. Two memorial services for Professor Hall are remembered. Copyright © 2011 Elsevier Inc. All rights reserved.

Conducting wall Hall thrusters in magnetic shielding and standard configurations

NASA Astrophysics Data System (ADS)

Grimaud, Lou; Mazouffre, Stéphane

2017-07-01

Traditional Hall thrusters are fitted with boron nitride dielectric discharge channels that confine the plasma discharge. Wall properties have significant effects on the performances and stability of the thrusters. In magnetically shielded thrusters, interactions between the plasma and the walls are greatly reduced, and the potential drop responsible for ion acceleration is situated outside the channel. This opens the way to the utilization of alternative materials for the discharge channel. In this work, graphite walls are compared to BN-SiO2 walls in the 200 W magnetically shielded ISCT200-MS and the unshielded ISCT200-US Hall thrusters. The magnetically shielded thruster shows no significant change in the discharge current mean value and oscillations, while the unshielded thruster's discharge current increases by 25% and becomes noticeably less stable. The electric field profile is also investigated through laser spectroscopy, and no significant difference is recorded between the ceramic and graphite cases for the shielded thruster. The unshielded thruster, on the other hand, has its acceleration region shifted 15% of the channel length downstream. Lastly, the plume profile is measured with planar probes fitted with guard rings. Once again the material wall has little influence on the plume characteristics in the shielded thruster, while the unshielded one is significantly affected.

The first vineyard concert hall in North America

NASA Astrophysics Data System (ADS)

Jaffe, Christopher; Rivera, Carlos

2002-11-01

The first vineyard or surround concert hall designed and built in the Western Hemisphere is the Sala Nezahualcoyotl in Mexico City. The Hall was completed in 1976 and is part of the Cultural Center at the Universidad Nacional Autonoma de Mexico. The hall was named after a Toltec poet, architect, and musician who lived in the 15th century and was the Renaissance man of his day. In order to provide the familiar traditional sound of the rectangular (shoebox) European Hall, the acoustic designers set the criteria for reverberation times through the frequency spectrum and the Initial Time Delay Gap at every seat in the house to match the measurements taken at the Grosser Musik vereinssaal in Vienna and Boston Symphony Hall. In this paper we discuss the techniques used to create the traditional sound in a vineyard hall and the reaction of musicians and audiences to the completed facility. The Sala was the model for Suntory Hall in Japan which in turn spawned a number of vineyard halls in Japan. Most recently, the vineyard style seems to be appealing to more and more symphonic organizations in Europe and North America.

Magnetic field mapping of the UCNTau magneto-gravitational trap: design study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Libersky, Matthew Murray

2014-09-04

The beta decay lifetime of the free neutron is an important input to the Standard Model of particle physics, but values measured using different methods have exhibited substantial disagreement. The UCN r experiment in development at Los Alamos National Laboratory (LANL) plans to explore better methods of measuring the neutron lifetime using ultracold neutrons (UCNs). In this experiment, UCNs are confined in a magneto-gravitational trap formed by a curved, asymmetric Halbach array placed inside a vacuum vessel and surrounded by holding field coils. If any defects present in the Halbach array are sufficient to reduce the local field near themore » surface below that needed to repel the desired energy level UCNs, loss by material interaction can occur at a rate similar to the loss by beta decay. A map of the magnetic field near the surface of the array is necessary to identify any such defects, but the array's curved geometry and placement in a vacuum vessel make conventional field mapping methods difficult. A system consisting of computer vision-based tracking and a rover holding a Hall probe has been designed to map the field near the surface of the array, and construction of an initial prototype has begun at LANL. The design of the system and initial results will be described here.« less

Alignment Measurements of the Microwave Anisotropy Probe (MAP) Instrument in a Thermal/Vacuum Chamber

NASA Technical Reports Server (NTRS)

Hill, Michael D.; Herrera, Acey A.; Crane, J. Allen; Packard, Edward A.; Aviado, Carlos; Sampler, Henry P.

2000-01-01

The Microwave Anisotropy Probe (MAP) Observatory, scheduled for a fall 2000 launch, is designed to measure temperature fluctuations (anisotropy) and produce a high sensitivity and high spatial resolution (approximately 0.2 degree) map of the cosmic microwave background (CMB) radiation over the entire sky between 22 and 90 GHz. MAP utilizes back-to-back Gregorian telescopes to focus the microwave signals into 10 differential microwave receivers, via 20 feed horns. Proper alignment of the telescope reflectors and the feed horns at the operating temperature of 90 K is a critical element to ensure mission success. We describe the hardware and methods used to validate the displacement/deformation predictions of the reflectors and the microwave feed horns during thermal/vacuum testing of the reflectors and the microwave instrument. The smallest deformation predictions to be measured were on the order of +/- 0.030 inches (+/- 0.762 mm). Performance of these alignment measurements inside a thermal/vacuum chamber with conventional alignment equipment posed several limitations. The most troublesome limitation was the inability to send personnel into the chamber to perform the measurements during the test due to vacuum and the temperature extremes. The photogrammetry (PG) system was chosen to perform the measurements since it is a non- contact measurement system, the measurements can be made relatively quickly and accurately, and the photogrammetric camera can be operated remotely. The hardware and methods developed to perform the MAP alignment measurements using PG proved to be highly successful. The measurements met the desired requirements, for the metal structures enabling the desired distortions to be measured resolving deformations an order of magnitude smaller than the imposed requirements. Viable data were provided to the MAP Project for a full analysis of the on-orbit performance of the Instrument's microwave system.

Turbulence Measurements in a Tropical Zoo Hall

NASA Astrophysics Data System (ADS)

Eugster, Werner; Denzler, Basil; Bogdal, Christian

2017-04-01

The Masoala rainforest hall of the Zurich Zoo, Switzerland, covers a ground surface area of 10,856 m2 and reaches 30 m in height. With its transparent ETFE foiled roof it provides a tropical climate for a large diversity of plants and animals. In combination with an effort to estimate dry deposition of elemental mercury, we made an attempt to measure turbulent transfer velocity with an ultrasonic anemometer inside the hall. Not surprising, the largest turbulence elements were on the order of the hall dimension. Although the dimensions of the hall seem to be small (200,000 m3) for eddy covariance flux measurements and the air circulation inside the hall was extremely weak, the spectra of wind velocity components and virtual (sonic) temperature obeyed the general statistical description expected under unconstrained outdoor measurement conditions. We will present results from a two-week measurement campaign in the Masoala rainforest hall and make a suggestion for the deposition velocity to be used to estimate dry deposition of atmospheric components to the tropical vegetation surface.

Observation of a high-energy tail in ion energy distribution in the cylindrical Hall thruster plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Youbong; Kim, Holak; Choe, Wonho, E-mail: wchoe@kaist.ac.kr

2014-10-15

A novel method is presented to determine populations and ion energy distribution functions (IEDFs) of individual ion species having different charge states in an ion beam from the measured spectrum of an E × B probe. The inversion of the problem is performed by adopting the iterative Tikhonov regularization method with the characteristic matrices obtained from the calculated ion trajectories. In a cylindrical Hall thruster plasma, an excellent agreement is observed between the IEDFs by an E × B probe and those by a retarding potential analyzer. The existence of a high-energy tail in the IEDF is found to be mainly due to singlymore » charged Xe ions, and is interpreted in terms of non-linear ion acceleration.« less

The Other Hall Effect: College Board Physics

ERIC Educational Resources Information Center

Sheppard, Keith; Gunning, Amanda M.

2013-01-01

Edwin Herbert Hall (1855-1938), discoverer of the Hall effect, was one of the first winners of the AAPT Oersted Medal for his contributions to the teaching of physics. While Hall's role in establishing laboratory work in high schools is widely acknowledged, his position as chair of the physics section of the Committee on College Entrance…

Chapin Hall Center for Children.

ERIC Educational Resources Information Center

Chicago Univ., IL. Chapin Hall Center for Children.

This document consists of two separate publications: (1) "The Power of Knowing", a brief 12-page description of the Chapin Hall Center for Children, and (2) "Projects and Publications", a 67-page list of the center's projects and publications as of Autumn 1997. "The Power of Knowing" describes the Chapin Hall Center…

Hall Thruster Technology for NASA Science Missions

NASA Technical Reports Server (NTRS)

Manzella, David; Oh, David; Aadland, Randall

2005-01-01

The performance of a prototype Hall thruster designed for Discovery-class NASA science mission applications was evaluated at input powers ranging from 0.2 to 2.9 kilowatts. These data were used to construct a throttle profile for a projected Hall thruster system based on this prototype thruster. The suitability of such a Hall thruster system to perform robotic exploration missions was evaluated through the analysis of a near Earth asteroid sample return mission. This analysis demonstrated that a propulsion system based on the prototype Hall thruster offers mission benefits compared to a propulsion system based on an existing ion thruster.

Numerical analysis of Hall effect on the performance of magnetohydrodynamic heat shield system based on nonequilibrium Hall parameter model

NASA Astrophysics Data System (ADS)

Li, Kai; Liu, Jun; Liu, Weiqiang

2017-01-01

Magnetohydrodynamic (MHD) heat shield system, a novel thermal protection technique in the hypersonic field, has been paid much attention in recent years. In the real flight condition, not only the Lorentz force but also the Hall electric field is induced by the interaction between ionized air post shock and magnetic field. In order to analyze the action mechanisms of the Hall effect, numerical methods of coupling thermochemical nonequilibrium flow field with externally applied magnetic field as well as the induced electric field are constructed and validated. Based on the nonequilibrium model of Hall parameter, numerical simulations of the MHD heat shield system is conducted under two different magnetic induction strengths (B0=0.2 T, 0.5 T) on a reentry capsule forebody. Results show that, the Hall effect is the same under the two magnetic induction strengths when the wall is assumed to be conductive. For this case, with the Hall effect taken into account, the Lorentz force counter stream diminishes a lot and the circumferential component dominates, resulting that the heat flux and shock-off distance approach the case without MHD control. However, for the insulating wall, the Hall effect acts in different ways under these two magnetic induction strengths. For this case, with the Hall effect taken into account, the performance of MHD heat shield system approaches the case neglecting the Hall effect when B0 equals 0.2 T. Such performance becomes worse when B0 equals 0.5 T and the aerothermal environment on the capsule shoulder is even worse than the case without MHD control.

Hall mobility in multicrystalline silicon

NASA Astrophysics Data System (ADS)

Schindler, F.; Geilker, J.; Kwapil, W.; Warta, W.; Schubert, M. C.

2011-08-01

Knowledge of the carrier mobility in silicon is of utmost importance for photovoltaic applications, as it directly influences the diffusion length and thereby the cell efficiency. Moreover, its value is needed for a correct quantitative evaluation of a variety of lifetime measurements. However, models that describe the carrier mobility in silicon are based on theoretical calculations or fits to experimental data in monocrystalline silicon. Multicrystalline (mc) silicon features crystal defects such as dislocations and grain boundaries, with the latter possibly leading to potential barriers through the trapping of charge carriers and thereby influencing the mobility, as shown, for example, by Maruska et al. [Appl. Phys. Lett. 36, 381 (1980)]. To quantify the mobilities in multicrystalline silicon, we performed Hall measurements in p-type mc-Si samples of various resistivities and different crystal structures and compared the data to majority carrier Hall mobilities in p-type monocrystalline floatzone (FZ) silicon. For lack of a model that provides reliable values of the Hall mobility in silicon, an empirical fit similar to existing models for conductivity mobilities is proposed based on Hall measurements of monocrystalline p-type FZ silicon. By comparing the measured Hall mobilities obtained from mc silicon with the corresponding Hall mobilities in monocrystalline silicon of the same resistivity, we found that the mobility reduction due to the presence of crystal defects in mc-Si ranges between 0% and 5% only. Mobility decreases of up to 30% as reported by Peter et al. [Proceedings of the 23rd European Photovoltaic Solar Energy Conference, Valencia, Spain, 1-5 September 2008], or even of a factor of 2 to 3 as detected by Palais et al. [Mater. Sci. Eng. B 102, 184 (2003)], in multicrystalline silicon were not observed.

Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators.

PubMed

Guterding, Daniel; Jeschke, Harald O; Valentí, Roser

2016-05-17

Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions.

A Gift for Reading Hall No. 1

ERIC Educational Resources Information Center

MacWilliams, Bryon

2009-01-01

In this article, the author describes Reading Hall No. 1 of the Russian State Library. He was placed in the first reading hall in the mid-1990s, when the Russian government still honored Soviet traditions of granting certain privileges to certain foreigners. In the first hall, the rules are different. He can request as many books as he wants. He…

Quantum hall ferromagnets

NASA Astrophysics Data System (ADS)

Kumar, Akshay

We study several quantum phases that are related to the quantum Hall effect. Our initial focus is on a pair of quantum Hall ferromagnets where the quantum Hall ordering occurs simultaneously with a spontaneous breaking of an internal symmetry associated with a semiconductor valley index. In our first example ---AlAs heterostructures--- we study domain wall structure, role of random-field disorder and dipole moment physics. Then in the second example ---Si(111)--- we show that symmetry breaking near several integer filling fractions involves a combination of selection by thermal fluctuations known as "order by disorder" and a selection by the energetics of Skyrme lattices induced by moving away from the commensurate fillings, a mechanism we term "order by doping". We also study ground state of such systems near filling factor one in the absence of valley Zeeman energy. We show that even though the lowest energy charged excitations are charge one skyrmions, the lowest energy skyrmion lattice has charge > 1 per unit cell. We then broaden our discussion to include lattice systems having multiple Chern number bands. We find analogs of quantum Hall ferromagnets in the menagerie of fractional Chern insulator phases. Unlike in the AlAs system, here the domain walls come naturally with gapped electronic excitations. We close with a result involving only topology: we show that ABC stacked multilayer graphene placed on boron nitride substrate has flat bands with non-zero local Berry curvature but zero Chern number. This allows access to an interaction dominated system with a non-trivial quantum distance metric but without the extra complication of a non-zero Chern number.

Double-cladding-fiber-based detection system for intravascular mapping of fluorescent molecular probes

NASA Astrophysics Data System (ADS)

Razansky, R. Nika; Rozental, Amir; Mueller, Mathias S.; Deliolanis, Nikolaos; Jaffer, Farouc A.; Koch, Alexander W.; Ntziachristos, Vasilis

2011-03-01

Early detection of high-risk coronary atherosclerosis remains an unmet clinical challenge. We have previously demonstrated a near-infrared fluorescence catheter system for two-dimensional intravascular detection of fluorescence molecular probes [1]. In this work we improve the system performance by introducing a novel high resolution sensor. The main challenge of the intravascular sensor is to provide a highly focused spot at an application relevant distance on one hand and a highly efficient collection of emitted light on the other. We suggest employing a double cladding optical fiber (DCF) in combination with focusing optics to provide a sensor with both highly focused excitation light and highly efficient fluorescent light collection. The excitation laser is coupled into the single mode core of DCF and guided through a focusing element and a right angle prism. The resulting side-fired beam exhibits a small spot diameter (50 μm) throughout a distance of up to 2 mm from the sensor. This is the distance of interest for intravascular coronary imaging application, determined by an average human coronary artery diameter. At the blood vessel wall, an activatable fluorescence molecular probe is excited in the diseased lesions. Next light of slightly shifted wavelength emits only in the places of the inflammations, associated with dangerous plaques [2]. The emitted light is collected by the cladding of the DCF, with a large collection angle (NA=0.4). The doublecladding acts as multimodal fiber and guides the collected light to the photo detection elements. The sensor automatically rotates and pulled-back, while each scanned point is mapped according to the amount of detected fluorescent emission. The resulting map of fluorescence activity helps to associate the atherosclerotic plaques with the inflammation process. The presented detection system is a valuable tool in the intravascular plaque detection and can help to differentiate the atherosclerotic plaques based on

Overview of Hall D Complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chudakov, Eugene A.

Hall D is a new experimental hall at Jefferson Lab, designed for experiments with a photon beam. The primary motivation for Hall D is the GlueX experiment [1,2], dedicated to meson spectroscopy. The Hall D complex consists of: An electron beam line used to extract the 5.5-pass electrons from the accelerator into the Tagger Hall. The designed beam energy is E e = 12 GeV;The Tagger Hall, where the electron beam passes through a thin radiator (~0.01% R.L.) and is deflected into the beam dump. The electrons that lost >30% of their energy in the radiator are detected with scintillatormore » hodoscopes providing a ~0.1% energy resolution for the tagged photons. Aligned diamond radiators allow to produce linearly polarized photons via the Coherent Bremsstrahlung. The beam dump is limited to 60 kW (5 µA at 12 GeV); The Collimator Cave contains a collimator for the photon beam and dipole magnets downstream in order to remove charged particles. The 3.4 mm diameter collimator, located about 75 m downstream of the radiator, selects the central cone of the photon beam increasing its average linear polarization, up to ~40%in the coherent peak at 9 GeV; Hall D contains several elements of the photon beam line, and themain spectrometer. A Pair Spectrometer consists of a thin converter, a dipole magnet, and a two-arm detector used to measure the energy spectrum of the photon beam. The main spectrometer is based on a 2-T superconducting solenoid, 4 m long and 1.85 m bore diameter. The liquid hydrogen target is located in the front part the solenoid. The charged tracks are detected with a set of drift chambers; photons are detected with two electromagnetic calorimeters. There are also scintillator hodoscopes for triggering and time-of-flight measurements. The spectrometer is nearly hermetic in an angular range of 1° < θ < 120 •. The momentum resolution is σ p /p ~ 1 ₋ ₋3% depending on the polar angle θ. The energy resolution of the electromagnetic calorimeters is about 7

Astronaut Hall of Fame

NASA Image and Video Library

2018-04-21

Former astronauts and space explorers, Thomas D. Jones, Ph.D., and Scott D. Altman, front row, center, left and right, respectively, were inducted into the U.S. Astronaut Hall of Fame Class of 2018 during a ceremony inside the Space Shuttle Atlantis attraction at NASA’s Kennedy Space Center Visitor Complex in Florida. They are standing with previous Hall of Famers, including, Curt Brown, back row, far left, chairman of the board, Astronaut Scholarship Foundation. Brown performed the induction ceremony. Also in the group is former astronaut and NASA administrator Charlie Bolden, in the center, behind Jones and Altman. In the back row, second from left is John Grunsfeld, who spoke on behalf of Altman during the ceremony. Directly behind Altman is Storey Musgrave, who spoke on behalf of Jones during the ceremony. Inductees into the Hall of Fame are selected by a committee of Hall of Fame astronauts, former NASA officials, flight directors, historians and journalists. The process is administered by the Astronaut Scholarship Foundation. To be eligible, an astronaut must have made his or her first flight at least 17 years before the induction. Candidates must be a U.S. citizen and a NASA-trained commander, pilot or mission specialist who has orbited the earth at least once. Including Altman and Jones, 97 astronauts have been inducted into the AHOF.

Dr. Hall and the work cure.

PubMed

Reed, Kathlyn L

2005-01-01

Herbert James Hall, MD (1870-1923), was a pioneer in the systematic and organized study of occupation as therapy for persons with nervous and mental disorders that he called the "work cure." He began his work in 1904 during the early years of the Arts and Crafts Movement in the United States. His primary interest was the disorder neurasthenia, a condition with many symptoms including chronic fatigue, stress, and inability to work or perform everyday tasks. The prevailing treatment of the day was absolute bed rest known as the "rest cure." Hall believed that neurasthenia was not caused by overwork but by faulty living habits that could be corrected through an ordered life schedule and selected occupations. He identified several principles of therapy that are still used today including graded activity and energy conservation. Dr. Adolph Meyer credits Hall for organizing the ideas on the therapeutic use of occupation (Meyer, 1922). Hall also provided the name American Occupational Therapy Association for the professional organization and served as the fourth president. For his many contributions to the profession Hall deserves to be recognized as a major contributor to the development and organization of occupational therapy.

Composite fermion theory for bosonic quantum Hall states on lattices.

PubMed

Möller, G; Cooper, N R

2009-09-04

We study the ground states of the Bose-Hubbard model in a uniform magnetic field, motivated by the physics of cold atomic gases on lattices at high vortex density. Mapping the bosons to composite fermions (CF) leads to the prediction of quantum Hall fluids that have no counterpart in the continuum. We construct trial states for these phases and test numerically the predictions of the CF model. We establish the existence of strongly correlated phases beyond those in the continuum limit and provide evidence for a wider scope of the composite fermion approach beyond its application to the lowest Landau level.

Magnet/Hall-Effect Random-Access Memory

NASA Technical Reports Server (NTRS)

Wu, Jiin-Chuan; Stadler, Henry L.; Katti, Romney R.

1991-01-01

In proposed magnet/Hall-effect random-access memory (MHRAM), bits of data stored magnetically in Perm-alloy (or equivalent)-film memory elements and read out by using Hall-effect sensors to detect magnetization. Value of each bit represented by polarity of magnetization. Retains data for indefinite time or until data rewritten. Speed of Hall-effect sensors in MHRAM results in readout times of about 100 nanoseconds. Other characteristics include high immunity to ionizing radiation and storage densities of order 10(Sup6)bits/cm(Sup 2) or more.

2017 Astronaut Hall of Fame Induction Ceremony

NASA Image and Video Library

2017-05-19

In the Space Shuttle Atlantis facility at the Kennedy Space Center Visitor Complex in Florida, Astronaut Scholarship Foundation Chairman Dan Brandenstein, left, also a Hall of Fame astronaut, presents inductee Michael Foale with his hall of fame medal. Former NASA Administrator Charlie Bolden, right, a Hall of Fame member, presented Foale for induction. During this year's ceremonies, space shuttle astronaut Ellen Ochoa also was enshrined.

2017 Astronaut Hall of Fame Induction Ceremony

NASA Image and Video Library

2017-05-19

In the Space Shuttle Atlantis facility at the Kennedy Space Center Visitor Complex in Florida, Astronaut Scholarship Foundation Chairman Dan Brandenstein, left, also a Hall of Fame astronaut, presents inductee Ellen Ochoa with her hall of fame medal. Former Johnson Space Center Director Mike Coats, right, a Hall of Fame member, presented Ochoa for induction. During this year's ceremonies, space shuttle astronaut Michael Foale also was enshrined.

Ted Hall and the science of biological microprobe X-ray analysis: a historical perspective of methodology and biological dividends.

PubMed

Gupta, B L

1991-06-01

This review surveys the emergence of electron probe X-ray microanalysis as a quantitative method for measuring the chemical elements in situ. The extension of the method to the biological sciences under the influence of Ted Hall is reviewed. Some classical experiments by Hall and his colleagues in Cambridge, UK, previously unpublished, are described; as are some of the earliest quantitative results from the cryo-sections obtained in Cambridge and elsewhere. The progress of the methodology is critically evaluated from the earliest starts to the present state of the art. Particular attention has been focused on the application of the method in providing fresh insights into the role of ions in cell and tissue physiology and pathology. A comprehensive list of references is included for a further pursuit of the topics by the interested reader.

Molecular mapping of chromosomes 17 and X

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barker, D.F.

1991-01-15

Progress toward the construction of high density genetic maps of chromosomes 17 and X has been made by isolating and characterizing a relatively large set of polymorphic probes for each chromosome and using these probes to construct genetic maps. We have mapped the same polymorphic probes against a series of chromosome breakpoints on X and 17. The probes could be assigned to over 30 physical intervals on the X chromosome and 7 intervals on 17. In many cases, this process resulted in improved characterization of the relative locations of the breakpoints with respect to each other and the definition ofmore » new physical intervals. The strategy for isolation of the polymorphic clones utilized chromosome specific libraries of 1--15 kb segments from each of the two chromosomes. From these libraries, clones were screened for those detecting restriction fragment length polymorphisms. The markers were further characterized, the chromosomal assignments confirmed and in most cases segments of the original probes were subcloned into plasmids to produce probes with improved signal to noise ratios for use in the genetic marker studies. The linkage studies utilize the CEPH reference families and other well-characterized families in our collection which have been used for genetic disease linkage work. Preliminary maps and maps of portions of specific regions of 17 and X are provided. We have nearly completed a map of the 1 megabase Mycoplasma arthritidis genome by applying these techniques to a lambda phage library of its genome. We have found bit mapping to be an efficient means to organize a contiguous set of overlapping clones from a larger genome.« less

A Comprehensive Investigation of Facility Effects on the Testing of High-Power Monolithic and Clustered Hall Thruster Systems

DTIC Science & Technology

2006-02-01

Propulsion Conference and Exhibit, Huntsville, AL, July 20-23, 2003. 83. Van Gilder, D. B., Boyd, I. D., Keidar, M., Particle Simulations of a Hall...ExB probe entrance during P5 operation, it is not possible to accurately measure the percentage of multiply-charged particles in the thruster plume...magnetic filter. Particles enter along the z-axis, directed into the page. (L = 5.85 cm, D = 2.54 cm) ......................... 54 Figure 2-17

Experimental mapping of DNA duplex shape enabled by global lineshape analyses of a nucleotide-independent nitroxide probe

PubMed Central

Ding, Yuan; Zhang, Xiaojun; Tham, Kenneth W.; Qin, Peter Z.

2014-01-01

Sequence-dependent variation in structure and dynamics of a DNA duplex, collectively referred to as ‘DNA shape’, critically impacts interactions between DNA and proteins. Here, a method based on the technique of site-directed spin labeling was developed to experimentally map shapes of two DNA duplexes that contain response elements of the p53 tumor suppressor. An R5a nitroxide spin label, which was covalently attached at a specific phosphate group, was scanned consecutively through the DNA duplex. X-band continuous-wave electron paramagnetic resonance spectroscopy was used to monitor rotational motions of R5a, which report on DNA structure and dynamics at the labeling site. An approach based on Pearson's coefficient analysis was developed to collectively examine the degree of similarity among the ensemble of R5a spectra. The resulting Pearson's coefficients were used to generate maps representing variation of R5a mobility along the DNA duplex. The R5a mobility maps were found to correlate with maps of certain DNA helical parameters, and were capable of revealing similarity and deviation in the shape of the two closely related DNA duplexes. Collectively, the R5a probe and the Pearson's coefficient-based lineshape analysis scheme yielded a generalizable method for examining sequence-dependent DNA shapes. PMID:25092920

A hemicyanine based ratiometric fluorescence probe for mapping lysosomal pH during heat stroke in living cells.

PubMed

Wu, Luling; Wang, Yang; James, Tony D; Jia, Nengqin; Huang, Chusen

2018-05-29

Heat stroke is a lethal condition which can cause dysfunction in the central nervous system, multi-organ damage and even death. However, there is still limited knowledge of the detailed mechanism about the roles of lysosomes in heat stroke due to lack of effective tools. Herein, we introduce our previously developed hemicyanine with a large D-π-A structure as the key fluorophore to develop a new fluorescent probe (CPY) for ratiometric mapping of lysosomal pH changes in live cells under a heat shock stimulus.

Effect of Background Pressure on the Performance and Plume of the HiVHAc Hall Thruster

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Kamhawi, Hani; Haag, Thomas

2013-01-01

During the Single String Integration Test of the NASA HiVHAc Hall thruster, a number of plasma diagnostics were implemented to study the effect of varying facility background pressure on thruster operation. These diagnostics include thrust stand, Faraday probe, ExB probe, and retarding potential analyzer. The test results indicated a rise in thrust and discharge current with background pressure. There was also a decrease in ion energy per charge, an increase in multiply-charged species production, a decrease in plume divergence, and a decrease in ion beam current with increasing background pressure. A simplified ingestion model was applied to determine the maximum acceptable background pressure for thrust measurement. The maximum acceptable ingestion percentage was found to be around 1%. Examination of the diagnostics results suggest the ionization and acceleration zones of the thruster were shifting upstream with increasing background pressure.

Mapping and controlling ultrafast dynamics of highly excited H 2 molecules by VUV-IR pump-probe schemes

DOE PAGES

Sturm, F. P.; Tong, X. M.; Palacios, A.; ...

2017-01-09

Here, we used ultrashort femtosecond vacuum ultraviolet (VUV) and infrared (IR) pulses in a pump-probe scheme to map the dynamics and nonequilibrium dissociation channels of excited neutral H 2 molecules. A nuclear wave packet is created in the B 1Σmore » $$+\\atop{u}$$ state of the neutral H 2 molecule by absorption of the ninth harmonic of the driving infrared laser field. Due to the large stretching amplitude of the molecule excited in the B 1Σ$$+\\atop{u}$$ electronic state, the effective H 2 + ionization potential changes significantly as the nuclear wave packet vibrates in the bound, highly electronically and vibrationally excited B potential-energy curve. We probed such dynamics by ionizing the excited neutral molecule using time-delayed VUV-or-IR radiation. We identified the nonequilibrium dissociation channels by utilizing three-dimensional momentum imaging of the ion fragments. We also found that different dissociation channels can be controlled, to some extent, by changing the IR laser intensity and by choosing the wavelength of the probe laser light. Furthermore, we concluded that even in a benchmark molecular system such as H 2*, the interpretation of the nonequilibrium multiphoton and multicolor ionization processes is still a challenging task, requiring intricate theoretical analysis.« less

Hall thruster with grooved walls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Hong; Ning Zhongxi; Yu Daren

2013-02-28

Axial-oriented and azimuthal-distributed grooves are formed on channel walls of a Hall thruster after the engine undergoes a long-term operation. Existing studies have demonstrated the relation between the grooves and the near-wall physics, such as sheath and electron near-wall transport. The idea to optimize the thruster performance with such grooves was also proposed. Therefore, this paper is devoted to explore the effects of wall grooves on the discharge characteristics of a Hall thruster. With experimental measurements, the variations on electron conductivity, ionization distribution, and integrated performance are obtained. The involved physical mechanisms are then analyzed and discussed. The findings helpmore » to not only better understand the working principle of Hall thruster discharge but also establish a physical fundamental for the subsequent optimization with artificial grooves.« less

Spin Hall Effects in Metallic Antiferromagnets

DOE PAGES

Zhang, Wei; Jungfleisch, Matthias B.; Jiang, Wanjun; ...

2014-11-04

In this paper, we investigate four CuAu-I-type metallic antiferromagnets for their potential as spin current detectors using spin pumping and inverse spin Hall effect. Nontrivial spin Hall effects were observed for FeMn, PdMn, and IrMn while a much higher effect was obtained for PtMn. Using thickness-dependent measurements, we determined the spin diffusion lengths of these materials to be short, on the order of 1 nm. The estimated spin Hall angles of the four materials follow the relationship PtMn > IrMn > PdMn > FeMn, highlighting the correlation between the spin-orbit coupling of nonmagnetic species and the magnitude of the spinmore » Hall effect in their antiferromagnetic alloys. These experiments are compared with first-principles calculations. Finally, engineering the properties of the antiferromagnets as well as their interfaces can pave the way for manipulation of the spin dependent transport properties in antiferromagnet-based spintronics.« less

Valley-chiral quantum Hall state in graphene superlattice structure

NASA Astrophysics Data System (ADS)

Tian, H. Y.; Tao, W. W.; Wang, J.; Cui, Y. H.; Xu, N.; Huang, B. B.; Luo, G. X.; Hao, Y. H.

2016-05-01

We theoretically investigate the quantum Hall effect in a graphene superlattice (GS) system, in which the two valleys of graphene are coupled together. In the presence of a perpendicular magnetic field, an ordinary quantum Hall effect is found with the sequence σxy=ν e^2/h(ν=0,+/-1,+/-2,\\cdots) . At the zeroth Hall platform, a valley-chiral Hall state stemming from the single K or K' valley is found and it is localized only on one sample boundary contributing to the longitudinal conductance but not to the Hall conductivity. Our findings may shed light on the graphene-based valleytronics applications.

Nonlinearity in the effect of an inhomogeneous Hall angle

NASA Astrophysics Data System (ADS)

Koon, Daniel W.

2007-03-01

The differential equation for the electric potential in a conducting material with an inhomogeneous Hall angle is extended to the large-field limit. This equation is solved for a square specimen, using a successive over-relaxation [SOR] technique for matrices of up to 101x101 size, and the Hall weighting function -- the effect of local pointlike perturbations on the measured Hall angle -- is calculated as both the unperturbed Hall angle, θH, and the perturbation, δθH, exceed the linear, small angle limit. Preliminary results show that the Hall angle varies by no more than 5% if both | θH |<1 and | δθH |<1. Thus, previously calculated results for the Hall weighting function can be used for most materials in all but the most extreme magnetic fields.

Giant Hall Photoconductivity in Narrow-Gapped Dirac Materials

NASA Astrophysics Data System (ADS)

Song, Justin C. W.; Kats, Mikhail A.

2016-12-01

Carrier dynamics acquire a new character in the presence of Bloch-band Berry curvature, which naturally arises in gapped Dirac materials (GDMs). Here we argue that photoresponse in GDMs with small band gaps is dramatically enhanced by Berry curvature. This manifests in a giant and saturable Hall photoconductivity when illuminated by circularly polarized light. Unlike Hall motion arising from a Lorentz force in a magnetic field, which impedes longitudinal carrier motion, Hall photoconductivity arising from Berry curvature can boost longitudinal carrier transport. In GDMs, this results in a helicity-dependent photoresponse in the Hall regime, where photoconductivity is dominated by its Hall component. We find that the induced Hall conductivity per incident irradiance is enhanced by up to six orders of magnitude when moving from the visible regime (with corresponding band gaps) to the far infrared. These results suggest that narrow-gap GDMs are an ideal test-bed for the unique physics that arise in the presence of Berry curvature, and open a new avenue for infrared and terahertz optoelectronics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buehler, Marc; Tartaglia, Michael; Tompkins, John

The Mu2e experiment at Fermilab is designed to explore charged lepton flavor violation by searching for muon-to-electron conversion. The magnetic field generated by a system of solenoids is crucial for Mu2e and requires accurate characterization to detect any flaws and to produce a detailed field map. Stringent physics goals are driving magnetic field specifications for the Mu2e solenoids. A field mapper is being designed, which will produce detailed magnetic field maps. The uniform field region of the spectrometer volume requires the highest level of precision (1 Gauss per 1 Tesla). During commissioning, multiple magnetic field maps will be generated tomore » verify proper alignment of all magnet coils, and to create the final magnetic field map. In order to design and build a precise field mapping system consisting of Hall and NRM probes, tolerances and precision for such a system need to be evaluated. In this paper we present a design for the Mu2e field mapping hardware, and discuss results from OPERA-3D simulations to specify parameters for Hall and NMR probes. We also present a fitting procedure for the analytical treatment of our expected magnetic measurements.« less

Air temperature gradient in large industrial hall

NASA Astrophysics Data System (ADS)

Karpuk, Michał; Pełech, Aleksander; Przydróżny, Edward; Walaszczyk, Juliusz; Szczęśniak, Sylwia

2017-11-01

In the rooms with dominant sensible heat load, volume airflow depends on many factors incl. pre-established temperature difference between exhaust and supply airflow. As the temperature difference is getting higher, airflow volume drops down, consequently, the cost of AHU is reduced. In high industrial halls with air exhaust grids located under the ceiling additional temperature gradient above working zone should be taken into consideration. In this regard, experimental research of the vertical air temperature gradient in high industrial halls were carried out for the case of mixing ventilation system The paper presents the results of air temperature distribution measurements in high technological hall (mechanically ventilated) under significant sensible heat load conditions. The supply airflow was delivered to the hall with the help of the swirl diffusers while exhaust grids were located under the hall ceiling. Basing on the air temperature distribution measurements performed on the seven pre-established levels, air temperature gradient in the area between 2.0 and 7.0 m above the floor was calculated and analysed.

Design and experimental observation of valley-Hall edge states in diatomic-graphene-like elastic waveguides

NASA Astrophysics Data System (ADS)

Zhu, Hongfei; Liu, Ting-Wei; Semperlotti, Fabio

2018-05-01

We report on the design and experimental validation of a two-dimensional phononic elastic waveguide exhibiting topological valley-Hall edge states. The lattice structure of the waveguide is inspired by diatomic graphene, and it is imprinted in an initially flat plate by means of geometric indentations. The indentations are distributed according to a hexagonal lattice structure which guarantees the existence of Dirac dispersion at the boundary of the Brillouin zone. Starting from this basic material, domain walls capable of supporting edge states can be obtained by contrasting waveguides having broken space-inversion symmetry (SIS) achieved by using local resonant elements. Our theoretical study shows that such material maps into the acoustic analog of the quantum valley-Hall effect, while numerical and experimental results confirm the existence of protected edge states traveling along the walls of topologically distinct domains.

Preliminary Study of Arcjet Neutralization of Hall Thruster Clusters (Postprint)

DTIC Science & Technology

2007-01-18

Clustered Hall thrusters have emerged as a favored choice for extending Hall thruster options to very high powers (50 kW - 150 kW). This paper...examines the possible use of an arcjet to neutralize clustered Hall thrusters, as the hybrid arcjet- Hall thruster concept can fill a performance niche...and helium, and then demonstrate the first successful operation of a low power Hall thruster -arcjet neutralizer package. In the surrogate anode studies

Interstitial duplication 8q22-q24: Report of a case proven by FISH with mapped cosmid probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wakui, Keiko; Ohashi, Hirofumi; Yamagishi, Akira

We report on a 6-month-old malformed female infant with a de novo interstitial duplication of an 8q22-q24 segment. She had an excess dark-band on the 8q distal region by GTG-banded chromosome analysis, which was likely to be 8q23. We performed FISH analysis using cosmid probes mapped to 8q23 and proved that the patient had an 8q duplication including the 8q23 region. 20 refs., 2 figs., 1 tab.

Hall Thruster

NASA Image and Video Library

2017-03-06

NASA Glenn engineer Dr. Peter Peterson prepares a high-power Hall thruster for ground testing in a vacuum chamber that simulates the environment in space. This high-powered solar electric propulsion thruster has been identified as a critical part of NASA’s future deep space exploration plans.

The quantum Hall effects: Philosophical approach

NASA Astrophysics Data System (ADS)

Lederer, P.

2015-05-01

The Quantum Hall Effects offer a rich variety of theoretical and experimental advances. They provide interesting insights on such topics as gauge invariance, strong interactions in Condensed Matter physics, emergence of new paradigms. This paper focuses on some related philosophical questions. Various brands of positivism or agnosticism are confronted with the physics of the Quantum Hall Effects. Hacking's views on Scientific Realism, Chalmers' on Non-Figurative Realism are discussed. It is argued that the difficulties with those versions of realism may be resolved within a dialectical materialist approach. The latter is argued to provide a rational approach to the phenomena, theory and ontology of the Quantum Hall Effects.

Hall devices improve electric motor efficiency

NASA Technical Reports Server (NTRS)

Haeussermann, W.

1979-01-01

Efficiency of electric motors and generators is reduced by radial magnetic forces created by symmetric fields within device. Forces are sensed and counteracted by Hall devices on excitation or control windings. Hall generators directly measure and provide compensating control of anu asymmetry, eliminating additional measurements needed for calibration feedback control loop.

Coping Behaviors of Residence Hall Directors

ERIC Educational Resources Information Center

Wilkes, Ben

2017-01-01

This mixed-methods study examined tertiary-level residence-hall directors' reported coping behaviors for three systems of stress: environmental, personal, and work. It surveyed a convenience sample of 128 respondents using the Brief COPE scale (Carver, 1997). Reported length of service, genders, and hall populations were matched with 28 types of…

A cavity ring-down spectroscopy sensor for real-time Hall thruster erosion measurements.

PubMed

Lee, B C; Huang, W; Tao, L; Yamamoto, N; Gallimore, A D; Yalin, A P

2014-05-01

A continuous-wave cavity ring-down spectroscopy sensor for real-time measurements of sputtered boron from Hall thrusters has been developed. The sensor uses a continuous-wave frequency-quadrupled diode laser at 250 nm to probe ground state atomic boron sputtered from the boron nitride insulating channel. Validation results from a controlled setup using an ion beam and target showed good agreement with a simple finite-element model. Application of the sensor for measurements of two Hall thrusters, the H6 and SPT-70, is described. The H6 was tested at power levels ranging from 1.5 to 10 kW. Peak boron densities of 10 ± 2 × 10(14) m(-3) were measured in the thruster plume, and the estimated eroded channel volume agreed within a factor of 2 of profilometry. The SPT-70 was tested at 600 and 660 W, yielding peak boron densities of 7.2 ± 1.1 × 10(14) m(-3), and the estimated erosion rate agreed within ~20% of profilometry. Technical challenges associated with operating a high-finesse cavity in the presence of energetic plasma are also discussed.

Thermally driven anomalous Hall effect transitions in FeRh

NASA Astrophysics Data System (ADS)

Popescu, Adrian; Rodriguez-Lopez, Pablo; Haney, Paul M.; Woods, Lilia M.

2018-04-01

Materials exhibiting controllable magnetic phase transitions are currently in demand for many spintronics applications. Here, we investigate from first principles the electronic structure and intrinsic anomalous Hall, spin Hall, and anomalous Nernst response properties of the FeRh metallic alloy which undergoes a thermally driven antiferromagnetic-to-ferromagnetic phase transition. We show that the energy band structures and underlying Berry curvatures have important signatures in the various Hall effects. Specifically, the suppression of the anomalous Hall and Nernst effects in the antiferromagnetic state and a sign change in the spin Hall conductivity across the transition are found. It is suggested that the FeRh can be used as a spin current detector capable of differentiating the spin Hall effect from other anomalous transverse effects. The implications of this material and its thermally driven phases as a spin current detection scheme are also discussed.

Comparisons and Evaluation of Hall Thruster Models

DTIC Science & Technology

2002-03-20

COVERED (FROM - TO) 20-04-2001 to 20-04-2002 4. TITLE AND SUBTITLE comparisons and Evaluation of Hall Thruster Models Unclassified 5a. CONTRACT NUMBER...TITLE AND SUBTITLE Comparisons and Evaluation of Hall Thruster Models 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5d. TASK NUMBER 6. AUTHOR(S...evaluation of Hall thruster models G. J. M. Hagelaar, J. Bareilles, L. Garrigues, and J.-P. Boeuf CPAT, Bâtiment 3R2, Université Paul Sabatier 118 Route

Extrinsic spin Hall effect in graphene

NASA Astrophysics Data System (ADS)

Rappoport, Tatiana

The intrinsic spin-orbit coupling in graphene is extremely weak, making it a promising spin conductor for spintronic devices. In addition, many applications also require the generation of spin currents in graphene. Theoretical predictions and recent experimental results suggest one can engineer the spin Hall effect in graphene by greatly enhancing the spin-orbit coupling in the vicinity of an impurity. The extrinsic spin Hall effect then results from the spin-dependent skew scattering of electrons by impurities in the presence of spin-orbit interaction. This effect can be used to efficiently convert charge currents into spin-polarized currents. I will discuss recent experimental results on spin Hall effect in graphene decorated with adatoms and metallic cluster and show that a large spin Hall effect can appear due to skew scattering. While this spin-orbit coupling is small if compared with what it is found in metals, the effect is strongly enhanced in the presence of resonant scattering, giving rise to robust spin Hall angles. I will present our single impurity scattering calculations done with exact partial-wave expansions and complement the analysis with numerical results from a novel real-space implementation of the Kubo formalism for tight-binding Hamiltonians. The author acknowledges the Brazilian agencies CNPq, CAPES, FAPERJ and INCT de Nanoestruturas de Carbono for financial support.

The shear-Hall instability in newborn neutron stars

NASA Astrophysics Data System (ADS)

Kondić, T.; Rüdiger, G.; Hollerbach, R.

2011-11-01

Aims: In the first few minutes of a newborn neutron star's life the Hall effect and differential rotation may both be important. We demonstrate that these two ingredients are sufficient for generating a "shear-Hall instability" and for studying its excitation conditions, growth rates, and characteristic magnetic field patterns. Methods: We numerically solve the induction equation in a spherical shell, with a kinematically prescribed differential rotation profile Ω(s), where s is the cylindrical radius. The Hall term is linearized about an imposed uniform axial field. The linear stability of individual azimuthal modes, both axisymmetric and non-axisymmetric, is then investigated. Results: For the shear-Hall instability to occur, the axial field must be parallel to the rotation axis if Ω(s) decreases outward, whereas if Ω(s) increases outward it must be anti-parallel. The instability draws its energy from the differential rotation, and occurs on the short rotational timescale rather than on the much longer Hall timescale. It operates most efficiently if the Hall time is comparable to the diffusion time. Depending on the precise field strengths B0, either axisymmetric or non-axisymmetric modes may be the most unstable. Conclusions: Even if the differential rotation in newborn neutron stars is quenched within minutes, the shear-Hall instability may nevertheless amplify any seed magnetic fields by many orders of magnitude.

Piezo-Hall effect and fundamental piezo-Hall coefficients of single crystal n-type 3C-SiC(100) with low carrier concentration

NASA Astrophysics Data System (ADS)

Qamar, Afzaal; Dao, Dzung Viet; Dinh, Toan; Iacopi, Alan; Walker, Glenn; Phan, Hoang-Phuong; Hold, Leonie; Dimitrijev, Sima

2017-04-01

This article reports the results on the piezo-Hall effect in single crystal n-type 3C-SiC(100) having a low carrier concentration. The effect of the crystallographic orientation on the piezo-Hall effect has been investigated by applying stress to the Hall devices fabricated in different crystallographic directions. Single crystal n-type 3C-SiC(100) and 3C-SiC(111) were grown by low pressure chemical vapor deposition at 1250 °C. Fundamental piezo-Hall coefficients were obtained using the piezo-Hall effect measurements as P11 = (-29 ± 1.3) × 10-11 Pa-1, P12 = (11.06 ± 0.5)× 10-11 Pa-1, and P44 = (-3.4 ± 0.7) × 10-11 Pa-1. It has been observed that the piezo-Hall coefficients of n-type 3C-SiC(100) show a completely different behavior as compared to that of p-type 3C-SiC.

Batch-fabricated high-performance graphene Hall elements

PubMed Central

Xu, Huilong; Zhang, Zhiyong; Shi, Runbo; Liu, Honggang; Wang, Zhenxing; Wang, Sheng; Peng, Lian-Mao

2013-01-01

Hall elements are by far the most widely used magnetic sensor. In general, the higher the mobility and the thinner the active region of the semiconductor used, the better the Hall device. While most common magnetic field sensors are Si-based Hall sensors, devices made from III-V compounds tend to favor over that based on Si. However these devices are more expensive and difficult to manufacture than Si, and hard to be integrated with signal-processing circuits for extending function and enforcing performance. In this article we show that graphene is intrinsically an ideal material for Hall elements which may harness the remarkable properties of graphene, i.e. extremely high carrier mobility and atomically thin active body, to create ideal magnetic sensors with high sensitivity, excellent linearity and remarkable thermal stability. PMID:23383375

How can we probe the atom mass currents induced by synthetic gauge fields?

NASA Astrophysics Data System (ADS)

Paramekanti, Arun; Killi, Matthew; Trotzky, Stefan

2013-05-01

Ultracold atomic fermions and bosons in an optical lattice can have quantum ground states which support equilibrium currents in the presence of synthetic magnetic fields or spin orbit coupling. As a tool to uncover these mass currents, we propose using an anisotropic quantum quench of the optical lattice which dynamically converts the current patterns into measurable density patterns. Using analytical calculations and numerical simulations, we show that this scheme can probe diverse equilibrium bulk current patterns in Bose superfluids and Fermi fluids induced by synthetic magnetic fields, as well as detect the chiral edge currents in topological states of atomic matter such as quantum Hall and quantum spin Hall insulators. This work is supported by NSERC of Canada and the Canadian Institute for Advanced Research.

Safety halls--an evaluation.

PubMed

Nyberg, Anders; Gregersen, Nils Petter; Nolén, Sixten; Engström, Inger

2005-01-01

In most countries, drivers licensing systems usually include teaching some aspects of using safety equipment (e.g., airbags and seat belts). However, there is now evidence worldwide that such education is inadequate, as indicated by, for example, the overrepresentation of young drivers who do not use seat belts. A randomized controlled study was conducted in Sweden to evaluate the effects of visiting a facility known as a "safety hall" in combination with the mandatory skid training. The results were assessed to determine the effects of the knowledge and attitudes of learner drivers in the following subjects: airbags, securing loads, seat belts, sitting posture, speed, and tires. An experimental group and a control group comprising 658 and 668 learners, respectively, answered identical questionnaires on three different occasions (pretest, posttest 1, and posttest 2). The results show that, for most of the topics considered, knowledge and attitudes in both groups were better at posttest 2 than at the pretest, and in general, the best knowledge and attitudes were found in the experimental group. The combined safety/skid training seems to have had the greatest effect on seat belts and loads. The findings also indicate that the safety halls can be further improved to achieve an even better effect. The use of safety halls has improved the knowledge and attitudes of learner drivers concerning several important areas related to traffic safety. Since knowledge and attitudes are important predictors of behavior, implementing safety halls can be expected to lead to improvements, especially regarding the use of safety belts and securing loads.

Alignment Measurements of the Microwave Anisotropy Probe (MAP) Instrument in a Thermal/Vacuum Chamber Using Photogrammetry

NASA Technical Reports Server (NTRS)

Hill, Michael D.; Herrera, Acey A.; Crane, J. Allen; Packard, Edward A.; Aviado, Carlos; Sampler, Henry P.; Obenschain, Arthur (Technical Monitor)

2000-01-01

The Microwave Anisotropy Probe (MAP) Observatory, scheduled for a late 2000 launch, is designed to measure temperature fluctuations (anisotropy) and produce a high sensitivity and high spatial resolution (< 0.3 deg at 90 GHz.) map of the cosmic microwave background (CMB) radiation over the entire sky between 22 and 90 GHz. MAP utilizes back-to-back Gregorian telescopes to focus the microwave signals into 10 differential microwave receivers, via 20 feed horns. Proper alignment of the telescope reflectors and the feed horns at the operating temperature of 90 K is a critical element to ensure mission success. We describe the hardware and methods used to validate the displacement/deformation predictions of the reflectors and the microwave feed horns during thermal/vacuum testing of the reflectors and the microwave instrument. The smallest deformations to be resolved by the measurement system were on the order of +/- 0.030 inches (0.762 mm). Performance of these alignment measurements inside a thermal/vacuum chamber with conventional alignment equipment posed several limitations. A photogrammetry (PG) system was chosen to perform the measurements since it is a non-contact measurement system, the measurements can be made relatively quickly and accurately, and the photogrammetric camera can be operated remotely. The hardware and methods developed to perform the MAP alignment measurements using PG proved to be highly successful. The PG measurements met the desired requirements, enabling the desired deformations to be measured and even resolved to an order of magnitude smaller than the imposed requirements. Viable data were provided to the MAP Project for a full analysis of the on-orbit performance of the Instrument's microwave system.

Hall viscosity and electromagnetic response of electrons in graphene

NASA Astrophysics Data System (ADS)

Sherafati, Mohammad; Principi, Alessandro; Vignale, Giovanni

The Hall viscosity is a dissipationless component of the viscosity tensor of an electron liquid with broken time- reversal symmetry, such as a two-dimensional electron gas (2DEG) in the quantum Hall state. Similar to the Hall conductivity, the Hall viscosity is an anomalous transport coefficient; however, while the former is connected with the current response, the latter stems from the stress response to a geometric deformation. For a Galilean-invariant system such as 2DEG, the current density is indeed the generator of the geometric deformation: therefore a connection between the Hall connectivity and viscosity is expected and by now well established. In the case of graphene, a non-Galilean-invariant system, the existence of such a connection is far from obvious, as the current operator is essentially different from the momentum operator. In this talk, I will first present our results of the geometric Hall viscosity of electrons in single-layer graphene. Then, from the expansion of the nonlocal Hall conductivity for small wave vectors, I demonstrate that, in spite of the lack of Galilean invariance, an effective mass can be defined such that the relationship between the Hall conductivity and the viscosity retains the form it has in Galilean-invariant systems, not only for a large number of occupied Landau levels, but also, with very high accuracy, for the undoped system.

Simmons Hall, Massachusetts.

ERIC Educational Resources Information Center

Amelar, Sarah

2003-01-01

Describes the design of Simmons Hall, an undergraduate dormitory at the Massachusetts Institute of Technology, including the educational context and design goals. Includes information on the architects, as well as floor plans and photographs. (EV)

A Behavioral Weight Control Program for Residence Hall Students.

ERIC Educational Resources Information Center

Domke, Jane A.; And Others

1981-01-01

Compared a weight control treatment specifically tailored to the needs of residence hall students with a standardized behavioral procedure. Although posttreatment results indicated a very slight and nonsignificant advantage for the residence hall condition, this was not true at follow-up. Suggests the residence hall procedure may be overly…

Roles of nonlocal conductivity on spin Hall angle measurement

NASA Astrophysics Data System (ADS)

Chen, Kai; Zhang, Shufeng

2017-10-01

Spin Hall angle characterizes the rate of spin-charge current conversion and it has become one of the most important material parameters for spintronics physics and device application. A long-standing controversy is that the spin Hall angles for a given material measured by spin pumping and by spin Hall torque experiments are inconsistent and they could differ by as much as an order of magnitude. By using the linear response spin transport theory, we explicitly formulate the relation between the spin Hall angle and measured variables in different experiments. We find that the nonlocal conductivity inherited in the layered structure plays a key role to resolve conflicting values of the spin Hall angle. We provide a generalized scheme for extracting spin transport coefficients from experimental data.

Effect of Background Pressure on the Plasma Oscillation Characteristics of the HiVHAc Hall Thruster

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Kamhawi, Hani; Lobbia, Robert B.; Brown, Daniel L.

2014-01-01

During a component compatibility test of the NASA HiVHAc Hall thruster, a high-speed camera and a set of high-speed Langmuir probes were implemented to study the effect of varying facility background pressure on thruster operation. The results show a rise in the oscillation frequency of the breathing mode with rising background pressure, which is hypothesized to be due to a shortening accelerationionization zone. An attempt is made to apply a simplified ingestion model to the data. The combined results are used to estimate the maximum acceptable background pressure for performance and wear testing.

Spin torque efficiency of Ta, W, and Pt in metallic bilayers evaluated by harmonic Hall and spin Hall magnetoresistance measurements

NASA Astrophysics Data System (ADS)

Lau, Yong-Chang; Hayashi, Masamitsu

2017-08-01

We investigate the efficiency of current-induced torque, i.e., the spin torque efficiency, in in-plane magnetized heavy metal/CoFeB/MgO heterostructures (heavy metals = Pt, W, and Ta) using the harmonic Hall technique and the spin Hall magnetoresistance. We find that the amplitude of the external magnetic field has a strong influence on the spin torque efficiency evaluation by the harmonic Hall measurements. This can be corrected by measuring the corresponding Hall resistance susceptibility. The sign and magnitude of the resulting Slonczewski-like spin torque efficiencies are in agreement with previous reports and the measurements utilizing the spin Hall magnetoresistance, except for the Pt underlayer films. The origin of the discrepancy for the Pt underlayer films is unclear. The field like torque efficiencies, upon subtracting the Oersted field contribution, are quite low or negligible. This is in significant contrast to what has been found for the field like torque in heterostructures with perpendicular magnetization. These results suggest that a more advanced model is required in order to describe accurately spin transport and momentum transfer at metallic interfaces.

Optical Diagnostic Characterization of High-Power Hall Thruster Wear and Operation

NASA Technical Reports Server (NTRS)

Williams, George J., Jr.; Soulas, George C.; Kamhawi, Hani

2012-01-01

Optical emission spectroscopy is employed to correlate BN insulator erosion with high-power Hall thruster operation. Specifically, actinometry leveraging excited xenon states is used to normalize the emission spectra of ground state boron as a function of thruster operating condition. Trends in the strength of the boron signal are correlated with thruster power, discharge voltage, and discharge current. In addition, the technique is demonstrated on metallic coupons embedded in the walls of the HiVHAc EM thruster. The OES technique captured the overall trend in the erosion of the coupons which boosts credibility in the method since there are no data to which to calibrate the erosion rates of high-power Hall thrusters. The boron signals are shown to trend linearly with discharge voltage for a fixed discharge current as expected. However, the boron signals of the higher-power NASA 300M and NASA 457Mv2 trend with discharge current and show an unexpectedly weak to inverse dependence on discharge voltage. Electron temperatures measured optically in the near-field plume of the thruster agree well with Langmuir probe data. However, the optical technique used to determine Te showed unacceptable sensitivity to the emission intensities. Near-field, single-frequency imaging of the xenon neutrals is also presented as a function of operating condition for the NASA 457 Mv2.

Sensitivity of resistive and Hall measurements to local inhomogeneities

NASA Astrophysics Data System (ADS)

Koon, Daniel W.; Wang, Fei; Hjorth Petersen, Dirch; Hansen, Ole

2013-10-01

We derive exact, analytic expressions for the sensitivity of resistive and Hall measurements to local inhomogeneities in a specimen's material properties in the combined linear limit of a weak perturbation over an infinitesimal area in a small magnetic field. We apply these expressions both to four-point probe measurements on an infinite plane and to symmetric, circular van der Pauw discs, obtaining functions consistent with published results. These new expressions speed up calculation of the sensitivity for a specimen of arbitrary shape to little more than the solution of two Laplace equation boundary-value problems of the order of N3 calculations, rather than N2 problems of total order N5, and in a few cases produces an analytic expression for the sensitivity. These functions provide an intuitive, visual explanation of how, for example, measurements can predict the wrong carrier type in n-type ZnO.

Intrinsic superspin Hall current

NASA Astrophysics Data System (ADS)

Linder, Jacob; Amundsen, Morten; Risinggârd, Vetle

2017-09-01

We discover an intrinsic superspin Hall current: an injected charge supercurrent in a Josephson junction containing heavy normal metals and a ferromagnet generates a transverse spin supercurrent. There is no accompanying dissipation of energy, in contrast to the conventional spin Hall effect. The physical origin of the effect is an antisymmetric spin density induced among transverse modes ky near the interface of the superconductor arising due to the coexistence of p -wave and conventional s -wave superconducting correlations with a belonging phase mismatch. Our predictions can be tested in hybrid structures including thin heavy metal layers combined with strong ferromagnets and ordinary s -wave superconductors.

HEDSA Town Hall Meeting

NASA Astrophysics Data System (ADS)

Afeyan, Bedros

2017-10-01

HEDSA will hold its Town Hall meeting on Wednesday October 25 at 12:30pm in the Wisconsin Center. The new steering committee members and HEDSA leadership will be announced. A report will be given on 2017 HEDSA activities. Program Managers from Federal Funding Agencies such as OFES, NNSA, AFOSR and NSF will provide updates on the state of sponsored research in HED plasmas, and to engage the community in an open dialogue. The HEDSA Town Hall is a ``bring your own lunch'' meeting. Current members of HEDSA and all graduate students are strongly encouraged to attend. To join HEDSA please visit HEDSA.org

Topological Hall Effect in Skyrmions: A Nonequilibrium Coherent Transport Approach

NASA Astrophysics Data System (ADS)

Yin, Gen; Zang, Jiadong; Lake, Roger

2014-03-01

Skyrmion is a topological spin texture recently observed in many materials with broken inversion symmetry. In experiments, one effective method to detect the skyrmion crystal phase is the topological Hall measurement. At adiabatic approximation, previous theoretical studies show that the Hall signal is provided by an emergent magnetic field, which explains the topological Hall effect in the classical level. Motivated by the potential device application of skyrmions as digital bits, it is important to understand the topological Hall effect in the mesoscopic level, where the electron coherence should be considered. In this talk, we will discuss the quantum aspects of the topological Hall effect on a tight binding setup solved by nonequilibrium Green's function (NEGF). The charge distribution, Hall potential distribution, thermal broadening effect and the Hall resistivity are investigated in detail. The relation between the Hall resistance and the DM interaction is investigated. Driven by the spin transferred torque (SST), Skyrmion dynamics is previously studied within the adiabatic approximation. At the quantum transport level, this talk will also discuss the non-adiabatic effect in the skyrmion motion with the presence of the topological Hall effect. This material is based upon work supported by the National Science Foundation under Grant Nos. NSF 1128304 and NSF 1124733. It was also supported in part by FAME, one of six centers of STARnet, an SRC program sponsored by MARCO and DARPA.

Training Top 10 Hall of Fame

ERIC Educational Resources Information Center

Training, 2012

2012-01-01

Microsoft Corporation and SCC Soft Computer are the newest inductees into the Training Top 10 Hall of Fame, joining the ranks of the 11 companies named to the hall since its inception in 2008 (Wyeth Pharmaceuticals subsequently was acquired by Pfizer Inc. in 2009). These 11 companies held Top 10 spots in the Training Top 50, Top 100, and now Top…

5. ROOFTOPS, ISHERWOOD HALL (BUILDING NO. 104), GRIFFIN (BUILDING NO. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. ROOFTOPS, ISHERWOOD HALL (BUILDING NO. 104), GRIFFIN (BUILDING NO. 110), MELVILLE HALL (BUILDING NO. 116) LOOKING WEST FROM CLOCK TOWER OF MAHAN HALL - U.S. Naval Academy, Annapolis, Anne Arundel County, MD

Design and Application of Hybrid Magnetic Field-Eddy Current Probe

NASA Technical Reports Server (NTRS)

Wincheski, Buzz; Wallace, Terryl; Newman, Andy; Leser, Paul; Simpson, John

2013-01-01

The incorporation of magnetic field sensors into eddy current probes can result in novel probe designs with unique performance characteristics. One such example is a recently developed electromagnetic probe consisting of a two-channel magnetoresistive sensor with an embedded single-strand eddy current inducer. Magnetic flux leakage maps of ferrous materials are generated from the DC sensor response while high-resolution eddy current imaging is simultaneously performed at frequencies up to 5 megahertz. In this work the design and optimization of this probe will be presented, along with an application toward analysis of sensory materials with embedded ferromagnetic shape-memory alloy (FSMA) particles. The sensory material is designed to produce a paramagnetic to ferromagnetic transition in the FSMA particles under strain. Mapping of the stray magnetic field and eddy current response of the sample with the hybrid probe can thereby image locations in the structure which have experienced an overstrain condition. Numerical modeling of the probe response is performed with good agreement with experimental results.

Anomalous Hall effect in calcium-doped lanthanum cobaltite and gadolinium

NASA Astrophysics Data System (ADS)

Baily, Scott Alan

The physical origin of the anomalous (proportional to magnetization) Hall effect is not very well understood. While many theories account for a Hall effect proportional to the magnetization of a material, these theories often predict effects significantly smaller than those found in ferromagnetic materials. An even more significant deficiency of the conventional theories is that they predict an anomalous Hall resistivity that is proportional to a power of the resistivity, and in the absence of a metal insulator transition cannot account for the anomalous Hall effect that peaks near TC. Recent models based on a geometric, or Berry, phase have had a great deal of success describing the anomalous Hall effect in double-exchange systems (e.g., lanthanum manganite and chromium dioxide). In gadolinium, as in double-exchange magnets, the exchange interaction is mediated by the conduction electrons and the anomalous Hall effect may therefore resemble that of CrO2 and other metallic double-exchange ferromagnets. Lanthanum cobaltite is similar to manganite in many ways, but a strong double-exchange interaction is not present. Calcium-doped lanthanum cobaltite films were found to have the largest anomalous Hall effect of any ferromagnetic metal. The primary purpose of this study is to gain insight into the origin of the anomalous Hall effect with the hope that these theories can be extended to account for the effect in other materials. The Hall resistivity, magnetoresistance, and magnetization of a Gadolinium single crystal were measured in fields up to 30 T. Cobaltite films were grown via laser ablation and characterized by a variety of techniques. Hall resistivity, magnetoresistance, magnetization, and magnetothermopower of L 1-xCaxCoO3 samples with 0.15 < x < 0.4 were measured in fields up to 7 T. The Gd results suggest that Berry's phase contributes partially to the Hall effect near TC. Berry's phase theories hold promise for explaining the large anomalous Hall effect in

Performance of an 8 kW Hall Thruster

DTIC Science & Technology

2000-01-12

For the purpose of either orbit raising and/or repositioning the Hall thruster must be capable of delivering sufficient thrust to minimize transfer...time. This coupled with the increasing on-board electric power capacity of military and commercial satellites, requires a high power Hall thruster that...development of a novel, high power Hall thruster , capable of efficient operation over a broad range of Isp and thrust. We call such a thruster the bi

Spontaneous Hall effect in a chiral p-wave superconductor

NASA Astrophysics Data System (ADS)

Furusaki, Akira; Matsumoto, Masashige; Sigrist, Manfred

2001-08-01

In a chiral superconductor with broken time-reversal symmetry a ``spontaneous Hall effect'' may be observed. We analyze this phenomenon by taking into account the surface properties of a chiral superconductor. We identify two main contributions to the spontaneous Hall effect. One contribution originates from the Bernoulli (or Lorentz) force due to spontaneous currents running along the surfaces of the superconductor. The other contribution has a topological origin and is related to the intrinsic angular momentum of Cooper pairs. The latter can be described in terms of a Chern-Simons-like term in the low-energy field theory of the superconductor and has some similarities with the quantum Hall effect. The spontaneous Hall effect in a chiral superconductor is, however, nonuniversal. Our analysis is based on three approaches to the problem: a self-consistent solution of the Bogoliubov-de Gennes equation, a generalized Ginzburg-Landau theory, and a hydrodynamic formulation. All three methods consistently lead to the same conclusion that the spontaneous Hall resistance of a two-dimensional superconducting Hall bar is of order h/(ekFλ)2, where kF is the Fermi wave vector and λ is the London penetration depth; the Hall resistance is substantially suppressed from a quantum unit of resistance. Experimental issues in measuring this effect are briefly discussed.

Semi-automatic 10/20 Identification Method for MRI-Free Probe Placement in Transcranial Brain Mapping Techniques.

PubMed

Xiao, Xiang; Zhu, Hao; Liu, Wei-Jie; Yu, Xiao-Ting; Duan, Lian; Li, Zheng; Zhu, Chao-Zhe

2017-01-01

The International 10/20 system is an important head-surface-based positioning system for transcranial brain mapping techniques, e.g., fNIRS and TMS. As guidance for probe placement, the 10/20 system permits both proper ROI coverage and spatial consistency among multiple subjects and experiments in a MRI-free context. However, the traditional manual approach to the identification of 10/20 landmarks faces problems in reliability and time cost. In this study, we propose a semi-automatic method to address these problems. First, a novel head surface reconstruction algorithm reconstructs head geometry from a set of points uniformly and sparsely sampled on the subject's head. Second, virtual 10/20 landmarks are determined on the reconstructed head surface in computational space. Finally, a visually-guided real-time navigation system guides the experimenter to each of the identified 10/20 landmarks on the physical head of the subject. Compared with the traditional manual approach, our proposed method provides a significant improvement both in reliability and time cost and thus could contribute to improving both the effectiveness and efficiency of 10/20-guided MRI-free probe placement.

Molecular mapping of chromosomes 17 and X. Progress report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barker, D.F.

1991-01-15

Progress toward the construction of high density genetic maps of chromosomes 17 and X has been made by isolating and characterizing a relatively large set of polymorphic probes for each chromosome and using these probes to construct genetic maps. We have mapped the same polymorphic probes against a series of chromosome breakpoints on X and 17. The probes could be assigned to over 30 physical intervals on the X chromosome and 7 intervals on 17. In many cases, this process resulted in improved characterization of the relative locations of the breakpoints with respect to each other and the definition ofmore » new physical intervals. The strategy for isolation of the polymorphic clones utilized chromosome specific libraries of 1--15 kb segments from each of the two chromosomes. From these libraries, clones were screened for those detecting restriction fragment length polymorphisms. The markers were further characterized, the chromosomal assignments confirmed and in most cases segments of the original probes were subcloned into plasmids to produce probes with improved signal to noise ratios for use in the genetic marker studies. The linkage studies utilize the CEPH reference families and other well-characterized families in our collection which have been used for genetic disease linkage work. Preliminary maps and maps of portions of specific regions of 17 and X are provided. We have nearly completed a map of the 1 megabase Mycoplasma arthritidis genome by applying these techniques to a lambda phage library of its genome. We have found bit mapping to be an efficient means to organize a contiguous set of overlapping@ clones from a larger genome.« less

Tutorial: Physics and modeling of Hall thrusters

NASA Astrophysics Data System (ADS)

Boeuf, Jean-Pierre

2017-01-01

Hall thrusters are very efficient and competitive electric propulsion devices for satellites and are currently in use in a number of telecommunications and government spacecraft. Their power spans from 100 W to 20 kW, with thrust between a few mN and 1 N and specific impulse values between 1000 and 3000 s. The basic idea of Hall thrusters consists in generating a large local electric field in a plasma by using a transverse magnetic field to reduce the electron conductivity. This electric field can extract positive ions from the plasma and accelerate them to high velocity without extracting grids, providing the thrust. These principles are simple in appearance but the physics of Hall thrusters is very intricate and non-linear because of the complex electron transport across the magnetic field and its coupling with the electric field and the neutral atom density. This paper describes the basic physics of Hall thrusters and gives a (non-exhaustive) summary of the research efforts that have been devoted to the modelling and understanding of these devices in the last 20 years. Although the predictive capabilities of the models are still not sufficient for a full computer aided design of Hall thrusters, significant progress has been made in the qualitative and quantitative understanding of these devices.

Measured Early Lateral Energy Fractions in Concert Halls and Opera Houses

NASA Astrophysics Data System (ADS)

BARRON, M.

2000-04-01

In the 30 years since early lateral reflections were first suggested as important for concert halls, spatial impression and source broadening have become almost universally accepted as essential characteristics of halls with good acoustics. Two objective measures of source broadening have been proposed. Measured values of the best defined of these measures, the early lateral energy fraction (LF), are considered here. Results from two independent measurement surveys are discussed. Comparisons of LF values by hall show a significant link between hall mean LF and hall width. There is however considerable overlap between measured LF values in different halls so the relevance of describing halls by their mean early lateral energy fraction values is questionable. The behaviour of LF values within auditoria is discussed for different concert hall plan forms and within opera houses. A measure of source broadening including sound level is proposed and results considered in the context of auditorium design.

Destruction of the Fractional Quantum Hall Effect by Disorder

DOE R&D Accomplishments Database

Laughlin, R. B.

1985-07-01

It is suggested that Hall steps in the fractional quantum Hall effect are physically similar to those in the ordinary quantum Hall effect. This proposition leads to a simple scaling diagram containing a new type of fixed point, which is identified with the destruction of the fractional states by disorder. 15 refs., 3 figs.

27. FIRST FLOOR CENTRAL HALL, EAST WALL, DETAIL OF ENTABLATURE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

27. FIRST FLOOR CENTRAL HALL, EAST WALL, DETAIL OF ENTABLATURE SHOWING EGG AND DART OVOLO AND GUTTAE OF THE THIRD MUTULE FROM THE SOUTHEAST CORNER - Independence Hall Complex, Independence Hall, 500 Chestnut Street, Philadelphia, Philadelphia County, PA

Intrinsic quantum spin Hall and anomalous Hall effects in h-Sb/Bi epitaxial growth on a ferromagnetic MnO2 thin film.

PubMed

Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

2016-06-07

Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.

Establishment of a Hall Thruster Cluster

DTIC Science & Technology

2004-02-01

DURIP funds were used to develop a Hall thruster cluster test facility centered around the University of Michigan Large Vacuum Test Facility and a 2x2 cluster of BUSEK 600 W BHT-600 Hall thrusters. This capability will facilitate our three-year program to address the issue of high-power CDT operation and to provide insight on how chamber effects influence CDT engine/cluster characteristics.

Direct observation of the skyrmion Hall effect

DOE PAGES

Jiang, Wanjun; Zhang, Xichao; Yu, Guoqiang; ...

2016-09-19

The well-known Hall effect describes the transverse deflection of charged particles (electrons/holes) as a result of the Lorentz force. Similarly, it is intriguing to examine if quasi-particles without an electric charge, but with a topological charge, show related transverse motion. Magnetic skyrmions with a well-defined spin texture with a unit topological charge serve as good candidates to test this hypothesis. In spite of the recent progress made on investigating magnetic skyrmions, direct observation of the skyrmion Hall effect has remained elusive. Here, by using a current-induced spin Hall spin torque, we experimentally demonstrate the skyrmion Hall effect, and the resultantmore » skyrmion accumulation, by driving skyrmions from the creep-motion regime (where their dynamics are influenced by pinning defects) into the steady-flow-motion regime. Lastly, the experimental observation of transverse transport of skyrmions due to topological charge may potentially create many exciting opportunities, such as topological selection.« less

Direct observation of the skyrmion Hall effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Wanjun; Zhang, Xichao; Yu, Guoqiang

The well-known Hall effect describes the transverse deflection of charged particles (electrons/holes) as a result of the Lorentz force. Similarly, it is intriguing to examine if quasi-particles without an electric charge, but with a topological charge, show related transverse motion. Magnetic skyrmions with a well-defined spin texture with a unit topological charge serve as good candidates to test this hypothesis. In spite of the recent progress made on investigating magnetic skyrmions, direct observation of the skyrmion Hall effect has remained elusive. Here, by using a current-induced spin Hall spin torque, we experimentally demonstrate the skyrmion Hall effect, and the resultantmore » skyrmion accumulation, by driving skyrmions from the creep-motion regime (where their dynamics are influenced by pinning defects) into the steady-flow-motion regime. Lastly, the experimental observation of transverse transport of skyrmions due to topological charge may potentially create many exciting opportunities, such as topological selection.« less

L'effet Hall Quantique

NASA Astrophysics Data System (ADS)

Samson, Thomas

Nous proposons une methode permettant d'obtenir une expression pour la conductivite de Hall de structures electroniques bidimensionnelles et nous examinons celle -ci a la limite d'une temperature nulle dans le but de verifier l'effet Hall quantique. Nous allons nous interesser essentiellement a l'effet Hall quantique entier et aux effets fractionnaires inferieurs a un. Le systeme considere est forme d'un gaz d'electrons en interaction faible avec les impuretes de l'echantillon. Le modele du gaz d'electrons consiste en un gaz bidimensionnel d'electrons sans spin expose perpendiculairement a un champ magnetique uniforme. Ce dernier est decrit par le potentiel vecteur vec{rm A} defini dans la jauge de Dingle ou jauge symetrique. Conformement au formalisme de la seconde quantification, l'hamiltonien de ce gaz est represente dans la base des etats a un-corps de Dingle |n,m> et exprime ainsi en terme des operateurs de creation et d'annihilation correspondants a_sp{ rm n m}{dag} et a _{rm n m}. Nous supposons de plus que les electrons du niveau fondamental de Dingle interagissent entre eux via le potentiel coulombien. La methode utilisee fait appel a une equation mai tresse a N-corps, de nature quantique et statistique, et verifiant le second principe de la thermodynamique. A partir de celle-ci, nous obtenons un systeme d'equations differentielles appele hierarchie d'equations quantique dont la resolution nous permet de determiner une equation a un-corps, dite de Boltzmann quantique, et dictant l'evolution de la moyenne statistique de l'operateur non-diagonal a _sp{rm n m}{dag } a_{rm n}, _{rm m}, sous l'action du champ electrique applique vec{rm E}(t). C'est sa solution Tr(p(t) a _sp{rm n m}{dag} a_{rm n},_ {rm m}), qui definit la relation de convolution entre la densite courant de Hall vec{rm J}_{rm H }(t) et le champ electrique vec {rm E}(t) dont la transformee de Laplace-Fourier du noyau nous fournit l'expression de la conductivite de Hall desiree. Pour une valeur de

Improved analysis techniques for cylindrical and spherical double probes.

PubMed

Beal, Brian; Johnson, Lee; Brown, Daniel; Blakely, Joseph; Bromaghim, Daron

2012-07-01

A versatile double Langmuir probe technique has been developed by incorporating analytical fits to Laframboise's numerical results for ion current collection by biased electrodes of various sizes relative to the local electron Debye length. Application of these fits to the double probe circuit has produced a set of coupled equations that express the potential of each electrode relative to the plasma potential as well as the resulting probe current as a function of applied probe voltage. These equations can be readily solved via standard numerical techniques in order to determine electron temperature and plasma density from probe current and voltage measurements. Because this method self-consistently accounts for the effects of sheath expansion, it can be readily applied to plasmas with a wide range of densities and low ion temperature (T(i)/T(e) ≪ 1) without requiring probe dimensions to be asymptotically large or small with respect to the electron Debye length. The presented approach has been successfully applied to experimental measurements obtained in the plume of a low-power Hall thruster, which produced a quasineutral, flowing xenon plasma during operation at 200 W on xenon. The measured plasma densities and electron temperatures were in the range of 1 × 10(12)-1 × 10(17) m(-3) and 0.5-5.0 eV, respectively. The estimated measurement uncertainty is +6%∕-34% in density and +∕-30% in electron temperature.

Theoretical analysis of a dual-probe scanning tunneling microscope setup on graphene.

PubMed

Settnes, Mikkel; Power, Stephen R; Petersen, Dirch H; Jauho, Antti-Pekka

2014-03-07

Experimental advances allow for the inclusion of multiple probes to measure the transport properties of a sample surface. We develop a theory of dual-probe scanning tunneling microscopy using a Green's function formalism, and apply it to graphene. Sampling the local conduction properties at finite length scales yields real space conductance maps which show anisotropy for pristine graphene systems and quantum interference effects in the presence of isolated impurities. Spectral signatures in the Fourier transforms of real space conductance maps include characteristics that can be related to different scattering processes. We compute the conductance maps of graphene systems with different edge geometries or height fluctuations to determine the effects of nonideal graphene samples on dual-probe measurements.

Teaching Representation Translations with Magnetic Field Experiments

ERIC Educational Resources Information Center

Tillotson, Wilson Andrew; McCaskey, Timothy; Nasser, Luis

2017-01-01

We have developed a laboratory exercise designed to help students translate between different field representations. It starts with students qualitatively mapping field lines for various bar magnet configurations and continues with a Hall probe experiment in which students execute a series of scaffolded tasks, culminating in the prediction and…

Piezo Voltage Controlled Planar Hall Effect Devices

PubMed Central

Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K. W.; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

2016-01-01

The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials. PMID:27329068

Piezo Voltage Controlled Planar Hall Effect Devices.

PubMed

Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K W; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

2016-06-22

The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials.

Quantum Hall effect in dual gated BiSbTeSe2 topological insulator

NASA Astrophysics Data System (ADS)

Chong, Su Kong; Han, Kyu Bum; Nagaoka, Akira; Harmer, Jared; Tsuchikawa, Ryuichi; Sparks, Taylor D.; Deshpande, Vikram V.

The discovery of topological insulators (TIs) has expanded the family of Dirac materials and enables the probing of exotic matter such as Majorana fermions and magnetic monopoles. Different from conventional 2D electron gas, 3D TIs exhibit a gapped insulating bulk and gapless topological surface states as a result of the strong spin-orbit coupling. BiSbTeSe2 is also known to be a 3D TI with a large intrinsic bulk gap of about 0.3 eV and a single Dirac cone surface state. The highly bulk insulating BiSbTeSe2 permits surface dominated conduction, which is an ideal system for the study of quantum Hall effect (QHE). Due to the spin-momentum locking, the Dirac fermions at the topological surface states have a degeneracy of one. In the QH regime, the Hall conductance is quantized to (n + 1 / 2) e2 / h , where n is an integer and the factor of half is related to Berry curvature. In this work, we study the QHE 3D TI using a dual gated BiSbTeSe2 device. By tuning the chemical potentials on top and bottom surfaces, integer QHE with Landau filling factors, ν = 0, +/-1, and +/-2 are observed.

Object Tracking Vision System for Mapping the UCN τ Apparatus Volume

NASA Astrophysics Data System (ADS)

Lumb, Rowan; UCNtau Collaboration

2016-09-01

The UCN τ collaboration has an immediate goal to measure the lifetime of the free neutron to within 0.1%, i.e. about 1 s. The UCN τ apparatus is a magneto-gravitational ``bottle'' system. This system holds low energy, or ultracold, neutrons in the apparatus with the constraint of gravity, and keeps these low energy neutrons from interacting with the bottle via a strong 1 T surface magnetic field created by a bowl-shaped array of permanent magnets. The apparatus is wrapped with energized coils to supply a magnetic field throughout the ''bottle'' volume to prevent depolarization of the neutrons. An object-tracking stereo-vision system will be presented that precisely tracks a Hall probe and allows a mapping of the magnetic field throughout the volume of the UCN τ bottle. The stereo-vision system utilizes two cameras and open source openCV software to track an object's 3-d position in space in real time. The desired resolution is +/-1 mm resolution along each axis. The vision system is being used as part of an even larger system to map the magnetic field of the UCN τ apparatus and expose any possible systematic effects due to field cancellation or low field points which could allow neutrons to depolarize and possibly escape from the apparatus undetected. Tennessee Technological University.

Nulling Hall-Effect Current-Measuring Circuit

NASA Technical Reports Server (NTRS)

Sullender, Craig C.; Vazquez, Juan M.; Berru, Robert I.

1993-01-01

Circuit measures electrical current via combination of Hall-effect-sensing and magnetic-field-nulling techniques. Known current generated by feedback circuit adjusted until it causes cancellation or near cancellation of magnetic field produced in toroidal ferrite core by current measured. Remaining magnetic field measured by Hall-effect sensor. Circuit puts out analog signal and digital signal proportional to current measured. Accuracy of measurement does not depend on linearity of sensing components.

Acoustic Requirements for a Multi-Purpose Hall.

ERIC Educational Resources Information Center

Schulte, W. Allen

2002-01-01

This case study examines the proposed design of a new lecture/recital hall in Centennial Hall at Lynchburg College that will be used for lectures, public events, a film studies course, and musical recitals. It explores the audio-visual challenges presented by the differing acoustical requirements for the building. (EV)

Design of a dual sensor probe array for internal field measurement in Versatile Experiment Spherical Torusa)

NASA Astrophysics Data System (ADS)

Jeong-hun, Yang; Chung, Kyoung-Jae; An, YoungHwa; Jung, Bong Ki; Jo, Jong Gab; Hwang, Y. S.

2012-10-01

A dual sensor probe array is designed and constructed for internal magnetic field measurement at Versatile Experiment Spherical Torus (VEST) at the Seoul National University. Simultaneous use of Hall sensors and chip inductors allows cross-calibration among the measurements and compensation for each other's weaknesses while their small sizes are expected to cause only mild plasma perturbations. Calibration of the dual sensor probe array, using a Helmholtz coil, shows good sensitivity for the magnetic field measurement of the VEST. Prior to Ohmic start-up, the magnetic field structure inside the vacuum chamber is measured by using the calibrated probe array. The dual sensor probe array is expected to be useful in analyzing the temporal magnetic field structure change during the magnetic reconnection and in reconstruction of the current profile during the discharge of the VEST device.

Experimental test of 200 W Hall thruster with titanium wall

NASA Astrophysics Data System (ADS)

Ding, Yongjie; Sun, Hezhi; Peng, Wuji; Xu, Yu; Wei, Liqiu; Li, Hong; Li, Peng; Su, Hongbo; Yu, Daren

2017-05-01

We designed a 200 W Hall thruster based on the technology of pushing down a magnetic field with two permanent magnetic rings. Boron nitride (BN) is an important insulating wall material for Hall thrusters. The discharge characteristics of the designed Hall thruster were studied by replacing BN with titanium (Ti). Experimental results show that the designed Hall thruster can discharge stably for a long time under a Ti channel. Experiments were performed to determine whether the channel and cathode are electrically connected. When the channel wall and cathode are insulated, the divergence angle of the plume increases, but the performance of the Hall thruster is improved in terms of thrust, specific impulse, anode efficiency, and thrust-to-power ratio. Ti exhibits a powerful antisputtering capability, a low emanation rate of gas, and a large structural strength, making it a potential candidate wall material in the design of low-power Hall thrusters.

Magnetometry of micro-magnets with electrostatically defined Hall bars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lachance-Quirion, Dany; Camirand Lemyre, Julien; Bergeron, Laurent

2015-11-30

Micro-magnets are key components for quantum information processing with individual spins, enabling arbitrary rotations and addressability. In this work, characterization of sub-micrometer sized CoFe ferromagnets is performed with Hall bars electrostatically defined in a two-dimensional electron gas. Due to the ballistic nature of electron transport in the cross junction of the Hall bar, anomalies such as the quenched Hall effect appear near zero external magnetic field, thus hindering the sensitivity of the magnetometer to small magnetic fields. However, it is shown that the sensitivity of the diffusive limit can be almost completely restored at low temperatures using a large currentmore » density in the Hall bar of about 10 A/m. Overcoming the size limitation of conventional etched Hall bars with electrostatic gating enables the measurement of magnetization curves of 440 nm wide micro-magnets with a signal-to-noise ratio above 10{sup 3}. Furthermore, the inhomogeneity of the stray magnetic field created by the micro-magnets is directly measured using the gate-voltage-dependent width of the sensitive area of the Hall bar.« less

Magnesium Hall Thruster

NASA Technical Reports Server (NTRS)

Szabo, James J.

2015-01-01

This Phase II project is developing a magnesium (Mg) Hall effect thruster system that would open the door for in situ resource utilization (ISRU)-based solar system exploration. Magnesium is light and easy to ionize. For a Mars- Earth transfer, the propellant mass savings with respect to a xenon Hall effect thruster (HET) system are enormous. Magnesium also can be combusted in a rocket with carbon dioxide (CO2) or water (H2O), enabling a multimode propulsion system with propellant sharing and ISRU. In the near term, CO2 and H2O would be collected in situ on Mars or the moon. In the far term, Mg itself would be collected from Martian and lunar regolith. In Phase I, an integrated, medium-power (1- to 3-kW) Mg HET system was developed and tested. Controlled, steady operation at constant voltage and power was demonstrated. Preliminary measurements indicate a specific impulse (Isp) greater than 4,000 s was achieved at a discharge potential of 400 V. The feasibility of delivering fluidized Mg powder to a medium- or high-power thruster also was demonstrated. Phase II of the project evaluated the performance of an integrated, highpower Mg Hall thruster system in a relevant space environment. Researchers improved the medium power thruster system and characterized it in detail. Researchers also designed and built a high-power (8- to 20-kW) Mg HET. A fluidized powder feed system supporting the high-power thruster was built and delivered to Busek Company, Inc.

20th Annual Residence Hall Construction Report

ERIC Educational Resources Information Center

Agron, Joe

2009-01-01

Even in difficult economic times, colleges and universities continue to invest in residence hall construction projects as a way to attract new students and keep existing ones on campus. According to data from "American School & University"'s 20th annual Residence Hall Construction Report, the median new project completed in 2008 was…

Anisotropic quantum quench in the presence of frustration or background gauge fields: A probe of bulk currents and topological chiral edge modes

NASA Astrophysics Data System (ADS)

Killi, Matthew; Trotzky, Stefan; Paramekanti, Arun

2012-12-01

Bosons and fermions, in the presence of frustration or background gauge fields, can form many-body ground states that support equilibrium charge or spin currents. Motivated by the experimental creation of frustration or synthetic gauge fields in ultracold atomic systems, we propose a general scheme by which making a sudden anisotropic quench of the atom tunneling across the lattice and tracking the ensuing density modulations provides a powerful and gauge-invariant route to probing diverse equilibrium current patterns. Using illustrative examples of trapped superfluid Bose and normal Fermi systems in the presence of artificial magnetic fluxes on square lattices, and frustrated bosons in a triangular lattice, we show that this scheme to probe equilibrium bulk current order works independent of particle statistics. We also show that such quenches can detect chiral edge modes in gapped topological states, such as quantum Hall or quantum spin Hall insulators.

Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping

NASA Astrophysics Data System (ADS)

Frasinski, L. J.; Zhaunerchyk, V.; Mucke, M.; Squibb, R. J.; Siano, M.; Eland, J. H. D.; Linusson, P.; v. d. Meulen, P.; Salén, P.; Thomas, R. D.; Larsson, M.; Foucar, L.; Ullrich, J.; Motomura, K.; Mondal, S.; Ueda, K.; Osipov, T.; Fang, L.; Murphy, B. F.; Berrah, N.; Bostedt, C.; Bozek, J. D.; Schorb, S.; Messerschmidt, M.; Glownia, J. M.; Cryan, J. P.; Coffee, R. N.; Takahashi, O.; Wada, S.; Piancastelli, M. N.; Richter, R.; Prince, K. C.; Feifel, R.

2013-08-01

When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called “partial covariance mapping” to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

Residence Hall Fires.

ERIC Educational Resources Information Center

Wright, Dorothy

1999-01-01

Discusses how one college's experience with a tragic fire in one of its residence halls prompted a reevaluation of its fire-prevention-and-response strategies. Staff training, sprinkler installation, new alarm systems, and exit hardware to help make building exiting more efficient are discussed. (GR)

Tunnelling anomalous and planar Hall effects (Conference Presentation)

NASA Astrophysics Data System (ADS)

Matos-Abiague, Alex; Scharf, Benedikt; Han, Jong E.; Hankiewicz, Ewelina M.; Zutic, Igor

2016-10-01

We theoretically show how the interplay between spin-orbit coupling (SOC) and magnetism can result in a finite tunneling Hall conductance, transverse to the applied bias. For two-dimensional tunnel junctions with a ferromagnetic lead and magnetization perpendicular to the current flow, the detected anomalous Hall voltage can be used to extract information not only about the spin polarization but also about the strength of the interfacial SOC. In contrast, a tunneling current across a ferromagnetic barrier on the surface of a three-dimensional topological insulator (TI) can induce a planar Hall response even when the magnetization is oriented along the current flow[1]. The tunneling nature of the states contributing to the planar Hall conductance can be switched from the ordinary to the Klein regimes by the electrostatic control of the barrier strength. This allows for an enhancement of the transverse response and a giant Hall angle, with the tunneling planar Hall conductance exceeding the longitudinal component. Despite the simplicity of a single ferromagnetic region, the TI/ferromagnet system exhibits a variety of functionalities. In addition to a spin-valve operation for magnetic sensing and storing information, positive, negative, and negative differential conductances can be tuned by properly adjusting the barrier potential and/or varying the magnetization direction. Such different resistive behaviors in the same system are attractive for potential applications in reconfigurable spintronic devices. [1] B. Scharf, A. Matos-Abiague, J. E. Han, E. M. Hankiewicz, and I. Zutic, arXiv:1601.01009 (2016).

NASA HERMeS Hall Thruster Electrical Configuration Characterization

NASA Technical Reports Server (NTRS)

Peterson, Peter Y.; Kamhawi, Hani; Huang, Wensheng; Yim, John; Herman, Daniel; Williams, George; Gilland, James; Hofer, Richard

2015-01-01

The NASA Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) Hall thruster has been the subject of extensive technology maturation in preparation for development into a flight ready propulsion system. Part of the technology maturation was to test the TDU-1 thruster in several ground based electrical configurations to assess the thruster robustness and suitability to successful in-space operation. The ground based electrical configuration testing has recently been demonstrated as an important step in understanding and assessing how a Hall thruster may operate differently in-space compared to ground based testing, and to determine the best configuration to conduct development and qualification testing. This paper describes the electrical configuration testing of the HERMeS TDU-1 Hall thruster in NASA Glenn Research Center's Vacuum Facility 5. The three electrical configurations examined were 1) thruster body tied to facility ground, 2) thruster floating, and 3) thruster body electrically tied to cathode common. The HERMeS TDU-1 Hall thruster was also configured with two different exit plane boundary conditions, dielectric and conducting, to examine the influence on the electrical configuration characterization.

Perception of music dynamics in concert hall acoustics.

PubMed

Pätynen, Jukka; Lokki, Tapio

2016-11-01

Dynamics is one of the principal means of expressivity in Western classical music. Still, preceding research on room acoustics has mostly neglected the contribution of music dynamics to the acoustic perception. This study investigates how the different concert hall acoustics influence the perception of varying music dynamics. An anechoic orchestra signal, containing a step in music dynamics, was rendered in the measured acoustics of six concert halls at three seats in each. Spatial sound was reproduced through a loudspeaker array. By paired comparison, naive subjects selected the stimuli that they considered to change more during the music. Furthermore, the subjects described their foremost perceptual criteria for each selection. The most distinct perceptual factors differentiating the rendering of music dynamics between halls include the dynamic range, and varying width of sound and reverberance. The results confirm the hypothesis that the concert halls render the performed music dynamics differently, and with various perceptual aspects. The analysis against objective room acoustic parameters suggests that the perceived dynamic contrasts are pronounced by acoustics that provide stronger sound and more binaural incoherence by a lateral sound field. Concert halls that enhance the dynamics have been found earlier to elicit high subjective preference.

Graphene/Si CMOS hybrid hall integrated circuits.

PubMed

Huang, Le; Xu, Huilong; Zhang, Zhiyong; Chen, Chengying; Jiang, Jianhua; Ma, Xiaomeng; Chen, Bingyan; Li, Zishen; Zhong, Hua; Peng, Lian-Mao

2014-07-07

Graphene/silicon CMOS hybrid integrated circuits (ICs) should provide powerful functions which combines the ultra-high carrier mobility of graphene and the sophisticated functions of silicon CMOS ICs. But it is difficult to integrate these two kinds of heterogeneous devices on a single chip. In this work a low temperature process is developed for integrating graphene devices onto silicon CMOS ICs for the first time, and a high performance graphene/CMOS hybrid Hall IC is demonstrated. Signal amplifying/process ICs are manufactured via commercial 0.18 um silicon CMOS technology, and graphene Hall elements (GHEs) are fabricated on top of the passivation layer of the CMOS chip via a low-temperature micro-fabrication process. The sensitivity of the GHE on CMOS chip is further improved by integrating the GHE with the CMOS amplifier on the Si chip. This work not only paves the way to fabricate graphene/Si CMOS Hall ICs with much higher performance than that of conventional Hall ICs, but also provides a general method for scalable integration of graphene devices with silicon CMOS ICs via a low-temperature process.

Radical probing of spliceosome assembly.

PubMed

Grewal, Charnpal S; Kent, Oliver A; MacMillan, Andrew M

2017-08-01

Here we describe the synthesis and use of a directed hydroxyl radical probe, tethered to a pre-mRNA substrate, to map the structure of this substrate during the spliceosome assembly process. These studies indicate an early organization and proximation of conserved pre-mRNA sequences during spliceosome assembly. This methodology may be adapted to the synthesis of a wide variety of modified RNAs for use as probes of RNA structure and RNA-protein interaction. Copyright © 2017 Elsevier Inc. All rights reserved.

Localization in a quantum spin Hall system.

PubMed

Onoda, Masaru; Avishai, Yshai; Nagaosa, Naoto

2007-02-16

The localization problem of electronic states in a two-dimensional quantum spin Hall system (that is, a symplectic ensemble with topological term) is studied by the transfer matrix method. The phase diagram in the plane of energy and disorder strength is exposed, and demonstrates "levitation" and "pair annihilation" of the domains of extended states analogous to that of the integer quantum Hall system. The critical exponent nu for the divergence of the localization length is estimated as nu congruent with 1.6, which is distinct from both exponents pertaining to the conventional symplectic and the unitary quantum Hall systems. Our analysis strongly suggests a different universality class related to the topology of the pertinent system.

Current-driven second-harmonic domain wall resonance in ferromagnetic metal/nonmagnetic metal bilayers: A field-free method for spin Hall angle measurements

NASA Astrophysics Data System (ADS)

Hajiali, M. R.; Hamdi, M.; Roozmeh, S. E.; Mohseni, S. M.

2017-10-01

We study the ac current-driven domain wall motion in bilayer ferromagnetic metal (FM)/nonmagnetic metal (NM) nanowires. The solution of the modified Landau-Lifshitz-Gilbert equation including all the spin transfer torques is used to describe motion of the domain wall in the presence of the spin Hall effect. We show that the domain wall center has a second-harmonic frequency response in addition to the known first-harmonic excitation. In contrast to the experimentally observed second-harmonic response in harmonic Hall measurements of spin-orbit torque in magnetic thin films, this second-harmonic response directly originates from spin-orbit torque driven domain wall dynamics. Based on the spin current generated by domain wall dynamics, the longitudinal spin motive force generated voltage across the length of the nanowire is determined. The second-harmonic response introduces additionally a practical field-free and all-electrical method to probe the effective spin Hall angle for FM/NM bilayer structures that could be applied in experiments. Our results also demonstrate the capability of utilizing FM/NM bilayer structures in domain wall based spin-torque signal generators and resonators.

High Voltage Hall Accelerator Propulsion System Development for NASA Science Missions

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Haag, Thomas; Huang, Wensheng; Shastry, Rohit; Pinero, Luis; Peterson, Todd; Dankanich, John; Mathers, Alex

2013-01-01

NASA Science Mission Directorates In-Space Propulsion Technology Program is sponsoring the development of a 3.8 kW-class engineering development unit Hall thruster for implementation in NASA science and exploration missions. NASA Glenn Research Center and Aerojet are developing a high fidelity high voltage Hall accelerator (HiVHAc) thruster that can achieve specific impulse magnitudes greater than 2,700 seconds and xenon throughput capability in excess of 300 kilograms. Performance, plume mappings, thermal characterization, and vibration tests of the HiVHAc engineering development unit thruster have been performed. In addition, the HiVHAc project is also pursuing the development of a power processing unit (PPU) and xenon feed system (XFS) for integration with the HiVHAc engineering development unit thruster. Colorado Power Electronics and NASA Glenn Research Center have tested a brassboard PPU for more than 1,500 hours in a vacuum environment, and a new brassboard and engineering model PPU units are under development. VACCO Industries developed a xenon flow control module which has undergone qualification testing and will be integrated with the HiVHAc thruster extended duration tests. Finally, recent mission studies have shown that the HiVHAc propulsion system has sufficient performance for four Discovery- and two New Frontiers-class NASA design reference missions.

Handheld magnetic probe with permanent magnet and Hall sensor for identifying sentinel lymph nodes in breast cancer patients.

PubMed

Sekino, Masaki; Kuwahata, Akihiro; Ookubo, Tetsu; Shiozawa, Mikio; Ohashi, Kaichi; Kaneko, Miki; Saito, Itsuro; Inoue, Yusuke; Ohsaki, Hiroyuki; Takei, Hiroyuki; Kusakabe, Moriaki

2018-01-19

The newly developed radioisotope-free technique based on magnetic nanoparticle detection using a magnetic probe is a promising method for sentinel lymph node biopsy. In this study, a novel handheld magnetic probe with a permanent magnet and magnetic sensor is developed to detect the sentinel lymph nodes in breast cancer patients. An outstanding feature of the probe is the precise positioning of the sensor at the magnetic null point of the magnet, leading to highly sensitive measurements unaffected by the strong ambient magnetic fields of the magnet. Numerical and experimental results show that the longitudinal detection length is approximately 10 mm, for 140 μg of iron. Clinical tests were performed, for the first time, using magnetic and blue dye tracers-without radioisotopes-in breast cancer patients to demonstrate the performance of the probe. The nodes were identified through transcutaneous and ex-vivo measurements, and the iron accumulation in the nodes was quantitatively revealed. These results show that the handheld magnetic probe is useful in sentinel lymph node biopsy and that magnetic techniques are widely being accepted as future standard methods in medical institutions lacking nuclear medicine facilities.

Facilty Focus: Residence Halls.

ERIC Educational Resources Information Center

Hunnewell, James F., Jr.

2002-01-01

Describes the Western Ridge Residence at Colorado College and Beard Hall at Wheaton College. The buildings feature multiple levels that take advantage of views and also help create a "homey" feeling. (EV)

Design, Qualification and Lessons Learned of the Shutter Calibration Mechanism for EnMAP Mission

NASA Astrophysics Data System (ADS)

Schmidt, Tilo; Muller, Silvio; Bergander, Arvid; Zajac, Kai; Seifart, Klaus

2015-09-01

The Shutter Calibration Mechanism (SCM) Assembly is one of three mechanisms which are developed by HTS for the EnMAP instrument in subcontract to OHB System AG Munich. EnMAP is the Environmental Mapping and Analysis Program of the German Space Agency DLR.The binary rotary encoder of the SCM using hall-effect sensors was already presented during ESMATS 2011. This paper summarizes the main functions and design features of the Hardware and focuses on qualification testing which has finished successfully in 2014. Of particular interest is the functional testing of the main drive including the precise hall-effect position sensing system and the test of the fail safe mechanism. In addition to standard test campaign required for QM also a shock emission measurement of the fail safe mechanism activation was conducted.Test conduction and results will be presented with focus on deviations from the expected behaviour, mitigation measures and on lessons learned.

A New Definition in Atlanta: Q&A with Beverly Hall

ERIC Educational Resources Information Center

Crow, Tracy

2010-01-01

Beverly Hall has been superintendent of Atlanta Public Schools since 1999. Before coming to Atlanta, Hall was state district superintendent of Newark Public Schools, deputy chancellor for instruction of New York City Public Schools, superintendent of Community School District 27 in New York City, and a principal in Brooklyn. Hall chairs Harvard…

Quantum Hall Ferroelectrics and Nematics in Multivalley Systems

NASA Astrophysics Data System (ADS)

Sodemann, Inti; Zhu, Zheng; Fu, Liang

2017-10-01

We study broken symmetry states at integer Landau-level fillings in multivalley quantum Hall systems whose low-energy dispersions are anisotropic. When the Fermi surface of individual pockets lacks twofold rotational symmetry, like in bismuth (111) [Feldman et al. , Observation of a Nematic Quantum Hall Liquid on the Surface of Bismuth, Science 354, 316 (2016), 10.1126/science.aag1715] and in Sn1 -xPbxSe (001) [Dziawa et al., Topological Crystalline Insulator States in Pb1 -xSnxSe , Nat. Mater. 11, 1023 (2012), 10.1038/nmat3449] surfaces, interactions tend to drive the formation of quantum Hall ferroelectric states. We demonstrate that the dipole moment in these states has an intimate relation to the Fermi surface geometry of the parent metal. In quantum Hall nematic states, like those arising in AlAs quantum wells, we demonstrate the existence of unusually robust Skyrmion quasiparticles.

Nonequilibrium Hall Response After a Topological Quench

NASA Astrophysics Data System (ADS)

Unal, F. Nur; Mueller, Erich; Oktel, M. O.

2017-04-01

We theoretically study the Hall response of a lattice system following a quench where the topology of a filled band is suddenly changed. In the limit where the physics is dominated by a single Dirac cone, we find that the change in the Hall conductivity is two-thirds of the quantum of conductivity. We explore this universal behavior in the Haldane model, and discuss cold-atom experiments for its observation. Beyond linear response, the Hall effect crosses over from fractional to integer values. We investigate finite-size effects, and the role of the harmonic confinement. Furthermore, we explore the magnetic field quenches in ladders formed in synthetic dimensions. This work is supported by TUBITAK, NSFPHY-1508300, ARO-MURI W9111NF-14-1-0003.

Electric Propulsion Options for a Magnetospheric Mapping Mission

NASA Technical Reports Server (NTRS)

Oleson, Steven; Russell, Chris; Hack, Kurt; Riehl, John

1998-01-01

The Twin Electric Magnetospheric Probes Exploring on Spiral Trajectories mission concept was proposed as a Middle Explorer class mission. A pre-phase-A design was developed which utilizes the advantages of electric propulsion for Earth scientific spacecraft use. This paper presents propulsion system analyses performed for the proposal. The proposed mission required two spacecraft to explore near circular orbits 0.1 to 15 Earth radii in both high and low inclination orbits. Since the use of chemical propulsion would require launch vehicles outside the Middle Explorer class a reduction in launch mass was sought using ion, Hall, and arcjet electric propulsion system. Xenon ion technology proved to be the best propulsion option for the mission requirements requiring only two Pegasus XL launchers. The Hall thruster provided an alternative solution but required two larger, Taurus launch vehicles. Arcjet thrusters did not allow for significant launch vehicle reduction in the Middle Explorer class.

End-hall thrusters

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.; Day, M. L.; Haag, T. W.

1990-01-01

The end-Hall thruster can provide electric propulsion with fixed masses, specific impulses, and power-to-thrust ratios intermediate of an arcjet and a gridded (electrostatic) ion thruster. With these characteristics, this thruster is a candidate for missions of intermediate difficulty, such as the north-south stationkeeping of geostationary satellites.

Atom Probe Tomographic Mapping Directly Reveals the Atomic Distribution of Phosphorus in Resin Embedded Ferritin

NASA Astrophysics Data System (ADS)

Perea, Daniel E.; Liu, Jia; Bartrand, Jonah; Dicken, Quinten; Thevuthasan, S. Theva; Browning, Nigel D.; Evans, James E.

2016-02-01

Here we report the atomic-scale analysis of biological interfaces within the ferritin protein using atom probe tomography that is facilitated by an advanced specimen preparation approach. Embedding ferritin in an organic polymer resin lacking nitrogen provided chemical contrast to visualise atomic distributions and distinguish the inorganic-organic interface of the ferrihydrite mineral core and protein shell, as well as the organic-organic interface between the ferritin protein shell and embedding resin. In addition, we definitively show the atomic-scale distribution of phosphorus as being at the surface of the ferrihydrite mineral with the distribution of sodium mapped within the protein shell environment with an enhanced distribution at the mineral/protein interface. The sample preparation method is robust and can be directly extended to further enhance the study of biological, organic and inorganic nanomaterials relevant to health, energy or the environment.

Atom Probe Tomographic Mapping Directly Reveals the Atomic Distribution of Phosphorus in Resin Embedded Ferritin

PubMed Central

Perea, Daniel E.; Liu, Jia; Bartrand, Jonah; Dicken, Quinten; Thevuthasan, S. Theva; Browning, Nigel D.; Evans, James E.

2016-01-01

Here we report the atomic-scale analysis of biological interfaces within the ferritin protein using atom probe tomography that is facilitated by an advanced specimen preparation approach. Embedding ferritin in an organic polymer resin lacking nitrogen provided chemical contrast to visualise atomic distributions and distinguish the inorganic-organic interface of the ferrihydrite mineral core and protein shell, as well as the organic-organic interface between the ferritin protein shell and embedding resin. In addition, we definitively show the atomic-scale distribution of phosphorus as being at the surface of the ferrihydrite mineral with the distribution of sodium mapped within the protein shell environment with an enhanced distribution at the mineral/protein interface. The sample preparation method is robust and can be directly extended to further enhance the study of biological, organic and inorganic nanomaterials relevant to health, energy or the environment. PMID:26924804

Study and Developement of Compact Permanent Magnet Hall Thrusters for Future Brazillian Space Missions

NASA Astrophysics Data System (ADS)

Ferreira, Jose Leonardo; Martins, Alexandre; Cerda, Rodrigo

2016-07-01

maneuvering. A joint brazillian space mission on the solar system has also been consider for the coming years. ASTER project is a mission to a near earth asteroid that is planned to be carried on using Hall thrusters. The PHALL project consists on plasma source design, construction and characterization of plasma propulsion engines based on Hall current generated inside a cylindrical channel with an axial electric field produced by a ring anode and a radial magnetic field produced by permanent magnets. One of the main advantage of PHALL thruster is the production of a steady state magnetic field by permanent magnets providing electron trapping and Hall current generation within a significant decrease on the electric energy supply. This advantage turns PHALL thruster into a specially good option when it comes to space usage for longer and deep space missions, where solar panels and electric energy storage on batteries is a limiting factor. This work also describes the Hall Plasma Source construction and characteristics and the plasma diagnostics system used on BID, an Integrated Plasma Diagnostic System. This system contains Langmuir probes that are used for plasma density and temperature measurements. Faraday Cup, Ion probes and Spectrograph (Andor SR-750-B2, within 435nm to 700nm) line broadening measurements are used to measure ion temperature and transport from Hall current channel to the ejected plasma plume. In order to control argon fuel purity a mass spectrometer is also planned to be used. Thrust and Specific Impulse measurements will also be shown. Important to notice relevant plasma physics phenomena investigation that may significantly interfere on PHALL performance. It is the occurrence of instabilities that can happen inside and outside of the Hall current channel. In order to better understand the turbulence and plasma oscillations that occur during the thruster operation, we propose and test a wide frequency range instability detection system based on a RF

Intrinsic Spin-Hall Effect in n-Doped Bulk GaAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-01-15

We show that the bulk Dresselhauss (k{sup 3}) spin-orbit coupling term leads to an intrinsic spin-Hall effect in n-doped bulk GaAs, but without the appearance of uniform magnetization. The spin-Hall effect in strained and unstrained bulk GaAs has been recently observed experimentally by Kato et. al. [1]. We show that the experimental result is quantitatively consistent with the intrinsic spin-Hall effect due to the Dresselhauss term, when lifetime broadening is taken into account. On the other hand, extrinsic contribution to the spin-Hall effect is several orders of magnitude smaller than the observed effect.

Graphene/Si CMOS Hybrid Hall Integrated Circuits

PubMed Central

Huang, Le; Xu, Huilong; Zhang, Zhiyong; Chen, Chengying; Jiang, Jianhua; Ma, Xiaomeng; Chen, Bingyan; Li, Zishen; Zhong, Hua; Peng, Lian-Mao

2014-01-01

Graphene/silicon CMOS hybrid integrated circuits (ICs) should provide powerful functions which combines the ultra-high carrier mobility of graphene and the sophisticated functions of silicon CMOS ICs. But it is difficult to integrate these two kinds of heterogeneous devices on a single chip. In this work a low temperature process is developed for integrating graphene devices onto silicon CMOS ICs for the first time, and a high performance graphene/CMOS hybrid Hall IC is demonstrated. Signal amplifying/process ICs are manufactured via commercial 0.18 um silicon CMOS technology, and graphene Hall elements (GHEs) are fabricated on top of the passivation layer of the CMOS chip via a low-temperature micro-fabrication process. The sensitivity of the GHE on CMOS chip is further improved by integrating the GHE with the CMOS amplifier on the Si chip. This work not only paves the way to fabricate graphene/Si CMOS Hall ICs with much higher performance than that of conventional Hall ICs, but also provides a general method for scalable integration of graphene devices with silicon CMOS ICs via a low-temperature process. PMID:24998222

Diagnostics Systems for Permanent Hall Thrusters Development

NASA Astrophysics Data System (ADS)

Ferreira, Jose Leonardo; Soares Ferreira, Ivan; Santos, Jean; Miranda, Rodrigo; Possa, M. Gabriela

This work describes the development of Permanent Magnet Hall Effect Plasma Thruster (PHALL) and its diagnostic systems at The Plasma Physics Laboratory of University of Brasilia. The project consists on the construction and characterization of plasma propulsion engines based on the Hall Effect. Electric thrusters have been employed in over 220 successful space missions. Two types stand out: the Hall-Effect Thruster (HET) and the Gridded Ion Engine (GIE). The first, which we deal with in this project, has the advantage of greater simplicity of operation, a smaller weight for the propulsion subsystem and a longer shelf life. It can operate in two configurations: magnetic layer and anode layer, the difference between the two lying in the positioning of the anode inside the plasma channel. A Hall-Effect Thruster-HET is a type of plasma thruster in which the propellant gas is ionized and accelerated by a magneto hydrodynamic effect combined with electrostatic ion acceleration. So the essential operating principle of the HET is that it uses a J x B force and an electrostatic potential to accelerate ions up to high speeds. In a HET, the attractive negative charge is provided by electrons at the open end of the Thruster instead of a grid, as in the case of the electrostatic ion thrusters. A strong radial magnetic field is used to hold the electrons in place, with the combination of the magnetic field and the electrostatic potential force generating a fast circulating electron current, the Hall current, around the axis of the Thruster, mainly composed by drifting electrons in an ion plasma background. Only a slow axial drift towards the anode occurs. The main attractive features of the Hall-Effect Thruster are its simple design and operating principles. Most of the Hall-Effect Thrusters use electromagnet coils to produce the main magnetic field responsible for plasma generation and acceleration. In this paper we present a different new concept, a Permanent Magnet Hall

Formulation of the relativistic quantum Hall effect and parity anomaly

NASA Astrophysics Data System (ADS)

Yonaga, Kouki; Hasebe, Kazuki; Shibata, Naokazu

2016-06-01

We present a relativistic formulation of the quantum Hall effect on Haldane sphere. An explicit form of the pseudopotential is derived for the relativistic quantum Hall effect with/without mass term. We clarify particular features of the relativistic quantum Hall states with the use of the exact diagonalization study of the pseudopotential Hamiltonian. Physical effects of the mass term to the relativistic quantum Hall states are investigated in detail. The mass term acts as an interpolating parameter between the relativistic and nonrelativistic quantum Hall effects. It is pointed out that the mass term unevenly affects the many-body physics of the positive and negative Landau levels as a manifestation of the "parity anomaly." In particular, we explicitly demonstrate the instability of the Laughlin state of the positive first relativistic Landau level with the reduction of the charge gap.

Hole mobilities and the effective Hall factor in p-type GaAs

NASA Astrophysics Data System (ADS)

Wenzel, M.; Irmer, G.; Monecke, J.; Siegel, W.

1997-06-01

We prove the effective Hall factor in p-GaAs to be larger than values discussed in the literature up to now. The scattering rates for the relevant scattering mechanisms in p-GaAs have been recalculated after critical testing the existing models. These calculations allow to deduce theoretical drift and theoretical Hall mobilities as functions of temperature which can be compared with measured data. Theoretical Hall factors in the heavy and light hole bands and an effective Hall factor result. The calculated room temperature values of the drift mobility and of the effective Hall factor are 118 cm2/V s and 3.6, respectively. The fitted acoustic deformation potential E1=7.9 eV and the fitted optical coupling constant DK=1.24×1011 eV/m are close to values published before. It is shown that the measured strong dependence of the Hall mobility on the Hall concentration is not mainly caused by scattering by ionized impurities but by the dependence of the effective Hall factor on the hole concentration.

4. MESS HALL, FRONT DETAIL OVER DOOR, LOOKING EAST. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. MESS HALL, FRONT DETAIL OVER DOOR, LOOKING EAST. - NIKE Missile Base C-84, Mess Hall, North of Launch Area Entrance Drive, east of Officers' Quarters & Administration Building, Barrington, Cook County, IL

3. MESS HALL, REAR SIDE, LOOKING NORTH. NIKE Missile ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. MESS HALL, REAR SIDE, LOOKING NORTH. - NIKE Missile Base SL-40, Mess Hall, East central portion of base, southeast of Barracks No. 2, northwest of Administration Building, Hecker, Monroe County, IL

2. MESS HALL, RIGHT SIDE, LOOKING EAST. NIKE Missile ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. MESS HALL, RIGHT SIDE, LOOKING EAST. - NIKE Missile Base SL-40, Mess Hall, East central portion of base, southeast of Barracks No. 2, northwest of Administration Building, Hecker, Monroe County, IL

ION ACOUSTIC TURBULENCE, ANOMALOUS TRANSPORT, AND SYSTEM DYNAMICS IN HALL EFFECT THRUSTERS

DTIC Science & Technology

2017-06-30

17394 4 / 13 HALL EFFECT THRUSTERS Hall Effect Thrusters (HET): Traditionally Modeled in R-Z Named for Hall Current in θ Uses Quasi -1D Electron Fluid...HET): Traditionally Modeled in R-Z Named for Hall Current in θ Uses Quasi -1D Electron Fluid Solve Ohm’s Law→ No e−-momentum Zθ Unrolled to YZ...Current in θ Uses Quasi -1D Electron Fluid Solve Ohm’s Law→ No e−-momentum Zθ Unrolled to YZ Electron ExB Drift Unmagnetized Ions Results in Hall Current

Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

PubMed

Mani, Arjun; Benjamin, Colin

2016-04-13

On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin-orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible--the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case.

Multiply charged ion generation according to magnetic field configurations in Hall thruster plasmas

NASA Astrophysics Data System (ADS)

Kim, Holak; Lee, Seunghun; Kim, Junbum; Lim, Youbong; Choe, Wonho; KIMS Collaboration

2016-09-01

Plasma propulsion is the most promising techniques to operate satellites for low earth orbit as well as deep space exploration. A typical plasma propulsion system is Hall thruster (HT) that uses crossed electromagnetic fields to ionize a propellant gas and to accelerate the ionized gas. In HT the tailoring of magnetic fields is significant due to that the electron confinement in the electromagnetic fields affects thruster performances such as thrust force, specific impulse, power efficiency, and life time. We designed an anode layer HT (TAL) with the magnetic field tailoring. The TAL is possible to keep discharge in 1 2 kilovolts, which voltage is useful to obtain high specific impulse The magnetic field tailoring is adapted to minimize undesirable heat dissipations and secondary electron emissions at a wall surrounding plasma In presentation, we will report TAL performances including thrust force, specific impulse, and anode efficiency measured by a pendulum thrust stand. This mechanical measurement will be compared to the plasma diagnostics conducted by angular Faraday probe, retarding potential analyzer, and ExB probe Grant No. 2014M1A3A3A02034510.

5. MESS HALL, RIGHT AND REAR SIDES, LOOKING NORTHEAST. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. MESS HALL, RIGHT AND REAR SIDES, LOOKING NORTHEAST. - NIKE Missile Base SL-40, Mess Hall, East central portion of base, southeast of Barracks No. 2, northwest of Administration Building, Hecker, Monroe County, IL

6. PHOTOCOPY, PLAN AND SCHEDULE DRAWING OF MESS HALL. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. PHOTOCOPY, PLAN AND SCHEDULE DRAWING OF MESS HALL. - NIKE Missile Base SL-40, Mess Hall, East central portion of base, southeast of Barracks No. 2, northwest of Administration Building, Hecker, Monroe County, IL

7. PHOTOCOPY, ELEVATION AND SECTION DRAWING OF MESS HALL. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. PHOTOCOPY, ELEVATION AND SECTION DRAWING OF MESS HALL. - NIKE Missile Base SL-40, Mess Hall, East central portion of base, southeast of Barracks No. 2, northwest of Administration Building, Hecker, Monroe County, IL

4. MESS HALL, FRONT AND LEFT SIDES, LOOKING SOUTHWEST. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. MESS HALL, FRONT AND LEFT SIDES, LOOKING SOUTHWEST. - NIKE Missile Base SL-40, Mess Hall, East central portion of base, southeast of Barracks No. 2, northwest of Administration Building, Hecker, Monroe County, IL

Modeling the Insertion Mechanics of Flexible Neural Probes Coated with Sacrificial Polymers for Optimizing Probe Design

PubMed Central

Singh, Sagar; Lo, Meng-Chen; Damodaran, Vinod B.; Kaplan, Hilton M.; Kohn, Joachim; Zahn, Jeffrey D.; Shreiber, David I.

2016-01-01

-designed to ensure successful insertion. Probability color maps were generated to visually compare the influence of design parameters. Statistical metrics derived from the color maps and multi-variable regression analysis confirmed that coating thickness and probe length were the most important features in influencing insertion potential. The model also revealed the effects of manufacturing flaws on insertion potential. PMID:26959021

Determination of intrinsic spin Hall angle in Pt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yi; Deorani, Praveen; Qiu, Xuepeng

2014-10-13

The spin Hall angle in Pt is evaluated in Pt/NiFe bilayers by spin torque ferromagnetic resonance measurements and is found to increase with increasing the NiFe thickness. To extract the intrinsic spin Hall angle in Pt by estimating the total spin current injected into NiFe from Pt, the NiFe thickness dependent measurements are performed and the spin diffusion in the NiFe layer is taken into account. The intrinsic spin Hall angle of Pt is determined to be 0.068 at room temperature and is found to be almost constant in the temperature range of 13–300 K.

Performance of a Low-Power Cylindrical Hall Thruster

NASA Technical Reports Server (NTRS)

Polzin, Kurt A.; Markusic, Thomas E.; Stanojev, Boris J.; Dehoyos, Amado; Raitses, Yevgeny; Smirnov, Artem; Fisch, Nathaniel J.

2007-01-01

Recent mission studies have shown that a Hall thruster which operates at relatively constant thrust efficiency (45-55%) over a broad power range (300W - 3kW) is enabling for deep space science missions when compared with slate-of-the-art ion thrusters. While conventional (annular) Hall thrusters can operate at high thrust efficiency at kW power levels, it is difficult to construct one that operates over a broad power envelope down to 0 (100 W) while maintaining relatively high efficiency. In this note we report the measured performance (I(sub sp), thrust and efficiency) of a cylindrical Hall thruster operating at 0 (100 W) input power.

Scanning probe acceleration microscopy (SPAM) in fluids: Mapping mechanical properties of surfaces at the nanoscale

NASA Astrophysics Data System (ADS)

Legleiter, Justin; Park, Matthew; Cusick, Brian; Kowalewski, Tomasz

2006-03-01

One of the major thrusts in proximal probe techniques is combination of imaging capabilities with simultaneous measurements of physical properties. In tapping mode atomic force microscopy (TMAFM), the most straightforward way to accomplish this goal is to reconstruct the time-resolved force interaction between the tip and surface. These tip-sample forces can be used to detect interactions (e.g., binding sites) and map material properties with nanoscale spatial resolution. Here, we describe a previously unreported approach, which we refer to as scanning probe acceleration microscopy (SPAM), in which the TMAFM cantilever acts as an accelerometer to extract tip-sample forces during imaging. This method utilizes the second derivative of the deflection signal to recover the tip acceleration trajectory. The challenge in such an approach is that with real, noisy data, the second derivative of the signal is strongly dominated by the noise. This problem is solved by taking advantage of the fact that most of the information about the deflection trajectory is contained in the higher harmonics, making it possible to filter the signal by “comb” filtering, i.e., by taking its Fourier transform and inverting it while selectively retaining only the intensities at integer harmonic frequencies. Such a comb filtering method works particularly well in fluid TMAFM because of the highly distorted character of the deflection signal. Numerical simulations and in situ TMAFM experiments on supported lipid bilayer patches on mica are reported to demonstrate the validity of this approach.

Cylindrical geometry hall thruster

DOEpatents

Raitses, Yevgeny; Fisch, Nathaniel J.

2002-01-01

An apparatus and method for thrusting plasma, utilizing a Hall thruster with a cylindrical geometry, wherein ions are accelerated in substantially the axial direction. The apparatus is suitable for operation at low power. It employs small size thruster components, including a ceramic channel, with the center pole piece of the conventional annular design thruster eliminated or greatly reduced. Efficient operation is accomplished through magnetic fields with a substantial radial component. The propellant gas is ionized at an optimal location in the thruster. A further improvement is accomplished by segmented electrodes, which produce localized voltage drops within the thruster at optimally prescribed locations. The apparatus differs from a conventional Hall thruster, which has an annular geometry, not well suited to scaling to small size, because the small size for an annular design has a great deal of surface area relative to the volume.

A Monolithic CMOS Magnetic Hall Sensor with High Sensitivity and Linearity Characteristics

PubMed Central

Huang, Haiyun; Wang, Dejun; Xu, Yue

2015-01-01

This paper presents a fully integrated linear Hall sensor by means of 0.8 μm high voltage complementary metal-oxide semiconductor (CMOS) technology. This monolithic Hall sensor chip features a highly sensitive horizontal switched Hall plate and an efficient signal conditioner using dynamic offset cancellation technique. An improved cross-like Hall plate achieves high magnetic sensitivity and low offset. A new spinning current modulator stabilizes the quiescent output voltage and improves the reliability of the signal conditioner. The tested results show that at the 5 V supply voltage, the maximum Hall output voltage of the monolithic Hall sensor microsystem, is up to ±2.1 V and the linearity of Hall output voltage is higher than 99% in the magnetic flux density range from ±5 mT to ±175 mT. The output equivalent residual offset is 0.48 mT and the static power consumption is 20 mW. PMID:26516864

A Monolithic CMOS Magnetic Hall Sensor with High Sensitivity and Linearity Characteristics.

PubMed

Huang, Haiyun; Wang, Dejun; Xu, Yue

2015-10-27

This paper presents a fully integrated linear Hall sensor by means of 0.8 μm high voltage complementary metal-oxide semiconductor (CMOS) technology. This monolithic Hall sensor chip features a highly sensitive horizontal switched Hall plate and an efficient signal conditioner using dynamic offset cancellation technique. An improved cross-like Hall plate achieves high magnetic sensitivity and low offset. A new spinning current modulator stabilizes the quiescent output voltage and improves the reliability of the signal conditioner. The tested results show that at the 5 V supply voltage, the maximum Hall output voltage of the monolithic Hall sensor microsystem, is up to ±2.1 V and the linearity of Hall output voltage is higher than 99% in the magnetic flux density range from ±5 mT to ±175 mT. The output equivalent residual offset is 0.48 mT and the static power consumption is 20 mW.

Earth Probe Total Ozone Mapping Spectrometer (TOMS) Data Product User's Guide

NASA Technical Reports Server (NTRS)

McPeters, R.; Bhartia, P. K.; Krueger, A.; Herman, J.; Wellemeyer, C.; Seftor, C.; Jaross, G.; Torres, O.; Moy, L.; Labow, G.;

Proton Knock-Out in Hall A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kees de Jager

Proton knock-out is studied in a broad program in Hall A at Jefferson Lab. The first experiment performed in Hall A studied the {sup 16}O(e,e'p) reaction. Since then proton knock-out experiments have studied a variety of aspects of that reaction, from single-nucleon properties to its mechanism, such as final-state interactions and two-body currents, in nuclei from {sup 2}H to {sup 16}O. In this review the results of this program will be summarized and an outlook given of future accomplishments.

Astronaut Hall of Fame Induction Ceremony

NASA Image and Video Library

2017-05-19

In a ceremony set beneath Space Shuttle Atlantis, veteran astronauts C. Michael Foale and Ellen Ochoa are inducted into the U.S. Astronaut Hall of Fame. Foale and Ochoa make up the 16th group of space shuttle astronauts to be inducted into the Hall of Fame, and their addition to the group brings the total number of inductees to 95. More than 20 legendary astronauts were on hand to welcome the inductees, including: Robert Cabana, Dan Brandenstein, Al Worden, Charlie Duke, Charles Bolden, Michael Coats, Robert Crippen, Rhea Seddon, and Fred Gregory.

Hall Sweet Home

ERIC Educational Resources Information Center

Oguntoyinbo, Lekan

2011-01-01

Many urban and commuter universities have their sights set on students who are unlikely to connect with the college and likely to fail unless the right strategies are put in place to help them graduate. In efforts to improve retention rates, commuter colleges are looking to an unusual suspect: residence halls. The author discusses how these…

Hall Effect Spintronics

DTIC Science & Technology

2014-01-01

ferromagnetic films with perpendicular anisotropy were examined, and finally, the magnetoresistance and Hall effect in Manganese- doped Germanium was...interest in ferromagnetic semiconductors. Germanium doped with Mn is particularly interesting Distribution A: Approved for public release...unavoidable, and doped films are strongly inhomogeneous with GexMny, metallic precipitates coexisting with Mn-rich regions and Mn dilute matrix

Observation of anomalous Hall effect in a non-magnetic two-dimensional electron system

PubMed Central

Maryenko, D.; Mishchenko, A. S.; Bahramy, M. S.; Ernst, A.; Falson, J.; Kozuka, Y.; Tsukazaki, A.; Nagaosa, N.; Kawasaki, M.

2017-01-01

Anomalous Hall effect, a manifestation of Hall effect occurring in systems without time-reversal symmetry, has been mostly observed in ferromagnetically ordered materials. However, its realization in high-mobility two-dimensional electron system remains elusive, as the incorporation of magnetic moments deteriorates the device performance compared to non-doped structure. Here we observe systematic emergence of anomalous Hall effect in various MgZnO/ZnO heterostructures that exhibit quantum Hall effect. At low temperatures, our nominally non-magnetic heterostructures display an anomalous Hall effect response similar to that of a clean ferromagnetic metal, while keeping a large anomalous Hall effect angle θAHE≈20°. Such a behaviour is consistent with Giovannini–Kondo model in which the anomalous Hall effect arises from the skew scattering of electrons by localized paramagnetic centres. Our study unveils a new aspect of many-body interactions in two-dimensional electron systems and shows how the anomalous Hall effect can emerge in a non-magnetic system. PMID:28300133

Nonlinear excitation of long-wavelength modes in Hall plasmas

NASA Astrophysics Data System (ADS)

Lakhin, V. P.; Ilgisonis, V. I.; Smolyakov, A. I.; Sorokina, E. A.

2016-10-01

Hall plasmas with magnetized electrons and unmagnetized ions exhibit a wide range of small scale fluctuations in the lower-hybrid frequency range as well as low-frequency large scale modes. Modulational instability of lower-hybrid frequency modes is investigated in this work for typical conditions in Hall plasma devices such as magnetrons and Hall thrusters. In these conditions, the dispersion of the waves in the lower-hybrid frequency range propagating perpendicular to the external magnetic field is due to the gradients of the magnetic field and the plasma density. It is shown that such lower-hybrid modes are unstable with respect to the secondary instability of the large scale quasimode perturbations. It is suggested that the large scale slow coherent modes observed in a number of Hall plasma devices may be explained as a result of such secondary instabilities.

Dynamics of Charge Carriers in Silicon Nanowire Photoconductors Revealed by Photo Hall Effect Measurements.

PubMed

Chen, Kaixiang; Zhao, Xiaolong; Mesli, Abdelmadjid; He, Yongning; Dan, Yaping

2018-04-24

Photoconductors have extraordinarily high gain in quantum efficiency, but the origin of the gain has remained in dispute for decades. In this work, we employ photo Hall effect to reveal the gain mechanisms by probing the dynamics of photogenerated charge carriers in silicon nanowire photoconductors. The results reveal that a large number of photogenerated minority electrons are localized in the surface depletion region and surface trap states. The same number of excess hole counterparts is left in the nanowire conduction channel, resulting in the fact that excess holes outnumber the excess electrons in the nanowire conduction channel by orders of magnitude. The accumulation of the excess holes broadens the conduction channel by narrowing down the depletion region, which leads to the experimentally observed high photo gain.

Performance Characteristics of a 5 kW Laboratory Hall Thruster

DTIC Science & Technology

1996-07-01

Characteristics of a 5 kW Laboratory Hall Thruster James M. Haas’, Frank S. Gulczinski III%, and Alec D. Gallimoret Plasmadynamics and Electric Propulsion...the information learned from the study of this thruster applicable to the understanding of its commercial counterparts. INTRODUCTION Hall thrusters are...few in number at this time; and those that do exist are intended primarily Current generation Hall thruster research has for flight qualification

Performance Potential of Plasma Thrusters: Arcjet and Hall Thruster Modeling

DTIC Science & Technology

1993-09-17

FUNDING NUMBERS Performance Potential of Plasma Thrusters: \\ Arcjet and Hall Thruster Modeling FQ 8671-9300908 S ,,G-AFOSR-91-0256 6. AUTHOR(S) Manuel...models for the internal physics and the performance of hydrogen arcjets and Hall thrusters , respectively. These are thought to represent the state of...work. 93-24268 14. SUBJECT TERMS IS. NUMBER OF PAGES Electric Propulsion, Arcjets, Hall Thrusters 15 16. PRICE COOE 17. SECURITY CLASSIFICATION I18

Spin Hall Effect in Doped Semiconductor Structures

NASA Astrophysics Data System (ADS)

Tse, Wang-Kong; Das Sarma, S.

2006-02-01

In this Letter we present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump and skew-scattering contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show that their effects scale as σxySJ/σxySS˜(ℏ/τ)/ɛF, with τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n- and p-doped 3D and 2D GaAs structures, obtaining σs/σc˜10-3-10-4, where σs(c) is the spin Hall (charge) conductivity, which is in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)]SCIEAS0036-807510.1126/science.1105514 in n-doped 3D GaAs system.

Spin Hall Effect in Doped Semiconductor Structures

NASA Astrophysics Data System (ADS)

Tse, Wang-Kong; Das Sarma, Sankar

2006-03-01

We present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump (SJ) and skew-scattering (SS) contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show their effects scale as σxy^SJ/σxy^SS ˜(/τ)/ɛF, where τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n-doped and p-doped 3D and 2D GaAs structures, obtaining analytical formulas for the SJ and SS contributions. Moreover, the ratio of the spin Hall conductivity to longitudinal conductivity is found as σs/σc˜10-3-10-4, in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)] in n-doped 3D GaAs system.

Proposed measurement of tagged deep inelastic scattering in Hall A of Jefferson lab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montgomery, Rachel; Annand, John; Dutta, Dipangkar

2017-03-01

A tagged deep inelastic scattering (TDIS) experiment is planned for Hall A of Jefferson Lab, which will probe the mesonic content of the nucleon directly. Low momentum recoiling (and spectator) protons will be measured in coincidence with electrons scattered in a deep inelastic regime from hydrogen (and deuterium) targets, covering kinematics of 8 < W2 < 18 GeV2, 1 < Q2 < 3 (GeV/c)2 and 0:05 < x < 0:2. The tagging technique will help identify scattering from partons in the meson cloud and provide access to the pion structure function via the Sullivan process. The experiment will yield themore » first TDIS results in the valence regime, for both proton and neutron targets. We present here an overview of the experiment.« less

OxfordGrid: a web interface for pairwise comparative map views.

PubMed

Yang, Hongyu; Gingle, Alan R

2005-12-01

OxfordGrid is a web application and database schema for storing and interactively displaying genetic map data in a comparative, dot-plot, fashion. Its display is composed of a matrix of cells, each representing a pairwise comparison of mapped probe data for two linkage groups or chromosomes. These are arranged along the axes with one forming grid columns and the other grid rows with the degree and pattern of synteny/colinearity between the two linkage groups manifested in the cell's dot density and structure. A mouse click over the selected grid cell launches an image map-based display for the selected cell. Both individual and linear groups of mapped probes can be selected and displayed. Also, configurable links can be used to access other web resources for mapped probe information. OxfordGrid is implemented in C#/ASP.NET and the package, including MySQL schema creation scripts, is available at ftp://cggc.agtec.uga.edu/OxfordGrid/.

Anomalous Hall Resistance in Bilayer Electron Systems

NASA Astrophysics Data System (ADS)

Ezawa, Z. F.; Suzuki, S.; Tsitsishvili, G.

2007-04-01

Interlayer phase coherence has revealed various novel features in bilayer quantum Hall (QH) systems. It is shown to make the QH resistance vanish instead of developing a Hall plateau in a bilayer counterflow geometry. It also induces another anomalous QH resistance discovered in a drag experiment. These theoretical results explain recent experimental data due to Kellogg et al. [PRL 93 (2004) 036801;PRL 88 (2002) 126804] and Tutuc et al.[PRL 93 (2004) 036802].

Interior detail of dispatch boards in main hall, facing west ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior detail of dispatch boards in main hall, facing west - International Longshoremen's & Warehousemen's Union Hall, Naval Civil Engineering Laboratory, Port Hueneme Road, Port Hueneme, Ventura County, CA

A Magnetic Plethysmograph Probe for Local Pulse Wave Velocity Measurement.

PubMed

P M, Nabeel; Joseph, Jayaraj; Sivaprakasam, Mohanasankar

2017-10-01

We present the design and experimental validation of an arterial compliance probe with dual magnetic plethysmograph (MPG) transducers for local pulse wave velocity (PWV) measurement. The MPG transducers (positioned at 23 mm distance apart) utilizes Hall-effect sensors and permanent magnets for arterial blood pulse detection. The MPG probe was initially validated on an arterial flow phantom using a reference method. Further, 20 normotensive subjects (14 males, age = 24 ± 3.5 years) were studied under two different physical conditions: 1) Physically relaxed condition, 2) Postexercise condition. Local PWV was measured from the left carotid artery using the MPG probe. Brachial blood pressure (BP) was measured to investigate the correlation of BP with local PWV. The proposed MPG arterial compliance probe was capable of detecting high-fidelity blood pulse waveforms. Reliable local pulse transit time estimates were assessed by the developed measurement system. Beat-by-beat local PWV was measured from multiple subjects under different physical conditions. A profound increment was observed in the carotid local PWV for all subjects after exercise (average increment = 0.42 ± 0.22 m/s). Local PWV values and brachial BP parameters were significantly correlated (r ≥ 0.72), except for pulse pressure (r = 0.42). MPG arterial compliance probe for local PWV measurement was validated. Carotid local PWV measurement, its variations due to physical exercise and correlation with BP levels were examined during the in vivo study. A novel dual MPG probe for local PWV measurement and potential use in cuffless BP measurement.

A maize map standard with sequenced core markers, grass genome reference points and 932 expressed sequence tagged sites (ESTs) in a 1736-locus map.

PubMed Central

Davis, G L; McMullen, M D; Baysdorfer, C; Musket, T; Grant, D; Staebell, M; Xu, G; Polacco, M; Koster, L; Melia-Hancock, S; Houchins, K; Chao, S; Coe, E H

1999-01-01

We have constructed a 1736-locus maize genome map containing1156 loci probed by cDNAs, 545 probed by random genomic clones, 16 by simple sequence repeats (SSRs), 14 by isozymes, and 5 by anonymous clones. Sequence information is available for 56% of the loci with 66% of the sequenced loci assigned functions. A total of 596 new ESTs were mapped from a B73 library of 5-wk-old shoots. The map contains 237 loci probed by barley, oat, wheat, rice, or tripsacum clones, which serve as grass genome reference points in comparisons between maize and other grass maps. Ninety core markers selected for low copy number, high polymorphism, and even spacing along the chromosome delineate the 100 bins on the map. The average bin size is 17 cM. Use of bin assignments enables comparison among different maize mapping populations and experiments including those involving cytogenetic stocks, mutants, or quantitative trait loci. Integration of nonmaize markers in the map extends the resources available for gene discovery beyond the boundaries of maize mapping information into the expanse of map, sequence, and phenotype information from other grass species. This map provides a foundation for numerous basic and applied investigations including studies of gene organization, gene and genome evolution, targeted cloning, and dissection of complex traits. PMID:10388831

Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results

NASA Technical Reports Server (NTRS)

Bennett, C. L.; Larson, D.; Weiland, J. L.; Jaorsik, N.; Hinshaw, G.; Odegard, N.; Smith, K. M.; Hill, R. S.; Gold, B.; Halpern, M;

An evaluation of krypton propellant in Hall thrusters

NASA Astrophysics Data System (ADS)

Linnell, Jesse Allen

Due to its high specific impulse and low price, krypton has long sparked interest as an alternate Hall thruster propellant. Unfortunately at the moment, krypton's relatively poor performance precludes it as a legitimate option. This thesis presents a detailed investigation into krypton operation in Hall thrusters. These findings suggest that the performance gap can be decreased to 4% and krypton can finally become a realistic propellant option. Although krypton has demonstrated superior specific impulse, the xenon-krypton absolute efficiency gap ranges between 2 and 15%. A phenomenological performance model indicates that the main contributors to the efficiency gap are propellant utilization and beam divergence. Propellant utilization and beam divergence have relative efficiency deficits of 5 and 8%, respectively. A detailed characterization of internal phenomena is conducted to better understand the xenon-krypton efficiency gap. Krypton's large beam divergence is found to be related to a defocusing equipotential structure and a weaker magnetic field topology. Ionization processes are shown to be linked to the Hall current, the magnetic mirror topology, and the perpendicular gradient of the magnetic field. Several thruster design and operational suggestions are made to optimize krypton efficiency. Krypton performance is optimized for discharge voltages above 500 V and flow rates corresponding to an a greater than 0.015 mg/(mm-s), where alpha is a function of flow rate and discharge channel dimensions (alpha = m˙alphab/Ach). Performance can be further improved by increasing channel length or decreasing channel width for a given flow rate. Also, several magnetic field design suggestions are made to enhance ionization and beam focusing. Several findings are presented that improve the understanding of general Hall thruster physics. Excellent agreement is shown between equipotential lines and magnetic field lines. The trim coil is shown to enhance beam focusing

Probing lipid membrane electrostatics

NASA Astrophysics Data System (ADS)

Yang, Yi

manner will be useful in identifying the biological effects of the dipole potential. Finally, heterogeneous model membranes were studied with fluid electric force microscopy (FEFM). Electrostatic mapping was demonstrated with 50 nm resolution. The capabilities of quantitative electrostatic measurement and lateral charge density mapping make AFM a unique and powerful probe of membrane electrostatics.

View of north front and west sides of hall, facing ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of north front and west sides of hall, facing south - International Longshoremen's & Warehousemen's Union Hall, Naval Civil Engineering Laboratory, Port Hueneme Road, Port Hueneme, Ventura County, CA

Mixed-state Hall effect of high-T(c) superconductors

NASA Astrophysics Data System (ADS)

Kang, Byeongwon

In this dissertation, we presented the study on the mixed-state Hall effect of high-Tc superconductors (HTSs). In order to understand the mechanisms of the puzzling phenomena in the mixed-state Hall effect of HTSs, the Hall sign anomaly and scaling behavior, Hall measurements are conducted in several HTS thin films. We investigate the mechanism of the sign reversal of the Hall resistivity in Tl-2201 films when the electronic band structure is varied through the underdoped, optimally doped, and overdoped regions. It is found that the Hall sign reversals are an intrinsic property of HTSs and determined by electronic band structure. Although pinning is not found to be the mechanism behind sign reversals, pinning can suppress the appearance of the Hall sign reversal. Therefore, it is concluded that two (or more) sign reversals are a generic behavior of HTSs. From a systematic study of the vortex phase diagram, we discover several new features of the vortex liquid. In the presence of pinning, the vortex-liquid phase can be divided into two regions, a glassy liquid (GL) where vortices remain correlated as manifested in non-Ohmic resistivity, and a regular liquid (RL) where resistivity becomes Ohmic as vortices become uncorrelated. The field dependence of the Hall angle is found to be linear in the RL and nonlinear in the GL. Generally the decoupling line (Hk- T), which is defined as a boundary between the GL and the RL, is lower than the depinning line (Hd-T). As pinning increases the Hk-T may approach the Hd-T, thus vortices are decoupled and depinned nearly simultaneously. For a weak pinning system, on the other hand, the Hk-T and the Hd-T are well separated so that single vortices remain pinned in the region Hk ≤ H ≥ Hd. The behavior of s xy is also investigated in the GL and the RL. In the GL s xy is observed to strongly depend on pinning due to the inter-vortex correlation whereas in the RL s xy is independent of pinning since the pinning effect is scaled out.

Accelerating 3D Hall MHD Magnetosphere Simulations with Graphics Processing Units

NASA Astrophysics Data System (ADS)

Bard, C.; Dorelli, J.

2017-12-01

The resolution required to simulate planetary magnetospheres with Hall magnetohydrodynamics result in program sizes approaching several hundred million grid cells. These would take years to run on a single computational core and require hundreds or thousands of computational cores to complete in a reasonable time. However, this requires access to the largest supercomputers. Graphics processing units (GPUs) provide a viable alternative: one GPU can do the work of roughly 100 cores, bringing Hall MHD simulations of Ganymede within reach of modest GPU clusters ( 8 GPUs). We report our progress in developing a GPU-accelerated, three-dimensional Hall magnetohydrodynamic code and present Hall MHD simulation results for both Ganymede (run on 8 GPUs) and Mercury (56 GPUs). We benchmark our Ganymede simulation with previous results for the Galileo G8 flyby, namely that adding the Hall term to ideal MHD simulations changes the global convection pattern within the magnetosphere. Additionally, we present new results for the G1 flyby as well as initial results from Hall MHD simulations of Mercury and compare them with the corresponding ideal MHD runs.

Magnetic field deformation due to electron drift in a Hall thruster

NASA Astrophysics Data System (ADS)

Liang, Han; Yongjie, Ding; Xu, Zhang; Liqiu, Wei; Daren, Yu

2017-01-01

The strength and shape of the magnetic field are the core factors in the design of the Hall thruster. However, Hall current can affect the distribution of static magnetic field. In this paper, the Particle-In-Cell (PIC) method is used to obtain the distribution of Hall current in the discharge channel. The Hall current is separated into a direct and an alternating part to calculate the induced magnetic field using Finite Element Method Magnetics (FEMM). The results show that the direct Hall current decreases the magnetic field strength in the acceleration region and also changes the shape of the magnetic field. The maximum reduction in radial magnetic field strength in the exit plane is 10.8 G for an anode flow rate of 15 mg/s and the maximum angle change of the magnetic field line is close to 3° in the acceleration region. The alternating Hall current induces an oscillating magnetic field in the whole discharge channel. The actual magnetic deformation is shown to contain these two parts.

Probing Zeolite Crystal Architecture and Structural Imperfections using Differently Sized Fluorescent Organic Probe Molecules.

PubMed

Hendriks, Frank C; Schmidt, Joel E; Rombouts, Jeroen A; Lammertsma, Koop; Bruijnincx, Pieter C A; Weckhuysen, Bert M

2017-05-05

A micro-spectroscopic method has been developed to probe the accessibility of zeolite crystals using a series of fluorescent 4-(4-diethylaminostyryl)-1-methylpyridinium iodide (DAMPI) probes of increasing molecular size. Staining large zeolite crystals with MFI (ZSM-5) topology and subsequent mapping of the resulting fluorescence using confocal fluorescence microscopy reveal differences in structural integrity: the 90° intergrowth sections of MFI crystals are prone to develop structural imperfections, which act as entrance routes for the probes into the zeolite crystal. Polarization-dependent measurements provide evidence for the probe molecule's alignment within the MFI zeolite pore system. The developed method was extended to BEA (Beta) crystals, showing that the previously observed hourglass pattern is a general feature of BEA crystals with this morphology. Furthermore, the probes can accurately identify at which crystal faces of BEA straight or sinusoidal pores open to the surface. The results show this method can spatially resolve the architecture-dependent internal pore structure of microporous materials, which is difficult to assess using other characterization techniques such as X-ray diffraction. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Timber Creek bunkhouse and mess hall, Rocky Mountain National Park. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Timber Creek bunkhouse and mess hall, Rocky Mountain National Park. Interior, kitchen and dining area, viewing north. - Timber Creek Bunkhouse & Mess Hall, Trail Ridge Road, Grand Lake, Grand County, CO

Hall effect spintronics for gas detection

NASA Astrophysics Data System (ADS)

Gerber, A.; Kopnov, G.; Karpovski, M.

2017-10-01

We present the concept of magnetic gas detection by the extraordinary Hall effect. The technique is compatible with the existing conductometric gas detection technologies and allows the simultaneous measurement of two independent parameters: resistivity and magnetization affected by the target gas. Feasibility of the approach is demonstrated by detecting low concentration hydrogen using thin CoPd films as the sensor material. The Hall effect sensitivity of the optimized samples exceeds 240% per 104 ppm at hydrogen concentrations below 0.5% in the hydrogen/nitrogen atmosphere, which is more than two orders of magnitude higher than the sensitivity of the conductance detection.

High-performance LED luminaire for sports hall

NASA Astrophysics Data System (ADS)

Lee, Xuan-Hao; Yang, Jin-Tsung; Chien, Wei-Ting; Chang, Jung-Hsuan; Lo, Yi-Chien; Lin, Che-Chu; Sun, Ching-Cherng

2015-09-01

In this paper, we present a luminaire design with anti-glare and energy-saving effects for sports hall. Compared with traditional lamps using in a badminton court, the average illuminance on the ground of the proposed LED luminaire is enhanced about 300%. Besides, the uniformity is obviously enhanced and improved. The switch-on speed of lighting in sports hall is greatly reduced from 5-10 minutes to 1 second. The simulation analysis and the corresponding experiment results are demonstrated.

Kids in the Hall.

ERIC Educational Resources Information Center

Swanquist, Barry

2000-01-01

Discusses resident hall furniture design that meets student needs as well as the needs of administrators and parents. Furniture design issues examined include the higher expectations of students in their living environment, the need for greater flexibility in space utilization, and adaptability to technology. (GR)

Detail of main hall porch on east elevation; camera facing ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of main hall porch on east elevation; camera facing west. - Mare Island Naval Shipyard, Wilderman Hall, Johnson Lane, north side adjacent to (south of) Hospital Complex, Vallejo, Solano County, CA

Interior detail of platform in main hall, with desk, flag, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior detail of platform in main hall, with desk, flag, and banners, facing south - International Longshoremen's & Warehousemen's Union Hall, Naval Civil Engineering Laboratory, Port Hueneme Road, Port Hueneme, Ventura County, CA

Useful Pedagogical Applications of the Classical Hall Effect

ERIC Educational Resources Information Center

Houari, Ahmed

2007-01-01

One of the most known phenomena in physics is the Hall effect. This is mainly due to its simplicity and to the wide range of its theoretical and practical applications. To complete the pedagogical utility of the Hall effect in physics teaching, I will apply it here to determine the Faraday constant as a fundamental physical number and the number…

Nonequilibrium Fractional Hall Response After a Topological Quench

NASA Astrophysics Data System (ADS)

Unal, Nur; Mueller, Erich; Oktel, M. O.

When a system is suddenly driven between two topologically different phases, aspects of the original topology survive the quench, but most physical observables (edge currents, Hall conductivity) appear to be non-universal. I will present the non-equilibrium Hall response of a Chern insulator following a quench where the mass term of a single Dirac cone changes sign. In the limit where the physics is dominated by a single Dirac cone, we theoretically find that the Hall conductivity universally changes by two-thirds of the quantum of conductivity. I will analyze this universal behavior by considering the Haldane model, and discuss experimental aspects for its observation in cold atoms. This work is supported by TUBITAK, NSFPHY-1508300, ARO-MURI W9111NF-14-1-0003.

Rule-based fault diagnosis of hall sensors and fault-tolerant control of PMSM

NASA Astrophysics Data System (ADS)

Song, Ziyou; Li, Jianqiu; Ouyang, Minggao; Gu, Jing; Feng, Xuning; Lu, Dongbin

2013-07-01

Hall sensor is widely used for estimating rotor phase of permanent magnet synchronous motor(PMSM). And rotor position is an essential parameter of PMSM control algorithm, hence it is very dangerous if Hall senor faults occur. But there is scarcely any research focusing on fault diagnosis and fault-tolerant control of Hall sensor used in PMSM. From this standpoint, the Hall sensor faults which may occur during the PMSM operating are theoretically analyzed. According to the analysis results, the fault diagnosis algorithm of Hall sensor, which is based on three rules, is proposed to classify the fault phenomena accurately. The rotor phase estimation algorithms, based on one or two Hall sensor(s), are initialized to engender the fault-tolerant control algorithm. The fault diagnosis algorithm can detect 60 Hall fault phenomena in total as well as all detections can be fulfilled in 1/138 rotor rotation period. The fault-tolerant control algorithm can achieve a smooth torque production which means the same control effect as normal control mode (with three Hall sensors). Finally, the PMSM bench test verifies the accuracy and rapidity of fault diagnosis and fault-tolerant control strategies. The fault diagnosis algorithm can detect all Hall sensor faults promptly and fault-tolerant control algorithm allows the PMSM to face failure conditions of one or two Hall sensor(s). In addition, the transitions between health-control and fault-tolerant control conditions are smooth without any additional noise and harshness. Proposed algorithms can deal with the Hall sensor faults of PMSM in real applications, and can be provided to realize the fault diagnosis and fault-tolerant control of PMSM.

Interior of Mess Hall, showing original columns and quarry tile ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior of Mess Hall, showing original columns and quarry tile floor - U.S. Naval Base, Pearl Harbor, Barracks & Mess Hall, Hornet Avenue between Liscome Bay & Enterprise Streets, Pearl City, Honolulu County, HI

Contextual view of ILWU Hall, facing northwest with commercial port ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Contextual view of ILWU Hall, facing northwest with commercial port buildings visible in the background - International Longshoremen's & Warehousemen's Union Hall, Naval Civil Engineering Laboratory, Port Hueneme Road, Port Hueneme, Ventura County, CA

Contextual view of ILWU Hall, facing southsouthwest, with ocean bank ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Contextual view of ILWU Hall, facing south-southwest, with ocean bank visible in the background - International Longshoremen's & Warehousemen's Union Hall, Naval Civil Engineering Laboratory, Port Hueneme Road, Port Hueneme, Ventura County, CA

Nonlinear dynamics induced anomalous Hall effect in topological insulators

PubMed Central

Wang, Guanglei; Xu, Hongya; Lai, Ying-Cheng

2016-01-01

We uncover an alternative mechanism for anomalous Hall effect. In particular, we investigate the magnetisation dynamics of an insulating ferromagnet (FM) deposited on the surface of a three-dimensional topological insulator (TI), subject to an external voltage. The spin-polarised current on the TI surface induces a spin-transfer torque on the magnetisation of the top FM while its dynamics can change the transmission probability of the surface electrons through the exchange coupling and hence the current. We find a host of nonlinear dynamical behaviors including multistability, chaos, and phase synchronisation. Strikingly, a dynamics mediated Hall-like current can arise, which exhibits a nontrivial dependence on the channel conductance. We develop a physical understanding of the mechanism that leads to the anomalous Hall effect. The nonlinear dynamical origin of the effect stipulates that a rich variety of final states exist, implying that the associated Hall current can be controlled to yield desirable behaviors. The phenomenon can find applications in Dirac-material based spintronics. PMID:26819223

Nonlinear dynamics induced anomalous Hall effect in topological insulators.

PubMed

Wang, Guanglei; Xu, Hongya; Lai, Ying-Cheng

2016-01-28

We uncover an alternative mechanism for anomalous Hall effect. In particular, we investigate the magnetisation dynamics of an insulating ferromagnet (FM) deposited on the surface of a three-dimensional topological insulator (TI), subject to an external voltage. The spin-polarised current on the TI surface induces a spin-transfer torque on the magnetisation of the top FM while its dynamics can change the transmission probability of the surface electrons through the exchange coupling and hence the current. We find a host of nonlinear dynamical behaviors including multistability, chaos, and phase synchronisation. Strikingly, a dynamics mediated Hall-like current can arise, which exhibits a nontrivial dependence on the channel conductance. We develop a physical understanding of the mechanism that leads to the anomalous Hall effect. The nonlinear dynamical origin of the effect stipulates that a rich variety of final states exist, implying that the associated Hall current can be controlled to yield desirable behaviors. The phenomenon can find applications in Dirac-material based spintronics.

NASA HERMeS Hall Thruster Electrical Configuration Characterization

NASA Technical Reports Server (NTRS)

Peterson, Peter; Kamhawi, Hani; Huang, Wensheng; Yim, John; Herman, Daniel; Williams, George; Gilland, James; Hofer, Richard

2016-01-01

NASAs Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) Hall thruster has been the subject of extensive technology maturation in preparation for development into a flight ready propulsion system. Part of the technology maturation was to test the TDU-1 thruster in several ground based electrical configurations to assess the thruster robustness and suitability to successful in-space operation. The ground based electrical configuration testing has recently been demonstrated as an important step in understanding and assessing how a Hall thruster may operate differently in space compared to ground based testing, and to determine the best configuration to conduct development and qualification testing. This presentation will cover the electrical configuration testing of the TDU-1 HERMeS Hall thruster in NASA Glenn Research Centers Vacuum Facility 5. The three electrical configurations examined are the thruster body tied to facility ground, thruster floating, and finally the thruster body electrically tied to cathode common. The TDU-1 HERMeS was configured with two different exit plane boundary conditions, dielectric and conducting, to examine the influence on the electrical configuration characterization.

Inverse spin Hall effect by spin injection

NASA Astrophysics Data System (ADS)

Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.

2007-09-01

Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.

Contextual view of ILWU Hall, facing east, with the city ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Contextual view of ILWU Hall, facing east, with the city of Port Hueneme visible in the background - International Longshoremen's & Warehousemen's Union Hall, Naval Civil Engineering Laboratory, Port Hueneme Road, Port Hueneme, Ventura County, CA

G. Stanley Hall and The Journal of Genetic Psychology: A Note.

PubMed

Hogan, John D

2016-01-01

The Journal of Genetic Psychology (originally called The Pedagogical Seminary) has a complicated history. Known primarily as a journal of development psychology, it was originally intended to be a journal of higher education. In addition, G. Stanley Hall created it, at least in part, to curry favor with Jonas Clark, the benefactor of Clark University. The journal had a cumbersome start, with irregular issues for most of its first decade. Hall was a hands-on editor, often contributing articles and reviews as well as the texts of many of his speeches. A substantial number of additional articles were written by Clark University faculty and fellows where Hall was president. After Hall.s death, the editor became Carl Murchison who eventually left Clark University with the journal and continued to publish it privately until his death. Through the years, the journal has been the source for many classic articles in developmental psychology.

Enhanced spin Hall ratios by Al and Hf impurities in Pt thin films

NASA Astrophysics Data System (ADS)

Nguyen, Minh-Hai; Zhao, Mengnan; Ralph, Daniel C.; Buhrman, Robert A.

The spin Hall effect (SHE) in Pt has been reported to be strong and hence promising for spintronic applications. In the intrinsic SHE mechanism, which has been shown to be dominant in Pt, the spin Hall conductivity σSH is constant, dependent only on the band structure of the spin Hall material. The spin Hall ratio θSH =σSH . ρ , on the other hand, should be proportional to the electrical resistivity ρ of the spin Hall layer. This suggests the possibility of enhancing the spin Hall ratio by introducing additional diffusive scattering to increase the electrical resistivity of the spin Hall layer. Our previous work has shown that this could be done by increasing the surface scattering by growing thinner Pt films in contact with higher resistivity materials such as Ta. In this talk, we discuss another approach: to introduce impurities of metals with negligible spin orbit torque into the Pt film. Our PtAl and PtHf alloy samples exhibit strong enhancement of the spin Hall torque efficiency with impurity concentration due to increased electrical resistivity. Supported in part by Samsung Electronics.

Very-Near-Field Plume Model of a Hall Thruster

DTIC Science & Technology

2003-07-20

UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP014988 TITLE: Very-Near-Field Plume Model of a Hall Thruster DISTRIBUTION...numbers comprise the compilation report: ADP014936 thru ADP015049 UNCLASSIFIED am 46 Very-Near-Field Plume Model of a Hall Thruster F. Taccogna’, S. LongoŖ

High Life: 17th Annual Residence Hall Construction Report

ERIC Educational Resources Information Center

Agron, Joe

2006-01-01

Residence hall construction continues to be a priority for colleges and universities. With enrollments on the upswing, higher-education institutions are spending more and building larger facilities to entice students to live on campus. This article presents the findings of "American School & University's" 17th annual Residence Hall Construction…

Tunable-φ Josephson junction with a quantum anomalous Hall insulator

NASA Astrophysics Data System (ADS)

Sakurai, Keimei; Ikegaya, Satoshi; Asano, Yasuhiro

2017-12-01

We theoretically study the Josephson current in a superconductor/quantum anomalous Hall insulator/superconductor junction by using the lattice Green function technique. When an in-plane external Zeeman field is applied to the quantum anomalous Hall insulator, the Josephson current J flows without a phase difference across the junction θ . The phase shift φ appearing in the current-phase relationship J ∝sin(θ -φ ) is proportional to the amplitude of Zeeman fields and depends on the direction of Zeeman fields. A phenomenological analysis of the Andreev reflection processes explains the physical origin of φ . In a quantum anomalous Hall insulator, time-reversal symmetry and mirror-reflection symmetry are broken simultaneously. However, magnetic mirror-reflection symmetry is preserved. Such characteristic symmetry properties enable us to have a tunable φ junction with a quantum Hall insulator.

Hall-effect Thruster Channel Surface Properties Investigation (PREPRINT)

DTIC Science & Technology

2011-03-03

Article 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Hall-effect Thruster Channel Surface Properties Investigation 5b...13. SUPPLEMENTARY NOTES For publication in the AIAA Journal of Propulsion and Power. 14. ABSTRACT Surface properties of Hall-effect thruster...incorporated into thruster simulations, and these models must account for evolution of channel surface properties due to thruster operation. Results from

The Hall Effect in Hydrided Rare Earth Films

NASA Astrophysics Data System (ADS)

Koon, D. W.; Azofeifa, D. E.; Clark, N.

We describe two new techniques for measuring the Hall effect in capped rare earth films during hydriding. In one, we simultaneously measure resistivity and the Hall coefficient for a rare earth film covered with four different thicknesses of Pd, recovering the charge transport quantities for both materials. In the second technique, we replace Pd with Mn as the covering layer. We will present results from both techniques.

Scanning nuclear resonance imaging of a hyperfine-coupled quantum Hall system.

PubMed

Hashimoto, Katsushi; Tomimatsu, Toru; Sato, Ken; Hirayama, Yoshiro

2018-06-07

Nuclear resonance (NR) is widely used to detect and characterise nuclear spin polarisation and conduction electron spin polarisation coupled by a hyperfine interaction. While the macroscopic aspects of such hyperfine-coupled systems have been addressed in most relevant studies, the essential role of local variation in both types of spin polarisation has been indicated in 2D semiconductor systems. In this study, we apply a recently developed local and highly sensitive NR based on a scanning probe to a hyperfine-coupled quantum Hall (QH) system in a 2D electron gas subject to a strong magnetic field. We succeed in imaging the NR intensity and Knight shift, uncovering the spatial distribution of both the nuclear and electron spin polarisation. The results reveal the microscopic origin of the nonequilibrium QH phenomena, and highlight the potential use of our technique in microscopic studies on various electron spin systems as well as their correlations with nuclear spins.

71. FIRST FLOOR, ROOM 101, ENTRANCE HALL (SIDE WITH FIRE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

71. FIRST FLOOR, ROOM 101, ENTRANCE HALL (SIDE WITH FIRE DETECTOR), ARCHWAY TO STAIR HALL 100, LOOKING UP, DETAIL OF ARCHWAY SOFFIT. - Octagon House, 1799 (1741) New York Avenue, Northwest, Washington, District of Columbia, DC

Electron Transport in Hall Thrusters

NASA Astrophysics Data System (ADS)

McDonald, Michael Sean

Despite high technological maturity and a long flight heritage, computer models of Hall thrusters remain dependent on empirical inputs and a large part of thruster development to date has been heavily experimental in nature. This empirical approach will become increasingly unsustainable as new high-power thrusters tax existing ground test facilities and more exotic thruster designs stretch and strain the boundaries of existing design experience. The fundamental obstacle preventing predictive modeling of Hall thruster plasma properties and channel erosion is the lack of a first-principles description of electron transport across the strong magnetic fields between the cathode and anode. In spite of an abundance of proposed transport mechanisms, accurate assessments of the magnitude of electron current due to any one mechanism are scarce, and comparative studies of their relative influence on a single thruster platform simply do not exist. Lacking a clear idea of what mechanism(s) are primarily responsible for transport, it is understandably difficult for the electric propulsion scientist to focus his or her theoretical and computational tools on the right targets. This work presents a primarily experimental investigation of collisional and turbulent Hall thruster electron transport mechanisms. High-speed imaging of the thruster discharge channel at tens of thousands of frames per second reveals omnipresent rotating regions of elevated light emission, identified with a rotating spoke instability. This turbulent instability has been shown through construction of an azimuthally segmented anode to drive significant cross-field electron current in the discharge channel, and suggestive evidence points to its spatial extent into the thruster near-field plume as well. Electron trajectory simulations in experimentally measured thruster electromagnetic fields indicate that binary collisional transport mechanisms are not significant in the thruster plume, and experiments

Evidence of in-plane ferromagnetic order probed by planar Hall effect in the geometry-confined ruthenate S r4R u3O10

NASA Astrophysics Data System (ADS)

Liu, Yan; Yang, Jiyong; Wang, Weike; Du, Haifeng; Ning, Wei; Ling, Langsheng; Tong, Wei; Qu, Zhe; Cao, Gang; Zhang, Yuheng; Tian, Mingliang

2017-04-01

The magnetic structure in the strongly correlated ruthenate S r4R u3O10 has been debated for a long time and still remains elusive. Here, we perform a systematically planar Hall effect study on a single-crystalline S r4R u3O10 nanostripe with a thickness of less than 100 nm. Large sharp switching behavior is observed in the planar Hall resistance, unambiguously indicating a strong anisotropic in-plane ferromagnetic order in the nanostripe, which is in contrast to the bulk system. Temperature-dependent evolution of the in-plane magnetism reveals that the in-plane spin order transforms from a single-domain state below a Curie temperature TC into a multidomain state below a critical temperature TM, probably due to the inherent strong spin-orbit coupling driven reconfiguration of spins between the c axis and the a b plane.

Universal DC Hall conductivity of Jain's state ν = N/2N +/- 1

NASA Astrophysics Data System (ADS)

Nguyen, Dung; Son, Dam

We present the Fermi-liquid theory of the fractional quantum Hall effect to describe Jain's states with filling fraction ν =N/2 N +/- 1 , that are near half filling. We derive the DC Hall conductivity σH (t) in closed form within the validity of our model. The results show that, without long range interaction, DC Hall conductivity has the universal form which doesn't depend on the detail of short range Landau's parameters Fn. When long range interaction is included, DC Hall conductivity depends on both long range interaction and Landau's parameters. We also analyze the relation between DC Hall conductivity and static structure factor. This work was supported by the Chicago MRSEC, which is funded by NSF through Grant DMR-1420709.

Kelvin-Helmholtz versus Hall magnetoshear instability in astrophysical flows.

PubMed

Gómez, Daniel O; Bejarano, Cecilia; Mininni, Pablo D

2014-05-01

We study the stability of shear flows in a fully ionized plasma. Kelvin-Helmholtz is a well-known macroscopic and ideal shear-driven instability. In sufficiently low-density plasmas, also the microscopic Hall magnetoshear instability can take place. We performed three-dimensional simulations of the Hall-magnetohydrodynamic equations where these two instabilities are present, and carried out a comparative study. We find that when the shear flow is so intense that its vorticity surpasses the ion-cyclotron frequency of the plasma, the Hall magnetoshear instability is not only non-negligible, but it actually displays growth rates larger than those of the Kelvin-Helmholtz instability.

Electronic transport in the quantum spin Hall state due to the presence of adatoms in graphene

NASA Astrophysics Data System (ADS)

Lima, Leandro; Lewenkopf, Caio

Heavy adatoms, even at low concentrations, are predicted to turn a graphene sheet into a topological insulator with substantial gap. The adatoms mediate the spin-orbit coupling that is fundamental to the quantum spin Hall effect. The adatoms act as local spin-orbit scatterer inducing hopping processes between distant carbon atoms giving origin to transverse spin currents. Although there are effective models that describe spectral properties of such systems with great detail, quantitative theoretical work for the transport counterpart is still lacking. We developed a multiprobe recursive Green's function technique with spin resolution to analyze the transport properties for large geometries. We use an effective tight-binding Hamiltonian to describe the problem of adatoms randomly placed at the center of the honeycomb hexagons, which is the case for most transition metals. Our choice of current and voltage probes is favorable to experiments since it filters the contribution of only one spin orientation, leading to a quantized spin Hall conductance of e2 / h . We also discuss the electronic propagation in the system by imaging the local density of states and the electronic current densities. The authors acknowledge the Brazilian agencies CNPq, CAPES, FAPERJ and INCT de Nanoestruturas de Carbono for financial support.

68. TURBINE HALL, LOOKING DOWN FROM THE CONTROL ROOM INTO ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

68. TURBINE HALL, LOOKING DOWN FROM THE CONTROL ROOM INTO TURBINE HALL AT UNITS 3, 5, AND 2) - Delaware County Electric Company, Chester Station, Delaware River at South end of Ward Street, Chester, Delaware County, PA

Residence Hall Discipline as a Function of Personality Type.

ERIC Educational Resources Information Center

Williams, W. C.; Nelson, Susan Innmon

1986-01-01

Administered personality measures to residence hall personnel (N=48) to test assertive, nonassertive, or hostile responses to describe residence hall disciplinary situations. Found that not all personnel were well suited to college student disciplining and that the personality tests could be used to identify individuals who may be best suited for…

Implementing Proactive Network Management Solutions in the Residence Halls

ERIC Educational Resources Information Center

Bedi, Param

2005-01-01

This paper discusses how to implement networking solutions in residence halls at Arcadia University in Philadelphia. Sections of the paper include: (1) About Arcadia University; (2) Residence Halls Network; (3) How Campus Manager Helped Arcadia University; (4) What Is Campus Manager; (5) How Campus Manager Works; (6) Campus Manager Remediation…

An End-to-End Model of a Hall Thruster

DTIC Science & Technology

2000-09-01

and deposition of sputtered material, simulation of the operator of a Hall Thruster in a vacuum tank and the extension to the near-plume of a...sophisticated Hall thruster transient hybrid PlC model which had been previously used only to describe the internal flow. The first two items have been

The ``cinquefoil" resistive/Hall measurement geometry

NASA Astrophysics Data System (ADS)

Koon, Daniel W.

2000-03-01

This talk begins by analyzing the charge transport weighting functions -- the sensitivity of resistive and Hall measurements to local macroscopic inhomogeneities -- of bridge-shaped transport specimens. As expected, such measurements sample only that region of the specimen between the central voltage electrodes, in the limit of narrow current channels connected by even narrower arms to the voltage electrodes. The bridge geometry has a few advantages over the van der Pauw cloverleaf geometry -- including ease in zeroing out the null-field Hall voltage -- but also some disadvantages. The talk concludes with an analysis of a hybrid geometry, the “cinquefoil” or five-leafed clover, which combines the best features of both.

High Performance Power Module for Hall Effect Thrusters

NASA Technical Reports Server (NTRS)

Pinero, Luis R.; Peterson, Peter Y.; Bowers, Glen E.

2002-01-01

Previous efforts to develop power electronics for Hall thruster systems have targeted the 1 to 5 kW power range and an output voltage of approximately 300 V. New Hall thrusters are being developed for higher power, higher specific impulse, and multi-mode operation. These thrusters require up to 50 kW of power and a discharge voltage in excess of 600 V. Modular power supplies can process more power with higher efficiency at the expense of complexity. A 1 kW discharge power module was designed, built and integrated with a Hall thruster. The breadboard module has a power conversion efficiency in excess of 96 percent and weighs only 0.765 kg. This module will be used to develop a kW, multi-kW, and high voltage power processors.

Interior view, groundfloor dining hall extending across the rotunda extension ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior view, ground-floor dining hall extending across the rotunda extension from it's northern exterior wall to its southern exterior wall, from the north. - U. S. Naval Asylum, Biddle Hall, Gray's Ferry Avenue, Philadelphia, Philadelphia County, PA

Suitable reverberation times for halls for rock and pop music.

PubMed

Adelman-Larsen, Niels Werner; Thompson, Eric R; Gade, Anders C

2010-01-01

The existing body of literature regarding the acoustic design of concert halls has focused almost exclusively on classical music, although there are many more performances of popular music, including rock and pop. Objective measurements were made of the acoustics of 20 rock music venues in Denmark and a questionnaire was used in a subjective assessment of those venues with professional rock musicians and sound engineers as expert listeners. Correlations between the measurements show that clarity, including bass frequencies down to 63 Hz, is important for the general impression of the acoustics of the hall. The best-rated halls in the study have reverberation times that are approximately frequency independent from 0.6 to 1.2 s for hall volumes from 1000 to 6000 m(3). The worst rated halls in the study had significantly higher reverberation times in the 63 and 125 Hz bands. Since most audiences at rock concerts are standing, absorption coefficients were measured with a standing audience from 63 Hz to 4 kHz. These measurements showed that a standing audience absorbs about five times as much energy in mid-/high-frequency bands as in low-frequency bands.

Coupling intensity between discharge and magnetic circuit in Hall thrusters

NASA Astrophysics Data System (ADS)

Wei, Liqiu; Yang, Xinyong; Ding, Yongjie; Yu, Daren; Zhang, Chaohai

2017-03-01

Coupling oscillation is a newly discovered plasma oscillation mode that utilizes the coupling between the discharge circuit and magnetic circuit, whose oscillation frequency spectrum ranges from several kilohertz to megahertz. The coupling coefficient parameter represents the intensity of coupling between the discharge and magnetic circuits. According to previous studies, the coupling coefficient is related to the material and the cross-sectional area of the magnetic coils, and the magnetic circuit of the Hall thruster. However, in our recent study on coupling oscillations, it was found that the Hall current equivalent position and radius have important effects on the coupling intensity between the discharge and magnetic circuits. This causes a difference in the coupling coefficient for different operating conditions of Hall thrusters. Through non-intrusive methods for measuring the Hall current equivalent radius and the axial position, it is found that with an increase in the discharge voltage and magnetic field intensity, the Hall current equivalent radius increases and its axial position moves towards the exit plane. Thus, both the coupling coefficient and the coupling intensity between the discharge and magnetic circuits increase. Contribution to the Topical Issue "Physics of Ion Beam Sources", edited by Holger Kersten and Horst Neumann.

Low-Cost, High-Performance Hall Thruster Support System

NASA Technical Reports Server (NTRS)

Hesterman, Bryce

2015-01-01

Colorado Power Electronics (CPE) has built an innovative modular PPU for Hall thrusters, including discharge, magnet, heater and keeper supplies, and an interface module. This high-performance PPU offers resonant circuit topologies, magnetics design, modularity, and a stable and sustained operation during severe Hall effect thruster current oscillations. Laboratory testing has demonstrated discharge module efficiency of 96 percent, which is considerably higher than current state of the art.

The Hall-induced stability of gravitating fluids

NASA Astrophysics Data System (ADS)

Karmakar, P. K.; Goutam, H. P.

2018-05-01

We analyze the stability behavior of low-density partially ionized self-gravitating magnetized unbounded dusty plasma fluid in the presence of the Hall diffusion effects (HDEs) in the non-ideal magnetohydrodynamic (MHD) equilibrium framework. The effects of inhomogeneous self-gravity are methodically included in the basic model tapestry. Application of the Fourier plane-wave perturbative treatment decouples the structuration representative parameters into a linear generalized dispersion relation (sextic) in a judicious mean-fluid approximation. The dispersion analysis shows that the normal mode, termed as the gravito-magneto-acoustic (GMA) mode, is drastically modified due to the HDEs. This mode is highly dispersive, and driven unstable by the Hall current resulting from the symmetry-breaking of electrons and ions relative to the magnetic field. The mode feature, which is derived from a modified induction with the positive Hall, is against the ideal MHD. It is further demonstrated that the HDEs play stabilizing roles by supporting the cloud against gravitational collapse. Provided that the HDEs are concurrently switched off, the collapse occurs on the global spatial scale due to enhanced inward accretion of the gravitating dust constituents. It is seen explicitly that the enhanced dust-charge leads to stabilizing effects. Besides, the Hall-induced fluctuations, as propagatory wave modes, exhibit both normal and anomalous dispersions. The reliability checkup of the entailed results as diverse corollaries and special cases are illustratively discussed in the panoptic light of the earlier paradigmatic predictions available in the literature.

A Small Modular Laboratory Hall Effect Thruster

NASA Astrophysics Data System (ADS)

Lee, Ty Davis

Electric propulsion technologies promise to revolutionize access to space, opening the door for mission concepts unfeasible by traditional propulsion methods alone. The Hall effect thruster is a relatively high thrust, moderate specific impulse electric propulsion device that belongs to the class of electrostatic thrusters. Hall effect thrusters benefit from an extensive flight history, and offer significant performance and cost advantages when compared to other forms of electric propulsion. Ongoing research on these devices includes the investigation of mechanisms that tend to decrease overall thruster efficiency, as well as the development of new techniques to extend operational lifetimes. This thesis is primarily concerned with the design and construction of a Small Modular Laboratory Hall Effect Thruster (SMLHET), and its operation on argon propellant gas. Particular attention was addressed at low-cost, modular design principles, that would facilitate simple replacement and modification of key thruster parts such as the magnetic circuit and discharge channel. This capability is intended to facilitate future studies of device physics such as anomalous electron transport and magnetic shielding of the channel walls, that have an impact on thruster performance and life. Preliminary results demonstrate SMLHET running on argon in a manner characteristic of Hall effect thrusters, additionally a power balance method was utilized to estimate thruster performance. It is expected that future thruster studies utilizing heavier though more expensive gases like xenon or krypton, will observe increased efficiency and stability.

Throttling Impacts on Hall Thruster Performance, Erosion, and Qualification for NASA Science Missions

NASA Technical Reports Server (NTRS)

Dankanich, John W.; DeHoyos, Amado

2007-01-01

With the SMART-1, Department of Defense, and commercial industry successes in Hall thruster technologies, NASA has started considering Hall thrusters for science missions. The recent Discovery proposals included a Hall thruster science mission and the In-Space Propulsion Project is investing in Hall thruster technologies. As the confidence in Hall thrusters improve, ambitious multi-thruster missions are being considered. Science missions often require large throttling ranges due to the 1/r(sup 2) power drop-off from the sun. Deep throttling of Hall thrusters will impact the overall system performance. Also, Hall thrusters can be throttled with both current and voltage, impacting erosion rates and performance. Last, electric propulsion thruster lifetime qualification has previously been conducted with long duration full power tests. Full power tests may not be appropriate for NASA science missions, and a combination of lifetime testing at various power levels with sufficient analysis is recommended. Analyses of various science missions and throttling schemes using the Aerojet BPT-4000 and NASA 103M HiVHAC thruster are presented.

3D Quantum Hall Effect of Fermi Arc in Topological Semimetals

NASA Astrophysics Data System (ADS)

Wang, C. M.; Sun, Hai-Peng; Lu, Hai-Zhou; Xie, X. C.

2017-09-01

The quantum Hall effect is usually observed in 2D systems. We show that the Fermi arcs can give rise to a distinctive 3D quantum Hall effect in topological semimetals. Because of the topological constraint, the Fermi arc at a single surface has an open Fermi surface, which cannot host the quantum Hall effect. Via a "wormhole" tunneling assisted by the Weyl nodes, the Fermi arcs at opposite surfaces can form a complete Fermi loop and support the quantum Hall effect. The edge states of the Fermi arcs show a unique 3D distribution, giving an example of (d -2 )-dimensional boundary states. This is distinctly different from the surface-state quantum Hall effect from a single surface of topological insulator. As the Fermi energy sweeps through the Weyl nodes, the sheet Hall conductivity evolves from the 1 /B dependence to quantized plateaus at the Weyl nodes. This behavior can be realized by tuning gate voltages in a slab of topological semimetal, such as the TaAs family, Cd3 As2 , or Na3Bi . This work will be instructive not only for searching transport signatures of the Fermi arcs but also for exploring novel electron gases in other topological phases of matter.

12. BUILDING 324, INTERIOR, ENTRY HALL AND STAIRWAY, FROM SOUTH ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

12. BUILDING 324, INTERIOR, ENTRY HALL AND STAIRWAY, FROM SOUTH ENTRY, LOOKING NORTH, WITH HALL LEADING TO GARAGE TO RIGHT OF STAIRWAY. - Oakland Naval Supply Center, Commanding Officers Residences, Between E & F Streets, West of Fourth Street, Oakland, Alameda County, CA

24. BEDROOM #1 INTERIOR SHOWING OPEN DOOR TO HALL WITH ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

24. BEDROOM #1 INTERIOR SHOWING OPEN DOOR TO HALL WITH HALL LINEN CLOSETS VISIBLE IN BACKGROUND, AND PARTIALLY OPEN DOOR TO CLOSET. VIEW TO EAST. - Big Creek Hydroelectric System, Powerhouse 8, Operator Cottage, Big Creek, Big Creek, Fresno County, CA

Mary E. Hall: Dawn of the Professional School Librarian

ERIC Educational Resources Information Center

Alto, Teresa

2012-01-01

A century ago, a woman named Mary E. Hall convinced school leaders of the need for the professional school librarian--a librarian who cultivated a love of reading, academic achievement, and independent learning skills. After graduating from New York City's Pratt Institute Library School in 1895, Hall developed her vision for the high school…

Hall Thruster With an External Acceleration Zone

DTIC Science & Technology

2005-09-14

Hall Thruster in a high vacuum environment. The ionized propellant velocities were measured using laser induced fluorescence of the excited state xenon ionic transition at 834.7 nm. Ion velocities were interrogated from the channel exit plane to a distance 30 mm from it. Both axial and cross-field (along the electron Hall current direction) velocities were measured. The results presented here, combined with those of previous work, highlight the high sensitivity of electron mobility inside and outside the channel, depending on the background gas density, type of wall

Quantum spin Hall phase in 2D trigonal lattice

DOE PAGES

Wang, Z. F.; Jin, Kyung -Hwan; Liu, Feng

2016-09-07

The quantum spin Hall (QSH) phase is an exotic phenomena in condensed-matter physics. Here we show that a minimal basis of three orbitals (s, p x, p y) is required to produce a QSH phase via nearest-neighbour hopping in a two-dimensional trigonal lattice. Tight-binding model analyses and calculations show that the QSH phase arises from a spin–orbit coupling (SOC)-induced s–p band inversion or p–p bandgap opening at Brillouin zone centre (Γ point), whose topological phase diagram is mapped out in the parameter space of orbital energy and SOC. Remarkably, based on first-principles calculations, this exact model of QSH phase ismore » shown to be realizable in an experimental system of Au/GaAs(111) surface with an SOC gap of ~73 meV, facilitating the possible room-temperature measurement. Finally, our results will extend the search for substrate supported QSH materials to new lattice and orbital types.« less

Quantum spin Hall phase in 2D trigonal lattice

PubMed Central

Wang, Z. F.; Jin, Kyung-Hwan; Liu, Feng

2016-01-01

The quantum spin Hall (QSH) phase is an exotic phenomena in condensed-matter physics. Here we show that a minimal basis of three orbitals (s, px, py) is required to produce a QSH phase via nearest-neighbour hopping in a two-dimensional trigonal lattice. Tight-binding model analyses and calculations show that the QSH phase arises from a spin–orbit coupling (SOC)-induced s–p band inversion or p–p bandgap opening at Brillouin zone centre (Γ point), whose topological phase diagram is mapped out in the parameter space of orbital energy and SOC. Remarkably, based on first-principles calculations, this exact model of QSH phase is shown to be realizable in an experimental system of Au/GaAs(111) surface with an SOC gap of ∼73 meV, facilitating the possible room-temperature measurement. Our results will extend the search for substrate supported QSH materials to new lattice and orbital types. PMID:27599580

First Firing of a 100-kW Nested-Channel Hall Thruster

DTIC Science & Technology

2013-09-01

Technical Paper 3. DATES COVERED (From - To) September 2013- December 2013 4. TITLE AND SUBTITLE First Firing of a 100-kW Nested-Channel Hall Thruster 5a...STATEMENT A: Approved for public release; distribution unlimited. 1 First Firing of a 100-kW Nested-channel Hall Thruster IEPC-2013-394...converting electrical power to directed kinetic power I. Introduction ESTING the channels of Hall thrusters has proven to be a viable method to increase

Judy Estes Hall (1940-2015).

PubMed

Sammons, Morgan T; Boucher, Andrew

2016-01-01

Presents an obituary for Judy Estes Hall, who passed away on November 24, 2015. Hall served as the Executive Officer of the National Register of Health Service Psychologists until her retirement in 2013. She is a recognized expert in the development of education and training standards for the profession of psychology, she also made significant contributions in the field of international psychology, where she was a renowned expert in cross-national credentialing and an advocate for commonality in licensing standards. She was the coauthor of one edited volume and author of more than 60 journal articles, book chapters, and professional publications. A passionate advocate for the advancement of women in psychology, a devoted mother and grandmother, a connoisseur of wine and international traveler extraordinaire, she touched the personal and professional lives of many. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Electron dynamics in Hall thruster

NASA Astrophysics Data System (ADS)

Marini, Samuel; Pakter, Renato

2015-11-01

Hall thrusters are plasma engines those use an electromagnetic fields combination to confine electrons, generate and accelerate ions. Widely used by aerospace industries those thrusters stand out for its simple geometry, high specific impulse and low demand for electric power. Propulsion generated by those systems is due to acceleration of ions produced in an acceleration channel. The ions are generated by collision of electrons with propellant gas atoms. In this context, we can realize how important is characterizing the electronic dynamics. Using Hamiltonian formalism, we derive the electron motion equation in a simplified electromagnetic fields configuration observed in hall thrusters. We found conditions those must be satisfied by electromagnetic fields to have electronic confinement in acceleration channel. We present configurations of electromagnetic fields those maximize propellant gas ionization and thus make propulsion more efficient. This work was supported by CNPq.

Redistributing Chern numbers and quantum Hall transitions in multi-band lattices

NASA Astrophysics Data System (ADS)

Yu, H. L.; Zhai, Z. Y.; Jiang, C.

2018-07-01

We numerically study the integer quantum Hall effect (IQHE) on m-band lattices. With continuous modulating the next-nearest-neighbor hopping integral t' , it is found that the full band is divided into 2 m - 1 regions. There are m - 1 critical regions with pseudogaps induced by the merging between the two adjacent subbands, where both Chern numbers of the correlating Landau subbands and the corresponding Hall plateau are not well-defined. The other m regions with different well-defined Chern numbers are separated by the above m - 1 critical regions. Due to the redistributing Chern numbers of system induced by the merging of subbands, the Hall conductance exhibits a peculiar phase transition, which is characterized by the direct change of Hall plateau state.

Effect of azimuthal diversion rail on an ATON-type Hall thruster

NASA Astrophysics Data System (ADS)

Xu, Zhang; Liqiu, Wei; Liang, Han; Yongjie, Ding; Daren, Yu

2017-03-01

A newly designed azimuthal diversion rail (ADR) is studied and used to enhance the ionization process in an ATON-type Hall thruster. The diversion rail efficiently reduces the neutral flow axial velocity, and hence, increases the resistance time of atoms in the discharge channel of the Hall thruster. Thrust performances, in terms of thrust, anode efficiency and ion beam divergence, are found to be improved because of the application of the diversion rail, especially at low mass flow rate conditions. Experiment results reveal that the ADR increases the mass utilization under insufficient mass flow rate operating conditions. The design of the ADR broadens the efficient operating range of Hall thrusters and has significant contribution to multi-mode Hall thruster development.

Concert halls with strong lateral reflections enhance musical dynamics.

PubMed

Pätynen, Jukka; Tervo, Sakari; Robinson, Philip W; Lokki, Tapio

2014-03-25

One of the most thrilling cultural experiences is to hear live symphony-orchestra music build up from a whispering passage to a monumental fortissimo. The impact of such a crescendo has been thought to depend only on the musicians' skill, but here we show that interactions between the concert-hall acoustics and listeners' hearing also play a major role in musical dynamics. These interactions contribute to the shoebox-type concert hall's established success, but little prior research has been devoted to dynamic expression in this three-part transmission chain as a complete system. More forceful orchestral playing disproportionately excites high frequency harmonics more than those near the note's fundamental. This effect results in not only more sound energy, but also a different tone color. The concert hall transmits this sound, and the room geometry defines from which directions acoustic reflections arrive at the listener. Binaural directional hearing emphasizes high frequencies more when sound arrives from the sides of the head rather than from the median plane. Simultaneously, these same frequencies are emphasized by higher orchestral-playing dynamics. When the room geometry provides reflections from these directions, the perceived dynamic range is enhanced. Current room-acoustic evaluation methods assume linear behavior and thus neglect this effect. The hypothesis presented here is that the auditory excitation by reflections is emphasized with an orchestra forte most in concert halls with strong lateral reflections. The enhanced dynamic range provides an explanation for the success of rectangularly shaped concert-hall geometry.

Magnetotransport properties of 8-Pmmn borophene: effects of Hall field and strain.

PubMed

Islam, S K Firoz

2018-07-11

The polymorph of 8-Pmmn borophene is an anisotropic Dirac material with tilted Dirac cones at two valleys. The tilting of the Dirac cones at two valleys are in opposite directions, which manifests itself via the valley dependent Landau levels in presence of an in-plane electric field (Hall field). The valley dependent Landau levels cause valley polarized magnetotransport properties in presence of the Hall field, which is in contrast to the monolayer graphene with isotropic non-tilted Dirac cones. The longitudinal conductivity and Hall conductivity are evaluated by using linear response theory in low temperature regime. An analytical approximate form of the longitudinal conductivity is also obtained. It is observed that the tilting of the Dirac cones amplifies the frequency of the longitudinal conductivity oscillation (Shubnikov-de Haas). On the other hand, the Hall conductivity exhibits graphene-like plateaus except the appearance of valley dependent steps which are purely attributed to the Hall field induced lifting of the valley degeneracy in the Landau levels. Finally we look into the different cases when the Hall field is applied to the strained borophene and find that valley dependency is fully dominated by strain rather than Hall field. Another noticeable point is that if the real magnetic field is replaced by the strain induced pseudo magnetic field then the electric field looses its ability to cause valley polarized transport.

Modeling an anode layer Hall thruster and its plume

NASA Astrophysics Data System (ADS)

Choi, Yongjun

This thesis consists of two parts: a study of the D55 Hall thruster channel using a hydrodynamic model; and particle simulations of plasma plume flow from the D55 Hall thruster. The first part of this thesis investigates the xenon plasma properties within the D55 thruster channel using a hydrodynamic model. The discharge voltage (V) and current (I) characteristic of the D55 Hall thruster are studied. The hydrodynamic model fails to accurately predict the V-I characteristics. This analysis shows that the model needs to be improved. Also, the hydrodynamic model is used to simulate the plasma flow within the D55 Hall thruster. This analysis is performed to investigate the plasma properties of the channel exit. It is found that the hydrodynamic model is very sensitive to initial conditions, and fails to simulate the complete domain of the D55 Hall thruster. However, the model successfully calculates the channel domain of the D55 Hall thruster. The results show that, at the thruster exit, the plasma density has a maximum value while the ion velocity has a minimum at the channel center. Also, the results show that the flow angle varies almost linearly across the exit plane and increases from the center to the walls. Finally, the hydrodynamic model results are used to estimate the plasma properties at the thruster nozzle exit. The second part of the thesis presents two dimensional axisymmetric simulations of xenon plasma plume flow fields from the D55 anode layer Hall thruster. A hybrid particle-fluid method is used for the simulations. The magnetic field near the Hall thruster exit is included in the calculation. The plasma properties obtained from the hydrodynamic model are used to determine boundary conditions for the simulations. In these simulations, the Boltzmann model and a detailed fluid model are used to compute the electron properties, the direct simulation Monte Carlo method models the collisions of heavy particles, and the Particle-In-Cell method models the

Contextual view of the Hall of Transportation from Yerba Buena ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Contextual view of the Hall of Transportation from Yerba Buena Island, showing Palace of Fine and Decorative Arts (Building 3) at far right, camera facing northwest - Golden Gate International Exposition, Hall of Transportation, 440 California Avenue, Treasure Island, San Francisco, San Francisco County, CA

Spin-hall-active platinum thin films grown via atomic layer deposition

NASA Astrophysics Data System (ADS)

Schlitz, Richard; Amusan, Akinwumi Abimbola; Lammel, Michaela; Schlicht, Stefanie; Tynell, Tommi; Bachmann, Julien; Woltersdorf, Georg; Nielsch, Kornelius; Goennenwein, Sebastian T. B.; Thomas, Andy

2018-06-01

We study the magnetoresistance of yttrium iron garnet/Pt heterostructures in which the Pt layer was grown via atomic layer deposition (ALD). Magnetotransport experiments in three orthogonal rotation planes reveal the hallmark features of spin Hall magnetoresistance. To estimate the spin transport parameters, we compare the magnitude of the magnetoresistance in samples with different Pt thicknesses. We check the spin Hall angle and the spin diffusion length of the ALD Pt layers against the values reported for high-quality sputter-deposited Pt films. The spin diffusion length of 1.5 nm agrees well with that of platinum thin films reported in the literature, whereas the spin Hall magnetoresistance Δ ρ / ρ = 2.2 × 10 - 5 is approximately a factor of 20 smaller compared to that of our sputter-deposited films. Our results demonstrate that ALD allows fabricating spin-Hall-active Pt films of suitable quality for use in spin transport structures. This work provides the basis to establish conformal ALD coatings for arbitrary surface geometries with spin-Hall-active metals and could lead to 3D spintronic devices in the future.

Macroscopic Quantum Phase-Locking Model for the Quantum Hall = Effect

NASA Astrophysics Data System (ADS)

Wang, Te-Chun; Gou, Yih-Shun

1997-08-01

A macroscopic model of nonlinear dissipative phase-locking between a Josephson-like frequency and a macroscopic electron wave frequency is proposed to explain the Quantum Hall Effect. It is well known that a r.f-biased Josephson junction displays a collective phase-locking behavior which can be described by a non-autonomous second order equation or an equivalent 2+1-dimensional dynamical system. Making a direct analogy between the QHE and the Josephson system, this report proposes a computer-solving nonlinear dynamical model for the quantization of the Hall resistance. In this model, the Hall voltage is assumed to be proportional to a Josephson-like frequency and the Hall current is assumed related to a coherent electron wave frequency. The Hall resistance is shown to be quantized in units of the fine structure constant as the ratio of these two frequencies are locked into a rational winding number. To explain the sample-width dependence of the critical current, the 2DEG under large applied current is further assumed to develop a Josephson-like junction array in which all Josephson-like frequencies are synchronized. Other remarkable features of the QHE such as the resistance fluctuation and the even-denominator states are also discussed within this picture.

Pair spectrometer hodoscope for Hall D at Jefferson Lab

DOE PAGES

Barbosa, Fernando J.; Hutton, Charles L.; Sitnikov, Alexandre; ...

2015-09-21

We present the design of the pair spectrometer hodoscope fabricated at Jefferson Lab and installed in the experimental Hall D. The hodoscope consists of thin scintillator tiles; the light from each tile is collected using wave-length shifting fibers and detected using a Hamamatsu silicon photomultiplier. Light collection was measured using relativistic electrons produced in the tagger area of the experimental Hall B.

Pair spectrometer hodoscope for Hall D at Jefferson Lab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barbosa, Fernando J.; Hutton, Charles L.; Sitnikov, Alexandre

We present the design of the pair spectrometer hodoscope fabricated at Jefferson Lab and installed in the experimental Hall D. The hodoscope consists of thin scintillator tiles; the light from each tile is collected using wave-length shifting fibers and detected using a Hamamatsu silicon photomultiplier. Light collection was measured using relativistic electrons produced in the tagger area of the experimental Hall B.

Admittance of multiterminal quantum Hall conductors at kilohertz frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernández, C.; Consejo, C.; Chaubet, C., E-mail: christophe.chaubet@univ-montp2.fr

2014-03-28

We present an experimental study of the low frequency admittance of quantum Hall conductors in the [100 Hz, 1 MHz] frequency range. We show that the frequency dependence of the admittance of the sample strongly depends on the topology of the contacts connections. Our experimental results are well explained within the Christen and Büttiker approach for finite frequency transport in quantum Hall edge channels taking into account the influence of the coaxial cables capacitance. In the Hall bar geometry, we demonstrate that there exists a configuration in which the cable capacitance does not influence the admittance measurement of the sample. In thismore » case, we measure the electrochemical capacitance of the sample and observe its dependence on the filling factor.« less

Modeling a Hall Thruster from Anode to Plume Far Field

DTIC Science & Technology

2008-12-31

Two dimensional ax symmetric simulations of xenon plasma plume flow fields from a D55 Anode layer Hall thruster is performed. A hybrid particle-fluid...method is used for the Simulations. The magnetic field surrounding the Hall thruster exit is included in the Calculation. The plasma properties

Farfield Plume Measurement and Analysis on the NASA-300M

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Shastry, Rohit; Soulas, George C.; Kamhawi, Hani

2013-01-01

NASA is developing a 15-kW Hall thruster to support future NASA missions. This activity is funded under the Space Technology Mission Directorate Solar Electric Propulsion Technology Demonstration project. As a part of the development process, the far-field plume characteristics of the NASA-300M, a 20-kW Hall thruster, were studied. The results will be used to study how various aspects of the operation of this thruster affect the overall performance. This data will be used to guide future design work and serve as a baseline for comparison to a magnetically shielded version of the NASA-300M that will be tested in the future. For this study, a far-field Faraday probe was swept in a polar fashion to map the ion current density. An ExB probe (Wien filter), two retarding potential analyzers, and a Langmuir probe were mounted at a fixed location on the thruster axis in the far-field plume. The data reduction method followed recommendations in recent studies by Brown, Reid, and Shastry with modifications that are tailored to the plasma plume environment of high-power Hall thrusters. Results from this and prior testing show that the plume is richer in doubly-charged ions, larger in spatial extent, and capable of greater probe heating than lower power thrusters. These characteristics require special treatment in experimental setup and data analysis, which will be the main focus of this paper. In particular, covered topics will include a new, more accurate, method of integration for analysis of the ExB probe data and effect of secondary electron emission on the Faraday probe data.

A highly sensitive CMOS digital Hall sensor for low magnetic field applications.

PubMed

Xu, Yue; Pan, Hong-Bin; He, Shu-Zhuan; Li, Li

2012-01-01

Integrated CMOS Hall sensors have been widely used to measure magnetic fields. However, they are difficult to work with in a low magnetic field environment due to their low sensitivity and large offset. This paper describes a highly sensitive digital Hall sensor fabricated in 0.18 μm high voltage CMOS technology for low field applications. The sensor consists of a switched cross-shaped Hall plate and a novel signal conditioner. It effectively eliminates offset and low frequency 1/f noise by applying a dynamic quadrature offset cancellation technique. The measured results show the optimal Hall plate achieves a high current related sensitivity of about 310 V/AT. The whole sensor has a remarkable ability to measure a minimum ± 2 mT magnetic field and output a digital Hall signal in a wide temperature range from -40 °C to 120 °C.

Observations of Hall Reconnection Physics Far Downstream of the X Line.

PubMed

Mistry, R; Eastwood, J P; Haggerty, C C; Shay, M A; Phan, T D; Hietala, H; Cassak, P A

2016-10-28

Observations made using the Wind spacecraft of Hall magnetic fields in solar wind reconnection exhausts are presented. These observations are consistent with the generation of Hall fields by a narrow ion inertial scale current layer near the separatrix, which is confirmed with an appropriately scaled particle-in-cell simulation that shows excellent agreement with observations. The Hall fields are observed thousands of ion inertial lengths downstream from the reconnection X line, indicating that narrow regions of kinetic dynamics can persist extremely far downstream.

1000 Hours of Testing Completed on 10-kW Hall Thruster

NASA Technical Reports Server (NTRS)

Mason, Lee S.

2001-01-01

Between the months of April and August 2000, a 10-kW Hall effect thruster, designated T- 220, was subjected to a 1000-hr life test evaluation. Hall effect thrusters are propulsion devices that electrostatically accelerate xenon ions to produce thrust. Hall effect propulsion has been in development for many years, and low-power devices (1.35 kW) have been used in space for satellite orbit maintenance. The T-220, shown in the photo, produces sufficient thrust to enable efficient orbital transfers, saving hundreds of kilograms in propellant over conventional chemical propulsion systems. This test is the longest operation ever achieved on a high-power Hall thruster (greater than 4.5 kW) and is a key milestone leading to the use of this technology for future NASA, commercial, and military missions.

Hall effect on magnetohydrodynamic instabilities at an elliptic magnetic stagnation line

NASA Astrophysics Data System (ADS)

Spies, Günther O.; Faghihi, Mustafa

1987-06-01

To answer the question whether the Hall effect removes the unphysical feature of ideal magnetohydrodynamics of predicting small wavelength kink instabilities at any elliptic magnetic stagnation line, a normal mode analysis is performed of the motion of an incompressible Hall fluid about cylindrical Z-pinch equilibria with circular cross sections. The eigenvalue loci in the complex frequency plane are derived for the equilibrium with constant current density. Every particular mode becomes stable as the Hall parameter exceeds a critical value. This value, however, depends on the mode such that it increases to infinity as the ideal growth rate decreases to zero, implying that there always remains an infinite number of slowly growing instabilities. Correspondingly, the stability criterion for equilibria with arbitrary current distributions is independent of the Hall parameter.

Quantum Hall effect in graphene with interface-induced spin-orbit coupling

NASA Astrophysics Data System (ADS)

Cysne, Tarik P.; Garcia, Jose H.; Rocha, Alexandre R.; Rappoport, Tatiana G.

2018-02-01

We consider an effective model for graphene with interface-induced spin-orbit coupling and calculate the quantum Hall effect in the low-energy limit. We perform a systematic analysis of the contribution of the different terms of the effective Hamiltonian to the quantum Hall effect (QHE). By analyzing the spin splitting of the quantum Hall states as a function of magnetic field and gate voltage, we obtain different scaling laws that can be used to characterize the spin-orbit coupling in experiments. Furthermore, we employ a real-space quantum transport approach to calculate the quantum Hall conductivity and investigate the robustness of the QHE to disorder introduced by hydrogen impurities. For that purpose, we combine first-principles calculations and a genetic algorithm strategy to obtain a graphene-only Hamiltonian that models the impurity.

Particle-in-cell simulations of Hall plasma thrusters

NASA Astrophysics Data System (ADS)

Miranda, Rodrigo; Ferreira, Jose Leonardo; Martins, Alexandre

2016-07-01

Hall plasma thrusters can be modelled using particle-in-cell (PIC) simulations. In these simulations, the plasma is described by a set of equations which represent a coupled system of charged particles and electromagnetic fields. The fields are computed using a spatial grid (i.e., a discretization in space), whereas the particles can move continuously in space. Briefly, the particle and fields dynamics are computed as follows. First, forces due to electric and magnetic fields are employed to calculate the velocities and positions of particles. Next, the velocities and positions of particles are used to compute the charge and current densities at discrete positions in space. Finally, these densities are used to solve the electromagnetic field equations in the grid, which are interpolated at the position of the particles to obtain the acting forces, and restart this cycle. We will present numerical simulations using software for PIC simulations to study turbulence, wave and instabilities that arise in Hall plasma thrusters. We have sucessfully reproduced a numerical simulation of a SPT-100 Hall thruster using a two-dimensional (2D) model. In addition, we are developing a 2D model of a cylindrical Hall thruster. The results of these simulations will contribute to improve the performance of plasma thrusters to be used in Cubesats satellites currenty in development at the Plasma Laboratory at University of Brasília.

Novel geometry for simultaneous resistive, Hall and optical measurement of MgHx thin films

NASA Astrophysics Data System (ADS)

Koon, D. W.; Griffin, C. C. W.; Ares, J. R.; Leardini, F.; Sanchez, C.

2009-03-01

We describe a novel specimen geometry we have used to simultaneously probe optical transmission, sheet resistance and sheet Hall resistance in 100nm Mg films during hydrogen absorption. A Mg-film cloverleaf overlaps four rectangular Pd pads at the corners of a glass slide, a variation on a two-pad geometry used by Ingason and Olafsson for resistive studies of Pd-capped MgHx films [J. Alloys and Compounds 404- 406 (2005), 469-72.]. Hydrogen diffuses laterally through the Pd pads before entering the magnesium layer from below. The sample holder also includes an LED-photodiode pair for measuring [monochromatic] optical transmission. We show that the simultaneous measurement of these three quantities during the metal-to-insulator transition in a hydriding MgHx film allows for a more complete understanding of the hydriding process in these films.

Observation of the fractional quantum Hall effect in graphene.

PubMed

Bolotin, Kirill I; Ghahari, Fereshte; Shulman, Michael D; Stormer, Horst L; Kim, Philip

2009-11-12

When electrons are confined in two dimensions and subject to strong magnetic fields, the Coulomb interactions between them can become very strong, leading to the formation of correlated states of matter, such as the fractional quantum Hall liquid. In this strong quantum regime, electrons and magnetic flux quanta bind to form complex composite quasiparticles with fractional electronic charge; these are manifest in transport measurements of the Hall conductivity as rational fractions of the elementary conductance quantum. The experimental discovery of an anomalous integer quantum Hall effect in graphene has enabled the study of a correlated two-dimensional electronic system, in which the interacting electrons behave like massless chiral fermions. However, owing to the prevailing disorder, graphene has so far exhibited only weak signatures of correlated electron phenomena, despite intense experimental and theoretical efforts. Here we report the observation of the fractional quantum Hall effect in ultraclean, suspended graphene. In addition, we show that at low carrier density graphene becomes an insulator with a magnetic-field-tunable energy gap. These newly discovered quantum states offer the opportunity to study correlated Dirac fermions in graphene in the presence of large magnetic fields.

Quantum Hall physics: Hierarchies and conformal field theory techniques

NASA Astrophysics Data System (ADS)

Hansson, T. H.; Hermanns, M.; Simon, S. H.; Viefers, S. F.

2017-04-01

The fractional quantum Hall effect, being one of the most studied phenomena in condensed matter physics during the past 30 years, has generated many ground-breaking new ideas and concepts. Very early on it was realized that the zoo of emerging states of matter would need to be understood in a systematic manner. The first attempts to do this, by Haldane and Halperin, set an agenda for further work which has continued to this day. Since that time the idea of hierarchies of quasiparticles condensing to form new states has been a pillar of our understanding of fractional quantum Hall physics. In the 30 years that have passed since then, a number of new directions of thought have advanced our understanding of fractional quantum Hall states and have extended it in new and unexpected ways. Among these directions is the extensive use of topological quantum field theories and conformal field theories, the application of the ideas of composite bosons and fermions, and the study of non-Abelian quantum Hall liquids. This article aims to present a comprehensive overview of this field, including the most recent developments.

Familial Pallister-Hall in adulthood.

PubMed

Talsania, Mitali; Sharma, Rohan; Sughrue, Michael E; Scofield, R Hal; Lim, Jonea

2017-10-01

Pallister Hall syndrome is autosomal dominant disorder usually diagnosed in infants and children. Current diagnostic criteria include presence of hypothalamic hamartoma, post axial polydactyly and positive family history, but the disease has variable manifestations. Herein we report Pallister Hall syndrome diagnosed in a family where both patients were adults. A 59 year old man developed seizures 4 years prior to our evaluation of him, at which time imaging showed a hypothalamic hamartoma. The seizures were controlled medically. He did well until he had visual changes after a traumatic head injury. Repeat MRI showed slight expansion of the mass with formal visual field testing demonstrating bitemporal hemianopsia. There was no evidence of pituitary dysfunction except for large urine volume. He underwent surgery to debulk the hamartoma and the visual field defects improved. There was no hypopituitarism post-operatively, and the polydyspia resolved. His 29 year old daughter also had seizures and hypothalamic hamartoma. Both patients had had polydactyly with prior surgical correction in childhood. The daughter underwent genetic testing, which revealed a previously undescribed heterozygous single base pair deletion in exon 13 of the GLI3 gene causing a frameshift mutation. Further investigation into family history revealed multiple members in previous generations with polydactyly and/or seizures. Pallister-Hall syndrome is caused by an inherited autosomal dominant or de novo mutation in GLI3 gene. This rare syndrome has not had prevalence defined, however. Generally, diagnoses are made in the pediatric population. Our report adds to the few cases detected in adulthood.

A Planar Hall Thruster for Investigating Electron Mobility in ExB Devices (Preprint)

DTIC Science & Technology

2007-08-24

Hall thruster that emits and collects the Hall current across a planar discharge channel is described. The planar Hall thruster (PHT) is being investigated for use as a test bed to study electron mobility in ExB devices. The planar geometry attempts to de-couple the complex electron motion found in annular thrusters by using simplified geometry. During this initial test, the PHT was operated at discharge voltages between 50-150 V to verify operability and stability of the device. Hall current was emitted by hollow cathode electron sources and

The Probe of Inflation and Cosmic Origins

NASA Astrophysics Data System (ADS)

Hanany, Shaul; Inflation Probe Mission Study Team

2018-01-01

The Probe of Inflation and Cosmic Origins will map the polarization of the cosmic microwave background over the entire sky with unprecedented sensitivity. It will search for gravity wave signals from the inflationary epoch, thus probing quantum gravity and constraining the energy scale of inflation; it will test the standard model of particle physics by measuring the number of light particles in the Universe and the mass of the neutrino; it will elucidate the nature of dark matter and search for new forms of matter in the early Universe; it will constrain star formation history over cosmic time; and it will determine the mechanisms of structure formation from galaxy cluster to stellar scales. I will review the status of design of this probe-scale mission.

New pathways towards efficient metallic spin Hall spintronics

DOE PAGES

Jungfleisch, Matthias Benjamin; Zhang, Wei; Jiang, Wanjun; ...

2015-11-16

Spin Hall effects (SHEs) interconvert spin- and charge currents due to spin- orbit interaction, which enables convenient electrical generation and detection of diffusive spin currents and even collective spin excitations in magnetic solids. Here, we review recent experimental efforts exploring efficient spin Hall detector materials as well as new approaches to drive collective magnetization dynamics and to manipulate spin textures by SHEs. As a result, these studies are also expected to impact practical spintronics applications beyond their significance in fundamental research.

Strong Intrinsic Spin Hall Effect in the TaAs Family of Weyl Semimetals

NASA Astrophysics Data System (ADS)

Sun, Yan; Zhang, Yang; Felser, Claudia; Yan, Binghai

2016-09-01

Since their discovery, topological insulators are expected to be ideal spintronic materials owing to the spin currents carried by surface states with spin-momentum locking. However, the bulk doping problem remains an obstacle that hinders such an application. In this work, we predict that a newly discovered family of topological materials, the Weyl semimetals, exhibits a large intrinsic spin Hall effect that can be utilized to generate and detect spin currents. Our ab initio calculations reveal a large spin Hall conductivity in the TaAs family of Weyl materials. Considering the low charge conductivity of semimetals, Weyl semimetals are believed to present a larger spin Hall angle (the ratio of the spin Hall conductivity over the charge conductivity) than that of conventional spin Hall systems such as the 4 d and 5 d transition metals. The spin Hall effect originates intrinsically from the bulk band structure of Weyl semimetals, which exhibit a large Berry curvature and spin-orbit coupling, so the bulk carrier problem in the topological insulators is naturally avoided. Our work not only paves the way for employing Weyl semimetals in spintronics, but also proposes a new guideline for searching for the spin Hall effect in various topological materials.

Hall Effect–Mediated Magnetic Flux Transport in Protoplanetary Disks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Xue-Ning; Stone, James M.

2017-02-10

The global evolution of protoplanetary disks (PPDs) has recently been shown to be largely controlled by the amount of poloidal magnetic flux threading the disk. The amount of magnetic flux must also coevolve with the disk, as a result of magnetic flux transport, a process that is poorly understood. In weakly ionized gas as in PPDs, magnetic flux is largely frozen in the electron fluid, except when resistivity is large. When the disk is largely laminar, we show that the relative drift between the electrons and ions (the Hall drift), and the ions and neutral fluids (ambipolar drift) can playmore » a dominant role on the transport of magnetic flux. Using two-dimensional simulations that incorporate the Hall effect and ambipolar diffusion (AD) with prescribed diffusivities, we show that when large-scale poloidal field is aligned with disk rotation, the Hall effect rapidly drags magnetic flux inward at the midplane region, while it slowly pushes flux outward above/below the midplane. This leads to a highly radially elongated field configuration as a global manifestation of the Hall-shear instability. This field configuration further promotes rapid outward flux transport by AD at the midplane, leading to instability saturation. In quasi-steady state, magnetic flux is transported outward at approximately the same rate at all heights, and the rate is comparable to the Hall-free case. For anti-aligned field polarity, the Hall effect consistently transports magnetic flux outward, leading to a largely vertical field configuration in the midplane region. The field lines in the upper layer first bend radially inward and then outward to launch a disk wind. Overall, the net rate of outward flux transport is about twice as fast as that of the aligned case. In addition, the rate of flux transport increases with increasing disk magnetization. The absolute rate of transport is sensitive to disk microphysics, which remains to be explored in future studies.« less

Gold nanoparticle-based probes for the colorimetric detection of Mycobacterium avium subspecies paratuberculosis DNA.

PubMed

Ganareal, Thenor Aristotile Charles S; Balbin, Michelle M; Monserate, Juvy J; Salazar, Joel R; Mingala, Claro N

2018-02-12

Gold nanoparticle (AuNP) is considered to be the most stable metal nanoparticle having the ability to be functionalized with biomolecules. Recently, AuNP-based DNA detection methods captured the interest of researchers worldwide. Paratuberculosis or Johne's disease, a chronic gastroenteritis in ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP), was found to have negative effect in the livestock industry. In this study, AuNP-based probes were evaluated for the specific and sensitive detection of MAP DNA. AuNP-based probe was produced by functionalization of AuNPs with thiol-modified oligonucleotide and was confirmed by Fourier-Transform Infrared (FTIR) spectroscopy. UV-Vis spectroscopy and Scanning Electron Microscopy (SEM) were used to characterize AuNPs. DNA detection was done by hybridization of 10 μL of DNA with 5 μL of probe at 63 °C for 10 min and addition of 3 μL salt solution. The method was specific to MAP with detection limit of 103 ng. UV-Vis and SEM showed dispersion and aggregation of the AuNPs for the positive and negative results, respectively, with no observed particle growth. This study therefore reports an AuNP-based probes which can be used for the specific and sensitive detection of MAP DNA. Copyright © 2018 Elsevier Inc. All rights reserved.

Real-Time Vision-Based Stiffness Mapping †.

PubMed

Faragasso, Angela; Bimbo, João; Stilli, Agostino; Wurdemann, Helge Arne; Althoefer, Kaspar; Asama, Hajime

2018-04-26

This paper presents new findings concerning a hand-held stiffness probe for the medical diagnosis of abnormalities during palpation of soft-tissue. Palpation is recognized by the medical community as an essential and low-cost method to detect and diagnose disease in soft-tissue. However, differences are often subtle and clinicians need to train for many years before they can conduct a reliable diagnosis. The probe presented here fills this gap providing a means to easily obtain stiffness values of soft tissue during a palpation procedure. Our stiffness sensor is equipped with a multi degree of freedom (DoF) Aurora magnetic tracker, allowing us to track and record the 3D position of the probe whilst examining a tissue area, and generate a 3D stiffness map in real-time. The stiffness probe was integrated in a robotic arm and tested in an artificial environment representing a good model of soft tissue organs; the results show that the sensor can accurately measure and map the stiffness of a silicon phantom embedded with areas of varying stiffness.

Real-Time Vision-Based Stiffness Mapping †

PubMed Central

Althoefer, Kaspar; Asama, Hajime

2018-01-01

This paper presents new findings concerning a hand-held stiffness probe for the medical diagnosis of abnormalities during palpation of soft-tissue. Palpation is recognized by the medical community as an essential and low-cost method to detect and diagnose disease in soft-tissue. However, differences are often subtle and clinicians need to train for many years before they can conduct a reliable diagnosis. The probe presented here fills this gap providing a means to easily obtain stiffness values of soft tissue during a palpation procedure. Our stiffness sensor is equipped with a multi degree of freedom (DoF) Aurora magnetic tracker, allowing us to track and record the 3D position of the probe whilst examining a tissue area, and generate a 3D stiffness map in real-time. The stiffness probe was integrated in a robotic arm and tested in an artificial environment representing a good model of soft tissue organs; the results show that the sensor can accurately measure and map the stiffness of a silicon phantom embedded with areas of varying stiffness. PMID:29701704

Overview of NASA Iodine Hall Thruster Propulsion System Development

NASA Technical Reports Server (NTRS)

Smith, Timothy D.; Kamhawi, Hani; Hickman, Tyler; Haag, Thomas; Dankanich, John; Polzin, Kurt; Byrne, Lawrence; Szabo, James

2016-01-01

NASA is continuing to invest in advancing Hall thruster technologies for implementation in commercial and government missions. The most recent focus has been on increasing the power level for large-scale exploration applications. However, there has also been a similar push to examine applications of electric propulsion for small spacecraft in the range of 300 kg or less. There have been several recent iodine Hall propulsion system development activities performed by the team of the NASA Glenn Research Center, the NASA Marshall Space Flight Center, and Busek Co. Inc. In particular, the work focused on qualification of the Busek 200-W BHT-200-I and development of the 600-W BHT-600-I systems. This paper discusses the current status of iodine Hall propulsion system developments along with supporting technology development efforts.

Topological Phase Transitions in the Photonic Spin Hall Effect

DOE PAGES

Kort-Kamp, Wilton Junior de Melo

2017-10-04

The recent synthesis of two-dimensional staggered materials opens up burgeoning opportunities to study optical spin-orbit interactions in semiconducting Dirac-like systems. In this work, we unveil topological phase transitions in the photonic spin Hall effect in the graphene family materials. It is shown that an external static electric field and a high frequency circularly polarized laser allow for active on-demand manipulation of electromagnetic beam shifts. The spin Hall effect of light presents a rich dependence with radiation degrees of freedom, and material properties, and features nontrivial topological properties. Finally, we discover that photonic Hall shifts are sensitive to spin and valleymore » properties of the charge carriers, providing an unprecedented pathway to investigate spintronics and valleytronics in staggered 2D semiconductors.« less

Standard deviations of composition measurements in atom probe analyses. Part I conventional 1D atom probe.

PubMed

Danoix, F; Grancher, G; Bostel, A; Blavette, D

2007-09-01

Atom probe is a very powerful instrument to measure concentrations on a sub nanometric scale [M.K. Miller, G.D.W. Smith, Atom Probe Microanalysis, Principles and Applications to Materials Problems, Materials Research Society, Pittsburgh, 1989]. Atom probe is therefore a unique tool to study and characterise finely decomposed metallic materials. Composition profiles or 3D mapping can be realised by gathering elemental composition measurements. As the detector efficiency is generally not equal to 1, the measured compositions are only estimates of actual values. The variance of the estimates depends on which information is to be estimated. It can be calculated when the detection process is known. These two papers are devoted to give complete analytical derivation and expressions of the variance on composition measurements in several situations encountered when using atom probe. In the first paper, we will concentrate on the analytical derivation of the variance when estimation of compositions obtained from a conventional one dimension (1D) atom probe is considered. In particular, the existing expressions, and the basic hypotheses on which they rely, will be reconsidered, and complete analytical demonstrations established. In the second companion paper, the case of 3D atom probe will be treated, highlighting how the knowledge of the 3D position of detected ions modifies the analytical derivation of the variance of local composition data.

The rotation of discs around neutron stars: dependence on the Hall diffusion

NASA Astrophysics Data System (ADS)

Faghei, Kazem; Salehi, Fatemeh

2018-01-01

In this paper, we study the dynamics of a geometrically thin, steady and axisymmetric accretion disc surrounding a rotating and magnetized star. The magnetic field lines of star penetrate inside the accretion disc and are twisted due to the differential rotation between the magnetized star and the disc. We apply the Hall diffusion effect in the accreting plasma, because of the Hall diffusion plays an important role in both fully ionized plasma and weakly ionized medium. In the current research, we show that the Hall diffusion is also an important mechanism in accreting plasma around neutron stars. For the typical system parameter values associated with the accreting X-ray binary pulsar, the angular velocity of the inner regions of disc departs outstandingly from Keplerian angular velocity, due to coupling between the magnetic field of neutron star and the rotating plasma of disc. We found that the Hall diffusion is very important in inner disc and increases the coupling between the magnetic field of neutron star and accreting plasma. On the other word, the rotational velocity of inner disc significantly decreases in the presence of the Hall diffusion. Moreover, the solutions imply that the fastness parameter decreases and the angular velocity transition zone becomes broad for the accreting plasma including the Hall diffusion.

G. Stanley Hall, Child Study, and the Teaching of Geography

ERIC Educational Resources Information Center

Koelsch, William A.

2002-01-01

G. Stanley Hall (1844-1924), founding president of Clark University, was a leader in the child study movement and a significant figure in psychology and education in the late nineteenth and early twentieth centuries. Hall had pronounced opinions on many educational subjects, including the teaching of geography. His criticisms and program for the…

Physical mapping of complex genomes

DOEpatents

Evans, G.A.

1993-06-15

A method for the simultaneous identification of overlapping cosmid clones among multiple cosmid clones and the use of the method for mapping complex genomes are provided. A library of cosmid clones that contains the DNA to be mapped is constructed and arranged in a manner such that individual clones can be identified and replicas of the arranged clones prepared. In preferred embodiments, the clones are arranged in a two dimensional matrix. In such embodiments, the cosmid clones in a row are pooled, mixed probes complementary to the ends of the DNA inserts in the pooled clones are synthesized, hybridized to a first replica of the library. Hybridizing clones, which include the pooled row, are identified. A second portion of clones is prepared by pooling cosmid clones that correspond to a column in the matrix. The second pool thereby includes one clone from the first portion pooled clones. This common clone is located on the replica at the intersection of the column and row. Mixed probes complementary to the ends of the DNA inserts in the second pooled portion of clones are prepared and hybridized to a second replica of the library. The hybridization pattern on the first and second replicas of the library are compared and cross-hybridizing clones, other than the clones in the pooled column and row, that hybridize to identical clones in the first and second replicas are identified. These clones necessarily include DNA inserts that overlap with the DNA insert in the common clone located at the intersection of the pooled row and pooled column. The DNA in the entire library may be mapped by pooling the clones in each of the rows and columns of the matrix, preparing mixed end-specific probes and hybridizing the probes from each row or column to a replica of the library. Since all clones in the library are located at the intersection of a column and a row, the overlapping clones for all clones in the library may be identified and a physical map constructed.

Effects of Ionospheric Hall Polarization on Magnetospheric Configurations and Dynamics in Global MHD Simulation

NASA Astrophysics Data System (ADS)

Nakamizo, A.; Yoshikawa, A.; Tanaka, T.

2017-12-01

We investigate how the M-I coupling and boundary conditions affects the results of global simulations of the magnetosphere. More specifically, we examine the effects of ionospheric Hall polarization on magnetospheric convection and dynamics by using an MHD code developed by Tanaka et al. [2010]. This study is motivated by the recently proposed idea that the ionospheric convection is modified by the ionospheric polarization [Yoshikawa et al., 2013]. We perform simulations for the following pairs of Hall conductance and IMF-By; Hall conductance set by αH = 2, 3.5, 5, and uniform distribution (1.0 [S] everywhere), where RH is the ratio of Hall to Pedersen conductance, and IMF-By of positive, negative, and zero. The results are summarized as follows. (a) Large-scale structure: In the cases of uniform Hall conductance, the magnetosphere is completely symmetric under the zero IMF-By. In the cases of non-uniform Hall conductance, the magnetosphere shows asymmetries globally even under the zero IMF-By. Asymmetries become severe for larger αH. The results indicate that ionospheric Hall polarization is one of the important factors to determine the global structure. (b) Formation of NENL: The location becomes closer to the earth and timing becomes earlier for larger RH. The difference is considered to be related to the combined effects of field lines twisting due to ionospheric Hall polarization and M-I energy/current closures. (c) Near-earth convection: In the cases of non-uniform Hall conductance, an inflection structure is formed around premidnight sector on equatorial plane inside 10 RE. Considering that the region 2 FAC is not sufficiently generated in MHD models, the structure corresponds to a convection reversal often shown in the RCM. Previous studies regard the structure as the Harang Reversal in the magnetosphere. In the cases of uniform Hall conductance, by contrast, such structure is not formed, indicating that the Harang Reversal may not be formed without the

NASA Chief Technologist Hosts Town Hall

NASA Image and Video Library

2010-05-24

NASA's Chief Technologists, Bobby Braun, hosts a Town Hall meeting to discuss agency-wide technology policy and programs at NASA Headquarters on Tuesday, May 25, 2010, in Washington. Photo Credit: (NASA/Carla Cioffi)

Cabana inducted into Hall of Fame

NASA Image and Video Library

2008-05-03

Former astronaut Al Worden (left) presents Stennis Space Center Director Bob Cabana with a gold medallion signifying his induction into the U.S. Astronaut Hall of Fame at Kennedy Space Center in Florida.

Suprathermal and Solar Energetic Particles - Key questions for the Interstellar Mapping and Acceleration Probe (IMAP)

NASA Astrophysics Data System (ADS)

Desai, M. I.; McComas, D. J.; Christian, E. R.; Mewaldt, R. A.; Schwadron, N.

2014-12-01

Solar energetic particles or SEPs from suprathermal (few keV) up to relativistic (~few GeV) speeds are accelerated near the Sun in at least two ways, namely, (1) by magnetic reconnection-driven processes during solar flares resulting in impulsive SEPs and (2) at fast coronal-mass-ejection-driven shock waves that produce large gradual SEP events. Large gradual SEP events are of particular interest because the accompanying high-energy (>10s MeV) protons pose serious radiation threats to human explorers living and working outside low-Earth orbit and to technological assets such as communications and scientific satellites in space. However, a complete understanding of SEP events has eluded us primarily because their properties, as observed near Earth orbit, are smeared due to mixing and contributions from many important physical effects. Thus, despite being studied for decades, several key questions regarding SEP events remain unanswered. These include (1) What are the contributions of co-temporal flares, jets, and CME shocks to impulsive and gradual SEP events?; (2) Do flares contribute to large SEP events directly by providing high-energy particles and/or by providing the suprathermal seed population?; (3) What are the roles of ambient turbulence/waves and self-generated waves?; (4) What are the origins of the source populations and how do their temporal and spatial variations affect SEP properties?; and (5) How do diffusion and scattering during acceleration and propagation through the interplanetary medium affect SEP properties observed out in the heliosphere? This talk describes how during the next decade, inner heliospheric measurements from the Solar Probe Plus and Solar Orbiter in conjunction with high sensitivity measurements from the Interstellar Mapping and Acceleration Probe will provide the ground-truth for various models of particle acceleration and transport and address these questions.

Non-Intrusive, Time-Resolved Hall Thruster Near-Field Electron Temperature Measurements

DTIC Science & Technology

2011-08-01

With the growing interest in Hall thruster technology, comes the need to fully characterize the plasma dynamics that determine performance. Of...instabilities characteristic of Hall thruster behavior, time resolved techniques must be developed. This study presents a non-intrusive method of

AGU Position Statements Addressed at Fall Meeting Town Hall

NASA Astrophysics Data System (ADS)

Hankin, Erik

2013-01-01

The AGU Outreach Committee and Public Affairs staff held a town hall at the 2012 Fall Meeting to discuss AGU position statements. The town hall, "AGU Position Statements: Announcing New Submission and Review Methods," held on Monday, 3 December, provided background on AGU position statements, recent changes to the review and writing processes, updates on statements under revision, and ways for members to utilize and impact position statements.