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  • 1
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    Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-09-15
    Description: Tri-methyl-indium (TMI) is used as an indium transport molecule to introduce indium atoms to reactive hot gas flows/combustion environments for spectroscopic diagnostics. A seeding system was constructed to allow the addition of an inert TMI laden carrier gas into an air/fuel mixture burning consequently on a burner. The amount of the seeded TMI in the carrier gas can be readily varied by controlling the vapor pressure through the temperature of the container. The seeding process was calibrated using the fluorescent emission intensity from the indium 6 2 S 1/2 → 5 2 P 1/2 and 6 2 S 1/2 → 5 2 P 3/2 transitions as a function of the calculated TMI seeding concentration over a range of 2–45 ppm. The response was found to be linear over the range 3–22.5 ppm; at concentrations above 25 ppm there is a loss of linearity attributable to self-absorption or loss of saturation of TMI vapor pressure in the carrier gas flow. When TMI was introduced into a post-combustion environment via an inert carrier gas, molecular transition from InH and InOH radicals were observed in the flame emission spectrum. Combined laser-induced fluorescence and absorption spectroscopy were applied to detect indium atoms in the TMI seeded flame and the measured atomic indium concentration was found to be at the ppm level. This method of seeding organometallic vapor like TMI to a reactive gas flow demonstrates the feasibility for quantitative spectroscopic investigations that may be applicable in various fields, e.g., chemical vapor deposition applications or temperature measurement in flames with two-line atomic fluorescence.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Invited Article: A precise instrument to determine the Planck constant, and the future kilogram (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-06-22
    Description: A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and the Planck constant is established by the practical realization of the electrical units derived from the Josephson and the quantum Hall effects. We describe in this paper the fourth-generation watt balance at the National Institute of Standards and Technology (NIST), and report our initial determination of the Planck constant obtained from data taken in late 2015 and the beginning of 2016. A comprehensive analysis of the data and the associated uncertainties led to the SI value of the Planck constant, h = 6.626 069 83(22) × 10 −34 J s. The relative standard uncertainty associated with this result is 34 × 10 −9 .
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    Preliminary consideration of CFETR ITER-like case diagnostic system (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-12
    Description: Chinese Fusion Engineering Test Reactor (CFETR) is a new superconducting tokamak device being designed in China, which aims at bridging the gap between ITER and DEMO, where DEMO is a tokamak demonstration fusion reactor. Two diagnostic cases, ITER-like case and towards DEMO case, have been considered for CFETR early and later operating phases, respectively. In this paper, some preliminary consideration of ITER-like case will be presented. Based on ITER diagnostic system, three versions of increased complexity and coverage of the ITER-like case diagnostic system have been developed with different goals and functions. Version A aims only machine protection and basic control. Both of version B and version C are mainly for machine protection, basic and advanced control, but version C has an increased level of redundancy necessary for improved measurements capability. The performance of these versions and needed R&D work are outlined.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 4
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    Large femtosecond third-order optical nonlinearity of Bi3.15Nd0.85Ti3O12 ferroelectric thin films (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-11-11
    Description: Both the linear and nonlinear optical properties of Bi 3.15 Nd 0.85 Ti 3 O 12 (BNT 0.85 ) ferroelectric thin films deposited on quartz substrates were investigated. The fundamental optical constants were determined as a function of light wavelength by optical transmittance measurements. By performing single-beam Z-scan experiments with femtosecond laser pulses at a wavelength of 800 nm, the two-photon absorption (TPA) coefficient β and third-order nonlinear refraction index γ were measured to be 1.15 × 10 2  cm/GW and −8.15 × 10 −3 cm 2 /GW, respectively. The large TPA is attributed to an indirect transition process via the intermediate energy levels and the large refractive nonlinearity is the result of the electronic polarization and ferroelectric polarization arisen from the femtosecond midinfrared radiation. The results indicate that the BNT 0.85 thin film is a promising candidate for applications in nonlinear photonic devices.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 5
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    Nonlinear optical absorption tuning in Bi3.15Nd0.85Ti3O12 ferroelectric thin films by thickness (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-04-08
    Description: The tunability of nonlinear optical (NLO) absorption in Bi 3.15 Nd 0.85 Ti 3 O 12 (BNT) ferroelectric thin films was investigated through the open aperture Z-scan method with femtosecond laser pulses at the wavelength of 800 nm. NLO absorption responses of the BNT films were observed to be highly sensitive to the film thickness. As the film thickness increases from 106.8 to 139.7 nm, the NLO absorption changes from saturable absorption (SA) to reverse saturable absorption (RSA). When the film thickness further increases to 312.9 nm, the RSA effect is enhanced. A band-gap-related competition between the ground-state excitation and the two-photon absorption is responsible for the absorption switching behavior. Such a tunable NLO absorption can widen the photonic application of the BNT thin films.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 6
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    Large enhancement of bulk spin polarization by suppressing CoMn anti-sites in Co2Mn(Ge0.75Ga0.25) Heusler alloy thin film (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-03-24
    Description: We have investigated the structure and magneto-transport properties of Co 2 Mn(Ge 0.75 Ga 0.25 ) (CMGG) Heusler alloy thin films with near-stoichiometric and Mn-rich compositions in order to understand the effect of Co-Mn anti-sites on bulk spin polarization. Anomalous x -ray diffraction measurements using synchrotron radiated x-rays confirmed that Co Mn anti-sites easily form in the near-stoichiometric CMGG compound at annealing temperature higher than 400 °C, while it can be suppressed in Mn-rich CMGG films. Accordingly, large enhancement in negative anisotropic magnetoresistance of CMGG films and giant magnetoresistance (GMR) in current-perpendicular-to-plane (CPP) pseudo spin valves were observed in the Mn-rich composition. A large resistance-area product change ( ΔRA ) of 12.8 mΩ μ m 2 was demonstrated in the CPP-GMR pseudo spin valves using the Mn-rich CMGG layers after annealing at 600 °C. It is almost twice of the maximum output observed in the CPP-GMR pseudo spin valves using the near-stoichiometric CMGG. These indicate that the spin polarization of CMGG is enhanced in the Mn-rich composition through suppressing the formation of Co Mn -antisites in CMGG films, being consistent with first-principle calculation results.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 7
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    Current-perpendicular-to-plane giant magnetoresistive properties in Co2Mn(Ge0.75Ga0.25)/Cu2TiAl/Co2Mn(Ge0.75Ga0.25) all-Heusler alloy pseudo spin valve (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-03-05
    Description: Nonmagnetic Cu 2 TiAl (CTA) Heusler compound is proposed as a new spacer material for all-Heusler alloy current-perpendicular-to-plane giant magnetoresistance devices based on first-principle calculations. The (001)-orientated Co 2 Mn(Ge 0.75 Ga 0.25 ) (CMGG)/CTA/CMGG epitaxial pseudo spin valve (PSV) grown on MgO(100) single crystal substrate showed relatively large MR output, Δ R A ∼ 5.4  mΩ  μ m 2 , which is comparable to that of the CMGG/Ag/CMGG PSV prepared with the same condition. Considering the short spin diffusion length in CTA, this result indicates a better electronic band matching for the CTA/CMGG interface than the Ag/CMGG interface in agreement with the first-principle calculation results. (001)- and (011)-orientated CMGG/CTA/CMGG PSV show similar MR outputs, indicating that the CTA spacer suppresses the orientation dependence of MR output which is usually observed in Ag-spacer CPP-PSV.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 8
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    Anisotropic magnetoresistance and current-perpendicular-to-plane giant magnetoresistance in epitaxial NiMnSb-based multilayers (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-01-09
    Description: We fabricated (001)-oriented C 1 b -NiMnSb epitaxial films on MgO substrate by a magnetron sputtering system and systematically investigated the structure, magnetic property, and anisotropic magnetoresistance (AMR) effect. NiMnSb film was deposited using a stoichiometric NiMnSb target which has Mn-deficient (Mn ∼ 28.7 at. %) off-stoichiometric composition ratio. We have investigated bulk spin-polarization in NiMnSb films by measuring AMR on the basis of recent study for half-metallic L 2 1 -Heusler compounds. Although the negative sign of AMR ratio, which is indicative of half-metallic nature, was observed in the single layer NiMnSb films, the magnitude of AMR ratio (−0.10% at RT) was about half of the largest value reported for half-metallic L 2 1 -Heusler compounds. The current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) devices of NiMnSb/Ag/NiMnSb show MR ratio of 13.2% at 10 K and 4.2% at 300 K, which is higher than the previous result for NiMnSb/Cu/NiMnSb CPP-GMR devices [Caballero et al ., J. Magn. Magn. Mater. 198–199 , 55 (1999)], but much less than the CPP-GMR using L 2 1 -Heusler electrodes. The reduction of intrinsic bulk spin-polarization originating from the Mn-deficiency in NiMnSb layer is expected to be the main reason for small MR values.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 9
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    Modelling for three dimensional coalescence of two bubbles (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-06-09
    Description: This paper is concerned with the three dimensional (3D) interaction and coalescence of two bubbles subject to buoyancy and the dynamics of the subsequent joined bubble using the boundary integral method (BIM). An improved density potential method is implemented to control the mesh quality. It helps to avoid the numerical instabilities, which occur after coalescence. Numerical convergence tests are conducted in terms of mesh sizes and time steps. The 3D numerical model agrees well with an axisymmetric BIM model for axisymmetric cases as well as experimental results captured by high-speed camera. The bubble jetting, interaction, and coalescence of the two bubbles depend on the maximum bubble radii, the centre distance between two bubbles at inception, and the angle β between the centre line and the direction of buoyancy. We investigate coalescence of two bubbles for β = 0, π /4, and π /2, respectively, and at various centre distances at inception. Numerical results presented include the bubble and jet shapes, the velocity, and pressure fields surrounding the bubbles, as well as the time histories of bubble volumes, jet velocities, and positions of centroid of the bubble system.
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 10
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    Study on splitting of a toroidal bubble near a rigid boundary (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-06-10
    Description: The splitting of a toroidal bubble near a rigid boundary is commonly observed in experiments, which is a quite complex phenomenon in bubble dynamics and still not yet well understood. In present study, the bubble splitting phenomenon is studied using the boundary integral method. The vortex ring model is extended to multiple vortex rings to simulate the interaction between two toroidal bubbles after splitting. Buoyancy and non-buoyancy cases are investigated numerically in this study. Numerical results with buoyancy effects show favorable agreement with the experimental observations, which validates the present model. Generally, the first split of the toroidal bubble occurs when an annular “sideways jet” collides with the other side of the bubble. After the toroidal bubble splitting, some new phenomena are found as follows: (i) An annular high pressure region is generated at the splitting location, and the maximum pressure is associated with the velocity differences between the two sides therein just before splitting. (ii) The total volume varies continuously, while the two sub-bubbles vary differently in volume after splitting. (iii) The sideways jet continues propagating on a sub-bubble surface, which would cause more splits or partial breakup of the splash film into droplets. This may be an important reason for the formation of bubble cloud and the rough bubble surface in the rebounding process.
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics (AIP)
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