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  • American Physical Society  (56)
  • American Institute of Physics (AIP)  (26)
  • 2010-2014  (21)
  • 2000-2004  (26)
  • 1995-1999  (35)
  • 1
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    Upgrade of the electron beam ion trap in Shanghai (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-09-04
    Description: Over the last few years the Shanghai electron beam ion trap (EBIT) has been successfully redesigned and rebuilt. The original machine, developed under collaboration with the Shanghai Institute of Applied Physics, first produced an electron beam in 2005. It could be tuned with electron energies between 1 and 130 keV and beam current up to 160 mA. After several years of operation, it was found that several modifications for improvements were necessary to reach the goals of better electron optics, higher photon detection, and ion injection efficiencies, and more economical running costs. The upgraded Shanghai-EBIT is made almost entirely from Ti instead of stainless steel and achieves a vacuum of less than 10 −10 Torr, which helps to minimize the loss of highly changed ions through charge exchange. Meanwhile, a more compact structure and efficient cryogenic system, and excellent optical alignment have been of satisfactory. The magnetic field in the central trap region can reach up till 4.8 T with a uniformity of 2.77 × 10 −4 . So far the upgraded Shanghai-EBIT has been operated up to an electron energy of 151 keV and a beam current of up to 218 mA, although promotion to even higher energy is still in progress. Radiation from ions as highly charged as Xe 53+, 54+ has been produced and the characterization of current density is estimated from the measured electron beam width.
    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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    Note: Design and initial results of a multi-pulsed intense electron beam source (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-06-20
    Description: A multi-pulsed intense electron beam source is introduced, including the design and the initial experimental results. The source can generate a burst of three pulses of intense electron beams with energy of 2–3 MeV and beam intensities of around 2.5 kA. An inductive adder is chosen to generate the pulsed diode voltages and a dispenser cathode is chosen to emit electron beams. The test results indicate that the design of the source is reliable. The multi-pulsed diode voltage is up to 2.5 MV and the beam intensities are more than 2 kA at the exit of the source with small variation.
    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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    Energetic-particle-induced electromagnetic geodesic acoustic mode in tokamak plasmas (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-07-22
    Description: Energetic-particle-induced kinetic electromagnetic geodesic acoustic modes (EKEGAMs) are numerically studied in low β (=plasma pressure/magnetic pressure) tokamak plasmas. The parallel component of the perturbed vector potential is considered along with the electrostatic potential perturbation. The effects of finite Larmor radius and finite orbit width of the bulk and energetic ions as well as electron parallel dynamics are all taken into account in the dispersion relation. Systematic harmonic and ordering analysis are performed for frequency and growth rate spectra of the EKEGAMs, assuming ( k ρ i ) ∼ q − 3 ∼ β ≪ 1 , where q , k , and ρ i are the safety factor, radial component of the EKEGAMs wave vector, and the Larmor radius of the ions, respectively. It is found that there exist critical β h / β i values, which depend, in particular, on pitch angle of energetic ions and safety factor, for the mode to be driven unstable. The EKEGAMs may also be unstable for pitch angle λ 0 B 〈 0.4 in certain parameter regions. Finite β effect of the bulk ions is shown to have damping effect on the EKEGAMs. Modes with higher radial wave vectors have higher growth rates. The damping from electron dynamics is found decreasing with decrease of the temperature ratio T e / T i . The modes are easily to be driven unstable in low safety factor q region and high temperature ratio T h / T i region. The harmonic features of the EKEGAMs are discussed as well.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 4
    Electronic Resource
    Electronic Resource
    Structural and magnetic properties of R(Fe1−yCoy)12−xNbx compounds (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2165-2171 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of RFe12−xNbx and R(Fe1−yCoy)11.3Nb0.7 compounds with R=Y, Tb, and Dy have been investigated in the concentration region defined by 0.6〈x〈0.8 and y≤0.3, where the compounds are single phase with the ThMn12-type of structure. The Curie temperature TC of the RFe12−xNbx compounds is almost independent of the Nb content whereas the saturation magnetization Ms decreases with increasing Nb content. The spin-reorientation temperature Tsr of the TbFe12−xNbx and DyFe12−xNbx compounds decreases monotonically with increasing x. Substitution of Co for Fe in RFe11.3Nb0.7 leads to a remarkable increase of TC and the appearance of a maximum in the Co-concentration dependence of Ms. In contrast, Tsr decreases monotonically with increasing Co content for both R=Tb and Dy. The modification of T- and R-sublattice anisotropy originating from a change of the Nb content and from substitution of Co for Fe was analyzed by combining crystalline electric field theory and the individual-site model. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1425441
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  • 5
    Electronic Resource
    Electronic Resource
    Composition, residual stress, and structural properties of thin tungsten nitride films deposited by reactive magnetron sputtering (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1380-1388 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin tungsten nitride (WNx) films were produced by reactive dc magnetron sputtering of tungsten in an Ar–N2 gas mixture. The effects of the variation of nitrogen partial pressure on the composition, residual stress, and structural properties of these films as well as the influence of postdeposition annealing have been studied. The films were analyzed in situ by a cantilever beam technique, and ex situ by x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, x-ray diffraction, and transmission electron microscopy (TEM). It was found that at N concentrations below 8 at. %, the films (typical 150 nm in thickness) were essentially bcc α-W. An amorphous phase was observed in the range of about 12–28 at. % N. When N concentrations reached ∼32 at. % or above, a single-phase structure of W2N was formed. Annealing of the as-deposited films resulted in crystallization of the amorphous or an improved crystallinity of the W2N structure, which was related to the N concentration. Stresses of all W and WNx films were compressive. As the N concentration was increased, the stress decreased and reached its lowest value for amorphous samples near 20 at. % N. Past this point, the compression of films rose again. These results can be ascribed to structural changes induced by the pressure-dependent variation in the average energy of particles bombarding the film during deposition. Cross-sectional TEM studies showed that all crystalline WNx films had columnar microstructures. The average column width near stoichiometry of W2N was ∼20±5 nm near the film surface. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373827
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  • 6
    Electronic Resource
    Electronic Resource
    Large change of the giant magnetoresistance behavior after changing the spacer from Cu to CuMn alloy in Co/spacer/Co structures (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5030-5032 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The giant magnetoresistance (GMR) effects in sandwiched Co/Cu/Co and Co/CuMn/Co structures have been investigated. The GMR oscillates with the spacer thickness for both cases, but is nearly antiphased. With diluted Mn atoms in the Cu spacer, the GMR curve as a function of the magnetic field changes a lot, and the saturation/switching field for GMR can be reduced greatly compared with that in Co/Cu/Co systems. This may indicate one way to obtain a highly sensitive GMR. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370081
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  • 7
    Electronic Resource
    Electronic Resource
    On the prediction of electromigration voiding using stress-based modeling (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4039-4041 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In modeling electromigration failure, it is common to employ the concept of a critical stress at which interconnect failure occurs. In this report, we illustrate that the atomic flux divergence, obtained directly from the one-dimensional stress-based modeling, is more appropriate in characterizing the formation of void in electromigration. A numerical analysis was carried out, to model the evolution of stress, atomic flux, and flux divergence in an aluminum line containing a fast-diffusion segment. The maximum flux divergence, not the maximum tensile stress, predicts the voiding location which is consistent with microscopic observations in the experiments of Joo et al. [Acta. Mater. 46, 1969 (1998); J. Appl. Phys. 85, 2108 (1999)] utilizing nanoindented single-crystal aluminum lines. This is because the flux divergence directly reflects the extent of matter depletion, and thus the propensity of voiding. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372452
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  • 8
    Electronic Resource
    Electronic Resource
    Residual stress, microstructure, and structure of tungsten thin films deposited by magnetron sputtering (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 177-187 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The residual stress and structural properties of tungsten thin films prepared by magnetron sputtering as a function of sputtering-gas pressure are reported. The films were analyzed in situ by a cantilever beam technique, and ex situ by x-ray diffraction, cross-sectional transmission electron microscopy (TEM), x-ray photoelectron spectroscopy, electron energy-loss spectrometry, and energy-filtered electron diffraction. It is found that the residual stress, microstructure, and surface morphology are clearly correlated. The film stresses, determined in real time during the film formation, depend strongly on the argon pressure and change from highly compressive to highly tensile in a relatively narrow pressure range of 12–26 mTorr. For pressures exceeding ∼60 mTorr, the stress in the film is nearly zero. It is also found that the nonequilibrium A15 W structure is responsible for the observed tensile stress, whereas the stable bcc W or a mixture of bcc W and A15 W are in compression. Cross-sectional TEM evidence indicates that the compressively stressed films contain a dense microstructure without any columns, while the films having tensile stress have a very columnar microstructure. High sputtering-gas pressure conditions yield dendritic-like film growth, resulting in complete relaxation of the residual tensile stresses. Structural details of the A15 W and amorphous W phases were also investigated at the atomic level using energy-filtered electron diffraction with reduced radial distribution function G(r) analysis. By comparing the experimental and simulated G(r) distributions, the A15 W structure is determined to be composed of ordered and stacking faulted W3W structures and the amorphous W has a disordered structure of W3O. The effect of oxygen in stabilizing the A15 phase found is explained on the basis of structural and thermodynamic stability. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371841
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  • 9
    Electronic Resource
    Electronic Resource
    Stresses, curvatures, and shape changes arising from patterned lines on silicon wafers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1388-1398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental and numerical results are presented on the evolution of stresses and the accompanying changes in the overall curvatures due to the patterning of silicon oxide lines on silicon wafers and subsequent thermal loading. The finite element analysis involves a generalized plane strain formulation, which is capable of predicting the wafer curvatures in directions parallel and perpendicular to the lines, for both the patterning and thermal cycling operations. The predictions compare reasonably well with systematic curvature measurements for several different geometrical combinations of the thickness, width and spacing of the patterned lines. The non-uniform stress fields within the fine lines and the substrate are also analyzed. It is shown both experimentally and theoretically that certain geometries of patterned lines on the substrate induce dramatic shape changes and reversals of curvature in the direction perpendicular to the lines. The mechanistic origin of this effect is identified to be the Poisson effect arising from the anisotropic strain coupling in the patterned structure. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362938
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  • 10
    Electronic Resource
    Electronic Resource
    Oxygen-induced amorphous structure of tungsten thin films (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2211-2213 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A combination of energy-filtered electron diffraction, electron energy-loss spectroscopy, transmission electron microscopy, and x-ray diffraction are used to establish that oxygen impurities incorporated in tungsten films prepared by magnetron sputtering in the early stage of the deposition play a dominant role in the formation of an amorphous phase. Energy-filtered electron diffraction data collected from a range of amorphous films were Fourier transformed to a reduced density function (RDF) and matched with an amorphous model. The results show that better agreement with the experimental RDF is achieved if the amorphous model consists of a random continuous matrix of clusters with W3O-like symmetry. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124967
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