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  • American Institute of Physics (AIP)  (326)
  • 1990-1994  (326)
  • 1965-1969
  • 1940-1944
  • 1990  (326)
  • 1
    Electronic Resource
    Electronic Resource
    Ion sources at the Novosibirsk Institute of Nuclear Physics (invited) : International conference on ion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 378-384 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A review of investigations in the physics and technology of ion sources, developed in the Institute of Nuclear Physics in Novosibirsk is presented. Distinctive features of physical processes and technical characteristics of plasma sources of gaseous ions, negative ion surface-plasma sources, electrohydrodynamic (liquid metal) ion sources are considered. In original design plasma sources, ion beams with a current of up to 90 A and energies 1–30 keV are formed by four-electrode multislit extraction systems from highly ionized, high brightness plasma flux, generated by an high-current arc discharge with a cold cathode in a small cross-section diaphragmed channel, and directed with a magnetic field of a special configuration. Plasma jet expansion for a very low ion temperature (0.1 eV) production is used. In surface plasma sources, the fluxes of negative ions are produced when electrons are captured from the electrode surface at the electron affinity level of sputtered and reflected particles. A discharge of a special type in a gas-cesium mixture with in a thin plasma layer between the negative ion emitter and emission holes is used. A number of versions of SPS with different types of discharges are considered: SPS which operate in pulse mode with H− beam current up to 11 A, with current 0.1 A, and high brightness for accelerators, for continuous mode operation. Specific features of physical processes in electrohydrodynamic (EHD) ion emitters are studied and the technology of production of different ions is worked out. The production of ion beams with high brightness from the dielectric melt in the EHD-emission regime is developed. The dynamics of spontaneous oscillation excitation with a quasidiscrete spectrum in the frequency range of up to 108 Hz, transient processes occurring at the emission disturbances, emission stability at low current, a physical model for calculating the emission surface dimensions, and the evolution of the ion momentum distribution function for the ion motion are studied. The utilization of the designed EHD sources in the ion microscope, in submicromachining and in high voltage accelerators are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141299
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  • 2
    Electronic Resource
    Electronic Resource
    Complex dynamics in domain wall motion (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5350-5351 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple model, exactly solvable except at two points, which simulates the dynamics of a single magnetic domain wall crossing a single impurity site in a ferromagnetic material, is solved numerically for some ranges of parameters. The dynamics are complex and very sensitively dependent on the physical parameters: the frequency and strength of the applied field, the strength of the pinning, the reversible permeability, the effective mass of the domain wall, the wall viscosity, and the amount of energy retained by the wall when it breaks free of the pinning site. An example of parameter choice that results in frequency quintupling is given. Phase space portraits, return maps, and total energy spectra are used to display the results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344608
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  • 3
    Electronic Resource
    Electronic Resource
    50-A ion source IK-50 for AMBAL-M device : International conference on ion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 401-402 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this paper an ion source design is described. An ion beam with a current of 50 A, an energy of 30 keV, and a pulse duration of 0.1 s is extracted from a rectangular plasma emitter with dimensions of 24×12 cm. A new way is used for creating a uniform plasma current density at the emission surface. The source is distinguished from the typical bucket sources by its high degree of monatomic ions, the absence of heating cathodes, and an original ion-optic system design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141304
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  • 4
    Electronic Resource
    Electronic Resource
    Laser-plasma generation of currents along a conductive target (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3140-3146 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Large electric currents have been observed along conductive targets on which plasma was initiated by means of spatially modulated radiation. Two successive pulses of TEA CO2laser with intensities I≤109 W/cm2 were used in the experiments. The most effective generation of the currents was observed during the second laser pulse delayed for 4 μs, when an asymmetric plasma "grating'' was produced on the target. Two different mechanisms for generating such currents in a closed circuit have been established. One of them results from a dipole moment of plasma, while the other is due to the processes at plasma-surface interface. To obtain correct measurements of the voltage induced by a laser plasma, a fiber optical modulator of light has been used for the first time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346408
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  • 5
    Electronic Resource
    Electronic Resource
    Non-steady-state photo-electromotive-force induced by dynamic gratings in partially compensated photoconductors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2216-2225 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper gives a thorough treatment of a new effect of non-steady-state photo-electromotive-force (emf). The effect consists of an alternating electric current arising in a short-circuited bulk sample of a photoconductor illuminated by a vibrating sinusoidal pattern. As a detailed theoretical analysis shows, the frequency transfer function of the effect is identical with that of a differentiating RC circuit having a time constant equal to the characteristic time of a space-charge grating formation within the sample volume τsc. For high excitation frequencies (ω(approximately-greater-than)τ−1sc), the photo-emf signal peaks at spatial frequency K=L−1D (LD is the mean diffusion length of photoinduced carriers) and the photovoltage amplitude in an open-circuit sample can be as high as kBT/e times the number of fringes of the interference pattern in the interelectrode spacing. The basic conclusions of the theoretical analysis of the effect are supported by the experimental evidence obtained for cubic photoconducting Bi12SiO20 crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346525
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  • 6
    Electronic Resource
    Electronic Resource
    Formation of (Ca1−xSrx)2PbO4 in Bi(Pb)-Sr-Ca-Cu-O system: Correlation with the formation of the 2223 high-Tc phase (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2304-2307 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray diffraction data of Bi1.4Pb0.6Sr2Ca2Cu3.6O10+x samples show a sharp change near the annealing temperature of 845 °C. Below this temperature a solid solution of (Ca0.867Sr0.133)2PbO4 is formed and prolonged annealing leads to transformation of the 2212 phase to the 2223 phase. Above this temperature, Ca2PbO4 is formed, and prolonged annealing leads to an irreversible transformation of both the 2212 phase and the 2223 phase to the 2201 phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346535
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  • 7
    Electronic Resource
    Electronic Resource
    Photoquenching phenomenon enhanced by proton irradiation in semi-insulating GaAs (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6517-6519 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In undoped semi-insulating GaAs, we have found that the quenching phenomena of photoconductance and infrared absorption are enhanced by proton irradiation above 1013 /cm2, accompanied by an increase in near-band-edge infrared absorption. These phenomena disappear with the annihilation of the proton-induced near-band absorption by annealing at 350 °C. It is suggested that the enhanced photoquenching phenomena arise from the increase in the quenchable component due to the transition from the ionized midgap electron trap (EL2+) to the neutral EL20.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346855
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  • 8
    Electronic Resource
    Electronic Resource
    A detailed Hall-effect analysis of sulfur-doped gallium antimonide grown by molecular-beam epitaxy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 131-137 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental data are presented for the Hall coefficient and the apparent Hall mobility over the temperature range 160–500 K for five samples of molecular-beam epitaxially grown sulfur-doped GaSb. The donor concentration of the different samples varied between 3.3×1017 and 7.5×1016 cm−3, and the native acceptor concentration between 8×1016 and 1.2×1016 cm−3. The samples show a large spread in the apparent carrier activation energy. A two valley compensated conduction model is presented that shows that the variation in apparent carrier activation energy results from different compensation ratios in the samples. This model also shows that the constant value of the Hall coefficient observed at high temperatures is not due to donor exhaustion but carrier promotion to the lower mobility L1 band. Using constraints provided by secondary ion mass spectrometry and capacitance-voltage measurements on the samples, as well as growth data, it is shown that a narrow spread of values for the donor binding energy around 60 meV is required to account for the data. It is suggested that this spread is due to the formation of a donor band and to the strongly attractive central cores of the sulphur donors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347098
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  • 9
    Electronic Resource
    Electronic Resource
    Micromagnetics of Co-based media: Experiment and model (invited) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5540-5543 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The micromagnetics of Co86Cr14 thin-film longitudinal recording media has been investigated using Lorentz transmission electron microscopy, in the Fresnel and differential phase contrast (DPC) modes. The media studied were 350-A(ring)-thick Co86Cr14 on a 200-A(ring) Cr layer, both of which were rf sputtered onto Si3N4 membranes for ease of observation in the TEM. Different magnetization states were investigated by imaging the sample at various points in the remanent hysteresis loop. This allowed direct comparison between experimental conditions and a micromagnetic computer model which assumes the media to be an array of single-domain particles, interacting via magnetostatics and moderate integranular exchange [J.-G. Zhu and H. N. Bertram, J. Appl. Phys. 63, 3248 (1988)]. The DPC imaging technique allows vector maps and two-dimensional histograms of the integrated in-plane magnetic induction to be obtained at each magnetization state for comparison with the computer model. The scale and displacement of magnetization vortices and ripple between different states was also investigated. Both experiment and model show increasing dispersion with increasing reversal field and motion of magnetization vortices. Comparison, using the model, of individual magnetization states in an applied field and at remanence indicate a strong influence of stray fields from the media on the DPC image contrast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345880
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  • 10
    Electronic Resource
    Electronic Resource
    High-resolution spectrum of the C–O stretch overtone band in methyl alcohol (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7049-7053 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Fourier-transform spectrum of the CH3OH overtone C–O stretching band (vCO=2←0) has been recorded in the range 1950–2060 cm−1, at a resolution of 0.004 cm−1. The spectrum is resolved into J multiplets, each displaying complicated substructure due to strong torsion–vibration–rotation effects. Within this structure, it has been possible so far to identify R and P branch transitions for K=0 and K=1 for both A and E torsional symmetry species for J≤24. The assignments are supported by combination differences derived from known ground-state frequencies. The identified branches have been analyzed in terms of effective state-dependent series-expansion parameters, and the leading terms in the torsion–rotation Hamiltonian have been derived for the second excited C–O stretching state. The vCO=2 torsional barrier height is obtained as 395.5±0.2 cm−1, and the effective B value as 23 671.9±1.3 MHz. In addition, the 34.946 cm−1 far-infrared laser line pumped by the 10R(48) CO2 laser line has been tentatively identified as the (nτK,J)v=(031+,16)2→(010+,15)2 transition, and its parent IR pump absorption as the P(031+,17) vCO=2←1 hot-band line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459427
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