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  • American Institute of Physics (AIP)  (254)
  • 1995-1999  (254)
  • 1965-1969
  • 1999  (125)
  • 1998  (129)
  • 1
    Electronic Resource
    Electronic Resource
    On the current emitted by Taylor cone-jets of electrolytes in vacuo: Implications for liquid metal ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2428-2434 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Approximate scaling laws for the charge and size of the drops ejected from the apex of Taylor cones run in the cone-jet mode (electrospray) are now available for highly conducting electrolytes (10−4 S/m〈K〈1 S/m) electrosprayed at atmospheric pressure. In order to confirm that such laws do also apply to Taylor cones in vacuo, the current versus liquid flow rate curves I(Q) characteristic of a given liquid are investigated both in vacuum and in atmospheric pressure air. Although the sprays of drops differ profoundly in both cases, the two corresponding I(Q) curves are nearly identical for relatively involatile liquids such as tributyl phosphate. A discussion on the possible relation between the behavior of Taylor cones of electrolytes of organic liquids and liquid metal ion sources (K∼106 S/m) is attempted, yielding insights on the role of space charge. However, the electrical conductivity variable which dominates the behavior of liquid cones of electrolytes appears to be irrelevant in liquid metals. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367002
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  • 2
    Electronic Resource
    Electronic Resource
    Steady state off-axis sawtoothing in the Rijnhuizen Tokamak project (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3898-3905 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A family of off-axis, or annular, instabilities has been studied using Thomson scattering, soft X-ray emission, and two electron cyclotron emission diagnostic systems. In the Rijnhuizen tokamak (RTP) [N. J. Lopes Cardozo et al., Plasma Physics and Controlled Nuclear Fusion Research 1992 (International Atomic Energy Agency, Vienna, 1993), Vol. 1, p. 271] these phenomena are invoked in a controlled way in discharges with specific (off-axis) deposition of electron cyclotron heating (ECH) and persist during most of the heating period, or during many current diffusion times. Based on coherent mode analysis at the crash time, the instabilities are associated with resonant surfaces near simple rational values of q (〈fraction SHAPE="CASE"〉32, 2, and 3). A parameter study shows an increase of reheat rate and a decrease of sawtooth period with increasing ECH power and — in contrast to observations in other experiments — with increASING density as well. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873652
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  • 3
    Electronic Resource
    Electronic Resource
    The Coulomb scattering effect on trapped particles bounce-resonance dissipation in magnetized toroidal plasmas (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1547-1553 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The solution of the Vlasov equation with a simplified Fokker–Planck collision operator is presented for axially symmetric tokamak plasmas with a circular cross section of magnetic surfaces. The analytical expression for the parallel component of the dielectric permittivity tensor of trapped particles is obtained. This expression is used for theoretical analyses of the collision effect on the bounce-resonance wave dissipation. Conditions for a collisionless description of radio-frequency (rf) oscillations are found. This dielectric tensor components can be used for computer calculations of the rf field structure and the rf dissipated power related to trapped electrons in tokamak plasmas. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873408
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  • 4
    Electronic Resource
    Electronic Resource
    On the relaxation of cold electrons and hot ions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 36-44 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relaxation process of a space uniform plasma composed of cold electrons and one species of hot ions is studied numerically using one- and two-dimensional Landau–Fokker–Planck codes. Relaxation of a monoenergetic ion beam is considered in possibly extreme temperature regimes. Special attention is paid to the deviation of the relaxation process from the classical picture, which is characterized by the close initial temperatures Te(very-much-greater-than)(me/mi)1/3Ti. The present results give quite a clear idea of the relaxation picture for any initial temperatures also in extreme temperature regimes. A difference scheme, preserving the number of particles and the energy, gives the possibility of solving the problem numerically without error accumulation, except for machine errors. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872673
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  • 5
    Electronic Resource
    Electronic Resource
    Violet and blue light amplification in Nd3+-doped fluoroindate glasses (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6782-6785 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report optical gain at 382 and 414 nm from Nd3+-doped fluroindate glasses after excitation with lasers operating either at 583 or 532 nm. Stimulated emission due to a frequency upconversion process results in increase of the emitted violet and blue light intensity and emission line narrowing. Large optical gain is measured by pump-probe spectroscopy using samples with various Nd3+ concentrations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370194
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  • 6
    Electronic Resource
    Electronic Resource
    Fast pulsed radar reflectometry for the Textor Tokamak : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1034-1037 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Progress in fusion research shows an increasing demand for diagnostics with high temporal and spatial resolution in order to study small and fast phenomena in fusion plasmas. Therefore, a new ten-channel pulsed radar reflectometer is under development for the TEXTOR Tokamak, to measure electron density profiles in the range of 0.4–4×1019 m−3 at a high repetition rate of 2 MHz. An additional feature of this diagnostic is the possibility to perform correlation measurements at 10 MHz repetition rate to investigate density fluctuations. The reflectometer will scan the plasma with 1-ns-long radar pulses in the 18–57 GHz range. In spite of the long flight time of the pulses of about 100 ns, the above mentioned high repetition rates could be achieved by time multiplexing the generation and reception of the radar pulses. Temporal selection of the received pulses is performed by fast switching of the local oscillators inputs of the heterodyne receiver, to generate time windows in which the reception of the reflected pulses is expected. An embedded VME controller will manage the system and store the data with a speed of 20 Msamples/s, up to a maximum of 64 Mbyte data per plasma shot. In order to facilitate the handling of such a huge amount of data, an advanced data reduction scheme is being developed. Remote operation with a fast data link from FZ Jülich (Germany) to FOM Nieuwegein (The Netherlands) will be possible. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149426
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  • 7
    Electronic Resource
    Electronic Resource
    Argon ion-induced dissociation of acetylene in an expanding Ar/C2H2 plasma (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2927-2929 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mass spectrometric and Langmuir probe measurements reveal that the plasma chemistry of an expanding Ar/C2H2 plasma which is used for deposition of hydrogenated amorphous carbon is dominated by argon ion-induced dissociation of the precursor gas. The ion-induced dissociation is very efficient leading to complete depletion under certain conditions. The ion fluence as determined from modeling the mass spectrometry results is in good agreement with Langmuir probe measurements suggesting a one-to-one relation between the argon ion and acetylene consumption. The good correlation found between the growth rate and the acetylene consumption rate expresses the efficient use of the dissociation products. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123968
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  • 8
    Electronic Resource
    Electronic Resource
    Optical properties of PrAg under pressure (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2025-2029 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present interband optical conductivity and oscillator strength calculations of PrAg within the linear muffin-tin orbital formalism in the atomic sphere approximation. We have compared the optical spectra for both the ferromagnetic and paramagnetic phases at normal pressure and found that exchange interaction has considerable influence on its optical properties, thereby ascertaining the ferromagnetic nature of PrAg. The oscillator strength or the transition probability plays a vital role in determining the magnitude and position of the peaks in the optical spectrum. Application of pressure decreases the optical conductivity at 0.4 Ryd but the crucial peak at around 0.04 Ryd is displaced to 0.08 Ryd with reduced magnitude. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368259
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  • 9
    Electronic Resource
    Electronic Resource
    Two-powder Nd2Fe14B magnets with DyGa-addition (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 388-393 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic and structural properties of sintered NdFeB magnets with addition of various amounts of DyGa as a separate powder are studied and compared with single-powder magnets of the same nominal composition. When the magnets are annealed above 640 °C, the coercivity decreases strongly as compared to magnets annealed below 640 °C. Decomposition of the δ phase (Nd6Fe14−xGax) accompanies this drop. Measurements of coercivity as a function of temperature show that the decomposition of the δ phase does not increase the effective demagnetization factor, but enlarges either the magnetic inhomogeneous region at the grain surface or the exchange coupling between the grains. Line faults, which are present within the Nd2Fe14B grains when the magnet is annealed below 640 °C, do not act as pinning centers. Phase analysis and diffusion profiles of the Dy and Ga concentration within the grains are made using electron probe micro-analysis. This shows that Ga forms Nd3Ga2 and Nd6Fe12.7Ga1.3 as intergranular phases. Its concentration within the Φ phase is significantly lower than in the Φ phase of single-powder magnets. At 1090 °C, a diffusion coefficient for Ga of D=2.5±0.1×10−15 m2/s is found. Dy is shown only to be present in that part of the Nd2Fe14B grain which has precipitated from the liquid during sintering. At the boundary of the Dy-free center and the outer part of the grain, an increased Dy concentration is found. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366734
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular hyperpolarizabilities of retinal derivatives (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5102-5106 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report measurements of the third-order optical susceptibilities of 13-cis and all-trans retinal derivatives in chloroform liquid solutions using the Z scan and the optical Kerr gate techniques, with laser pulses of 70 ps and 60 fs, at 532 and 800 nm, respectively. The corresponding second hyperpolarizabilities of those molecules are estimated and the results compared to those obtained from semiempirical time-dependent Hartree–Fock calculations. The observed trends for the values of the nonlinear response are explained in terms of the π electron delocalization along the polyenic chain of the molecules. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479766
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