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  • 1990-1994  (16)
  • 1970-1974  (4)
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  • 1
    Digitale Medien
    Digitale Medien
    Neutron depolarization in reentrant spin glasses Ni1−xMnx (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5232-5234 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Polarization analysis of the transmitted beam was performed using a pulsed neutron source in a reentrant spin-glass (RSG) system Ni1−xMnx, for a concentration range (0.23≤x≤0.28) encompassing the critical concentration. The same samples were previously used to determine the magnetic phase diagram by magnetization measurements. The polarization P was measured as a function of temperature (15≤T≤300 K), neutron wavelength (3≤λ≤10 A(ring)) and applied field (7 Oe≤H≤125 Oe). Unlike other RSG systems, P measured in a 7 Oe field decreases at all temperatures below the Curie temperature even for the samples close to the critical concentration. The wavelength dependence of the polarization indicates the existence of magnetic domains whose size δ decreases with increasing x from a few tenths of micrometers at x=0.23 to a few thousands of angströms at x=0.25. No depolarization occurs for x〉0.25. As shown for x=0.23, the irreversibilities of the polarization, which depends on the cooling conditions, indicate that the domain arrangement freezes at low temperature. Clearly, in NiMn, the drop of the susceptibility at low temperature does not result from a decrease of the size or magnetization of the domains but from a slowing down of their mobility.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.344620
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  • 2
    Digitale Medien
    Digitale Medien
    Partition in power transfer and dissipation rate in self-sustained turbulence (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1154-1158 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Power partition and energy dissipation rates are examined for a self-sustained stationary turbulence of a high-n ballooning mode in a tokamak plasma. It is found that the power to excite fluctuations is almost equally transferred to perpendicular ion motion and to parallel electron motion. The ratio of the thermalized power, which excites and sustains the turbulence, to the total power lost by energy diffusion is found to be of the order of the broken symmetry parameter, i.e., the inverse aspect ratio, a/R. The dissipation rates of the fluctuations due to the thermal conductivity, the electron viscosity, and the ion viscosity are also calculated separately. The dissipation is dominated by that associated with the thermal conductivity. The relation between the induced global flux and the microscopic dissipation is also derived. It is found that a fractional part of order a/R of the dissipated power is effective in sustaining the turbulent modes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.870711
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  • 3
    Digitale Medien
    Digitale Medien
    Thickness of the layer of high shear radial electric field in JFT-2M H-mode plasmas (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 116-119 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The poloidal rotation velocity profiles both in low-confinement (L) and high-confinement (H) mode measured in JAERI Fusion Torus 2 Modified (JFT-2M) [Phys. Rev. Lett. 65, 1364 (1990)] are compared with H-mode models based on ion orbit loss. The profiles of poloidal rotation velocity measured in L and H modes are consistent with the calculation which consists of ion orbit loss model. The observed dependence of the thickness of the layer of high shear Er on poloidal gyroradius is explained by the radial transport of poloidal rotation velocity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.870944
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  • 4
    Digitale Medien
    Digitale Medien
    Thermal and electric oscillation driven by orbit loss in helical systems (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 796-798 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Coupled oscillation of the radial electric field, the heating power, and the plasma temperature in helical systems is analyzed. This oscillation is caused by the influence of the radial electric field on the direct loss of injected fast ions. The damped oscillations of the radial electric field, temperature and fast-ion loss are predicted. Conditions for the occurrence of the mode and the oscillation frequency are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.870774
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  • 5
    Digitale Medien
    Digitale Medien
    A compact neutron counter telescope with thick radiator (COTETRA) for fusion experiments (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1636-1643 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A new type of neutron spectrometer, which is called COTETRA (counter telescope with thick radiator), has been developed for diagnosing DT fusion plasma. It is based on the recoil proton measurement and has such advantages as: (1) direct measurement of the neutron energy without the unfolding procedure, (2) sufficiently fine energy resolution and high detection efficiency for 14 MeV neutrons, (3) wide dynamic range of counting rate, and (4) good n–γ discrimination. A prototype of COTETRA was constructed and tested using a DT neutron accelerator. The energy resolution of 5.3%±0.9% was obtained for 14 MeV neutron with the detection efficiency of 1.3×10−4 [counts/(n/cm2)]. A Monte Carlo simulation code was developed and the performances of COTETRA were examined. The calculation agrees with the results of the experiment within its margin of error and suggests that energy resolution up to 3% with a detection efficiency of 10−5 [counts/(n/cm2)] could be achieved if the condition of the radiator could be successfully adjusted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1144852
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  • 6
    Digitale Medien
    Digitale Medien
    Rapid thermal oxidation of thin nitride dielectrics deposited on rapid thermal nitrided polycrystalline silicon (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1313-1315 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: This letter compares the effects of two different oxidation techniques, i.e., rapid thermal and conventional wet (steam) oxidations, on the dielectric breakdown and charge trapping characteristics of thin Si3N4 films deposited on rapid thermally nitrided polycrystalline silicon. Results show that, in addition to the low thermal budget, rapid-thermal-oxidized Si3N4 shows superior time-dependent dielectric breakdown characteristics in terms of reduced defect densities and improved film intrinsic properties. Compared to wet-oxidized dielectrics, suppressed charge trapping is observed for rapid-thermal-oxidized Si3N4 stacked dielectrics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.107576
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  • 7
    Digitale Medien
    Digitale Medien
    Theory of pseudoclassical confinement and transition to L mode (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3299-3303 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A theory of the self-sustained turbulence is developed for resistive plasma in toroidal devices. Pseudoclassical confinement is obtained in the low-temperature limit. As temperature increases, the current diffusivity prevails upon resistivity, and the turbulence nature changes so as to recover the L-mode transport. Comparison with experimental observation on this transition is made. The Hartmann number is also given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860626
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  • 8
    Digitale Medien
    Digitale Medien
    Nonresonant current drive and helicity injection by radio-frequency waves (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 539-549 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Current drive via nonresonant interaction between radio-frequency (rf) waves and plasma is studied. The averaged force of rf waves acting on each species of a plasma can be divided into a resonant force and a nonresonant one. A part of the nonresonant force cannot be expressed by a gradient of a scalar potential and remains after integrating along the direction of the force. This force mainly acts as an internal force among plasma species and the net momentum input from the wave to the plasma is usually small. This process is not included in the conventional current drive schemes but is associated with the rf wave helicity injection. Quantitative analysis using a one-dimensional kinetic wave code is applied to waves in the ion cyclotron range of frequencies and low-frequency Alfvén waves in a large tokamak. The driven current is estimated taking account of the effect of the toroidally trapped particles. The spatial profile of the forces acting on electrons and ions as well as the driven current are obtained. The parameter dependence of the current drive efficiency on the wave number, the plasma density, the temperature, and the toroidal magnetic field is compared with the estimate based on a local analysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860539
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  • 9
    Digitale Medien
    Digitale Medien
    Analysis of the current-diffusive ballooning mode (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3702-3711 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The current-diffusive ballooning mode is analyzed in the tokamak plasma. This mode is destabilized by the current diffusivity (i.e., the electron viscosity) and stabilized by the thermal conductivity and ion viscosity. By use of the ballooning transformation, the eigenmode equation is solved. An analytic solution is obtained by the strong ballooning limit. Numerical calculation is also performed to confirm the analytic theory. The growth rate of the mode and the mode structure are analyzed. The stability boundary is derived in terms of the current diffusivity, thermal conductivity, ion viscosity, and the pressure gradient for the given shear parameter. This result is applied to express the thermal conductivity in terms of the pressure gradient, magnetic configurational parameters (such as the safety factor, shear, and aspect ratio), and the Prandtl numbers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860841
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  • 10
    Digitale Medien
    Digitale Medien
    Chain-breaking phenolic antioxidants: steric and electronic effects in polyalkylchromanols, tocopherol analogs, hydroquinones, and superior antioxidants of the polyalkylbenzochromanol and naphthofuran class (1993)
    s.l. : American Chemical Society
    The @journal of organic chemistry 58 (1993), S. 7416-7420 
    Details
    ISSN: 1520-6904
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/jo00078a020
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