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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1011-1013 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new second harmonic heterodyne electron cyclotron emission system with high spatial resolution (≤15 mm) and a large number of channels (32) for dense profile coverage will be installed on Alcator C-Mod. The system will provide detailed radial electron temperature profiles and core temperature fluctuation measurements. The collection system is composed of elliptical and parabolic mirrors coupled to two overmoded waveguides to provide high poloidal spatial resolution necessary for T˜e measurements. Four radiometer sections cover the frequency range of 234–306 GHz, coupled to four optimized intermediate frequency modules with eight channels of detectors, amplifiers, dividers, and filters providing the profile information. A separate filter arrangement allows for temperature fluctuation measurements utilizing correlation techniques. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3359-3360 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present preliminary performance results for a new type of imaging microscope operating in the EUV and soft x-ray regions. This microscope is a true transmission microscope in which an unmagnified image of the sample is formed by differential absorption of the x-ray beam as it passes through the sample. The unmagnified photon image is converted into low energy secondary electrons at a thin CsI photocathode, and the subsequent electron pattern is magnified and imaged using a simple 3-lens system. Conversion of the magnified electron patern into visible photons occurs at a fine grain phosphor viewed by a CCD detector/computer combination that allows parallel detection of the original photon image in near real time with approximately 1000× magnification. The microscope has a theoretical resolution of 20 nm and a potentially wide range of uses including biology, materials science studies, and investigations into magnetic dichroism effects. The design and preliminary imaging results of the microscope will be presented and future directions discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 427-429 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A system for vertically observing the second-harmonic electron-cyclotron emissions from the TEXT-U tokamak in conjunction with fundamental electron-cyclotron heating is described. Using external collection optics and heterodyne receivers, measurements of the distribution function can be performed over two-thirds of the plasma radius and on transport time scales. Observations are typically of electrons with energy E〈100 keV and either steep or shallow pitch angle, depending upon the toroidal viewing angle relative to the plasma current. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 451-453 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Radial scans of high-frequency electron temperature fluctuations T˜e,rms have been performed in TEXT-U ohmic discharges. The measurements were accomplished by using a technique correlating the electron cyclotron emission at two disjoint frequency bands emitted from essentially the same plasma volume. Focusing and defocusing the optics allows one to estimate the poloidal k spectrum of these fluctuations. Applying the analysis stroboscopically synchronized with the sawtooth oscillations it is shown that, in the central region of the plasma, sawteeth are the dominant contribution to low-frequency modes. Additionally, by adjusting the frequency of one of the bands, one can separate the two volumes and thus estimate the radial correlation length of T˜e,rms. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4574-4576 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-walled carbon nanotubes (SWCNs) encapsulated in multiwalled WS2 nanotubes are produced by pyrolyzing a mixture of WO3−x and SWCNs in N2/H2S atmosphere. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1194-1196 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport of material from target to substrate has been monitored in the pulsed laser deposition of Pb(Ti0.48Zr0.52)O3 films on p-doped Si(100) using two in situ diagnostics, namely plume fluorescence spectroscopy and plume ion mass spectrometry. The as-grown PZT films are specular, with thicknesses which decrease from 350 to 250 nm on a radius 5 mm from the center and show a dielectric hysteresis with typical remanent polarizations and coercive fields of 0.2 μC/cm2 and 124 kV/cm, respectively. The analysis of the plume fluorescence emission and ionic yield indicates that oxidation of the ablated material occurs during transport from target to substrate and that, in order to grow ferroelectric thin films, the substrate should be located in the region of the plume where the relative concentrations of metal oxides and clusters increase.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4967-4969 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An effort to develop La manganites for possible sensor applications has led to the successful growth of La1−xBxMnO3−δ (B=Sr, Ca) thin films on single crystal MgO, Al2O3, and LaAlO3 substrates. Here we concentrate on Sr-doped material on LaAlO3 with Curie temperature Tc=262±2 K. Tc was determined from magnetization measurements using Arrott plots, and agrees well with the observed resistivity peak in zero applied magnetic field (H). This Tc corresponds closely to a Sr content x=0.17 reported in bulk materials. At H=60 kOe the maximum magnetoresistance Δρ/ρ(approximate)0.95. No discernible hysteresis, as might be expected for structural phase transitions, was observed. When plotted as a function of reduced temperature T/Tc, the magnetization extrapolated to zero H is best fit by a Brillouin function with an effective spin value 〈S〉 much larger than the 〈S〉=1.9 indicated by the composition. This may be indicative of magnetic polaron formation, especially near the magnetic and transport transition temperatures. At temperatures far below Tc there is an increase in resistivity of the thin films, which is considerably modified by the application of a field of 50 kOe. The conductivity, however, remains finite as the temperature approaches zero, indicating transport in states close to but above the mobility edge. © 1997 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3793-3795 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of applying an electric field across a quasi-phase-matched frequency doubling lithium tantalate waveguide has been investigated. The waveguide was fabricated by a two-stage ion exchange process in pyrophosphoric acid. An electric field of 2 kV/mm was found to shift the phase matching wavelength by 0.05 nm. It is estimated that more optimized waveguides could produce wavelength shifts of ±4 nm for an applied electric field of ±20 kV/mm and could compensate for temperature variations of ±67 °C. © 1996 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 9791-9796 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured rotational excitation into rotational states J=3, 4, and 5 for H2 scattered from Pd(111) as a function of surface temperature and incident translational energy. Excitation is found to occur even when the incident H2 translational energy is less than the energy level spacing between the initial and final rotational states. Thus, part of the excitation energy is coming from the surface, not from solely translational–rotational energy coupling. There is a strong surface temperature dependence to the rotational excitation that is well described by an Arrhenius-type expression. When fit to the Arrhenius equation, the apparent activation energy is less than the rotational energy level spacing and decreases as the translational energy of the incident molecules is increased. Based on inspection of the calculated H2/Pd(111) potential energy surface, we attribute this lowered activation energy to an extension of the bond length when the molecule interacts with the surface. The stretching of the molecular bond increases the moment of inertia of the molecule, which then decreases the spacing between the rotational energy levels. We suggest that the final states of molecules which do not dissociate reflect features of the potential energy surface associated with open, dissociative pathways. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 3718-3732 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Two implementations of the backward Euler method for simulating molecular fluids are compared with Brownian dynamics and molecular dynamics simulations of a single diatomic molecule, liquid argon, a single butane molecule, and liquid butane. By comparison with standard molecular dynamics results, backward Euler simulations give different thermodynamic properties for liquids; predict liquid structures which are too solidlike; and incorrectly represent dynamical relaxation processes. The backward Euler methods allows longer time steps to be used in simulations at the cost of an energy minimization at every time step. Even when time steps more than 20 times larger than that required for energy and momentum conservation are used, neither implementation of the backward Euler algorithm is more accurate than standard molecular dynamics calculations with the same time step. We conclude that the new methods offer no computational advantages over more usual methods for simulating molecular fluids and that they often predict incorrect results. © 1995 American Institute of Physics.
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