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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2481-2483 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-crystalline films of La2−xSrxCuO4 have been grown epitaxially on SrTiO3, NdGaO3, and LaSrAlO4 substrates by laser ablation. We show that record values of the superconducting transition temperature may be achieved by high-pressure annealing in oxygen. The films exhibit values of Tco above 38 K, as well as a linear variation of the resistivity with T and excellent crystal quality. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1614-1616 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed an anomalous behavior of reverse-bias leakage current in Hg1−xCdxTe n+-on-p photodiodes at 77 K as a function of total 10 MeV electron dose. For ZnS/SiO2 passivated planar configurations of photodiodes with 0.25〈x〈0.5, the leakage current increases superlinearly with increasing total dose greater than 10 krad, saturates at doses between 100 and 200 krad, followed by a dramatic recovery that is sometimes complete to near-preradiation values. For x(approximately-equal-to)0.2, very little or no recovery is observed. The effects of 60CO gamma irradiation are nearly identical.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2002-2010 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Turbulent features in a shock tube's contact surface with 2NO2〈=〉N2O4 are explored. Turbulent densities and velocities show an overall power-law dependence in the fluctuation spectra. At fixed reactant percentages, turbulence increases with increasing Reynolds number. At fixed Reynolds numbers, increasing the reactant percentages cause a reduction in turbulence and an increase in the relative strength of discrete high-frequency components in the density fluctuation spectra. The reliability of conventional chemical modeling for this system apparently decreases with increasing turbulence in a manner suggestive of reaction rate distortion, consistent with theoretical speculation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2122-2126 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Toroidal Alfvén eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into plasmas at low magnetic field in the Tokamak Fusion Test Reactor (TFTR) [Proceedings of the 11th International Conference on Plasma Physics and Controlled Fusion Research (IAEA, Vienna, 1987), Vol. 1, p. 51]. The injection velocities were comparable to the Alfvén speed. The modes were identified by measurements from Mirnov coils and beam emission spectroscopy (BES). TAE modes appear in bursts whose repetition rate increases with beam power. The neutron emission rate exhibits sawtoothlike behavior and the crashes always coincide with TAE bursts. This indicates ejection of fast ions from the plasma until these modes are stabilized. The dynamics of growth and stabilization were investigated at various plasma currents and magnetic fields. The results indicate that the instability can effectively clamp the number of energetic ions in the plasmas. The observed instability threshold is discussed in light of recent theories. In addition to these TAE modes, intermittent oscillations at three times the fundamental TAE frequency were observed by Mirnov coils, but no corresponding signal was found in BES. It appears that these high-frequency oscillations do not have a direct effect on the plasma neutron source strength.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 3138-3138 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1145-1148 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Neutron cameras with horizontal and vertical views have been designed for ITER, based on systems used on JET and TFTR. The cameras consist of fan-shaped arrays of collimated flight tubes, with suitably chosen detectors situated outside the biological shield. The sight lines view the ITER plasma through slots in the shield blanket and penetrate the vacuum vessel, cryostat, and biological shield through stainless steel windows. This article analyzes the expected performance of several neutron camera arrangements for ITER. In addition to the reference designs, we examine proposed compact cameras, in which neutron fluxes are inferred from 16N decay gammas in dedicated flowing water loops, and conventional cameras with fewer sight lines and more limited fields of view than in the reference designs. It is shown that the spatial sampling provided by the reference designs is sufficient to satisfy target measurement requirements and that some reduction in field of view may be permissible. The accuracy of measurements with 16N-based compact cameras is not yet established, and they fail to satisfy requirements for parameter range and time resolution by large margins. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 569-572 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Neutron diagnostics will play a prominent role in the control and evaluation of thermonuclear plasmas in ignition device to test engineering concepts (ITER). As in present D-T experiments, measurements of neutron yield and of fusion power and power density are essential. In addition, the spectral width of the 14.1-MeV t(d,n)α neutron emission should be a reliable indicator of ion temperature in an ignited plasma. More detailed measurements of the neutron spectrum may allow determination of the densities of tritium, deuterium, and confined alpha particles. Although the central fusion power density in ITER will be comparable to the maximum values obtainable in TFTR and JET, neutron flux on the first wall will be ten times higher, and the neutron yield per discharge will be about five orders of magnitude greater than previously experienced. The thermal and radiation shielding necessary to protect the ITER superconducting coils from the intense flux at the first wall will restrict diagnostic access for neutron cameras and spectrometers, complicate the design of material activation systems, and limit the applicability of conventional calibration techniques for neutron source strength monitors. These considerations, together with unprecedented reliability requirements and the need for full remote handling of many components, pose demanding challenges for the design of the ITER neutron diagnostic systems. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 916-918 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The original ZnS based NE451 detectors become saturated at the highest levels of D-D operation. A new less sensitive detector configuration, also based on ZnS crystals, was designed and tested at PPPL in order to extend the collimator capabilities to D-T plasma operation. The new detector design is composed of a thin layer of ZnS powder uniformly deposited between two layers of Plexiglas. The detector capabilities are further extended by upgraded signal processing electronics for a total enhancement of ∼1000× compared to the original detector system. An array of these detectors has been installed on TFTR in tandem with the original detector system. The current mode is presently being implemented on the original NE451 detectors. This will extend their capabilities and allow for greater overlap in data taken in the crossover region between the two detector systems. The performance of the collimator system will be illustrated by neutron data obtained during D-T operation. © 1995 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 920-922 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A ΔE-E type proton recoil telescope, called COTETRA, was developed and is presently being applied to TFTR D-T fusion experiments. Two types of COTETRA were prepared for this experiment. One set is used primarily for high-resolution measurements of the neutron energy and uses Si diode as an E detector (set A), while another set (set B) uses a plastic scintillator to attain high count-rate capability. Both sets of COTETRA have small physical dimensions and use fast NIM electronic modules for high neutron flux rate measurements. A data acquisition system has been developed for the TFTR CAMAC system. A calibration experiment has been performed using a D-T neutron generator. Energy resolution of 4.0% is obtained for set A. Set B is expected to work at a count rate of up to 104 cps, which corresponds to a neutron flux rate of ∼109 (n/cm2)/s at the detector position. Currently, both of them are installed under the multichannel neutron collimator of TFTR. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 891-893 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The two most sensitive TFTR fission-chamber detectors were absolutely calibrated in situ by a D-T neutron generator (∼5×107 n/s) rotated once around the torus in each direction, with data taken at about 45 positions. The combined uncertainty for determining fusion neutron rates, including the uncertainty in the total neutron generator output (±9%), counting statistics, the effect of coil coolant, detector stability, cross calibration to the current mode or log Campbell mode and to other fission chambers, and plasma position variation, is about ±13%. The NE-451 (ZnS) scintillators and 4He proportional counters that view the plasma in up to 10 collimated sightlines were calibrated by scanning the neutron generator radially and toroidally in the horizontal midplane across the flight tubes of 7 cm diam. Spatial integration of the detector responses using the calibrated signal per unit chord-integrated neutron emission gives the global neutron source strength with an overall uncertainty of ±14% for the scintillators and ±15% for the 4He counters. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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