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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4999-5001 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic domain structures of thick and small area (45×45×5 μm3) Fe-M(Zr or Ta)-N films were observed by a scanning Kerr-effect microscope (SKEM). The important factors in controlling the magnetic domains are the magnetostriction and the uniaxial anisotropy. By changing the N content in bcc Fe and the Ar pressure during sputtering, the saturation magnetostriction constant λs and the anisotropy field Hk were controlled in the range of 3×10−6–6×10−6 and 10–130 A/m, respectively. Clear and consecutive changes in the domain structures were observed by varying the film's λs, Hk, and stress σ, and the observed structures agree qualitatively with the structures predicted by theoretical calculations. The wall structure where Bloch-like rotations and the Neel-like rotations are combined was observed by SKEM. The metal in gap heads using different λs and Hk films were fabricated and the output at 20 MHz was measured. A lower Hk is not necessarily better for obtaining a higher output in high-frequency ranges. The head output depends on the film's magnetic domain structure, and the structure can be controlled by changing the λs and Hk. © 1996 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 66 (1995), S. 923-925 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A calibration experiment of the neutron counters of the Compact Helical System (CHS) has been carried out in order to determine the calibration factor which relates the neutron-counter output to the extended neutron source of a torus plasma. The instruments employed in the present experiment include a BF3 proportional counter, a 3He proportional counter, an NE213 organic liquid scintillator. The BF3 counter was installed at the center of the CHS torus and the other two detectors were installed outside the torus. A total of 64 toroidal angles along the magnetic axis of plasma were surveyed by the movement of a 252Cf neutron source. The poloidal cross section of the CHS plasma is elliptical in shape and rotates toroidally with the same period as that of the helical coil. The spatial distribution of 25 local point efficiencies in three poloidal cross sections with elongated orientations of 0°, 45°, and 90° were investigated in order to determine the influence of the plasma profile on the calibration factor. The shadow and scattering effects were clearly observed by the center counter when the source was located behind the helical coil. The calibration factor for the BF3 counter, obtained by averaging the point efficiencies over all the toroidal angles, was 3.6×10−4 counts per neutron, about several ten times greater than those of the counters located outside the torus. Details of the calibration setup and the analysis of experimental results are presented. © 1995 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 63 (1992), S. 3694-3700 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Active control of beam trajectories using four sets of sweep plates is proposed for a heavy ion beam probe (HIBP) system on helical plasma, such as torsatron, stellarator, etc., in order to solve problems arising from the complicated beam trajectories in its nonaxisymmetrical magnetic field. By this method, a series of the probing beam trajectories giving a whole potential distribution can be managed to pass at a particular point (detector aperture) with the same angle. An equation is introduced as a guiding principle to simplify the optimization process of geometrical configuration of the HIBP system, which will be adjusted for different magnetic configurations by only changing the sweep plate voltages.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An efficient neutron diagnostic system has been established and applied to deuterium experiments on compact helical system. A neutron counter was installed at the center of the torus, and the detection efficiency was about two orders of magnitude higher than the values of most toroidal fusion devices. The effect of the stray magnetic field on the operation of a proportional counter was experimentally confirmed to be negligibly small. The ion temperature, as low as 400 eV, was obtained from neutron measurement with a time resolution of 1 ms. The decay time of neutron emission rate after the termination of a 1% deuterium-doped beam was measured and the confinement time of neutral beam-injected fast ions was estimated. The fast ion confinement was clearly improved by strengthening the toroidal magnetic field. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 445-448 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to determine the magnitude and the position of the plasma current in a long pulsed tokamak such as the International Thermonuclear Experimental Reactor (ITER), it is urged to establish a reliable method which is free from the zero-level drift of the integrator as well as the radiation damage for the steady-state magnetic field measurement. For this purpose, we have developed a hybrid system, a combination of a conventional magnetic probe for the measurement of fast varying magnetic field and a rotating coil magnetic probe for that of slowly varying field. The rotating coil is energized by an air turbine to avoid electromagnetic interference and the induce signal with a constant rotation frequency is picked up through a transformer to eliminate mechanical contacts. An automatic gain control circuit is also designed for the compensation of rotation speed fluctuation. The system is proved to achieve a flat frequency response with a proper choice of cross over frequency for high- and low-frequency systems. The rotating coil probe is tested for over 170 h without any trouble. The probe was applied to the poloidal magnetic field measurement on the TRIAM-1M long pulsed tokamak, and proved to work satisfactorily. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1636-1643 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1292-1295 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Preferentially oriented epitaxial Y-Ba-Cu-O films were prepared on (100) SrTiO3 substrates by oxygen reactive ion beam sputtering. The epitaxial orientations were varied by controlling both substrate temperature and oxygen parital pressure. c-axis oriented films tended to be formed at higher substrate temperatures (〉620 °C) and lower oxygen pressures (〈3×10−3 Torr). In contrast, a/c- and a-axis oriented films were formed at lower substrate temperatures (〈600 °C) and higher oxygen pressures (〉3×10−3 Torr). The best Tc (end) of 82 K was observed in one of the c-axis oriented film without post-annealing. The tendency for preferential orientation can be well understood in terms of the lattice mismatch between the substrate and the film, the lattice constants of which depend on oxygen deficiency.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 936-938 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Annealing effects of Y-Ba-Cu-O superconductor thin films implanted by 200-keV Ne+ have been investigated. Transition temperature (Tc) end points for 0, 1×1014, 1×1015, and 1×1016 ions/cm2 doses are 75, 71, 62, and 16 K, respectively. The film implanted at 1×1017 ions/cm2 dose indicates nonsuperconductors. The c-lattice constant increases were observed for the implanted films. It is confirmed that the superconducting characteristics for film, which is implanted at 1×1016 ions/cm2 dose, are recovered by annealing in O2 atmosphere at 940 °C for 4 h. Moreover, microcrystal growth caused by annealing the implanted film was observed on the surface.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5998-6000 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization in a VCR thick film magnetic head with 10-μm-thick poles was measured by a scanning Kerr effect microscope (SKEM) and calculated by a three-dimensional finite element method (FEM) including a time dependent term. The SKEM measurements were achieved at the rubbing surface of the heads and it was observed that the vertical magnetization component to the surface has peaks at both side edges of the poles and the peak height ratio to height at the pole center becomes larger as the driving frequency increases. These measurement results were in good agreement with the FEM calculations. The comparison with the measurements and the calculations for a ferrite head shows that the magnetization peaks are attributed to both the eddy currents and the geometrical effects.
    Type of Medium: Electronic Resource
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