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  • Electronic Resource  (63)
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  • Electronic Resource  (63)
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  • 11
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1560-1562 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plug potential is formed experimentally, even without high energy sloshing ion population in the end-mirror cells of a tandem mirror. It has been shown analytically that the plug potential can be formed in the present experimental conditions by using the plausible distribution functions of ions and electrons and a small ionization source. In this paper, the required ionization rate is estimated for the continuous potential profile around the plug by using Emmert's source. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron diagnostics are applied to a deuterium plasma mixed with protons in the central cell of the GAMMA 10 tandem mirror [Inutake et al., Phys. Rev. Lett. 55, 939 (1985)]. The deuterium ions are heated with a slow ion cyclotron wave tuned to the fundamental deuterium resonance near the mid-plane of the central cell while the plasma is sustained with the fundamental resonance heating of protons in the minimum-B anchor cells. The measurement is based on in situ calibration to determine the transmission efficiency through machine walls and the counting efficiency of the detection system for neutrons emitted from 252Cf with energy close to that in the deuterium–deuterium (D–D) fusion reaction. The observation shows that the count rate of neutrons increases with diamagnetism, and this relation is accounted for in terms of fusion reaction between deuterium ions with a transverse temperature exceeding 10 keV. Discrepancies among ion temperatures determined with different diagnostics are mostly attributed to insufficient knowledge of the profiles of plasma parameters. The results indicate that the neutron measurement can be added as a powerful diagnostic tool for hot ions if combined with more detailed profile measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2321-2327 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Confinement of ion cyclotron resonance heating (ICRH) plasmas in the GAMMA 10 tandem mirror [Phys. Rev. Lett. 55, 159 (1985)] has been investigated. Magnetohydrodynamic (MHD) stability is provided by the axisymmetrized minimum-B system. Ion confining and thermal barrier potentials are produced only by electron cyclotron resonance heating (ECRH). Ions are heated to several keV and hot ion modes, where Ti/Te(approximately-greater-than)(mi/me)1/3, are produced. Ion pressure in the central cell increases approximately linearly both with the power radiated from the antennas and with the magnetic field. A record ion temperature of about 10 keV is obtained at the maximum magnetic field (∼0.57 T). Thermonuclear fusion neutrons are detected in a deuterium/hydrogen mixture plasma for the first time in a tandem mirror. In typical GAMMA 10 operations, strong radial electric fields are naturally produced, and density fluctuations are suppressed. Axial confinement of the core plasma is consistent with the classical potential confinement, indicating radial confinement is better than axial confinement. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 3986-3995 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal dike is a new concept for controlling energy transport carried by electrons along open magnetic field lines by enhancing mirror-reflection with assistance of electron cyclotron resonance heating (ECRH). Quantitative analyses are made to evaluate merits of thermal dike and to clarify requirements for efficient use of it. Heating response function is applied for trajectory analyses of electrons streaming through the ECRH zone. Substantial power gain is obtained under a configuration with a high mirror ratio between the reflection point and the resonance point and with a large scale length of the magnetic gradient in the resonance zone. Thermal dike is shown to be beneficial both in tandem mirrors and in diverters in tori. Discussions are made also on a basic experiment program of thermal dike in the GAMMA 10 tandem mirror.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2972-2981 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A response function [Y. Kiwamoto et al., Phys. Plasmas 1, 834 (1994)] for higher harmonic cyclotron resonance heating is constructed through the analysis of electron trajectory under harmonic heating in an inhomogeneous magnetic field. General expressions of orbital displacement and energy gain for higher harmonic resonance are obtained. Phase-averaged energy gain of electrons by n-th harmonic electron cyclotron resonance heating (ECRH) is larger by a factor of n, if the effect of the orbital displacement from the unperturbed orbit is correctly included, than that evaluated based on an unperturbed orbit assuming small k⊥ρ. The energy gain for finite k⊥ρ is also obtained. These results are confirmed with a numerical calculation for second harmonics. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2532-2543 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is suggested experimentally that a plug potential forms in a different mechanism from the originally expected scenario in the present tandem mirror [T. Tamano, Phys. Plasmas 2, 2321 (1995)]. That is, the formation requires only electron cyclotron resonance heating experimentally. In this manuscript, therefore, the plug potential with continuous axial profile is analytically shown to be created with the plausible ion and electron distribution functions in a present tandem mirror, i.e., passing ions, mirror trapped ions in the thermal barrier, passing electrons, φ-trapped electrons in a plug potential, and the small amount of ions that are born around the plug region.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3319-3323 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A gold neutral beam probe system which uses a microchannel plate (MCP) as a beam detector is being constructed in order to measure the electrostatic potential at the inner mirror throat (IMT) of the plug/barrier cell in the tandem mirror. The MCP detector was newly designed so as to be able to be used in the IMT strong magnetic field. The characteristics of the MCP gain were measured on a test stand with the strong magnetic field. The characteristic curves of the relative MCP gain were described as functions of the magnetic field strength, the MCP bias voltage, and the angle between the magnetic field and the capillary axis of the MCP. It was found that the newly designed MCP detector was useful for the potential measurement at the IMT region. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A millimeter-wave two-dimensional imaging array has been developed for diagnostics of magnetically confined plasmas. It is applied to the plug cell of the GAMMA 10 tandem mirror, and measures time evolution of radial and axial line-density and electron cyclotron emission (ECE) profiles in one plasma shot. The monolithic-type GaAs Schottky diode detector having an antenna and built-in amplifier on a GaAs substrate is newly fabricated using monolithic microwave integrated circuit (MMIC) technology. This novel detector is developed to attain high frequency response up to submillimeter-wave region and wideband heterodyne characteristics, and is expected to be applied to ECE imaging in a large helical device. The response of the detector is compared with that of the hybrid-type detector using beam-lead Schottky barrier diodes. The first experimental result of the ECE measurement is reported using a heterodyne radiometer with the MMIC detector. © 1999 American Institute of Physics.
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  • 19
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A gold neutral beam probe system was improved by adopting a multichannel ion detector and adding sweeping functions of beam energy, deflector voltage, and electrode voltage of the analyzer to the system to measure the fluctuations and time evolution of the two-dimensional space potentials with fast resolving time during one shot. Positions of the beam spot on the multichannel detector corresponding to the ionizing points of the beam in the plasma were simulated precisely as a function of the beam energy and the injection angle. A potential derivation formula was determined taking into consideration both the numerical and experimental results, and the reproducibility of the potential profile was checked. Two-dimensional potential profiles were measured in the optimization experiment of the microwave injection angles for formation of the plug potential. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Semiconductor ion detectors are developed and characterized for the purpose of the use for high-output and wide-energy-sensitive upgraded ion diagnostics. In particular, the theoretical basis for the simulation of the semiconductor ion-energy response along with its experimental verification using monoenergetic ion beams is investigated. High-output-current semiconductor signals ranging from one to three orders of magnitude larger than those from widely employed commercially available silicon-surface-barrier detectors are attained in the ion-energy region above 0.2 keV. These data are found to be well fitted by the developed simulation results. In order to observe ion signals alone under the complicated condition of the simultaneous incidence of ions, electrons, and x rays, we develop an upgraded electrostatic ion-energy spectrometer, having specific structures with obliquely positioned multiple grids. The combination of the installation of such a low-ion-energy-sensitive semiconductor detector and this novel-structured ion spectrometer provides a new electrostatic large-output and low-energy-sensitive ion spectrometer having no signal disturbances from the other plasma species and giving no perturbations to ambient plasma-confining magnetic fields. Accordingly, this novel compact-sized electrostatic ion spectrometer using a single-channel semiconductor collector provides temporal-evolution data on ion-energy spectra during a single plasma shot alone; therefore, this spectrometer is usefully applicable to the opportunities of the observations of ion parameters in both divertor and hot-core regions. © 1999 American Institute of Physics.
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