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  • 1
    Electronic Resource
    Electronic Resource
    Technique for measuring the two-port scattering matrix of a plasma current drive antenna during high power operation (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1168-1175 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a technique to routinely measure the scattering matrix of a radio frequency (rf) current drive antenna in a magnetic fusion experiment during high power operation. This technique can be used under any conditions of phase or amplitude of excitation. It involves modulation of the phase of the rf voltage applied to each of the antenna ports by a few degrees, measurement of the complex forward and reflected voltages, detection of the phase modulation, and solution of a 2×2 matrix problem to yield the scattering matrix. Further calculation then yields the antenna's impedance matrix. Because it involves only a small modulation, this method can be used to routinely monitor matching, decoupling, or plasma loading and to provide input to tuning calculations so that the matching and phasing conditions can be maintained. We show results for the case of 400 kW Alfvèn wave current drive experiments on the Phaedrus-T tokamak. We also show how the results can be used to tune the antenna. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147879
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  • 2
    Electronic Resource
    Electronic Resource
    Alpha-driven magnetohydrodynamics (MHD) and MHD-induced alpha loss in the Tokamak Fusion Test Reactor : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1610-1616 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Alpha-driven toroidal Alfvén eigenmodes (TAEs) are observed as predicted by theory in the post-neutral beam phase in high central q (safety factor) deuterium–tritium (D–T) plasmas in the Tokamak Fusion Test Reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)]. The mode location, poloidal structure, and the importance of q profile for TAE instability are discussed. So far no alpha particle loss due to these modes was detected due to the small mode amplitude. However, alpha loss induced by kinetic ballooning modes (KBMs) was observed in high-confinement D–T discharges. Particle orbit simulation demonstrates that the wave–particle resonant interaction can explain the observed correlation between the increase in alpha loss and appearance of multiple high-n (n≥6, n is the toroidal mode number) modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872363
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  • 3
    Electronic Resource
    Electronic Resource
    Fast wave damping on non-Maxwellian electrons (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2915-2921 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theoretical studies of fast wave damping on electrons are presented. Different regimes of importance for fast wave plasma heating and current drive in tokamaks are considered. Various cases of Maxwellian and multi-Maxwellian, isotropic and anisotropic electron distribution functions are investigated. In all cases, fast wave damping on electrons is due to three terms: Landau damping, transit-time magnetic pumping (TTMP), and the cross-term effect. Expressions for all these terms are derived for all regimes considered. Although in most cases Landau damping, TTMP, and the cross-term effect are the same order of magnitude, regimes are found that can be referred to as the pure Landau damping regimes, or pure TTMP regimes. A key parameter that defines the character of fast wave damping is found: δα=ε2/γαεε3. In simplified form, and far from resonances, it can be written as δα≈−2ω2/ΩiΩeβα, where α specifies the appropriate regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860164
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  • 4
    Electronic Resource
    Electronic Resource
    Three-dimensional mode structure of the drift cyclotron loss-cone instability in a mirror trap (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3439-3444 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The three-dimensional mode structure of the drift cyclotron loss-cone (DCLC) instability is characterized in an axisymmetric mirror machine. It is shown, for this experiment, that (1) the azimuthal mode structure does not assume the geometry associated with an azimuthal normal mode φ˜=f (r,z)exp(imθ) with a single integral value of m, (2) the presence of a cool-ion plasma stream does not, in general, stabilize the mode globally, and (3) the axial mode characteristics have finite structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865860
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  • 5
    Electronic Resource
    Electronic Resource
    Perpendicular ion energy analyzer for hot-ion plasmas (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1463-1464 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A miniature analyzer probe is described for measuring the component of the ion energy distribution perpendicular to the confining magnetic field in a hot-ion plasma. The analyzer employs the magnetic field to exclude electrons due to their small gyroradii. Ions are selectively retarded by a positively biased collector. The limits on the operating regime of this analyzer are calculated. The device is used in the MIX 1 mirror machine where we measure an ion temperature of ∼100 eV and plasma density (approximately-greater-than)1011 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138533
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    Paper (German National Licenses)
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