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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1318-1325 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In recent experiments with combined fast wave current drive (FWCD) and deuterium neutral beam injection on the DIII-D tokamak [Luxon et al., Fusion Technol. 8, 441 (1985)], an enhanced fusion reactivity and fast ion energy content have been observed in the presence of FWCD, with a concomitant low FWCD efficiency [Petty et al., Radio Frequency Power in Plasmas (AIP, New York, 1997), p. 225]. In this paper, we investigate whether high-harmonic ion cyclotron damping could be responsible for the low FWCD efficiency in these experiments, since a number of high-harmonic hydrogen and deuterium cyclotron resonance layers existed in the plasma. The main analysis tool is the ion cyclotron range of frequencies code PION [Eriksson et al., Nucl. Fusion 33, 1037 (1993)], modified to allow multiple frequencies simultaneously as was done in the DIII-D experiments. According to the PION modeling, high harmonic damping of fast wave power can give rise to enhanced fusion reactivity and fast ion energy content, which is consistent with the experimental observations. © 2002 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)
    Physics of Plasmas 2 (1995), S. 450-458 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A weakly relativistic theory of current drive by parallel acceleration of electrons in toroidal geometry is presented. Analytic expressions of efficiency are obtained for superthermal and subthermal electrons. By using a few adjustable parameters for intermediate energies, an accurate formula for the efficiency is obtained by fitting numerical results. This includes trapping effects and is valid for all frequencies up to the lower hybrid range of frequencies. It is found that for low-frequency fast-wave current drive, the relativistic and nonrelativistic efficiencies agree to within 15% up to 500 keV, although the relativistic corrections to power absorption and current density can be much larger separately. Relativistic effects on the efficiency become prominent at lower energies for Landau damping. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mission of the National Spherical Torus Experiment (NSTX) is to extend the understanding of toroidal physics to low aspect ratio (R/a(similar, equals)1.25) in low collisionality regimes. NSTX is designed to operate with up to 6 MW of high harmonic fast wave (HHFW) heating and current drive, 5 MW of neutral beam injection (NBI) and co-axial helicity injection (CHI) for noninductive startup. Initial experiments focused on establishing conditions that will allow NSTX to achieve its aims of simultaneous high βt and high-bootstrap current fraction, and to develop methods for noninductive operation, which will be necessary for Spherical Torus power plants. Ohmic discharges with plasma currents up to 1 MA and with a range of shapes and configurations were produced. Density limits in deuterium and helium reached 80% and 120% of the Greenwald limit, respectively. Significant electron heating was observed with up to 2.3 MW of HHFW. Up to 270 kA of toroidal current for up to 200 ms was produced noninductively using CHI. Initial NBI experiments were carried out with up to two beam sources (3.2 MW). Plasmas with stored energies of up to 140 kJ and βt=21% were produced. © 2001 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)
    Physics of Fluids 30 (1987), S. 3633-3635 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relativistic wave–particle resonance condition imposes a harmonic-overlap constraint on electron-cyclotron current drive. Specifically, for fundamental cyclotron resonance the current-drive efficiency cannot be increased by raising the minimum resonant energy ε1 above about 115 keV. A limiting efficiency corresponding to an even lower ε1 follows for microwave beams with realistic width and angular divergence.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of fusion energy 2 (1982), S. 207-224 
    ISSN: 1572-9591
    Keywords: tokamaks ; fusion reactors ; plasma physics ; ignition ; transport ; performance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Studies have been performed to explore various plasma burn scenarios for a tokamak test reactor which could follow the next generation of large tokamak experiments. Tradeoffs between an ignited burning plasma and a sub-ignited driven plasma are examined in terms of device size and performance as a fusion engineering test facility. It is found that plasma performance levels, measured by ignition margin, amplification factorQ, and fusion power output, increase with device size, more optimistic transport scaling laws, lower magnetic field ripple, and higherΒ. The performance of a generally low stress (B 0=4 T) reference device, with major radiusR=4.5 m and minor radiusa=1.3 m in a D-shaped (κ=1.6) plasma has been evaluated over a wide range of operating parameters. In particular, a moderate fusion power output of 300 MW is obtained, the driven plasma havingQ≅ 10, an edge ripple of 1%, and a density ranging between 1.0 and 1.5×1014 cm−3. The same device operated at a higher general level of stress (B 0=5.3 T) is predicted to achieve ignition, but is not required for the mission of an engineering test facility and would entail greater technical risk.
    Type of Medium: Electronic Resource
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