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  • American Institute of Physics (AIP)  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    Progress in internal transport barrier plasmas with lower hybrid current drive and heating in JET (Joint European Torus) : Review,Tutorial and Invited Papers from the 43rd Annual Meeting of the APS Division of Plasma Physics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 2156-2164 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In optimized shear plasmas in the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)], safety factor (q) profiles with negative magnetic shear are produced by applying lower hybrid (LH) waves during the plasma current ramp-up phase. These plasmas produce a barrier to the electron energy transport. The radius at which the barrier is located increases with the LH wave power. When heated with high power from ion cyclotron resonance heating and neutral beam injection, they can additionally produce transient internal transport barriers (ITBs) seen on the ion temperature, electron density, and toroidal rotation velocity profiles. Due to recent improvements in coupling, q profile control with LH current drive in ITB plasmas with strong combined heating can be explored. These new experiments have led to ITBs sustained for several seconds by the LH wave. Simulations show that the current driven by the LH waves peaks at the ITB location, indicating that it can act in the region of low magnetic shear. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1469026
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  • 2
    Electronic Resource
    Electronic Resource
    Coupled full-wave and ray-tracing numerical treatment of mode conversion in a tokamak plasma (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 911-922 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new approach for the numerical description of tokamak plasma waves in the ion cyclotron range of frequencies is discussed. It implies coupling of the full-wave and ray-tracing codes and is capable of unified treatment of waves of completely different scale and behavior. The method is applied for simulations of the electron heating scenario, based on fast wave (FW)–ion Bernstein wave (IBW) mode conversion near the ion–ion hybrid resonance in Tore Supra [B. Saoutic et al., Phys. Rev. Lett. 76, 1647 (1996)]. The two-dimensional full-wave "ALCYON" code [D. J. Gambier and A. Samain, Nucl. Fus. 25, 283 (1985)] is used to describe the global FW field pattern in the plasma volume. A small-scale-waves filter, introduced into the code, artificially damps the mode-converted power, which is further prescribed to IBW rays. Remnant small-scale fields are extracted from the global pattern to provide information necessary for IBW rays to start. Three-dimensional evolution of IBW rays is simulated by the "RAYS" ray-tracing code [Yu. Petrov, Nucl. Fus. 34, 63 (1994)], being unrestricted by finite mesh size and finite Larmor radius effects. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873888
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  • 3
    Electronic Resource
    Electronic Resource
    One-dimensional full wave treatment of mode conversion process at the ion–ion hybrid resonance in a bounded tokamak plasma (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 885-896 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A consistent picture of the mode conversion (MC) process at the ion–ion hybrid resonance in a bounded plasma of a tokamak is discussed, which clarifies the role of the global fast wave interference and cavity effects in the determination of the MC efficiency. This picture is supported by simulations with the kinetic code "VICE" [Fraboulet et al., "One-D full-wave description of plasma emission and absorption in the Ion Cyclotron Range of Frequency in tokamaks," submitted to Phys. Plasmas]. The concept of the "global resonator," formed by the R=n(parallel)2 boundary cutoffs [Saoutic et al., Phys. Rev. Lett. 76, 1647 (1996)], is justified, as well as the importance of a proper tunneling factor choice ηcr=0.22 [Ram et al., Phys. Plasmas 3, 1976 (1996)]. The MC scheme behavior appears to be very sensitive to the MC layer position relative to the global wave field pattern. Optimal MC regimes are found to be attainable without requirement of a particular parallel wave number choice. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873328
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  • 4
    Electronic Resource
    Electronic Resource
    Energy description of wave-plasma interaction in the ion cyclotron range of frequency: Application to fast wave absorption and emission in tokamaks (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 4318-4330 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An alternative description of the energy transfer between an electromagnetic wave and a tokamak plasma is presented. It involves the evaluation of local coefficients of emission and absorption and leads to rapid numerical procedures. This method allows a coherent description of emission and absorption processes and is thus particularly suited for the determination of the rf electromagnetic energy radiated from the plasma, as is shown by calculating ion cyclotron emission spectra. Furthermore, this "fluid" energy description proves also useful for the evaluation of the fast wave plasma absorption during ion cyclotron range of frequency (ICRF) heating: a fast "fluid" one-dimensional slab numerical code has been developed. It cannot cope with singularities of the wave vector such as resonance or cutoff, but it is well adapted to scenario designs of fast wave direct coupling to electrons and evaluation of partitioning of energy between species in the case of ions high harmonics. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872594
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  • 5
    Electronic Resource
    Electronic Resource
    Hamiltonian analysis of fast wave current drive in tokamak plasmas (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 2908-2925 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Hamiltonian formalism is used to address the problem of the direct resonant interaction between the fast magnetosonic wave and the electrons in a tokamak plasma. The intrinsic stochasticity of the electron trajectories in phase space is first derived. Together with extrinsic decorrelation processes, it assesses the validity of the quasilinear approximation for the kinetic studies of fast wave current drive (FWCD). A full-wave solution of the Maxwell–Vlasov set of equations provides the exact pattern of the wave fields in the tokamak geometry, consistent with a realistic antenna spectrum. The local quasilinear diffusion tensor is then derived from the wave fields and the driven current density profile, the power deposition profile and the current drive efficiency are computed, including possible nonlinear effects in the kinetic equation. Several applications of FWCD on existing and future machines are given, and the combination of FWCD with other noninductive current drive methods is investigated. Finally, an analytical expression for the current drive efficiency is derived in the moderate to high single-pass absorption regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870531
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  • 6
    Electronic Resource
    Electronic Resource
    TORE SUPRA fast reciprocating radio frequency probea) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1210-1215 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A fast reciprocating ion cyclotron range of frequencies (ICRF) probe was installed and operated on TORE SUPRA during 1992/1993. The body of the probe was originally used on the ATF experiment at Oak Ridge National Laboratory. The probe was adapted for use on TORE SUPRA, and mounted on one of the two fast reciprocating probe mounts. The probe consists of two orthogonal single-turn wire loops, mounted so that one loop senses toroidal rf magnetic fields and the other senses poloidal rf magnetic fields. The probe began operation in June, 1993. The probe active area is approximately 5 cm long by 2 cm, and the reciprocating mount has a slow stroke (5 cm/s) of 30 cm and a fast stroke (1.5 m/s) of about 10 cm. The probe was operated at distances from the plasma edge ranging from 30 to −5 cm (i.e., inside the last closed flux surface). The probe design, electronics, calibration, data acquisition, and data processing are discussed. First data from the probe are presented as a function of ICRF power, distance from the plasma, loop orientation, and other plasma parameters. Initial data show parametric instabilities do not play an important role for ICRF in the TORE SUPRA edge and scrape-off-layer (SOL) plasmas. Additionally it is observed that the probe signal has little or no dependence on position in the SOL/plasma edge. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146008
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  • 7
    Electronic Resource
    Electronic Resource
    TORE SUPRA fast reciprocating radio frequency probe (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 816-816 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A fast reciprocating ion cyclotron range of frequencies (ICRF) probe was installed and operated on TORE SUPRA during 1992/1993. The body of the probe was originally used on the ATF experiment at Oak Ridge National Laboratory. The probe was adapted for use on TORE SUPRA, and mounted on one of the two fast reciprocating probe mounts. The probe consists of two orthogonal single-turn wire loops, mounted so that one loop senses toroidal rf magnetic fields and the other senses poloidal rf magnetic fields. The probe began operation in June, 1993. The probe active area is approximately 5 cm long by 2 cm, and the reciprocating mount has a slow stroke (5 cm/s) of 30 cm and a fast stroke (1.5 m/s) of about 10 cm. The probe was operated at distances from the plasma edge ranging from 30 to −5 cm (i.e., inside the last closed flux surface). The probe design, electronics, calibration, data acquisition, and data processing are discussed. First data from the probe are presented as a function of ICRF power, distance from the plasma, loop orientation, and other plasma parameters. Initial data show parametric instabilities do not play an important role for ICRF in the TORE SUPRA edge and scrape-off-layer (SOL) plasmas. Additionally it is observed that the probe signal has little or no dependence on position in the SOL/plasma edge. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146231
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  • 8
    Electronic Resource
    Electronic Resource
    Hamiltonian theory of the ion cyclotron minority heating dynamics in tokamak plasmas (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 137-150 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The question of heating a tokamak plasma by means of electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is considered in the perspective of large rf powers and in the low collisionality regime. In such a case, the quasilinear theory (QLT) is validated by the Hamiltonian dynamics of the wave–particle interaction which exceeds the threshold of the intrinsic stochasticity. The Hamiltonian dynamics is represented by the evolution of a set of three canonical action angle variables well adapted to the tokamak magnetic configuration. This approach allows derivation of the rf diffusion coefficient with very few assumptions. The distribution function of the resonant ions is written as a Fokker–Planck equation but the emphasis is put on the QL diffusion instead of on the usual diffusion induced by collisions. The Fokker–Planck equation is then given a variational form from which a solution is derived in the form of a semianalytical trial function of three parameters: the percentage of resonant particles contained in the tail, an isotropic width ΔT, and an anisotropic width ΔP. This solution is successfully tested against real experimental observations. It is shown that in the case of the JET tokamak [Plasma Phys. Controlled Fusion 30, 1467 (1988)] the distribution function is influenced by adiabatic barriers which in turn limit the Hamiltonian stochasticity domain within energy values typically in the MeV range. Consequently and for a given ICRF power, the tail energy excursion is lower and its concentration higher than that from a bounce-averaged prediction. This may actually be an advantage for machines like JET [Plasma Phys. Controlled Fusion 30, 1467 (1988)] considering the energy range required to simulate the α-particle behavior in a relevant fusion reactor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859951
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