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  • 1
    Electronic Resource
    Electronic Resource
    On the stabilization of neoclassical tearing modes by electron cyclotron waves (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3561-3570 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The control of neoclassical tearing modes in tokamaks by means of electron cyclotron current drive and heating is investigated. The nonlinear evolution of the amplitude in absence and in presence of the stabilizing terms of an auxiliary current inside the island and of the associate heating is solved self-consistently with the evolution of the rotation frequency for International Thermonuclear Experimental Reactor (ITER) reference magnetic equilibrium [ITER-JCT and Home Teams, Plasma Phys. Controlled Fusion 37, A19 (1995)]. It is shown that, unless the wall braking torque is neutralized by external means, neoclassical tearing modes in ITER will be locked in a very short time. On the other hand, for rotating islands, the beneficial effect of modulating the current source in phase with the island rotation is pointed out, after an analysis of the time scales of the relevant phenomena (time response of the driven current, island rotation frequency, power pulse duration, and inductive response of the plasma). Consideration is given to different effects that may reduce the efficiency of the control of the flux reconnection rate and to the benefits of wall stabilization associated to the island rotation frequency. A quantitative assessment of the EC (electron cyclotron) power required to keep the island width at a reasonable level is given, both in absence and in presence of wall stabilization. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873633
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  • 2
    Electronic Resource
    Electronic Resource
    Density scaling of the threshold for locked mode instability in the presence of toroidal field ripple in a tokamak (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 4017-4022 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear excitation of magnetic islands in a tokamak by external resonant magnetic perturbation is examined. The perturbation amplitude threshold for the appearance of a locked mode is determined for a tokamak with a rippled toroidal field. It is shown that the critical value of the magnetic field is increased by the ripple induced damping of toroidal rotation. Qualitative aspects of the experimentally observed reduced scaling of the threshold density for mode locking, are predicted in the regime of low viscosity and dominant plasma inertial effects. In such a case the scaling is shown to be close to ni∼B˜r1/2 rather than ni∼B˜r3/2 as predicted by the usual theory. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872521
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  • 3
    Electronic Resource
    Electronic Resource
    Theory and calculation of current profile control near rational surfaces in a tokamak by electron cyclotron waves (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 978-984 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of electron cyclotron current drive (ECCD) on nonlinear resistive magnetohydrodynamic (MHD) perturbations in a tokamak is analyzed. Along the ray trajectories of electron cyclotron wave (ECW) beams injected from the low-field side in the ordinary mode (O-mode) polarization, the power deposition, and current drive efficiencies are calculated using fully relativistic analytical expressions. The driven current is inserted in a consistent theory of nonlinear magnetic island evolution, which provides the scaling of the radio-frequency (RF) driven current required to control magnetic reconnection in terms of the plasma equilibrium parameters and optical properties. It is shown that the threshold for error field driven islands can be increased by ECCD and that the current profile around the q=2 rational surface can be shaped to control the evolution of rotating magnetic islands by modulation of the gyrotron power source. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871803
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  • 4
    Electronic Resource
    Electronic Resource
    Rotating nonlinear magnetic islands in a tokamak plasma (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1581-1598 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear dynamics of rotating low m (poloidal mode number) tearing modes in a tokamak with external resonant magnetic perturbations is examined. Nonlinear evolution equations for the island width and the toroidal rotation frequency are derived within the two-fluid magnetohydrodynamic model, taking into account the plasma rotation and neoclassical parallel viscosity. The nonlinear stability of magnetic islands interacting with a static external magnetic perturbation is considered, and the critical magnetic field for the appearance of a locked mode is determined. It is shown that the coupling of the perpendicular and longitudinal plasma flow due to the neoclassical plasma viscosity enhances the amplitude of the critical magnetic field compared to the value obtained in a slab approximation. The perpendicular plasma viscosity causes a finite phase shift between the applied external field and the magnetic island, and further increases the value of the critical magnetic field required to induce a magnetic island. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871308
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  • 5
    Electronic Resource
    Electronic Resource
    Self-diffraction effects of electron cyclotron Gaussian beams on noninductively driven current in the International Thermonuclear Experimental Reactor tokamak (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 4140-4147 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of diffractive effects not included in standard ray tracing calculations on electron cyclotron current drive (ECCD) is analyzed for an International Thermonuclear Experimental Reactor (ITER) [P. H. Rebut, Fusion Eng. Design 30, 85 (1995)] tokamak configuration, using a quasioptical approach. The power absorbed and the current generated by highly collimated Gaussian beams of electron cyclotron waves (ECW) is calculated using realistic ITER equilibria, relativistic treatment of the wave propagation, and of the driven current, expressed in the formalism of 13 moments transport equations. Effects of beam diffraction on the generated current profile are found to be non-negligible, particularly for off-axis power deposition. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871546
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  • 6
    Electronic Resource
    Electronic Resource
    Orbit effects on the particles and energy flow in the poloidal field null region of a tokamak axisymmetric divertor (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1173-1178 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion transport through the separatrix of a tokamak with a poloidal divertor is reconsidered, to reconcile the interpretation of results from different diagnostics and understand the unexpected multiplet structure of the heat deposition on the targets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860907
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  • 7
    Electronic Resource
    Electronic Resource
    Control of tearing mode instabilities by localized electron-cyclotron wave heating (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 501-506 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resistive tearing mode instabilities are driven by unfavorable current gradients at the position where the safety factor q is rational. Their dynamics in the presence of radio-frequency (rf) power absorption in the electron-cyclotron wavelength range is investigated by means of a hybrid transport-magnetohydrodynamic (MHD) code and analytic considerations. A panorama of possibilities of stabilization and control of disruptions in tokamaks is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865436
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  • 8
    Electronic Resource
    Electronic Resource
    Feedback control of rotating resistive modes (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1623-1629 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To gain information for the design of practical feedback schemes, the response of nonlinear resistive modes to boundary conditions imposed by external conductors and resistive vessels is analyzed in the time domain. Newly derived explicit dynamical equations describe the nonlinear evolution of the tearing mode island width and frequency of rotation. These equations are appropriate to explain previous experimental and theoretical results quantitatively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.867004
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  • 9
    Electronic Resource
    Electronic Resource
    Tearing-mode control by localised electron cyclotron heating in FTU tokamak
    Amsterdam : Elsevier
    Physics Letters A 118 (1986), S. 191-194 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(86)90255-0
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  • 10
    Electronic Resource
    Electronic Resource
    Bifurcated Tokamak equilibria with vanishing edge current density
    Amsterdam : Elsevier
    Physics Letters A 143 (1990), S. 393-399 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(90)90379-3
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