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Feb 2013

Volume 20, Issue 2, Articles (02xxxx)

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Phys. Plasmas 20, 022303 (2013); http://dx.doi.org/10.1063/1.4790639 (12 pages)

Julio J. Martinell and Diego del-Castillo-Negrete
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back to top Magnetically Confined Plasmas, Heating, Confinement

The Hamiltonian structure and Euler-Poincaré formulation of the Vlasov-Maxwell and gyrokinetic systems

J. Squire, H. Qin, W. M. Tang, and C. Chandre

Phys. Plasmas 20, 022501 (2013); http://dx.doi.org/10.1063/1.4791664 (14 pages) | Cited 1 time

Online Publication Date: 13 February 2013

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We present a new variational principle for the gyrokinetic system, similar to the Maxwell-Vlasov action presented in H. Cendra et al., [J. Math. Phys. 39, 3138 (1998)]. The variational principle is in the Eulerian frame and based on constrained variations of the phase space fluid velocity and particle distribution function. Using a Legendre transform, we explicitly derive the field theoretic Hamiltonian structure of the system. This is carried out with a modified Dirac theory of constraints, which is used to construct meaningful brackets from those obtained directly from Euler-Poincaré theory. Possible applications of these formulations include continuum geometric integration techniques, large-eddy simulation models, and Casimir type stability methods.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.25.Dg Plasma kinetic equations

On the toroidal plasma rotations induced by lower hybrid waves

Xiaoyin Guan, Hong Qin, Jian Liu, and Nathaniel J. Fisch

Phys. Plasmas 20, 022502 (2013); http://dx.doi.org/10.1063/1.4791666 (11 pages)

Online Publication Date: 13 February 2013

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A theoretical model is developed to explain the plasma rotations induced by lower hybrid waves in Alcator C-Mod. In this model, torodial rotations are driven by the Lorentz force on the bulk-electron flow across flux surfaces, which is a response of the plasma to the resonant-electron flow across flux surfaces induced by the lower hybrid waves. The flow across flux surfaces of the resonant electrons and the bulk electrons are coupled through the radial electric field initiated by the resonant electrons, and the friction between ions and electrons transfers the toroidal momentum to ions from electrons. An improved quasilinear theory with gyrophase dependent distribution function is developed to calculate the perpendicular resonant-electron flow. Toroidal rotations are determined using a set of fluid equations for bulk electrons and ions, which are solved numerically by a finite-difference method. Numerical results agree well with the experimental observations in terms of flow profile and amplitude. The model explains the strong correlation between torodial flow and internal inductance observed experimentally, and predicts both counter-current and co-current flows, depending on the perpendicular wave vectors of the lower hybrid waves.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.55.Fa Tokamaks, spherical tokamaks
02.70.Bf Finite-difference methods
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

Development of an identification method of pressure anisotropy based on equilibrium analysis and magnetics

Y. Asahi, Y. Suzuki, K. Y. Watanabe, and W. A. Cooper

Phys. Plasmas 20, 022503 (2013); http://dx.doi.org/10.1063/1.4791665 (7 pages)

Online Publication Date: 14 February 2013

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We evaluate the fluxes measured by the magnetic flux loops installed in LHD by using a three dimensional MHD equilibrium analysis code, ANIMEC, which enable us to directly determine the calibration function between the anisotropic pressure and the measured fluxes for the non-axisymmetric plasmas for the first time. The result indicates that the diamagnetic flux represents a nearly single-valued function of the beta perpendicular with respect to the field, and the saddle loop flux represents a nearly single-valued function of an equally weighted average of the beta values parallel and perpendicular to the field, regardless of the pressure anisotropy or the amount of energetic trapped particles. The values of the beta perpendicular to the field and the equal weighting averaged beta estimated by the single-valued functions (calibration functions) are investigated in order to clarify the magnitude of deviation from those original values, and the range of anisotropy where the beta value evaluated by the magnetic flux measurement is calculated within a 10% error.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.55.Jd Magnetic mirrors, gas dynamic traps

Lower hybrid instability driven by mono-energy α-particles with finite pitch angle spread in a plasma

Pawan Kumar, Vishwesh Singh, and V. K. Tripathi

Phys. Plasmas 20, 022504 (2013); http://dx.doi.org/10.1063/1.4792262 (4 pages)

Online Publication Date: 14 February 2013

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A kinetic formalism of lower hybrid wave instability, driven by mono-energy α-particles with finite pitch angle spread, is developed. The instability arises through cyclotron resonance interaction with high cyclotron harmonics of α-particles. The α-particles produced in D-T fusion reactions have huge Larmor radii (∼10 cm) as compared to the wavelength of the lower hybrid wave, whereas their speed is an order of magnitude smaller than the speed of light in vacuum. As a result, large parallel phase velocity lower hybrid waves, suitable for current drive in tokamak, are driven unstable via coupling to high cyclotron harmonics. The growth rate decreases with increase in pitch angle spread of the beam. At typical electron density of ∼1019 m−3, magnetic field ∼4 Tesla and α-particle concentration ∼0.1%, the large parallel phase velocity lower hybrid wave grows on the time scale of 20 ion cyclotron periods. The growth rate decreases with plasma density.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.25.Dg Plasma kinetic equations
52.55.Fa Tokamaks, spherical tokamaks
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)

Toroidal modeling of interaction between resistive wall mode and plasma flow

Yueqiang Liu and Youwen Sun

Phys. Plasmas 20, 022505 (2013); http://dx.doi.org/10.1063/1.4793449 (14 pages) | Cited 1 time

Online Publication Date: 21 February 2013

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The non-linear interplay between the resistive wall mode (RWM) and the toroidal plasma flow is numerically investigated in a full toroidal geometry, by simultaneously solving the initial value problems for the n = 1 RWM and the n = 0 toroidal force balance equation. Here, n is the toroidal mode number. The neoclassical toroidal viscous torque is identified as the major momentum sink that brakes the toroidal plasma flow during the non-linear evolution of the RWM. This holds for a mode that is initially either unstable or stable. For an initially stable RWM, the braking of the flow, and hence the eventual growth of the mode, depends critically on the initial perturbation amplitude.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.55.Tn Ideal and resistive MHD modes; kinetic modes
52.65.-y Plasma simulation
02.30.-f Function theory, analysis
02.60.-x Numerical approximation and analysis
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Local thermodynamics of a magnetized, anisotropic plasma

R. D. Hazeltine, S. M. Mahajan, and P. J. Morrison

Phys. Plasmas 20, 022506 (2013); http://dx.doi.org/10.1063/1.4793735 (8 pages)

Online Publication Date: 26 February 2013

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An expression for the internal energy of a fluid element in a weakly coupled, magnetized, anisotropic plasma is derived from first principles. The result is a function of entropy, particle density and magnetic field, and as such plays the role of a thermodynamic potential: it determines in principle all thermodynamic properties of the fluid element. In particular it provides equations of state for the magnetized plasma. The derivation uses familiar fluid equations, a few elements of kinetic theory, the MHD version of Faraday's law, and certain familiar stability and regularity conditions.
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52.25.Kn Thermodynamics of plasmas
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
64.30.Jk Equations of state of nonmetals
65.20.Jk Studies of thermodynamic properties of specific liquids
52.25.Dg Plasma kinetic equations

Studies of the fast ion energy spectra in TJ-II

A. Bustos, J. M. Fontdecaba, F. Castejón, J. L. Velasco, M. Tereshchenko, and J. Arévalo

Phys. Plasmas 20, 022507 (2013); http://dx.doi.org/10.1063/1.4793731 (7 pages) | Cited 1 time

Online Publication Date: 27 February 2013

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The dynamics of the neutral beam injection fast ions in the TJ-II stellarator is studied in this paper from both the theoretical and experimental points of view. The code Integrator of Stochastic Differential Equations for Plasmas (ISDEP) is used to estimate the fast ion distribution function in 3D:1D in real space and 2D in velocity space, considering the 3D structure of TJ-II, the electrostatic potential, non turbulent collisional transport, and charge exchange losses. The results of ISDEP are compared with the experimental data from the compact neutral particle analyzer, which measures the outgoing neutral flux spectra in the energy range E∈(1−45)  keV.
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52.50.Gj Plasma heating by particle beams
52.55.Jd Magnetic mirrors, gas dynamic traps
52.70.Nc Particle measurements
52.75.-d Plasma devices
52.65.Pp Monte Carlo methods
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