Phys. Plasmas (1994-Present) - Physics of Plasmas

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The physics basis for ignition using indirect-drive targets on the National Ignition Facility

John D. Lindl, Peter Amendt, Richard L. Berger, S. Gail Glendinning, Siegfried H. Glenzer, Steven W. Haan, Robert L. Kauffman, Otto L. Landen, and Laurence J. Suter

Phys. Plasmas 11, 339 (2004); http://dx.doi.org/10.1063/1.1578638 (153 pages) | Cited 170 times

Online Publication Date: 20 January 2004

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The 1990 National Academy of Science final report of its review of the Inertial Confinement Fusion Program recommended completion of a series of target physics objectives on the 10-beam Nova laser at the Lawrence Livermore National Laboratory as the highest-priority prerequisite for proceeding with construction of an ignition-scale laser facility, now called the National Ignition Facility (NIF). These objectives were chosen to demonstrate that there was sufficient understanding of the physics of ignition targets that the laser requirements for laboratory ignition could be accurately specified. This research on Nova, as well as additional research on the Omega laser at the University of Rochester, is the subject of this review. The objectives of the U.S. indirect-drive target physics program have been to experimentally demonstrate and predictively model hohlraum characteristics, as well as capsule performance in targets that have been scaled in key physics variables from NIF targets. To address the hohlraum and hydrodynamic constraints on indirect-drive ignition, the target physics program was divided into the Hohlraum and Laser–Plasma Physics (HLP) program and the Hydrodynamically Equivalent Physics (HEP) program. The HLP program addresses laser–plasma coupling, x-ray generation and transport, and the development of energy-efficient hohlraums that provide the appropriate spectral, temporal, and spatial x-ray drive. The HEP experiments address the issues of hydrodynamic instability and mix, as well as the effects of flux asymmetry on capsules that are scaled as closely as possible to ignition capsules (hydrodynamic equivalence). The HEP program also addresses other capsule physics issues associated with ignition, such as energy gain and energy loss to the fuel during implosion in the absence of alpha-particle deposition. The results from the Nova and Omega experiments approach the NIF requirements for most of the important ignition capsule parameters, including drive temperature, drive symmetry, and hydrodynamic instability. This paper starts with a review of the NIF target designs that have formed the motivation for the goals of the target physics program. Following that are theoretical and experimental results from Nova and Omega relevant to the requirements of those targets. Some elements of this work were covered in a 1995 review of indirect-drive [J. D. Lindl, “Development of the indirect-drive approach to inertial confinement fusion and the target physics basis for ignition and gain,” Phys. Plasmas 2, 3933 (1995)]. In order to present as complete a picture as possible of the research that has been carried out on indirect drive, key elements of that earlier review are also covered here, along with a review of work carried out since 1995. © 2004 American Institute of Physics.

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52.57.-z	Laser inertial confinement
52.50.Jm	Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
28.52.Cx	Fueling, heating and ignition
52.38.Dx	Laser light absorption in plasmas (collisional, parametric, etc.)
52.59.Px	Hard X-ray sources

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Observation of collisionless inward propagation of electrons into helical vacuum magnetic surfaces via stochastic magnetic fields

H. Himura, H. Wakabayashi, M. Fukao, Z. Yoshida, M. Isobe, S. Okamura, C. Suzuki, S. Nishimura, K. Matsuoka, K. Toi, and H. Yamada

Phys. Plasmas 11, 492 (2004); http://dx.doi.org/10.1063/1.1635823 (4 pages) | Cited 14 times

Online Publication Date: 20 January 2004

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Electrons are injected into a stochastic magnetic region (SMR) of a stellarator vacuum configuration. Remarkably, when the SMR is present, some field-following electrons in the SMR move inwardly across the last closed flux surface. This inward propagation occurs in a collisionless process, but it is never observed for cases where the SMR is lost, nor is the electron density small in the SMR. These suggest the existence of cross-field transport that is associated with free-streaming of electrons along the stochastically wandering field lines in the SMR. © 2004 American Institute of Physics.

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52.25.Fi	Transport properties
52.70.Ds	Electric and magnetic measurements
52.55.Jd	Magnetic mirrors, gas dynamic traps

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Kinetic theory of dusty plasmas. V. The hydrodynamic equations

V. N. Tsytovich and U. de Angelis

Phys. Plasmas 11, 496 (2004); http://dx.doi.org/10.1063/1.1634255 (11 pages) | Cited 19 times

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The collisional hydrodynamic equations for electrons, ions, and dust particles in dusty plasmas are derived from the kinetic equations [V. N. Tsytovich and U. de Angelis, Phys. Plasmas 6, 1093 (1999)] which consistently take into account the elastic and inelastic (charging) collisions of plasma particles with dust and the effects of dust charge fluctuations. These equations are valid in the parameter regime where the collisions of plasma particles with dust dominate with respect to the binary plasma collisions. New expressions for the fluid collision frequencies, transport coefficients, viscosity, and ion drag are found and compared with previous results. © 2004 American Institute of Physics.

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52.27.Lw	Dusty or complex plasmas; plasma crystals
52.25.Dg	Plasma kinetic equations
52.25.Fi	Transport properties
52.20.Hv	Atomic, molecular, ion, and heavy-particle collisions
52.20.Fs	Electron collisions
52.30.-q	Plasma dynamics and flow
52.65.Kj	Magnetohydrodynamic and fluid equation
52.25.Gj	Fluctuation and chaos phenomena

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Generalized electron Bernstein modes in a plasma with a kappa velocity distribution

R. L. Mace

Phys. Plasmas 11, 507 (2004); http://dx.doi.org/10.1063/1.1635824 (16 pages) | Cited 19 times

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Perpendicularly propagating electron Bernstein modes in a uniformly magnetized plasma having an isotropic kappa velocity distribution are investigated within the framework of a fully electromagnetic plasma model but one which ignores particle relativistic effects. The dispersion relations for the Bernstein mode waves are found to be significantly dependent on the spectral index, κ, of the electron kappa distribution. In particular, waves with frequencies exceeding the upper hybrid frequency are seen to occupy a diminishing range of frequencies above the nearest cyclotron harmonic as κ is reduced. The Bernstein mode wave whose frequency lies closest to the upper hybrid frequency is found to couple to the cold plasma, electromagnetic Z mode, as it does in a Maxwellian plasma. For waves whose frequencies lie below the upper hybrid frequency, diminishing κ gives rise to an increasingly weak dependence of frequency on wave number and a slower frequency fall off with this parameter, but the frequency occupies the entire intraharmonic band here. All Bernstein modes are observed to become significantly electromagnetic at very long wavelengths, or small wave numbers, having in general elliptical polarization whose elliptical eccentricity depends on κ and wave number. At smaller wavelengths the modes are found to be electrostatic to a very good approximation, irrespective of κ value. The significance of the results to the interpretation of banded emissions in planetary magnetospheres is briefly discussed. © 2004 American Institute of Physics.

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52.35.Hr	Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.35.Fp	Electrostatic waves and oscillations (e.g., ion-acoustic waves)
95.30.Qd	Magnetohydrodynamics and plasmas
94.30.Tz	Electromagnetic wave propagation
52.35.Py	Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Qz	Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
96.12.Jt	Atmospheres

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Thermal instability of ionized dusty plasmas

Madhurjya P. Bora

Phys. Plasmas 11, 523 (2004); http://dx.doi.org/10.1063/1.1636478 (6 pages) | Cited 2 times

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We investigate the role of thermal instability, arising from radiative cooling of an optically thin, ionized, dusty plasma, by linear stability analysis. The corresponding isobaric stability condition for condensation mode is found to be modified significantly by the concentration of finite sized, relatively heavy, and negatively charged dust particles. It has been shown that the radiation condensation mode is severely affected by the presence of dust particles. A distinct departure from the classical behavior (Field 1965) is that the existence of unstable acoustic modes depends on the dust-charge fluctuation parameter and is not affected by the cooling through radiation. © 2004 American Institute of Physics.

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52.27.Lw	Dusty or complex plasmas; plasma crystals
52.25.Kn	Thermodynamics of plasmas

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Low-frequency instabilities in a laboratory magnetized plasma column

E. Gravier, F. Brochard, G. Bonhomme, T. Pierre, and J. L. Briançon

Phys. Plasmas 11, 529 (2004); http://dx.doi.org/10.1063/1.1636479 (9 pages) | Cited 18 times

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A detailed analysis of the phase velocity of unstable low-frequency waves is performed in a laboratory magnetized plasma column. The measurement of the radial profiles of the density, electron temperature and plasma potential allows to determine the radial profile of the electric drift velocity and electron diamagnetic drift for increasing values of the magnetic field. In the case of a large diameter plasma column, only diamagnetic drift waves without E×B Doppler shift occur. On the other hand, in the case of a restricted diameter plasma column, the radial electric field induces a rotation of the plasma column. At low magnetic field the recorded unstable waves are in that case flute modes propagating azimuthally at the E×B drift velocity. © 2004 American Institute of Physics.

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52.35.Qz	Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.35.Py	Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.25.-b	Plasma properties
52.35.Kt	Drift waves
52.25.Gj	Fluctuation and chaos phenomena
52.30.-q	Plasma dynamics and flow
52.70.Ds	Electric and magnetic measurements

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Excitation of electron Bernstein waves by a gyrating relativistic electron beam in a plasma slab

Asheel Kumar and V. K. Tripathi

Phys. Plasmas 11, 538 (2004); http://dx.doi.org/10.1063/1.1637345 (4 pages) | Cited 4 times

Online Publication Date: 20 January 2004

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A nonlocal theory of excitation of electron Bernstein waves in a magnetized plasma column by a gyrating relativistic electron beam has been developed. The beam response is obtained using the Vlasov equation. For a one-dimensional parabolic density profile of the background plasma, the mode structure equation yields Hermite polynomial eigenfunctions. The growth of the Bernstein wave occurs via a fast cyclotron interaction. For a typical case when the electron cyclotron frequency is comparable to the electron plasma frequency and beam velocity v_b ≈ 0.8c, the growth rate is maximum for k_⊥ρ₀ ≈ 5. The nonlocal effects reduce the growth rate. © 2004 American Institute of Physics.

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52.40.Mj	Particle beam interactions in plasmas
52.35.Hr	Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.27.Ny	Relativistic plasmas
52.25.-b	Plasma properties
52.65.Ff	Fokker-Planck and Vlasov equation

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Magnetic-curvature-driven interchange modes in dusty plasmas

I. Sandberg and P. K. Shukla

Phys. Plasmas 11, 542 (2004); http://dx.doi.org/10.1063/1.1640621 (6 pages) | Cited 6 times

Online Publication Date: 20 January 2004

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The magnetic-curvature-driven interchange mode instability of a weakly inhomogeneous dusty plasma is rigorously investigated. It is shown that the electric drift convection of the equilibrium dust charge density is a stabilizing factor for long wavelength interchange modes. In a fully nonlinear regime, the finite amplitude interchange modes may self-organize in the form of a dipolar vortex. The present results should be useful in the understanding of the properties of the interchange mode turbulence in nonuniform magnetized plasmas containing charged dust particles. © 2004 American Institute of Physics.

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52.35.Py	Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Mw	Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.27.Lw	Dusty or complex plasmas; plasma crystals
52.35.Ra	Plasma turbulence

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Stability of drift waves in the presence of dust

S. Sen

Phys. Plasmas 11, 548 (2004); http://dx.doi.org/10.1063/1.1633553 (4 pages) | Cited 1 time

Online Publication Date: 20 January 2004

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In the presence of dust particles in the plasma, it is shown that the well-known stability of the drift wave in a sheared slab geometry does not hold. Due to the presence of dust particles in tokamaks, the magnetic shear damping is reduced drastically. As a result, both the collisionless and collisional (dissipative) drift modes become unstable under the typical parameter regimes of a tokamak. Consequently, drift waves must still be considered as an underlying dynamic of anomalous transport in tokamak edges, where dust particles are found to be abundant. © 2004 American Institute of Physics.

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52.65.-y	Plasma simulation
52.35.Ra	Plasma turbulence

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Landau damping

W. E. Drummond

Phys. Plasmas 11, 552 (2004); http://dx.doi.org/10.1063/1.1628685 (9 pages) | Cited 10 times

Online Publication Date: 20 January 2004

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The damping of a longitudinal plasma wave of finite amplitude is considered. It is shown that the Landau result is the first term in a systematic expansion in a small parameter, and the corrections for finite wave amplitude are shown to be fifth order in the small parameter. The contributions to the damping from particles with different velocities near the phase velocity are explicitly calculated and this leads to a simple physical picture of the damping process. © 2004 American Institute of Physics.

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52.25.Fi	Transport properties
52.35.Fp	Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.65.-y	Plasma simulation

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Spectral energy transfer and generation of turbulent structures in toroidal plasma

H. Xia and M. G. Shats

Phys. Plasmas 11, 561 (2004); http://dx.doi.org/10.1063/1.1637607 (11 pages) | Cited 24 times

Online Publication Date: 20 January 2004

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Nonlinear energy cascades in turbulent spectra are studied in the H-1 toroidal heliac [S. M. Hamberger et al., Fusion Technol. 17, 123 (1990)] using the spectral energy transfer estimation and the amplitude correlation technique. An inverse energy cascade of the spectral energy from the unstable range is shown to be responsible for the generation of the large-scale coherent structures dominating turbulence spectra. Among such structures are zonal flows which are also found to be generated via the inverse cascade. The generation of zonal flows is correlated with the increased strength in the nonlinear energy transfer. The onset of the strongly sheared radial electric field across the low–high (L–H) transition dramatically changes the energy transfer in the spectra and the spectral power of the fluctuations. © 2004 American Institute of Physics.

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52.35.Ra	Plasma turbulence
52.35.Mw	Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.30.-q	Plasma dynamics and flow
52.55.Jd	Magnetic mirrors, gas dynamic traps

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Streamer formation and collapse in electron temperature gradient driven turbulence

Ö. D. Gürcan and P. H. Diamond

Phys. Plasmas 11, 572 (2004); http://dx.doi.org/10.1063/1.1637920 (12 pages) | Cited 10 times

Online Publication Date: 20 January 2004

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A simple model is useful to understand the formation and persistence of radially elongated structures (streamers) in electron temperature gradient (ETG) driven modes. The ETG model is very similar to the thermal Rossby wave model, a system of broad interest. The detailed correspondence of these two models is discussed. Streamer formation in this simple model is analyzed using the modulational stability method. In the inviscid limit of the model, an amplitude equation similar to the nonlinear Schrödinger equation (NLS) is derived. This equation has a second derivative cubic nonlinearity and is identified as a special case of a more general higher order NLS. Analytical solutions are found in the form of travelling waves and a localized thorn. Using the Lagrangian structure of the amplitude equation, it is shown that one-dimensional collapse in the poloidal direction is possible in this system for certain parameter values, and for sufficiently localized inital flow. This identifies a parameter regime basin in which there is an attractor with the structure of a thin extended streamer. In the viscous limit, another amplitude equation, which is a certain special case of the generalized complex Ginzburg–Landau equation, is obtained. Fixed points of the corresponding dynamical system are identified and their stability is investigated. © 2004 American Institute of Physics.

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52.80.-s	Electric discharges
52.35.Py	Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Mw	Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Ra	Plasma turbulence
52.25.Kn	Thermodynamics of plasmas

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Complete theory for Langmuir envelope solitons in dusty plasmas

P. K. Shukla and Bengt Eliasson

Phys. Plasmas 11, 584 (2004); http://dx.doi.org/10.1063/1.1641031 (11 pages) | Cited 11 times

Online Publication Date: 20 January 2004

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A complete theory for Langmuir envelope solitons in an unmagnetized dusty plasma is presented, taking into account interactions between finite amplitude Langmuir waves and fully nonlinear dust ion-acoustic (DIA), dust acoustic (DA), and ion hole (IH) perturbations. For this purpose, a nonlinear Schrödinger equation is employed for the Langmuir wave envelope and expressions for plasma slow responses are derived, including a modified (by the Langmuir wave ponderomotive force) Boltzmann electron distribution and appropriate ion and dust density distributions for fully nonlinear dispersive DIA, DA, and IH perturbations, which include departure from the quasi-neutrality condition. In the stationary frame, the governing equations can be cast in the form of a Hamiltonian which is used to check the accuracy of the numerical scheme predicting stationary localized solutions of our governing nonlinear equations. Numerical results reveal different classes of Langmuir envelope solitons (cavitons) whose features differ from those in an electron-ion plasma without dust. Ion and dust thermal effects for the DIA and DA waves, respectively, have been included. It is suggested that new beam-plasma experiments in laboratory dust plasmas should be conducted to verify our theoretical predictions of cavitons. © 2004 American Institute of Physics.

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52.27.Lw	Dusty or complex plasmas; plasma crystals
52.35.Fp	Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.25.-b	Plasma properties
52.35.Sb	Solitons; BGK modes

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Magnetic diagnostic responses for compact stellarators

Steven P. Hirshman, Edward A. Lazarus, James D. Hanson, Stephen F. Knowlton, and Lang L. Lao

Phys. Plasmas 11, 595 (2004); http://dx.doi.org/10.1063/1.1637347 (9 pages) | Cited 8 times

Online Publication Date: 20 January 2004

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The formulation of magnetic diagnostic response functions for a three-dimensional stellarator plasma is described. Reciprocity relations are used to compute unique response functions for each type of magnetic diagnostic. Green’s function response tables (databases) are generated from which both external coil and internal plasma current contributions to diagnostic signals can be rapidly computed. Applications to compact stellarators are described. © 2004 American Institute of Physics.

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52.70.Ds

Electric and magnetic measurements

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Numerical study of tokamak equilibria with arbitrary flow

L. Guazzotto, R. Betti, J. Manickam, and S. Kaye

Phys. Plasmas 11, 604 (2004); http://dx.doi.org/10.1063/1.1637918 (11 pages) | Cited 38 times

Online Publication Date: 20 January 2004

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The effects of toroidal and poloidal flows on the equilibrium of tokamak plasmas are numerically investigated using the code FLOW. The code is used to determine the changes in the profiles induced by large toroidal flows on NSTX-like equilibria [with NSTX being the National Spherical Torus Experiment, M. Ono, S.M. Kaye, Y.-K.M. Peng et al., Nucl. Fusion 40, 557 (2000)] where flows exceeding the sound speed lead to a considerable outward shift of the plasma. The code is also used to study the effects of poloidal flow when the flow velocity profile varies from subsonic to supersonic with respect to the poloidal sound speed. It is found that pressure and density profiles develop a pedestal structure characterized by radial discontinuities at the transonic surface where the poloidal velocity abruptly jumps from subsonic to supersonic values. These results confirm the conclusions of the analytic theory of R. Betti and J. P. Freidberg [Phys. Plasmas 7, 2439 (2000)], derived for a low-β, large aspect ratio tokamak with a circular cross section. © 2004 American Institute of Physics.

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52.65.Kj	Magnetohydrodynamic and fluid equation
52.25.Fi	Transport properties
52.35.Py	Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

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Global eigenmodes of low frequency waves in field-reversed configuration plasmas

Naotaka Iwasawa, Shigefumi Okada, and Seiichi Goto

Phys. Plasmas 11, 615 (2004); http://dx.doi.org/10.1063/1.1638752 (10 pages) | Cited 2 times

Online Publication Date: 20 January 2004

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Global eigenmodes of low frequency waves in field reversed configuration (FRC) plasmas have been obtained using the magnetohydrodynamic (MHD) model and one-dimensional equilibrium model. Dispersion relation and radial structure of the global wave fields are shown for the azimuthal mode number m = 0. The results are compared with the results of a low frequency wave heating experiment. Possibilities of ion heating by the ion cyclotron damping, the transit-time magnetic damping, and Landau damping are discussed. © 2004 American Institute of Physics.

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52.35.Bj	Magnetohydrodynamic waves (e.g., Alfven waves)
52.30.Cv	Magnetohydrodynamics (including electron magnetohydrodynamics)
52.58.Lq	Z-pinches, plasma focus, and other pinch devices
52.50.Qt	Plasma heating by radio-frequency fields; ICR, ICP, helicons

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Plasma flow and confinement in the vicinity of a rotating island in collisional tokamak plasmas

K. C. Shaing

Phys. Plasmas 11, 625 (2004); http://dx.doi.org/10.1063/1.1639911 (8 pages) | Cited 7 times

Online Publication Date: 20 January 2004

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The theory for the electric field, plasma flows, and plasma confinement in the vicinity of a rotating magnetic island in tokamaks [Phys. Plasmas 9, 3470 (2002)] is extended to the collisional plasmas, i.e., the plateau-Pfirsch–Schluter regime. The electric field that is parallel to the magnetic field B, E_∥, is assumed to vanish. It is found that plasmas flow in the toroidal direction at the same rate as the island rotation frequency. Island rotation frequency is calculated using an island-induced symmetry-breaking viscosity. The radial electric field in the vicinity of the island is also determined from the toroidal momentum balance equation that includes island-induced toroidal viscosity. © 2004 American Institute of Physics.

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52.25.Fi	Transport properties
52.55.Fa	Tokamaks, spherical tokamaks

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Edge-driven rotating magnetic field current drive of field-reversed configurations

Richard D. Milroy and Kenneth E. Miller

Phys. Plasmas 11, 633 (2004); http://dx.doi.org/10.1063/1.1641381 (6 pages) | Cited 21 times

Online Publication Date: 20 January 2004

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Field-reversed configurations (FRCs) are created and sustained using a rotating magnetic field (RMF) in the Translation Confinement and Sustainment experiment. Normally this experiment is operated in a manner where the RMF only partially penetrates the plasma column. This method of operation may have significant advantages in producing less disturbances to the bulk of the FRC, but requires driving an overall radially inward flow to maintain E_θ(r) = 0 everywhere (through the V_rB_z term in the generalized Ohm’s law). However, some RMF penetration is still required at the field null R, where B_z = 0. For some experimental conditions it appears that the RMF does not even penetrate as far as the null, raising the question as to how E_θ(r = R) can be maintained at zero despite a finite η_⊥j_θ(r = R). Numerical simulations with a resistivity profile that is sharply peaked near the plasma edge yield similar profiles, and provide insight into this physical process. An inner magnetic structure forms, which rotates at a much lower frequency than the RMF. A tearing and reconnection process produces a torque transfer from the outer RMF to the inner structure, allowing it to act as an RMF downshifted to a lower frequency, and thus provide current drive to the inner region of the FRC. This mode of RMF current drive is being called “edge-driven mode.” © 2004 American Institute of Physics.

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52.58.Lq	Z-pinches, plasma focus, and other pinch devices
52.30.Cv	Magnetohydrodynamics (including electron magnetohydrodynamics)
52.70.Ds	Electric and magnetic measurements
52.65.Kj	Magnetohydrodynamic and fluid equation
52.35.Vd	Magnetic reconnection
52.25.Fi	Transport properties
52.40.Hf	Plasma-material interactions; boundary layer effects
52.35.Py	Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Qz	Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

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Aspect ratio scaling of ideal no-wall stability limits in high bootstrap fraction tokamak plasmas

J. E. Menard, M. G. Bell, R. E. Bell, D. A. Gates, S. M. Kaye, B. P. LeBlanc, R. Maingi, S. A. Sabbagh, V. Soukhanovskii, and D. Stutman

Phys. Plasmas 11, 639 (2004); http://dx.doi.org/10.1063/1.1640623 (8 pages) | Cited 14 times

Online Publication Date: 20 January 2004

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Recent experiments in the low aspect ratio National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] have achieved normalized beta values twice the conventional tokamak limit at low internal inductance and with significant bootstrap current. These experimental results have motivated a computational re-examination of the plasma aspect ratio dependence of ideal no-wall magnetohydrodynamic stability limits. These calculations find that the profileoptimized no-wall stability limit in high bootstrap fraction regimes is well described by a nearly aspect ratio invariant normalized beta parameter utilizing the total magnetic field energy density inside the plasma. However, the scaling of normalized beta with internal inductance is found to be strongly aspect ratio dependent at sufficiently low aspect ratio. These calculations and detailed stability analyses of experimental equilibria indicate that the nonrotating plasma no-wall stability limit has been exceeded by as much as 30% in NSTX in a high bootstrap fraction regime. © 2004 American Institute of Physics.

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52.55.Fa	Tokamaks, spherical tokamaks
28.52.Av	Theory, design, and computerized simulation

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Mode- and plasma rotation in a resistive shell reversed-field pinch

J.-A. Malmberg, J. Brzozowski, P. R. Brunsell, M. Cecconello, and J. R. Drake

Phys. Plasmas 11, 647 (2004); http://dx.doi.org/10.1063/1.1639016 (12 pages) | Cited 8 times

Online Publication Date: 20 January 2004

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Mode rotation studies in a resistive shell reversed-field pinch, EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Control. Fusion 43, 1 (2001)] are presented. The phase relations and nonlinear coupling of the resonant modes are characterized and compared with that expected from modeling based on the hypothesis that mode dynamics can be described by a quasi stationary force balance including electromagnetic and viscous forces. Both m = 0 and m = 1 resonant modes are studied. The m = 1 modes have rotation velocities corresponding to the plasma flow velocity (20–60 km/s) in the core region. The rotation velocity decreases towards the end of the discharge, although the plasma flow velocity does not decrease. A rotating phase locked m = 1 structure is observed with a velocity of about 60 km/s. The m = 0 modes accelerate throughout the discharges and reach velocities as high as 150–250 km/s. The observed m = 0 phase locking is consistent with theory for certain conditions, but there are several conditions when the dynamics are not described. This is not unexpected because the assumption of quasi stationarity for the mode spectra is not fulfilled for many conditions. Localized m = 0 perturbations are formed in correlation with highly transient discrete dynamo events. These perturbations form at the location of the m = 1 phase locked structure, but rotate with a different velocity as they spread out in the toroidal direction. © 2004 American Institute of Physics.

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52.58.Lq	Z-pinches, plasma focus, and other pinch devices
52.30.-q	Plasma dynamics and flow
52.35.Qz	Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

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Off-axis electron cyclotron heating and the sandpile paradigm for transport in tokamak plasmas

T. K. March, S. C. Chapman, R. O. Dendy, and J. A. Merrifield

Phys. Plasmas 11, 659 (2004); http://dx.doi.org/10.1063/1.1639017 (7 pages) | Cited 6 times

Online Publication Date: 20 January 2004

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Previous observations that suggest a substantial role for nondiffusive energy transport in tokamaks subjected to off-axis electron cyclotron heating (ECH) are compared to the output from a sandpile model. The observations considered include local and global aspects of temperature profile evolution in the DIII-D [for example, C. C. Petty and T. C. Luce, Nucl. Fusion 34, 121 (1994)] and RTP (Rijnhuizen Tokamak Project) [for example, M. R. de Baar, M. N. A. Beurskens, G. M. D. Hogeweij, and N. J. Lopes Cardozo, Phys. Plasmas 6, 4645 (1999)] tokamaks. The sandpile model employed is an extension, to incorporate noncentral fueling, of one used previously to address tokamak physics issues [S. C. Chapman, R. O. Dendy, and B. Hnat, Phys. Rev. Lett. 86, 2814 (2001)]. It is found that there are significant points of resemblance between the phenomenology of the noncentrally fueled sandpile and of the tokamaks with off-axis ECH. This suggests that the essential ingredient of the sandpile model, namely avalanching conditioned by a local critical gradient, may be one of the key transport effects generated by the tokamak plasma physics. © 2004 American Institute of Physics.

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52.55.Fa	Tokamaks, spherical tokamaks
52.50.Qt	Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.25.Fi	Transport properties

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Microislands in tokamaks

A. B. Mikhailovskii, E. A. Kovalishen, M. S. Shirokov, S. V. Konovalov, V. S. Tsypin, F. F. Kamenets, T. Ozeki, and T. Takizuka

Phys. Plasmas 11, 666 (2004); http://dx.doi.org/10.1063/1.1640377 (11 pages) | Cited 4 times

Online Publication Date: 20 January 2004

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Analytical treatment of magnetic islands with high poloidal mode numbers and widths smaller than ion Larmor radius (microislands) is presented. The profile functions and rotation frequencies of microislands in the scope of the standard two-fluid magnetohydrodynamics are investigated. The effects of anomalous perpendicular resistivity and anomalous perpendicular electron heat conductivity are included. It is shown that, in such a problem statement, the microislands are described in terms of two profile functions, one of which characterizes the electric field and perturbed plasma density (the microisland profile function) and second—perturbed electron temperature (the electron temperature profile function). Analytical expressions for these profile functions in the case of stationary microislands are derived. Contribution of the oscillatory parallel electric current (the polarization current) into the generalized Rutherford equation for the stationary island width is calculated. The problem of rotation frequencies of microislands is discussed. It is shown that, as in the case of large-scale magnetic islands, for calculation of these frequencies, it is necessary to take into account nonstationarities of profile functions in the near-separatrix region. These nonstationarities are due to discontinuities of the derivatives of profile functions with respect to island magnetic flux. It is shown that the contribution of these nonstationarities into the equation for the rotation frequency does not depend on this frequency. This leads to the conclusion that taking into account only the electron dissipation is insufficient for calculation of the rotation frequency. It is suggested that for such a calculation the ion dissipation should also be involved. © 2004 American Institute of Physics.

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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.)
52.25.Fi	Transport properties
52.55.Fa	Tokamaks, spherical tokamaks

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Destruction of invariant surfaces and magnetic coordinates for perturbed magnetic fields

S. R. Hudson

Phys. Plasmas 11, 677 (2004); http://dx.doi.org/10.1063/1.1640379 (9 pages) | Cited 10 times

Online Publication Date: 20 January 2004

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Straight-field-line coordinates are constructed for nearly integrable magnetic fields. The coordinates are based on the robust, noble-irrational rotational-transform surfaces, whose existence is determined by an application of Greene’s residue criterion. A simple method to locate these surfaces is described. Sequences of surfaces with rotational-transform converging to low order rationals maximize the region of straight-field-line coordinates. © 2004 American Institute of Physics.

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52.30.Cv	Magnetohydrodynamics (including electron magnetohydrodynamics)
52.55.Jd	Magnetic mirrors, gas dynamic traps
52.35.Mw	Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Py	Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
05.45.Pq	Numerical simulations of chaotic systems

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Testing of an edge thermal instability stabilization model for the low-to-high mode power threshold

W. M. Stacey

Phys. Plasmas 11, 686 (2004); http://dx.doi.org/10.1063/1.1641382 (4 pages) | Cited 1 time

Online Publication Date: 20 January 2004

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A test of a new model for the low-to-high (L–H) mode power threshold, based on the stabilization of edge thermal instabilities, is made by comparison with a set of DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] discharges at times just prior to a L–H transition. Agreement is found between the measured power crossing the separatrix just prior to the L–H transition and the predicted power threshold for the stabilization of transport enhancing thermal instabilities. © 2004 American Institute of Physics.

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52.35.Qz	Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.25.Fi	Transport properties
52.55.Fa	Tokamaks, spherical tokamaks

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Instabilities of ablation fronts in inertial confinement fusion: A comparison with flames

P. Clavin and L. Masse

Phys. Plasmas 11, 690 (2004); http://dx.doi.org/10.1063/1.1634969 (16 pages) | Cited 21 times

Online Publication Date: 20 January 2004

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A comparison with flames sheds new light on the dynamics of ablation fronts in inertial confinement fusion (ICF). The mathematical formulation of the problem in ICF is the same as for flames propagating upwards. The difference concerns the Froude number F_r, yielding a different order of magnitude for the nondimensional wave number of the marginally stable disturbances. When the thermal conductivity varies strongly, as is the case in ICF, a wide range of characteristic (diffusive) lengths is involved across the wave structure. For disturbances with intermediate wavelengths, a “universal” diffusive relaxation rate of thermal waves is exhibited with no dependence on the heat conductivity. This is a key point for describing the dynamics of strongly accelerated ablation fronts whose marginally stable wavelength is much shorter than the total wave thickness. The coupling of hydrodynamics and heat conduction is analyzed in a way similar to flame theory, through the derivation of a kinematic relation for the ablation front including its thermal relaxation. A transition between the regimes of flames and ablation fronts in ICF is exhibited with decreasing F_r. For a moderate acceleration, F_r≫1, the result for flames is recovered. For a large acceleration, F_r of order unity, the thermal relaxation, when coupled with hydrodynamics, is shown to damp out the Darrieus–Landau instability, yielding the known result in ICF for strongly accelerated ablation fronts. For a wide class of models, including the simple two-length-scale model, the description is shown to be independent of the model. A weakly nonlinear analysis, valid irrespective of the number of unstable modes, is carried out for describing the early development of nonlinear structures of the ablation front in ICF. The role of the Darrieus–Landau instability at the early stage of irradiation is pointed out. © 2004 American Institute of Physics.

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Show PACS

52.35.Py	Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.25.Fi	Transport properties
28.52.Av	Theory, design, and computerized simulation
52.35.Qz	Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

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BROWSE VOLUMES

BROWSE EARLY VOLUMES

Feb 2004

Volume 11, Issue 2, pp. 339-852

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