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May 2000

Volume 7, Issue 5, pp. 1341-2248

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Effect of field ionization on interaction of an intense subpicosecond laser pulse with foils

A. Zhidkov and A. Sasaki

Phys. Plasmas 7, 1341 (2000); http://dx.doi.org/10.1063/1.873775 (4 pages) | Cited 14 times

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The effect of transient ionization in an intense, short laser pulse irradiated foil is investigated via a simulation based on the collisional particle-in-cell method coupled with the atomic kinetics. A strong electric field induced by superthermal electrons causes significant plasma ionization at the rear surface of the target. The plasma induced field ionization is found to dominate the production of the multiple-charged ions at the rear surface of the foil, which are accelerated forward up to multi mega electron volts by irradiation of a subpicosecond laser pulse with intensities from 1019 to 1020 W/cm2. © 2000 American Institute of Physics.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.65.-y Plasma simulation

Observation of shock wave elimination by a plasma in a Mach-2.5 flow

S. P. Kuo, Iraj M. Kalkhoran, Daniel Bivolaru, and Lester Orlick

Phys. Plasmas 7, 1345 (2000); http://dx.doi.org/10.1063/1.873776 (4 pages) | Cited 19 times

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An experimental study on the influence of a plasma on the structure of an attached conical shock front appearing at the front end of a missile-shaped model has been carried out in a Mach-2.5 flow. The tip and the body of the model are designed as the cathode and anode for gaseous discharge, which produces a spraylike plasma moving around the tip. It is observed that the plasma has caused the shock front to separate from the model. The shock wave moves upstream in the form of a detached bow shock a sensible distance away from the model tip. The detached shock front appears to be highly dispersed in its new location as seen in the shadow video graphs of the flow. As the discharge current increases, experimental evidence shown in the video further reveals a distinct state of the flow without the presence of any shock wave. © 2000 American Institute of Physics.
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52.35.Tc Shock waves and discontinuities
52.30.-q Plasma dynamics and flow
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Zonal flow generation by parametric instability in magnetized plasmas and geostrophic fluids

A. I. Smolyakov, P. H. Diamond, and V. I. Shevchenko

Phys. Plasmas 7, 1349 (2000); http://dx.doi.org/10.1063/1.873950 (3 pages) | Cited 95 times

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Two-dimensional magnetized plasmas and geostrophic fluids exhibit a common nonlinearity due to the advection of vorticity. It is shown here that due to this nonlinearity, the propagation of small scale wave packets is accompanied by instability of a low frequency, long wavelength component. This instability is the coherent hydrodynamic generalization of the resonant type mean flow instability identified recently [P. H. Diamond, M. N. Rosenbluth, F. L. Hinton, M. Malkov, J. Fleischer, and A. Smolyakov, 17th IAEA Fusion Energy Conference, IAEA-CN-69/TH3/1, Yokohama, 1998 (to be published, International Atomic Energy Agency, Vienna)]. The mechanism discussed here, along with the resonant type, constitutes the “hydrodynamic” and “kinetic” regimes of the same process, similar to the case of plasma-beam instabilities. It is suggested that this generic mechanism is responsible for the generation of mean flow in atmospheres of rotating planets and magnetized plasmas. © 2000 American Institute of Physics.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Ra Plasma turbulence
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.

Off-midplane launch of electron Bernstein waves for current drive in overdense plasmas

C. B. Forest, P. K. Chattopadhyay, R. W. Harvey, and A. P. Smirnov

Phys. Plasmas 7, 1352 (2000); http://dx.doi.org/10.1063/1.873951 (4 pages) | Cited 36 times

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Numerical modeling shows that localized, efficient current drive is possible in overdense toroidal plasmas (such as reversed field pinches and spherical tokamaks) using perpendicular launch of electron Bernstein waves. The wave directionality required for driving current can be obtained by launching the waves above or below the midplane of the torus and is a geometric effect related to the poloidal magnetic field. Wave absorption is strong, a result of the electrostatic nature of the waves, giving efficient suprathermal tail formation and current drive. © 2000 American Institute of Physics.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.50.Gj Plasma heating by particle beams
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back to top Basic Plasma Phenomena, Waves, Instabilities

The compressible plane current-vortex sheet

R. B. Dahlburg and G. Einaudi

Phys. Plasmas 7, 1356 (2000); http://dx.doi.org/10.1063/1.873952 (10 pages) | Cited 14 times

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The plane current-vortex sheet is a magnetohydrodynamic configuration in which a vortex sheet lies at the location of an electric current sheet. Most previous research on this structure has focused on the incompressible situation. In this paper some effects of compressibility on the linear stability properties of the plane current-vortex sheet are examined. The relevant compressible equations are derived and then solved by a new magnetohydrodynamic extension of the SPEctral Compressible Linear Stability (SPECLS) algorithm, a Chebyshev collocation code. Of particular interest is an investigation of how the properties of the low sonic Mach number (M) analogs of previously investigated incompressible unstable modes vary as M is increased to supersonic values. It is found that, in general, the growth rates of these modes decrease as M increases. However, new unstable modes are found to appear at high M. These new modes, which have a finite phase velocity, are also found to be weakly evanescent and oscillatory in the cross-stream direction. Further data is presented on the influence of the streamwise and spanwise wave numbers, and also the Alfvén number. The morphology of the perturbations is also discussed, with an emphasis on the temperature and mass density structure. A short discussion is also given of the effect of spatial variation of the zeroth-order temperature and mass density fields, a situation that would arise when magnetofluids with different thermodynamic properties are brought into contact with each other. © 2000 American Institute of Physics.
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52.65.-y Plasma simulation
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.
47.65.-d Magnetohydrodynamics and electrohydrodynamics
95.30.Qd Magnetohydrodynamics and plasmas

Hydrodynamic regime of two-dimensional electron magnetohydrodynamics

Sheikh Dastgeer, Amita Das, and Predhiman Kaw

Phys. Plasmas 7, 1366 (2000); http://dx.doi.org/10.1063/1.873953 (8 pages) | Cited 16 times

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A detailed numerical simulation studying certain aspects of turbulence in the electron magnetohydrodynamic (EMHD) model is presented. In particular, new studies have been carried out in a parameter regime where the typical turbulent length scales are comparable to or smaller than the electron skin depth. This is the regime where the EMHD turbulence has similar traits to the hydrodynamic turbulence and the wave propagation effects due to whistlers are believed to be inconsequential. © 2000 American Institute of Physics.
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52.38.-r Laser-plasma interactions

Mechanism of dust-acoustic instability in a direct current glow discharge plasma

V. E. Fortov, A. G. Khrapak, S. A. Khrapak, V. I. Molotkov, A. P. Nefedov, O. F. Petrov, and V. M. Torchinsky

Phys. Plasmas 7, 1374 (2000); http://dx.doi.org/10.1063/1.873954 (7 pages) | Cited 77 times

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An observation of low frequency waves spontaneously excited in a dc glow discharge dusty plasma is reported. To analyze possible reasons for the instability observed, a linear dispersion relation which takes into account collisions with neutrals, dust grain charge variations, ion drift, and forces acting on dust particles is derived. Numerical analysis of the dispersion relation shows that the observed instability is the result of dust charge variations in the presence of external charge-dependent forces together with the ion drift effect. © 2000 American Institute of Physics.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.35.Dm Sound waves
back to top Nonlinear Phenomena, Turbulence, Transport

The split-weight particle simulation scheme for plasmas

Igor Manuilskiy and W. W. Lee

Phys. Plasmas 7, 1381 (2000); http://dx.doi.org/10.1063/1.873955 (5 pages) | Cited 38 times

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An efficient numerical method for treating electrons in magnetized plasmas has been developed. The scheme, which is based on the perturbative (δf) gyrokinetic particle simulation, splits the particle electron responses into adiabatic and nonadiabatic parts. The former is incorporated into the gyrokinetic Poisson’s equation, while the latter is calculated dynamically with the aid of the charge conservation equation. The new scheme affords us the possibility of suppressing unwanted high-frequency oscillations and, in the meantime, relaxing the Courant condition for the thermal particles moving in the parallel direction. It is most useful for studying low-frequency phenomena in plasmas. As an example, one-dimensional drift wave simulation has been carried out using the scheme and the results are presented in this paper. This methodology can easily be generalized to problems in three-dimensional toroidal geometry, as well as those in unmagnetized plasmas. © 2000 American Institute of Physics.
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52.65.-y Plasma simulation

Nonlocal radiative forces in fully-ionized plasmas

A. Tahraoui, A. Bendib, and K. Bendib

Phys. Plasmas 7, 1386 (2000); http://dx.doi.org/10.1063/1.873956 (11 pages) | Cited 8 times

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The solution of the Fokker–Planck equation which contains the contribution of high-frequency electric fields is presented. For this, the projection operators of the Krook collision operator and the semicollisional propagator computed with the continued fractions were used. Both elastic and inelastic momentum transfer from the high-frequency electric field to electrons have been considered. The contributions of such high-frequency electric fields to the stress tensor and to the mean change of momentum due to electron–ion collisions are derived in the whole collisionality range. As a result, in the collisionless range, these contributions led to a new force which is 1.6 (instead of 4/3) more important than the Miller force. In the collisional range, the radiative force due to the inverse bremsstrahlung absorption is recovered and a new contribution which arises from the mean change of momentum due to collisions is found. © 2000 American Institute of Physics.
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52.20.-j Elementary processes in plasmas
52.25.Fi Transport properties
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma

Experimental study of fluctuations excited by a narrow temperature filament in a magnetized plasma

A. T. Burke, J. E. Maggs, and G. J. Morales

Phys. Plasmas 7, 1397 (2000); http://dx.doi.org/10.1063/1.873957 (11 pages) | Cited 7 times

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A systematic study is made of the spontaneous growth of fluctuations in temperature, density, and magnetic field in a narrow (on the order of the electron skin depth) field-aligned temperature filament embedded in a large magnetized plasma. Two broad classes of fluctuation (“low” and “high” frequency modes) have been identified and studied in detail. A high-frequency drift-Alfvén mode grows at frequencies about one tenth the ion gyrofrequency in the region of the filament where the temperature gradient is large. The measured radial profiles of the density and magnetic field fluctuations associated with this mode agree well with theoretical predictions. The high-frequency mode has been observed to exhibit several interesting nonlinear features, including steepening wave form, progression in azimuthal mode number, coupling to the low frequency mode with subsequent sideband generation, and eventually a transition to broad band turbulence. The nature of the low-frequency mode which has frequencies about one fiftieth of the ion gyrofrequency is less certain, but it has been identified as a spatially localized, azimuthally symmetric mode consisting primarily of temperature fluctuations. Both the high and low-frequency modes give rise to electron heat transport at rates in excess of the classical values. © 2000 American Institute of Physics.
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52.25.Fi Transport properties
52.35.Kt Drift waves
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.35.Ra Plasma turbulence
back to top Magnetically Confined Plasmas, Heating, Confinement

Statistical characterization of fluctuation wave forms in the boundary region of fusion and nonfusion plasmas

E. Sánchez, C. Hidalgo, D. López-Bruna, I. García-Cortés, R. Balbín, M. A. Pedrosa, B. van Milligen, C. Riccardi, G. Chiodini, J. Bleuel, M. Endler, B. A. Carreras, and D. E. Newman

Phys. Plasmas 7, 1408 (2000); http://dx.doi.org/10.1063/1.873958 (9 pages) | Cited 68 times

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The statistical properties of plasma fluctuations have been investigated in the plasma boundary region of fusion (tokamaks and stellarators) and nonfusion plasmas. Fluctuations in ion saturation current and floating potential have a near-Gaussian character in the proximity of the velocity shear layer (rsh). However, fluctuations deviate from a Gaussian distribution when moving inside of the plasma edge (r<rsh) or into the scrape-off layer region (r>rsh). Furthermore, fluctuations show sporadic pulses that are asymmetric in time. The present analysis shows a coupling of those pulses and the averaged flow in the shear layer region. © 2000 American Institute of Physics.
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52.55.-s Magnetic confinement and equilibrium
52.35.Ra Plasma turbulence

Paths to ignition by radio frequency heating during the B-field ramp

J. R. Myra, R. E. Aamodt, and D. A. D’Ippolito

Phys. Plasmas 7, 1417 (2000); http://dx.doi.org/10.1063/1.873959 (4 pages)

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To conserve transformer volt-seconds, power to toroidal magnetic field coils, and to trigger an early transition into high confinement (H) mode, where the requirements on auxiliary power are lower, rf heating during the B-field ramp phase of ignition-class tokamaks is considered. The scheme is analyzed by modifying the usual plasma operating condition diagrams to apply to the ramp phase where the magnetic field, plasma current, and density are changing. It is shown that ion cyclotron range-of-frequencies direct electron heating during the ramp phase of IGNITOR [B. Coppi, M. Nassi, and L. E. Sugiyama, Phys. Scr. 45, 112 (1992)], as proposed by Majeski [R. Majeski, in AIP Conference Proceedings 485—Radio Frequency Power in Plasmas, Annapolis, MD (AIP, New York, 1999), p. 353], may be useful in optimizing the operating condition path to ignition. © 2000 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.50.Gj Plasma heating by particle beams
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects

A hydrocarbon reaction model for low temperature hydrogen plasmas and an application to the Joint European Torus

D. A. Alman, D. N. Ruzic, and J. N. Brooks

Phys. Plasmas 7, 1421 (2000); http://dx.doi.org/10.1063/1.873960 (12 pages) | Cited 55 times

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A model of collisional processes of hydrocarbons in hydrogen plasmas has been developed to aid in computer modeling efforts relevant to plasma–surface interactions. It includes 16 molecules (CH up to CH4, C2H to C2H6, and C3H to C3H6) and four reaction types (electron impact ionization/dissociative ionization, electron impact dissociation, proton impact charge exchange, and dissociative recombination). Experimental reaction rates or cross sections have been compiled, and estimates have been made for cases where these are not available. The proton impact charge exchange reaction rates are calculated from a theoretical model using molecular polarizabilities. Dissociative recombination rates are described by the equation A/TB where parameter A is fit using polarizabilities and B is estimated from known reaction rates. The electron impact ionization and dissociation cross sections are fit to known graphs using four parameters: threshold energy, maximum value of the cross section, energy at the maximum, and a constant for the exponential decay as energy increases. The model has recently been used in an analysis of the Joint European Torus [P. H. Rebut, R. J. Bickerton, and B. E. Keen, Nucl. Fusion 25, 1011 (1985)] MARK II carbon inner divertor using the WBC Monte Carlo impurity transport code. The updated version of WBC, which includes the full set of hydrocarbon reactions, helps to explain an observed asymmetry in carbon deposition near the divertor. © 2000 American Institute of Physics.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.55.Fa Tokamaks, spherical tokamaks
52.40.Hf Plasma-material interactions; boundary layer effects
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
34.80.Gs Molecular excitation and ionization
34.50.Gb Electronic excitation and ionization of molecules
34.70.+e Charge transfer
82.20.Pm Rate constants, reaction cross sections, and activation energies

Fast particle destabilization of toroidicity-induced Alfvén eigenmodes in the National Spherical Torus Experiment

N. N. Gorelenkov, C. Z. Cheng, G. Y. Fu, S. Kaye, R. White, and M. V. Gorelenkova

Phys. Plasmas 7, 1433 (2000); http://dx.doi.org/10.1063/1.873961 (4 pages) | Cited 7 times

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Toroidicity-induced Alfvén eigenmode (TAE) stability in the National Spherical Torus Experiment (NSTX) [S. M. Kaye, M. Ono, Y.-K. M. Peng et al., Fusion Technol. 36, 16 (1999)] is analyzed using the improved NOVA-K code [N. N. Gorelenkov, C. Z. Cheng, and G. Y. Fu, Phys. Plasmas 6, 2802 (1999)], which includes finite orbit width and Larmor radius effects and is able to predict the saturation amplitude for the mode using the quasilinear theory. A broad spectrum of unstable global TAEs with different toroidal mode numbers is predicted. Due to the strong poloidal field and the presence of the magnetic well in NSTX, better particle confinement in the presence of TAEs in comparison with tokamaks is illustrated making use of the ORBIT code [R. B. White and M. S. Chance, Phys. Fluids 27, 2455 (1984)]. © 2000 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.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects

Poloidal flows and enhanced reverse shear bifurcation in tokamaks

R. Srinivasan and K. Avinash

Phys. Plasmas 7, 1437 (2000); http://dx.doi.org/10.1063/1.873962 (6 pages) | Cited 1 time

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The effect of poloidal flow shear on transition to enhanced reverse shear (ERS) mode in tokamaks is studied. A model is examined where the flow-fluctuation equilibrium evolves in time as a function of pressure gradients. Under some conditions the transition to the ERS phase occurs via as s-fold catastrophe and is accompanied by a spike in poloidal flow generation where poloidal flow shear is reversed. The nature of the transition is found to depend critically on the ratio of factors controlling the damping and generation of poloidal flow shear. The turbulence level shows a periodic bursting behavior which is suppressed in the ERS phase. The relevance of these results to recent observations from the Tokamak Fusion Test Reactor [R. E. Bell et al., Phys. Rev. Lett. 81, 1429 (1998)] is briefly discussed. © 2000 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.30.-q Plasma dynamics and flow
52.25.Fi Transport properties
52.25.Gj Fluctuation and chaos phenomena

Kinetic simulations of the formation and stability of the field-reversed configuration

Yu. A. Omelchenko

Phys. Plasmas 7, 1443 (2000); http://dx.doi.org/10.1063/1.873963 (9 pages) | Cited 13 times

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The Field-Reversed Configuration (FRC) is a high-beta compact toroidal plasma confined primarily by poloidal fields. In the FRC the external field is reversed on axis by the diamagnetic current carried by thermal plasma particles. A three-dimensional, hybrid, particle-in-cell (zero-inertia fluid electrons, and kinetic ions), code FLAME, previously used to study ion rings [Yu. A. Omelchenko and R. N. Sudan, J. Comp. Phys. 133, 146 (1997)], is applied to investigate FRC formation and tilt instability. Axisymmetric FRC equilibria are obtained by simulating the standard experimental reversed theta-pinch technique. These are used to study the nonlinear tilt mode in the “kinetic” and “fluid-like” cases characterized by “small” ( ∼ 3) and “large” ( ∼ 12) ratios of the characteristic radial plasma size to the mean ion gyro-radius, respectively. The formation simulations have revealed the presence of a substantial toroidal (azimuthal) magnetic field inside the separatrix, generated due to the stretching of the poloidal field by a sheared toroidal electron flow. This is shown to be an important tilt-stabilizing effect in both cases. On the other hand, the tilt mode stabilization by finite Larmor radius effects has been found relatively insignificant for the chosen equilibria. © 2000 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.)
52.55.Jd Magnetic mirrors, gas dynamic traps
52.65.Rr Particle-in-cell method

Toroidal field effects on dipole equilibrium and stability at finite plasma pressure

Peter J. Catto and S. I. Krasheninnikov

Phys. Plasmas 7, 1452 (2000); http://dx.doi.org/10.1063/1.873964 (7 pages) | Cited 4 times

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The influence of a toroidal magnetic field on the equilibrium and stability of a plasma confined by the magnetic field of a point dipole is considered, since it may be necessary to introduce a toroidal magnetic field to smooth electron heating or other asymmetries in the toroidal direction that can lead to toroidal electric fields and a loss of confinement due to radial E×B drift. To begin, a toriodal magnetic field is shown to restore confinement by reducing electron heating departures from axisymmetry. Then the Grad–Shafranov equation for a point dipole in the presence of a toroidal field is solved to explicitly demonstrate that an equilibrium exists. Finally, it is shown that a toroidal magnetic field destabilizes the otherwise stable point dipole ballooning modes at high plasma pressure. Consequently, if a toroidal magnetic field is necessary to remove toroidal heating asymmetries in a dipole equilibrium, the heating may have to be performed transiently or at lower plasma pressures. © 2000 American Institute of Physics.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)

Effect of edge biasing on electrostatic fluctuations and particle transport in a nonfusion magnetoplasma

C. Riccardi, C. Bevilacqua, G. Chiodini, and M. Fontanesi

Phys. Plasmas 7, 1459 (2000); http://dx.doi.org/10.1063/1.873965 (8 pages) | Cited 5 times

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This paper concerns experiments about the role of a radial electric field on the plasma turbulence in a toroidal magnetoplasma, and the possibility of anomalous transport reduction through the application of external biasing potentials to the plasma edge. The experiments show, for positive applied bias potential, a progressive reduction of radial anomalous particle flux, as well as electrostatic fluctuations. Some results on statistical and spectral properties of plasma and density fluctuations are reported. © 2000 American Institute of Physics.
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52.35.Ra Plasma turbulence
52.55.Fa Tokamaks, spherical tokamaks
52.55.Jd Magnetic mirrors, gas dynamic traps
52.25.Gj Fluctuation and chaos phenomena
52.25.Fi Transport properties

Poloidal field effects on fundamental minority ion cyclotron resonance heating in a tokamak plasma

S. C. Jun, Kaya Imre, D. C. Stevens, Harold Weitzner, and C. S. Chang

Phys. Plasmas 7, 1467 (2000); http://dx.doi.org/10.1063/1.873966 (12 pages) | Cited 3 times

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Minority ion fundamental cyclotron resonance is studied in a large tokamak in which the geometrical optics approximation applies off resonance and the minority average speed is less than the wave phase speeds. Poloidal equilibrium magnetic field effects are included, which lead to nontrivially nonlocal integrodifferential equations for the wave fields. Exact reciprocity relation is given as well as explicit analytic solutions for the transmission coefficients for both the high and low field side incidences. Numerical solutions are needed only for the high field side incident reflection coefficient. Numerical schemes are described and numerical results are presented together with a reliable error bound. Typically, energy absorption increases with poloidal field. The energy absorption increases with minority density at low values of minority density. However, it decreases at high minority density. Poloidal field effects weaken the dependence of energy absorption on the toroidal wave number. © 2000 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.50.Gj Plasma heating by particle beams

The radial and poloidal localization of fast magnetoacoustic eigenmodes in tokamaks

T. Fülöp, M. Lisak, Ya. I. Kolesnichenko, and D. Anderson

Phys. Plasmas 7, 1479 (2000); http://dx.doi.org/10.1063/1.873967 (8 pages) | Cited 6 times

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Edge-localized fast magnetoacoustic eigenmodes (FME) may be responsible for the observed superthermal ion cyclotron emission in recent deuterium/deuterium (DD) and deuterium/tritium (DT) experiments. These modes can be driven unstable by resonant interaction with a small population of energetic ions (e.g., fusion alphas), having an anisotropic distribution in velocity space, provided that the mode frequency is close to the ion cyclotron frequency. In the present paper, the radial and poloidal structure of these eigenmodes is analyzed, by solving the two-dimensional (2D) eigenmode equation both numerically and analytically using a variational approach. In particular, the conditions for the mode localization and the dependence of the mode structure on aspect ratio and ellipticity are investigated. The eigenmode is found to be radially localized near the plasma edge. In a tokamak with finite aspect ratio, the mode is localized also poloidally near the outer midplane edge. The existence of localized solutions for both sign of the poloidal mode number is found to be sensitive to the ellipticity, the magnitude of parallel wave number and the plasma density profile. © 2000 American Institute of Physics.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.55.Fa Tokamaks, spherical tokamaks
51.10.+y Kinetic and transport theory of gases

Legendre polynomial expansion method for evaluating multipole moments of current density in toroidal devices

Seong-Heon Seo, Jay Kim, S. H. Huh, W. Choe, Hong-Young Chang, and Seung-Ho Jeong

Phys. Plasmas 7, 1487 (2000); http://dx.doi.org/10.1063/1.873968 (7 pages) | Cited 1 time

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It is found that multipole moments of toroidal current are given by the coefficients of the Legendre polynomial expansion of the magnetic field on a meridian contour. Using this fact and the orthogonality of the Legendre polynomials, a method is proposed for evaluating the moments from magnetic field measurements through an open-contour. As an application, exact expressions of the first few order moments and the current center position are formulated. Results show that this method is applicable to any aspect ratio tokamaks without the limitation of small displacement of the current center. © 2000 American Institute of Physics.
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52.70.-m Plasma diagnostic techniques and instrumentation
07.55.Ge Magnetometers for magnetic field measurements
52.55.Fa Tokamaks, spherical tokamaks

Electron transport in Tore Supra with fast wave electron heating

W. Horton, P. Zhu, G. T. Hoang, T. Aniel, M. Ottaviani, and X. Garbet

Phys. Plasmas 7, 1494 (2000); http://dx.doi.org/10.1063/1.873969 (17 pages) | Cited 57 times

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The hot electron plasmas (Te>2Ti) in Tore Supra (Equipe Tore Supra (presented by R. Aymar) in Plasma Physics and Controlled Nuclear Fusion Research [Proc. 12th Int. Conf., Nice, 1988 (IAEA, Vienna, 1989), Vol. 1, p. 9]) driven by fast wave electron heating (FWEH) are analyzed for thermal transport. Both neoclassical and anomalous transport processes are taken into account. The dominant power flow is through the electron channel of anomalous thermal diffusivity. The electron and ion temperature gradient driven instabilities are analyzed for a well documented discharge and shown to explain the diffusivities inferred from the steady state power balance analysis. The discharges are maintained in a quasi-steady state for periods up to 100 global energy replacement times. A large Tore Supra database is tested against two models for the turbulent electron thermal conductivity. Good correlation is obtained with an updated version of the collisionless skin depth formula. The electrostatic turbulence-based formula for electron temperature gradient (ETG) mode performs poorly in the core but well in the outer plasma. The electromagnetic turbulence theory based formula for ETG mode is benchmarked with the empirical Taroni–Bohm formula derived from Joint European Torus (JET) data. © 2000 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.25.Fi Transport properties
52.50.Gj Plasma heating by particle beams
52.35.Ra Plasma turbulence
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

Theory of filamentation instability and stimulated Brillouin scattering with nonlocal hydrodynamics

V. Yu. Bychenkov, W. Rozmus, A. V. Brantov, and V. T. Tikhonchuk

Phys. Plasmas 7, 1511 (2000); http://dx.doi.org/10.1063/1.873970 (9 pages) | Cited 20 times

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A linear theory of stimulated Brillouin scattering and filamentation instabilities has been formulated using nonlocal transport equations for a laser heated plasma, resulting in a model which is fully equivalent to a linearized kinetic description. The inverse-Bremsstrahlung heating, nonlocal energy redistribution, and ponderomotive laser–plasma interactions are correctly taken into account contributing to a new generalized driving force for these instabilities. Temporal and spatial growth rates, thresholds and dominant perturbation wavelengths are obtained. This theory predicts substantial modifications of the ponderomotive results for conditions relevant to many laser plasma interaction experiments. A new nonlocal and nonlinear model of laser propagation in weakly collisional plasmas has been derived. © 2000 American Institute of Physics.
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52.38.Bv Rayleigh scattering; stimulated Brillouin and Raman scattering
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.)
52.25.Fi Transport properties
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Dg Plasma kinetic equations
52.38.-r Laser-plasma interactions
52.20.-j Elementary processes in plasmas

Plasma harmonic emission from laser interactions with dense plasma

R. Ondarza-Rovira and T. J. M. Boyd

Phys. Plasmas 7, 1520 (2000); http://dx.doi.org/10.1063/1.873971 (11 pages) | Cited 11 times

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A nonlinear procedure is used to account for the mechanism of laser harmonic generation to high orders and plasma emission in laser-dense plasma interactions. A Lagrangian model is used to describe harmonic generation in terms of the oscillatory behavior of an electron plasma. It is shown that the effect of pulse shaping constitutes an important issue for the generation and enhancement of harmonics. It is found that in the presence of electron density perturbations further harmonics beyond the order that corresponds to the upper shelf plasma density can be excited. Computations were performed for mildly relativistic electrodynamics and time scales where wave breaking effects do not take place. Using particle-in-cell (PIC) simulations, plasma emission was observed for the interaction of laser light with super-critical density plasmas with spectral characteristics resembling those found from the fluid model. © 2000 American Institute of Physics.
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52.38.-r Laser-plasma interactions
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.65.Rr Particle-in-cell method

A novel charged-particle diagnostic for compression in inertial confinement fusion targets

P. B. Radha, S. Skupsky, R. D. Petrasso, and J. M. Soures

Phys. Plasmas 7, 1531 (2000); http://dx.doi.org/10.1063/1.873972 (8 pages) | Cited 5 times

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A new technique for diagnosing compression in multiple regions of inertial confinement fusion targets is discussed. This diagnostic uses knock-on deuterons and protons that have been elastically scattered by 14.1 MeV deuterium–tritium (DT) fusion neutrons. The target is composed of three different materials: DT gas contained in a plastic shell overcoated by deuterated plastic. The effect on the knock-on deuteron spectrum of mixing of these layers from hydrodynamic instabilities is also discussed. © 2000 American Institute of Physics.
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52.58.-c Other confinement methods
52.70.Nc Particle measurements
28.52.Cx Fueling, heating and ignition
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
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