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Dec 1999

Volume 6, Issue 12, pp. 4405-4799

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Demonstration of a 10 kW average power 94 GHz gyroklystron amplifier

M. Blank, B. G. Danly, B. Levush, J. P. Calame, K. Nguyen, D. Pershing, J. Petillo, T. A. Hargreaves, R. B. True, A. J. Theiss, G. R. Good, K. Felch, B. G. James, P. Borchard, P. Cahalan, et al.

Phys. Plasmas 6, 4405 (1999); http://dx.doi.org/10.1063/1.873726 (5 pages) | Cited 21 times

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The experimental demonstration of a high average power W-band (75–110 GHz) gyroklystron amplifier is reported. The gyroklystron has produced 118 AW peak output power and 29.5% electronic efficiency in the TE011 mode using a 66.7 kV, 6 A electron beam at 0.2% rf duty factor. At this operating point, the instantaneous full width at half-maximum (FWHM) bandwidth is 600 MHz. At 11% rf duty factor, the gyroklystron has produced up to 10.1 kW average power at 33% electronic efficiency with a 66 kV, 4.15 A electron beam. This represents world record performance for an amplifier at this frequency. At the 10.1 kW average power operating point, the FWHM bandwidth is 420 MHz. At higher magnetic fields and lower beam voltages, larger bandwidths can be achieved at the expense of peak and average output power. © 1999 American Institute of Physics.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Generalized action invariants for drift waves-zonal flow systems

A. I. Smolyakov and P. H. Diamond

Phys. Plasmas 6, 4410 (1999); http://dx.doi.org/10.1063/1.873725 (4 pages) | Cited 52 times

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Generalized action invariants are identified for various models of drift wave turbulence in the presence of the mean shear flow. It is shown that the wave kinetic equation describing the interaction of the small scale turbulence and large scale shear flow can be naturally writen in terms of these invariants. Unlike the wave energy, which is conserved as a sum of small- and large-scale components, the generalized action invariant is shown to correspond to a quantity which is conserved for the small scale component alone. This invariant can be used to construct canonical variables leading to a different definition of the wave action (as compared to the case without shear flow). It is suggested that these new canonical action variables form a natural basis for the description of the drift wave turbulence with a mean shear flow. © 1999 American Institute of Physics.
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52.35.Kt Drift waves
52.35.Ra Plasma turbulence
52.30.-q Plasma dynamics and flow
52.25.Dg Plasma kinetic equations

Dust–Coulomb waves in dense dusty plasmas

N. N. Rao

Phys. Plasmas 6, 4414 (1999); http://dx.doi.org/10.1063/1.873727 (4 pages) | Cited 42 times

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Dusty plasmas can be considered as tenuous, dilute or dense when the dust fugacity parameter f ≡ 4πnd0λD2R ∼ NDR/λD satisfies f≪1, ∼1, or ≫1, where nd0, λD and R denote, respectively, the dust number density, the plasma Debye length and the dust grain size (radius), and ND = nd0λD3 is the dust plasma parameter. Dense dusty plasmas are shown to support a new kind of ultra low-frequency electrostatic dust mode which may be called the “Dust–Coulomb Wave” (DCW). In contrast to the dust–acoustic wave (DAW) and the dust–lattice wave (DLW) which exist even for constant grain charge, DCWs are accompanied by dust charge as well as number density perturbations which are proportional to each other. For frequencies much smaller than the grain charging frequency, DCWs propagate as normal modes with the phase speed CDC ≡ qd0/math, where qd0 (md) is the charge (mass) of the dust grains. In the long wavelength limit, the DCW phase speed is much smaller than that of DAW (CDA), and scales as ∼ CDA/math. Thus, for a given wave number, the frequency regime for the existence of DCW is much lower than the DAW regime. A comparison between the three types of dust–modes (DCWs, DAWs, and DLWs) has been carried out. © 1999 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.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
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Tests of causality: Experimental evidence that sheared E×B flow alters turbulence and transport in tokamaks

Keith H. Burrell

Phys. Plasmas 6, 4418 (1999); http://dx.doi.org/10.1063/1.873728 (18 pages) | Cited 101 times

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A prime goal in physics research is the development of theories which have the universality needed to explain a wide range of observations. Developed over the past decade, the model of turbulence decorrelation and stabilization by sheared E×B flow has the universality needed to explain the turbulence reduction and confinement improvement seen in the edge and core of a wide range of magnetic confinement devices. Because the E×B shear, turbulence, and transport are all intimately intertwined in multiple feedback loops, devising experiments to test whether E×B shear causes a change in turbulence and transport has been a major challenge for experimentalists. Over the past five years, there have been at least four clear demonstrations of causality performed in tokamak plasmas, both at the plasma edge on Doublet III-D (DIII-D) [Plasma Physics and Controlled Fusion Research 1985 (International Atomic Energy Agency, Vienna, 1986) Vol. I, p.159] and Tokamak Experiment for Technologically Oriented Research (TEXTOR) [Plasma Physics and Controlled Nuclear Fusion Research 1990 (International Atomic Energy Agency, Vienna, 1991) Vol. I, p. 473] and further into the plasma core on DIII-D and Tokamak Fusion Test Reactor [Phys. Plasmas 5, 1577 (1998)]. This paper discusses these tests in detail; the results agree with the expectations from the E×B shear model. This paper also discusses similarities between flow shear effects in plasmas and in neutral fluids and provides examples of flow shear reduction of turbulence in neutral fluids under the proper conditions. © 1999 American Institute of Physics.
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52.25.Fi Transport properties
52.55.Fa Tokamaks, spherical tokamaks
52.55.Jd Magnetic mirrors, gas dynamic traps

Role of computer modeling of plasmas in the 21st century

John M. Dawson

Phys. Plasmas 6, 4436 (1999); http://dx.doi.org/10.1063/1.873729 (8 pages) | Cited 4 times

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For much of their history plasmas have been characterized by complex unpredictable behavior. This stemmed from their general nonlinear turbulent behavior, from the difficulties of carrying out controlled experiments, and from the limitations of theory. Recently this situation has changed quite dramatically with the phenomenal growth in the capabilities of computer modeling. Contact between predictions and experiments have been made over a broad range of problems. In the 21st century the power of modeling will continue to grow; the techniques for using the tool will grow and our ability to understand the complex results will improve. In this endeavor the most critical factor is the human factor. Humans must create the models; they must make sense of the results; they must condense the results to a simplified form that is useful to others. Given the importance of plasmas to human activities and in the universe, these advances point to important developments. © 1999 American Institute of Physics.
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52.65.Tt Gyrofluid and gyrokinetic simulations
52.65.Rr Particle-in-cell method
52.27.Ny Relativistic plasmas
96.50.Ek Heliopause and solar wind termination

Transport in accretion disks

John F. Hawley and Steven A. Balbus

Phys. Plasmas 6, 4444 (1999); http://dx.doi.org/10.1063/1.873730 (6 pages) | Cited 4 times

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Astrophysical accretion disks are powered by the release of gravitational potential energy as gas spirals down onto a compact star or black hole. The dynamics and evolution of accretion disks depend upon how angular momentum is transported outward from one fluid element to another. The nature of this process was unclear for many years. Since the early 1990s, however, considerable progress has been made in understanding how turbulence arises and transports angular momentum in astrophysical accretion disks. Accretion disks are generally highly conducting plasmas; the equations governing their evolution are those of ideal magnetohydrodynamics. Although a hydrodynamical disk would be locally stable, the combination of a weak subthermal magnetic field and outwardly decreasing differential rotation rapidly generates magnetohydrodynamical turbulence via a remarkably simple linear instability. Thus, turbulent accretion disks are fundamentally magnetohydrodynamical in nature. © 1999 American Institute of Physics.
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97.10.Ex Stellar atmospheres (photospheres, chromospheres, coronae, magnetospheres); radiative transfer; opacity and line formation
95.30.Qd Magnetohydrodynamics and plasmas
47.20.Ft Instability of shear flows (e.g., Kelvin-Helmholtz)
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back to top Basic Plasma Phenomena, Waves, Instabilities

Laboratory studies of magnetic vortices. I. Directional radiation of whistler waves based on helicity injection

R. L. Stenzel and J. M. Urrutia

Phys. Plasmas 6, 4450 (1999); http://dx.doi.org/10.1063/1.873731 (8 pages) | Cited 9 times

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A novel principle for the directional excitation of whistler waves is demonstrated in a laboratory experiment. It is based on helicity conservation of electron magnetohydrodynamic fields in plasmas. Whistler wave packets propagating in opposite directions to a static magnetic field have opposite signs of helicity. Injection of helicity of one sign produces radiation in one direction. This is accomplished with an antenna consisting of a loop linked through a torus. Directionality of 20 dB is readily achieved. The direction of radiation is electronically reversible. Transmission between two antennas is unidirectional, hence nonreciprocal. Possible applications include secure communication, direction finding, and efficient power deposition in radio frequency (rf) heating. © 1999 American Institute of Physics.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)

Laboratory studies of magnetic vortices. II. Helicity reversal during reflection of a magnetic vortex at a conducting boundary

R. L. Stenzel, J. M. Urrutia, and M. C. Griskey

Phys. Plasmas 6, 4458 (1999); http://dx.doi.org/10.1063/1.873732 (9 pages) | Cited 6 times

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The reflection of a magnetic vortex from a conducting boundary is studied experimentally in a large laboratory plasma. The parameter regime is that of electron magnetohydrodynamics and the vortex consists of a spheromak-like magnetic field perturbation propagating in the whistler mode along a uniform background magnetic field. In this work we focus on the helicity properties of the vortex magnetic field, electron velocity, and vorticity. The reflection conserves magnetic energy but reverses the sign of all helicities. The change in topology arises from a self-consistent reversal of one linked vector field without involving helicity injection, reconnection, or dissipation processes. The breakdown of helicity conservation and the frozen-in concept is explained by the presence of a vacuum-like sheath at the plasma–boundary interface. © 1999 American Institute of Physics.
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52.30.-q Plasma dynamics and flow
52.65.Kj Magnetohydrodynamic and fluid equation
02.40.Pc General topology

Quantum drift waves

B. Shokri and A. A. Rukhadze

Phys. Plasmas 6, 4467 (1999); http://dx.doi.org/10.1063/1.873733 (5 pages) | Cited 54 times

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The results of theoretical analysis of the oscillation spectrum of a plasma placed in a very strong quantizing magnetic field are presented. It is shown that in ultra-quantum limit, when all particles occupy the first Landau level, in an inhomogeneous quantized two-component plasma, volume quantum drift waves arise. These waves become unstable under some circumstances. © 1999 American Institute of Physics.
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52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.35.Kt Drift waves

Uniform-density, spherical electron focus

D. C. Barnes

Phys. Plasmas 6, 4472 (1999); http://dx.doi.org/10.1063/1.873734 (7 pages) | Cited 8 times

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An equilibrium electron distribution is exhibited which forms a uniform electron density focus within a spherical system. Such a focus may be used to form a spherical, harmonic well for ion focusing as previously discussed. A self-consistent density and space-charge potential are calculated and the optimum focus radius is determined. Nonideal effects on electron and ion motion in the resulting electrostatic well are briefly discussed and strategies for their minimization are derived. © 1999 American Institute of Physics.
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52.58.Qv Electrostatic and high-frequency confinement
52.27.Jt Nonneutral plasmas

Flow driven resistive wall instability

B. M. Veeresha, S. N. Bhattacharyya, and K. Avinash

Phys. Plasmas 6, 4479 (1999); http://dx.doi.org/10.1063/1.873735 (8 pages) | Cited 4 times

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The stability of a perfectly conducting fluid layer flowing along a magnetic field, parallel to a finitely conducting thin wall is examined. Finite layer width and compressibility of the fluid are shown to significantly lower the flow velocity required for instability to set in. The effect of axial flow on the stability of a cylindrical pinch surrounded by a resistive wall is examined. Flow is shown to have a destabilizing effect. © 1999 American Institute of Physics.
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52.30.-q Plasma dynamics and flow
52.55.Fa Tokamaks, spherical tokamaks
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Covariant descriptions of the relativistic guiding-center dynamics

Alexei Beklemishev and Massimo Tessarotto

Phys. Plasmas 6, 4487 (1999); http://dx.doi.org/10.1063/1.873736 (10 pages) | Cited 3 times

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The relativistic guiding center dynamics of charged particles is described in terms of noncanonical variables. The gyrokinetic transformation is obtained using the perturbative Lagrangian approach with a fully relativistic, four-dimensional covariant formulation. It is shown that the definition of the ignorable gyrophase (as well as those of the magnetic moment and the gyrocenter energy) is not unique, and allows for several free functions in the gyrokinetic transformation. This freedom can be interpreted as a choice of the reference frame. One of these frames, namely that moving with the relativistic version of the math×math-drift velocity, generates the simplest and intuitive description. © 1999 American Institute of Physics.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.55.Jd Magnetic mirrors, gas dynamic traps
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.

Autoresonant (nonstationary) excitation of a collective nonlinear mode

J. Fajans, E. Gilson, and L. Friedland

Phys. Plasmas 6, 4497 (1999); http://dx.doi.org/10.1063/1.873737 (7 pages) | Cited 22 times

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The autoresonant (nonlinear phase locking) manipulation of the diocotron mode in a non-neutral plasma is investigated. Autoresonance is a very general phenomenon in driven nonlinear oscillator and wave systems. By sweeping or chirping the drive frequency, autoresonance allows the amplitude of a nonlinear wave to be controlled without the use of feedback. The experimental results, including a novel scaling relation, are in excellent agreement with a simple theoretical model. These are the first controlled laboratory studies of autoresonance in a collective plasma system. © 1999 American Institute of Physics.
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52.27.Jt Nonneutral plasmas
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
05.45.Xt Synchronization; coupled oscillators

Collisional delta-f scheme with evolving background for transport time scale simulations

S. Brunner, E. Valeo, and J. A. Krommes

Phys. Plasmas 6, 4504 (1999); http://dx.doi.org/10.1063/1.873738 (18 pages) | Cited 46 times

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The δf approach is extended for simulating the transport time-scale evolution of near-Maxwellian distributions in collisional plasmas. This involves simultaneously advancing weighted marker particles for representing the intrinsically kinetic component δf, and fluid equations for the parameters of the shifted Maxwellian background fSM. The issue of increasing numerical noise in a collisional δf algorithm, due to marker particle weight spreading, is addressed in detail, and a solution to this problem is proposed. To obtain higher resolution in critical regions of phase space, a practical procedure for implementing sources and sinks of marker particles is developed. As a proof of principal, this set of methods is applied for computing electrical Spitzer conductivity as well as collisional absorption in a homogeneous plasma. © 1999 American Institute of Physics.
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52.65.Ff Fokker-Planck and Vlasov equation
52.65.Pp Monte Carlo methods
52.38.-r Laser-plasma interactions

A self-consistent analysis of a collisional presheath

Monojoy Goswami and H. Ramachandran

Phys. Plasmas 6, 4522 (1999); http://dx.doi.org/10.1063/1.873739 (11 pages) | Cited 7 times

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A one-dimensional plasma discharge is analyzed under steady state conditions. Using simple models for source and collisions, a first-order differential equation is obtained that simultaneously describes both the bulk and the presheath of the plasma. This equation is numerically solved in various regimes and physically interesting quantities such as the ratio of bulk to edge density and the size of the inertial terms in the bulk region are presented. Analytic expressions are obtained for profiles when collision frequency is assumed constant. Findings include nB/nSE ∼ 2.5 for highly collisional systems, significant flow in the bulk plasma, and modified I–V characteristics. © 1999 American Institute of Physics.  
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52.80.Hc Glow; corona
52.40.Hf Plasma-material interactions; boundary layer effects
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Dielectric tensor for inhomogeneous plasmas in inhomogeneous magnetic field

R. Gaelzer, L. F. Ziebell, and O. J. G. Silveira

Phys. Plasmas 6, 4533 (1999); http://dx.doi.org/10.1063/1.873740 (9 pages) | Cited 1 time

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The derivation of explicit expressions for the effective dielectric tensor to be utilized in the dispersion relation for weakly inhomogeneous plasmas is discussed. The general expressions obtained are useful for situations with simultaneous existence of weak inhomogeneities in density and magnetic field. The particular case of a Maxwellian distribution in velocity space for the electron population is discussed, and relatively compact expressions for the dielectric tensor are obtained, which depend on the inhomogeneous plasma dispersion function introduced by [Gaelzer et al., Phys. Rev. E 55, 5859 (1997)] and ultimately on the well-known Fried–Conte function and its derivatives. © 1999 American Institute of Physics.
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52.25.Mq Dielectric properties
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
94.30.Tz Electromagnetic wave propagation
back to top Nonlinear Phenomena, Turbulence, Transport

Bäcklund transformations, a simple transformation and exact solutions for dust-acoustic solitary waves in dusty plasma consisting of cold dust particles and two-temperature isothermal ions

A. H. Khater, A. A. Abdallah, O. H. El-Kalaawy, and D. K. Callebaut

Phys. Plasmas 6, 4542 (1999); http://dx.doi.org/10.1063/1.873741 (6 pages) | Cited 7 times

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Dusty plasma with inertial dust fluid and two-temperature ions admits both compressive and rarefactive solitary waves. The Korteweg-de Vries equations (KdV-type equations) with cubic nonlinearity at the critical density of low-temperature isothermal ions are considered to discuss properties of dust-acoustic solitary waves. In the vicinity of the critical density of low-temperature ions, a KdV-type equation with mixed nonlinearity is discussed. The method of characteristics is used and the Bäcklund transformations (BTs) are employed to generate new solutions from the old ones. Another new solution of the KdV–mKdV equation is obtained using a simple transformation between the sine-Gordon equation and a linear equation combined with an extension of the tanh method of Malfliet. © 1999 American Institute of Physics.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.35.Sb Solitons; BGK modes
52.25.Kn Thermodynamics of plasmas

Nonlinear relativistic gyrokinetic Vlasov-Maxwell equations

Alain J. Brizard and Anthony A. Chan

Phys. Plasmas 6, 4548 (1999); http://dx.doi.org/10.1063/1.873742 (11 pages) | Cited 29 times

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A set of self-consistent nonlinear gyrokinetic equations is derived for relativistic charged particles in a general nonuniform magnetized plasma. Full electromagnetic-field fluctuations are considered with spatial and temporal scales given by the low-frequency gyrokinetic ordering. Self-consistency is obtained by combining the nonlinear relativistic gyrokinetic Vlasov equation with the low-frequency Maxwell equations in which charge densities and current densities are expressed in terms of moments of the gyrokinetic Vlasov distribution. For these self-consistent gyrokinetic equations, a low-frequency energy conservation law is also derived. © 1999 American Institute of Physics.
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52.65.Tt Gyrofluid and gyrokinetic simulations
52.27.Ny Relativistic plasmas
94.30.Lr Magnetic storms, substorms

Evidence for second-order oscillations at the Best frequency in direct numerical simulations of the Vlasov equation

L. Nocera and A. Mangeney

Phys. Plasmas 6, 4559 (1999); http://dx.doi.org/10.1063/1.873743 (6 pages) | Cited 5 times

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Quantitative evidence for second-order oscillations occurring at the frequency predicted by Best [Physica 74, 183 (1974)] and by Sedláček and Nocera [J. Plasma Phys. 48, 367 (1992)] is provided by direct, ab initio numerical simulations of the Vlasov equation. These oscillations are relevant both for their intrinsic connection to the more customary plasma echo (also retrieved), for their diagnostic applications to the study of turbulence, and for the high accuracy needed to reproduce them. This latter fact is used as a sensitive test for the numerical integration, which indeed reproduces both known and new features of the oscillations, including nonlinear Landau damping, particle trapping, and the oscillations’ frequencies, in excellent agreement with theory. © 1999 American Institute of Physics.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.65.-y Plasma simulation
52.35.Ra Plasma turbulence

Three-dimensional particle simulation of plasma instabilities and collisionless reconnection in a current sheet

Ritoku Horiuchi and Tetsuya Sato

Phys. Plasmas 6, 4565 (1999); http://dx.doi.org/10.1063/1.873744 (10 pages) | Cited 63 times

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Generation of anomalous resistivity and dynamical development of collisionless reconnection in the vicinity of a magnetically neutral sheet are investigated by means of a three-dimensional particle simulation. For no external driving source, two different types of plasma instabilities are excited in the current layer. The lower hybrid drift instability (LHDI) is observed to grow in the periphery of current layer in an early period, while a drift kink instability (DKI) is triggered at the neutral sheet in a late period as a result of the nonlinear deformation of the current sheet by the LHDI. A reconnection electric field grows at the neutral sheet in accordance with the excitation of the DKI. When an external driving field exists, the convective electric field penetrates into the current layer through the particle kinetic effect and collisionless reconnection is triggered by the convective electric field earlier than the DKI is excited. It is also found that the anisotropic ion distribution is formed through the anomalous ion heating by the DKI. © 1999 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.)
52.65.Rr Particle-in-cell method
94.30.cl Magnetotail

Dispersion of ideal particles in a two-dimensional model of electrostatic turbulence

V. Naulin, A. H. Nielsen, and J. Juul Rasmussen

Phys. Plasmas 6, 4575 (1999); http://dx.doi.org/10.1063/1.873745 (11 pages) | Cited 30 times

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The dispersion of ideal test particles in electrostatic drift-wave turbulence is investigated numerically. A self-consistent model with an internal instability drive is used to obtain the turbulent two-dimensional (2D) flow-field. It is shown that nonlinear couplings lead to the formation of coherent vortical structures in the flow. The dispersion of the particles is found to be anisotropic, with the weakest dispersion in the direction of the density gradient. By distinguishing between particles trapped in structures and free particles, it is demonstrated that the trapping and subsequent displacement of particles by nonlinear vortex structures enhances the particle diffusion in the direction of the background density gradient. Conditional diffusion coefficients are obtained showing that particles trapped by the vortex structures are convected by the structures. The time a particle on the average stays trapped in the structure is closely related to the lifetime of the vortical structures. The relation between the diffusion coefficient obtained from the test particle dispersion and an effective diffusion coefficient obtained from the cross-field turbulent flux is discussed. © 1999 American Institute of Physics.
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52.35.Kt Drift waves
52.25.Fi Transport properties
47.27.Rc Turbulence control
47.32.C- Vortex dynamics

Turbulent magnetohydrodynamic dynamo based on alpha and cross-helicity effects, with special reference to geomagnetic fields

Akira Yoshizawa, Nobumitsu Yokoi, and Hirofumi Kato

Phys. Plasmas 6, 4586 (1999); http://dx.doi.org/10.1063/1.873746 (11 pages) | Cited 9 times

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Magnetohydrodynamic (MHD) state in a wide-gap spherical shell mimicking the earth’s outer core is examined with resort to the mean-field or turbulent-dynamo theory. In the dynamo, the induced mean magnetic field is in a quasi-force-free state under a large alpha effect. The saturation level of the field is determined through the alignment with the mean velocity under a cross-helicity effect. On this basis, the following characteristics of the induced field are elucidated: The energy of the magnetic field becomes much larger than the kinetic one of the fluid motion driven by buoyancy force; the Lorentz force coming from the field remains less dominant than the buoyancy force; the toroidal component of the field is larger than the poloidal one. © 1999 American Institute of Physics.
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52.30.-q Plasma dynamics and flow
91.25.Cw Origins and models of the magnetic field; dynamo theories

Pitch-angle diffusion of relativistic electrons due to resonant interactions with whistler waves

Rodica Ciurea-Borcia, Gilles Matthieussent, Jacques Solomon, Edouard Le Bel, and Françoise Simonet

Phys. Plasmas 6, 4597 (1999); http://dx.doi.org/10.1063/1.873747 (10 pages) | Cited 1 time

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Pitch-angle diffusion phenomenon caused by resonant interactions between parallel whistler waves and relativistic electrons is examined for the Van Allen radiation belts. Thus, the quasilinear pitch-angle diffusion equation for the relativistic case is derived. From this equation, in stationary conditions, one computes the wave spectrum, the distribution function, the particle lifetime, and the trapped electron flux between the magnetic mirrors. The present results may explain phenomena occurring in Earth’s magnetosphere. © 1999 American Institute of Physics.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.40.Mj Particle beam interactions in plasmas
94.30.-d Physics of the magnetosphere
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
back to top Magnetically Confined Plasmas, Heating, Confinement

Effect of isotope mass on transport simulations of Joint European Torus high-mode plasmas with Edge Localized Modes

Glenn Bateman, Arnold H. Kritz, Vassili V. Parail, and J. G. Cordey

Phys. Plasmas 6, 4607 (1999); http://dx.doi.org/10.1063/1.873724 (8 pages) | Cited 9 times

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The effect of isotopic mass on heat and particle transport in Joint European Torus (JET) [P.-H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasma discharges is studied using the Multi-Mode model in the BALDUR predictive transport code [Bateman et al., Phys. Plasmas 5, 1793 (1998)]. Temperature and density profiles from these simulations generally agree with the experimentally measured profiles for high-mode JET discharges with Edge Localized Modes in hydrogen, deuterium, and tritium discharges. It is surprising that a purely gyro-Bohm transport model, used in these simulations, correctly predicts the experimentally observed improvement in confinement as the isotope mass is increased—given the fact that gyro-Bohm diffusion coefficients increase with isotope mass when the shapes of all the plasma profiles are held fixed. However, in the JET experiment, it was found that the electron and ion temperature at the top of the edge pedestal increases systematically as the isotope mass in increased (J. G. Cordey et al., Report No. JET-P (98)53, 1998). The numerical simulations reported here show that this increase in the edge temperatures and subsequent broadening of the temperature profiles account for the improvement in confinement as the isotope mass is increased. © 1999 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.65.-y Plasma simulation
52.25.Fi Transport properties

Characterization of the frequency ranges of the plasma edge fluctuation spectra

B. A. Carreras, R. Balbin, B. van Milligen, M. A. Pedrosa, I. Garcia-Cortes, E. Sanchez, C. Hidalgo, J. Bleuel, M. Endler, H. Thomsen, A. Chankin, S. Davies, K. Erents, and G. F. Matthews

Phys. Plasmas 6, 4615 (1999); http://dx.doi.org/10.1063/1.873748 (7 pages) | Cited 19 times

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Frequency spectra of fluctuations for the ion saturation current, floating potential, and turbulent transport measured in the plasma edge of plasma confinement experiments (tokamaks and stellarators) have been analyzed to identify the frequency ranges characterized by a power dependence. Three main regions can be identified. For the intermediate frequency region, the decay of the spectra is close to 1/f, as is expected in self-organized criticality systems. This region is particularly important for the role that it plays in plasma transport and the self-similarity of the fluctuations and fluxes. The effect of plasma rotation on the decay indices has also been studied. © 1999 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.55.Jd Magnetic mirrors, gas dynamic traps
52.35.Ra Plasma turbulence
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