On electron Bernstein waves in spherical tori

Ram, A. K.; Decker, J.; Peysson, Y.

doi:10.1017/s0022377805003636

Cited by 20 publications

(22 citation statements)

References 14 publications

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“…Except for the non-relativistic damping term, we implemented and compared the weakly relativistic damping model of Decker & Ram [8], the weakly-relativistic model due to Saveliev [9] and a routine that integrates numerically the fully-relativistic dispersion tensor in the momentum space along the resonance curve [10]. The relative computational times are compared in Figure 1.…”

Section: Relativistic and Electromagnetic Effects In Ebw Damping (Raymentioning

confidence: 99%

“…Even the propagation properties can be influenced by relativistic effects, as shown by Nelson-Melby et al [28]. We have started to study EBWs at the high temperature plasma using AMR and R2D2 [10], which is a fully relativistic dispersion solver for any EC waves (including EBWs). For CFNS parameters with central temperature of 35 keV, we performed some initial R2D2 runs; however, convergence problems seem to arise for T e > 15 keV, which was rather unexpected.…”

Section: Ebw Propagation In a High-temperature Plasmamentioning

confidence: 99%

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Ebw Physics of Ece in NSTX

Vahala¹

2012

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Section: Relativistic and Electromagnetic Effects In Ebw Damping (Raymentioning

confidence: 99%

Section: Ebw Propagation In a High-temperature Plasmamentioning

confidence: 99%

Ebw Physics of Ece in NSTX

Vahala¹

2012

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“…Unlike the non-relativistic calculations [8], the dispersion relation (29) and density of power dissipated (30) can no longer be expressed in terms of any standard functions. They have to be computed numerically [15]. The code R2D2 solves the fully relativistic dispersion relation (5) in the EC range of frequencies and calculates the wave polarization, energy flow density, and density of power dissipated.…”

Section: F Weakly Relativistic Approximation For Obliquely Propagatimentioning

confidence: 99%

“…In Section III the formalism of Section II is applied to electron Bernstein waves. The approximations used in Section II are justified by comparing the results obtained from the analytical model with the numerical results obtained from the code R2D2 [15] which calculates the exact relativistic linear wave characteristics. The EBW dispersion characteristics, their polarization, the associated energy flow density, and the density of power absorbed are calculated as a function of various plasma and wave parameters.…”

Section: Introductionmentioning

confidence: 99%

Relativistic description of electron Bernstein waves

Decker

Ram

2006

Physics of Plasmas

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The application of the extraordinary and ordinary electron cyclotron waves for heating and current drive in overdense, magnetized plasmas is restricted. For frequencies near low harmonics of the electron cyclotron frequency these waves are cutoff near the edge of the plasma. For higher frequencies the interaction of the waves with electrons is weak leading to very low absorption of wave power. However, electron Bernstein waves provide means for heating and current drive in overdense plasmas since they have no density cutoffs and are strongly damped near harmonics of the electron cyclotron resonance. This paper discusses properties of electron Bernstein waves that make them an attractive means for delivering energy and momentum to electrons. An approximate analytical model for electrostatic waves in the weakly relativistic and weak damping limits is developed. From this model the propagation and damping characteristics of electron Bernstein waves and their dependence on plasma parameters are derived. It is found that relativistic effects are necessary to properly describe the resonant interaction of electron Bernstein waves with electrons. The characteristics of electron Bernstein wave propagation and damping are very different depending on whether the electron cyclotron harmonic resonance is approached from the low-or the high-field side. The results from the analytical model and the associated analysis agree well with the results from the exact numerical calculations. This validates the physics of the simplifying assumptions on which the model is based. The electron Bernstein waves are completely damped well before the electron cyclotron resonance due to the Doppler shift. Within the damping region the waves interact with suprathermal electrons thereby having the potential for efficient current drive.

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“…Furthermore, for EC waves, the description has to be relativistic so that the damping of the waves and their interaction with electrons are described correctly [4][5][6][7]. In this paper, for an axisymmetric toroidal equilibrium, we derive a relativistic diffusion operator for the interaction of RF waves with electrons in the presence of non-axisymmetric magnetic field perturbations.…”

Section: Introductionmentioning

confidence: 99%

Quasilinear theory of electron transport by radio frequency waves and nonaxisymmetric perturbations in toroidal plasmas

2008

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The use of radio frequency (RF) waves to generate plasma current and to modify the current profile in magnetically confined fusion devices is well documented. The current is generated by the interaction of electrons with an appropriately tailored spectrum of externally launched RF waves.In theoretical and computational studies, the interaction of RF waves with electrons is represented by a quasilinear diffusion operator. The balance, in steady state, between the quasilinear operator and the collision operator gives the modified electron distribution from which the generated current can be calculated. In this paper the relativistic operator for momentum and spatial diffusion of electrons due to RF waves and non-axisymmetric magnetic field perturbations is derived. Relativistic treatment is necessary for the interaction of electrons with waves in the electron cyclotron (EC) range of frequencies. The spatial profile of the RF waves is treated in general so that diffusion due to localized beams is included. The non-axisymmetry magnetic field perturbations can be due to magnetic islands as in neoclassical tearing modes. The plasma equilibrium is expressed in terms of the magnetic flux coordinates of an axisymmetric toroidal plasma. The electron motion is described by guiding center coordinates using the action-angle variables of motion in an axisymmetric toroidal equilibrium. The Lie perturbation technique is used to derive a diffusion operator which is non-singular and time dependent. The resulting action diffusion equation describes resonant and non-resonant momentum and spatial diffusion. Momentum space diffusion leads to current generation in the plasma and spatial diffusion describes the effect of RF waves and magnetic perturbations on spatial evolution of the current profile. Depending on the symmetry of the equilibrium and the corresponding relation of the action variables to the configuration space variables, additionally to diffusion along the radial direction, poloidal and toroidal electron diffusion is also described. In deriving the diffusion operator, no statistical assumption, such as the Markovian assumption, for the underlying electron dynamics, is imposed. Consequently, the operator is time dependent and valid for a dynamical phase space that is a mix of correlated regular orbits and decorrelated chaotic orbits. The diffusion operator is expressed in a form suitable for implementation in a numerical code.2

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On electron Bernstein waves in spherical tori

Abstract: This paper summarizes the theoretical and numerical results we have obtained for the excitation and propagation of electron Bernstein waves in spherical tokamak plasmas.

Cited by 20 publications

References 14 publications

Ebw Physics of Ece in NSTX

Ebw Physics of Ece in NSTX

Relativistic description of electron Bernstein waves

Quasilinear theory of electron transport by radio frequency waves and nonaxisymmetric perturbations in toroidal plasmas

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