Co-counter asymmetry in fast wave heating and current drive

Jaeger, E. F.; Carter, M.D.; Berry, L. A.; Batchelor, D. B.; Forest, C.B.; Weitzner, Harold

doi:10.1088/0029-5515/38/1/301

Cited by 22 publications

(17 citation statements)

References 10 publications

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“…The tokamak magnetic field gives a preferred direction to the E×B drift pattern and is responsible for convecting plasma preferentially into the bottom of the antenna. Recently, 23 it has been demonstrated that this heat flux asymmetry reverses with reversal of the tokamak B-field, consistent with the rf-driven convection mechanism (although power flow asymmetries due to the Hall term may also play a role 26 ). Convective physics modifies fluxes into the antenna, affects sputtering, electron sheath heating (not discussed here) and, importantly, modifies the electron density profile in front of the antenna.…”

Section: Fw Launch Antenna-edge Interactions: Rf Sheathsmentioning

confidence: 72%

Nonlinear ICRF-plasma interactions

et al. 2006

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Abstract. The well developed linear theory of ICRF (including FW, HHFW and IBW) interactions with plasma has enjoyed considerable success in describing antenna coupling and wave propagation, and provides a well-known framework for calculating power absorption, current drive, etc. In some situations, less well studied nonlinear effects are of interest, such as flow drive, ponderomotive forces, rf sheaths, parametric decay and related interactions with the edge plasma. Standard ICRF codes have begun to integrate this physics to achieve improved modeling capabilities. This paper concentrates on basic rf-plasma-interaction physics with illustrative applications to tokamaks. For FW antennas, the parallel electric field near launching structures is known to drive rf-sheaths which can give rise to convective cells, interaction with plasma "blobs", impurity production, and edge power dissipation. In addition to sheaths, IBW waves in the edge plasma are subject to strong ponderomotive effects and parametric decay. In the core plasma, slow waves can sometimes induce nonlinear effects. Mechanisms by which these waves can influence the radial electric field and its shear are summarized, and related to the general (reactive-ponderomotive and dissipative) force on a plasma from rf waves. It is argued that there are significant opportunities now for new predictive capabilities by advances in integrated simulation.

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Section: Fw Launch Antenna-edge Interactions: Rf Sheathsmentioning

confidence: 72%

Nonlinear ICRF-plasma interactions

et al. 2006

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“…But when a poloidal field is introduced, the Bernstein waves are formed with a strong up-down asymmetry. This is partly due to the natural up-down asymmetry of the antenna's radiated power spectrum 34 and partly due to an upshift in the k ʈ spectrum caused by the poloidal magnetic field. The results show no evidence of weakly damped, spatially localized eigenmodes.…”

Section: Discussionmentioning

confidence: 99%

“…7, the Bernstein waves are excited with a strong up-down asymmetry caused by the poloidal magnetic field, B . This is partly due to the natural up-down asymmetry of the antenna's radiated power spectrum 34 and partly due to an upshift in the k ʈ spectrum caused by the poloidal magnetic field. The asymmetry in the antenna spectrum occurs even in the absence of a poloidal magnetic field and is caused by Hall terms, or off-diagonal terms ( 2 ) in the conductivity tensor of Eq.…”

Section: Mode Conversion In Two Dimensionsmentioning

confidence: 99%

“…Rather, it is due to strong single-pass absorption in combination with the updown asymmetry in the antenna's radiated power spectrum. 34 In Fig. 9, where B and n are both positive, waves propagate away from the antenna at an upward angle with respect to the equatorial plane.…”

Section: High-harmonic Fast-wave Heating In Two Dimensionsmentioning

confidence: 99%

“…The plasma absorption ͑i.e., antenna loading͒ is always highest when the phasing of the antenna (n ) is such that the driven current is in the same direction as the plasma current. 34 It is important to point out that the Solov'ev equilibrium may not accurately represent the minimum ͉B͉ configuration produced in some high ␤ cases. However, the purpose of the present work is not to compare in detail with experiments, but rather to demonstrate the ability to calculate high harmonic heating selfconsistently in 2-D.…”

Section: High-harmonic Fast-wave Heating In Two Dimensionsmentioning

confidence: 99%

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All-orders spectral calculation of radio-frequency heating in two-dimensional toroidal plasmas

et al. 2001

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Spectral calculations of radio-frequency (rf) heating in tokamak plasmas are extended to two dimensions (2-D) by taking advantage of new computational tools for distributed memory, parallel computers. The integral form of the wave equation is solved in 2-D without any assumption regarding the smallness of the ion Larmor radius (ρ) relative to the perpendicular wavelength (λ⊥). Results are therefore applicable to all orders in k⊥ρ, where k⊥=2π/λ⊥. Previous calculations of rf wave propagation and heating in 2-D magnetized plasmas have relied on finite Larmor radius expansions (k⊥ρ≪1) and are thus limited to relatively long wavelengths. In this paper, no such assumption is made, and we consider short wavelength processes such as the excitation and absorption of ion Bernstein waves in 2-D with k⊥ρ>1. Results show that this phenomenon is far more complex than simple one-dimensional plasma models would suggest. Other applications include fully self-consistent 2-D solutions for high-harmonic fast-wave heating in spherical tokamaks. These calculations require the storage and inversion of a very large, dense matrix, but numerical convergence can be improved by writing the plasma current in the laboratory frame of reference. To accurately represent the wave spectrum in this frame, the local plasma conductivity is corrected to first order in ρ/L, where L is the equilibrium scale length. This correction is necessary to ensure accuracy in calculating the wave spectrum and hence the fraction of power absorbed by ions and electrons.

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Evaluating the efficiency of radiofrequency heating in tokamaks: the impact of orbital topology and poloidal inhomogeneity

Eester

2001

J. Plasma Phys.

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Radiofrequency heating in toroidal geometry is described. Starting from a general theory, expressions for the dielectric response and the radiofrequency diffusion operator are obtained. The computationally most efficient simplified expressions bear a close resemblance to the results of uniform plasma theory, but differ from them in their interpretation. In cases where the simplified expressions do not describe the physics faithfully, more general but computationally slower ones are available. Rigorously accounting for the geometry and the wave field yields fine structure that is commonly overlooked. Aside from causing the well-known k∥-upshift or downshift impacting on the Doppler shift, the non-zero poloidal magnetic field modifies the orbital topology and forces one to account for the poloidal inhomogeneity of the static magnetic field. The expressions obtained restore intuition on how an electric field interacts with a charged particle, but, in so doing, cast doubt on the degree of realism of predictions of simplified models that do not account for the constructive or destructive interference phenomena introduced by the orbital topology non-uniformity. The expressions represent a numerical challenge, but show the necessity for the detailed description: the ‘coarse-graining’ underlying simplified models yields a result that has the right order of magnitude for interference related to crosstalk between resonances or multiple encounters with a given resonance, but may be an order of magnitude wrong for predictions on the combined effect of a poloidal mode spectrum. A Fokker–Planck code BATCH (Bounce-Averaged Tool for Cyclotron Heating), relying on the expressions obtained, is presented and some results are discussed.

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Co-counter asymmetry in fast wave heating and current drive

Cited by 22 publications

References 10 publications

Nonlinear ICRF-plasma interactions

Nonlinear ICRF-plasma interactions

All-orders spectral calculation of radio-frequency heating in two-dimensional toroidal plasmas

Evaluating the efficiency of radiofrequency heating in tokamaks: the impact of orbital topology and poloidal inhomogeneity

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