Toroidal effects on propagation, damping, and linear mode conversion of lower hybrid waves

Ignat, D.

doi:10.1063/1.863500

Cited by 65 publications

(38 citation statements)

References 9 publications

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“…For the case of the lower hybrid wave propagation in tokamak plasmas, the toroidal effect, i.e. the breakdown of the poloidal symmetry of the system, causes a shift of the parallel wave number and its evolution 12,13 , which is related to the current drive efficiency and the wave energy deposition layer.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and numerical studies of wave-packet propagation in tokamak plasmas

Zonca

Cardinali

2012

Physics of Plasmas

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Theoretical and numerical studies of wave-packet propagation are presented to analyze the time varying 2D mode structures of electrostatic fluctuations in tokamak plasmas, using general flux coordinates. Instead of solving the 2D wave equations directly, the solution of the initial value problem is used to obtain the 2D mode structure, following the propagation of wave-packets generated by a source and reconstructing the time varying field. As application, the 2D WKB method is applied to investigate the shaping effects (elongation and triangularity) of tokamak geometry on the lower hybrid wave propagation and absorbtion. Meanwhile, the mode structure decomposition (MSD) method is used to handle the boundary conditions and simplify the 2D problem to two nested 1D problems. The MSD method is related to that discussed earlier by Zonca and Chen [Phys. Fluids B 5, 3668 (1993)], and reduces to the well-known "ballooning formalism" [J. W. Connor, R. J. Hastie, and J. B. Taylor, Phys. Rev. Lett. 40, 396 (1978)], when spatial scale separation applies. This method is used to investigate the time varying 2D electrostatic ITG mode structure with a mixed WKB-fullwave technique. The time varying field pattern is reconstructed and the time asymptotic structure of the wave-packet propagation gives the 2D eigenmode and the corresponding eigenvalue. As a general approach to investigate 2D mode structures in tokamak plasmas, our method also applies for electromagnetic waves with general source/sink terms, either by an internal/external antenna or nonlinear wave interaction with zonal structures.

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Section: Introductionmentioning

confidence: 99%

Theoretical and numerical studies of wave-packet propagation in tokamak plasmas

Zonca

Cardinali

2012

Physics of Plasmas

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“…[3,4]. Such effects are not included here because, as stated in the main text, the aim of this work is to assess how magnetic ripple alone can modify the propagation of the LH wave, as compared to the straight cylindrical geometry.…”

Section: And 2 Clearlymentioning

confidence: 99%

“…The modeling of LH current drive has largely relied on ray tracing as a privileged tool to describe the propogation and absorption of the LH wave [3 -11]. In particular, ray tracing has shown that the poloidal inhomogeneity inherent in the toroidal geometry and the resulting nonconstancy of the poloidal mode number along ray trajectories may strongly affect LH wave propagation [3,4] and are important in explaining many features of LH current drive [5,6,8 -11]. The variations in the poloidal mode number and, consequently, in the component of the wave vector parallel to the equilibrium magnetic field are, in many cases, sufficiently large to allow the launched LH wave to bridge the spectral gap between its initial parallel phase velocity and the much lower value that is required for current generation via electron Landau damping [5,6,11].…”

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confidence: 99%

Effects of Magnetic Ripple on Lower-Hybrid Wave Propagation

Bizarro¹,

Ferreira²,

Rodrigues³

et al. 1995

Phys. Rev. Lett.

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Ray tracing is used in a periodically inhomogeneous cylindrical plasma to demonstrate the importance for lower-hybrid (LH) wave propogation of the magnetic ripple caused by the discrete nature of the toroidal-field coils in a tokamak. It is shown that magnetic ripple may induce Hamiltonian chaos in the ray motion and thus lead to strong variations in the component of the wave vector parallel to the equilibrium magnetic field. Therefore magnetic ripple can be effective in bridging the spectral gap

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“…Until recently numerical modeling of LHCD has consisted, for the most part, of toroidal ray tracing codes and Fokker Planck (FP) solvers [1][2][3]. Ray tracing approximates the wave as a bundle of rays under the assumption of the validity of Wenzel-Kramers-Brillouin (WKB) approximation, and is used to calculate the path of waves and the evolution of their wave vector.…”

Section: Introductionmentioning

confidence: 99%

Full Wave Simulation of Lower Hybrid Waves in ITER Plasmas Based on the Finite Element Method

Meneghini

Shiraiwa

2010

Plasma and Fusion Research

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The first lower hybrid (LH) full wave simulation of an ITER-scale plasma is presented. LHEAF [O. Meneghini et al., Phys. Plasmas 16, (2009)], an efficient LH full wave solver based on Finite Element Method (FEM) was used. In this study the scalability of the LHEAF approach was investigated, and the possibility of using massive parallel computer for solving extremely large problems was shown. In reactor scale plasmas, LH waves having a typical n ≈ 2 are expected to be absorbed in the periphery of the plasma. In order to exploit the spatial localization of the LH waves, LHEAF is modified to consider only the region of plasma where the wave fields are non-zero. By this approach, the size of the computational domain was reduced by more than a factor of 10. In this simulation, the magnetic equilibrium and the density and temperature profiles proposed for AT operation scenario on ITER are used. In addition, the wide SOL is supposed to play an important role in the propagation of the LH waves on ITER, and its presence was included in the simulation. For a Maxwellian plasma the power deposition profile is narrow and peaks at r/a ≈ 0.7.

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Toroidal effects on propagation, damping, and linear mode conversion of lower hybrid waves

Cited by 65 publications

References 9 publications

Theoretical and numerical studies of wave-packet propagation in tokamak plasmas

Theoretical and numerical studies of wave-packet propagation in tokamak plasmas

Effects of Magnetic Ripple on Lower-Hybrid Wave Propagation

Full Wave Simulation of Lower Hybrid Waves in ITER Plasmas Based on the Finite Element Method

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