Full-wave calculation of the O–X–B mode conversion of Gaussian beams in a cylindrical plasma

Köhn, A.; Cappa, Á.; Holzhauer, E.; Castejón, F.; Fernández, Á.; Stroth, U.

doi:10.1088/0741-3335/50/8/085018

Cited by 51 publications

(75 citation statements)

References 21 publications

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“…If the blob is positioned far away from the center of the microwave beam, the angular dependence of the conversion efficiency exhibits a Gaussian behavior, as expected (see Ref. [4]). As soon as the center of the density perturbation is within the beam width of the microwave beam, a reduction of the conversion efficiency sets in.…”

Section: The Impact On the O-x Conversionsupporting

confidence: 83%

“…As has been shown in Ref. [4], the curvature of the mode conversion layer can be compensated for by appropriate shaping of the microwave beam leading to same results as without plasma curvature. Therefore, the assumption of a straight conversion layer is justified.…”

Section: The Impact On the O-x Conversionmentioning

confidence: 61%

“…A linear increasing profile is chosen with a normalized density gradient of k 0 L n = 30 (corresponding to the one used in Ref. [4]). The magnetic field is set to a constant value of Y = ω ce /ω 0 = 0.8.…”

Section: The Impact On the O-x Conversionmentioning

confidence: 99%

“…[4], separate simulations in a toroidal and a poloidal plane are carried out. In the toroidal geometry, the magnetic field points into one of the directions of the 2D computational grid, whereas in the poloidal geometry the magnetic field points outwards of the computational grid.…”

Section: The Impact On the O-x Conversionmentioning

confidence: 99%

“…The simulations are performed with the 2D full-wave code IPF-FDMC [4]. The scattering process of microwaves at the blob-like perturbations is, in addition, analyzed with the 3D full-wave code EMIT-3D [5].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Influence of density fluctuations on the O–X mode conversion and on microwave propagation

Köhn

Williams

Vann

et al. 2015

EPJ Web of Conferences

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Abstract. Full-wave simulations are performed in order to investigate the interaction of plasma density perturbations and microwaves. The perturbations are divided into two cases: A single blob-like structure and a fully turbulent density profile. The resulting scattering of a microwave beam and the effect on the O-X mode conversion are presented for both cases. Quantitative analyses are performed as a function of the average size and position of the perturbations. The usage of spatial coordinates normalized to the vacuum wavelength of the microwave allows to easily adopt the results to a specific problem.

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Section: The Impact On the O-x Conversionsupporting

confidence: 83%

Section: The Impact On the O-x Conversionmentioning

confidence: 61%

Section: The Impact On the O-x Conversionmentioning

confidence: 99%

Section: The Impact On the O-x Conversionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Influence of density fluctuations on the O–X mode conversion and on microwave propagation

Köhn

Williams

Vann

et al. 2015

EPJ Web of Conferences

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Dynamic Simulation of the Electron Bernstein Wave Heating Under NBI Conditions in TJ–II Plasmas

Cappa¹,

López‐Bruna

Castejón

et al. 2011

Contrib. Plasma Phys.

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In this work, we have calculated the expected properties of the Electron Bernstein Wave (EBW) heating using the O-X-B double mode conversion scenario in a plasma that evolves from Electron Cyclotron Resonance (ECR) to Neutral Beam Injection (NBI) heating in the TJ-II device. For this purpose, a transport simulation that reproduces the time evolution of a typical collapsing plasma heated by a combination of ECR and NBI power has been used. It is seen that the predicted EBW absorption depends strongly on the plasma characteristics, whose time evolution depends in turn on the heating properties. Therefore, the need of consistently computing the ray tracing and the plasma evolution is underlined. The fraction of the absorbed EBW heating power becomes very high as soon as the O mode cutoff layer appears. This guarantees the overlapping of both EBW and ECR heating, thus avoiding excessive plasma cooling when the wave cutoff is reached. The EBW power deposition profile evolves from off-axis to a much more centred shape that persists until the radiative collapse quenches the plasma.

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Study Electron Cyclotron Double Mode Conversion in Overdense Plasma

et al. 2019

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Double mode conversion from ordinary mode O to extraordinary mode X is used to achieve electron Bernstein wave (EBWs) for the electron cyclotron resonance heating (ECRH). The efficiency of the mode conversion depends on many parameters including the density gradient L n , magnetic field source B 0 and optimum launching angle N z. An analytical formalism together with a numerical computation have been employed, considering W7X stellarator main parameters, such as 140 GH z , k 0 = 29 cm −1 , 2.5 T and 2.4 ×10 20 m −3 , in order to investigate the efficiency of the mode conversion. The values of the density gradient Ln, obtained by numerical simulation, are from 1 to 10 cm. These values of L n correspond to the power transmission window T OSX from 88 to 29%. Moreover, the dispersion relation of the EBW mode propagation up to 10 harmonics, ω = 10ω ce , has been plotted to help a better visualization of the EBW mode heating. Finally, the power deposition profiles around the resonance layers were calculated and presented.

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Full-wave calculation of the O–X–B mode conversion of Gaussian beams in a cylindrical plasma

Cited by 51 publications

References 21 publications

Influence of density fluctuations on the O–X mode conversion and on microwave propagation

Influence of density fluctuations on the O–X mode conversion and on microwave propagation

Dynamic Simulation of the Electron Bernstein Wave Heating Under NBI Conditions in TJ–II Plasmas

Study Electron Cyclotron Double Mode Conversion in Overdense Plasma

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