Full-wave calculations of the O-X mode conversion process

Hansen, F. R.; Lynov, Jens-Peter; Maroli, C.; Petrillo, V.

doi:10.1017/s0022377800013064

Cited by 39 publications

(46 citation statements)

References 17 publications

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“…The heating pulse duration used for the plasma startup experiments will be 10-50 ms. For EBW heating and current drive studies during the plasma current flattop the gyrotron pulse length will be increased to 1-5 s, and a second 1 MW gyrotron will be installed. Coupling to the EBWs in the plasma will be accomplished via O-mode to slow X-mode to EBW (O-X-B) double mode conversion [10][11][12]. An actively-cooled, concave steerable mirror launcher with a focal length of about 45 cm, capable of withstanding a 5 s duration, 2 MW heating pulse, will focus the 28 GHz power on the EBW mode conversion layer.…”

Section: Design Of the Nstx-u 28 Ghz Heating Systemmentioning

confidence: 99%

ECRH/EBWH system for NSTX-U

Taylor

Ellis

Harvey

et al. 2012

EPJ Web of Conferences

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Abstract. The National Spherical Torus Experiment Upgrade (NSTX-U) will operate at an axial toroidal field of up to 1 T, about twice the field available on NSTX. A 28 GHz electron cylotron resonance heating (ECRH) system is currently being planned for NSTX-U. A 1 MW 28 GHz gyrotron will be employed. Intially the system will use short, 10-50 ms, 1 MW pulses for ECRH-assisted discharge start-up. Later the pulse length will be extended to 1-5 s to study electron Bernstein wave heating (EBWH) during the plasma current flat top. A mirror launcher will be used to couple microwave power to the plasma via O-mode to the slow X-mode to EBW (O-X-B) double mode conversion. This paper presents a pre-conceptual design for the ECRH/EBWH system proposed for NSTX-U and includes ray tracing and Fokker-Planck modeling results for 28 GHz ECRH during plasma start-up and EBW heating and current drive during the plasma current flattop of a NSTX-U advanced H-mode plasma scenario.

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Section: Design Of the Nstx-u 28 Ghz Heating Systemmentioning

confidence: 99%

ECRH/EBWH system for NSTX-U

Taylor

Ellis

Harvey

et al. 2012

EPJ Web of Conferences

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“…If we assume that the plasma inhomogeneity is along the x-direction, then for a given frequency and n = 0, i.e., propagation across the magnetic field, the roots of (6) are plotted in Fig. 1.…”

Section: Dispersion Characteristics Of Electron Cyclotron Wavesmentioning

confidence: 99%

“…[3][4][5][6][7] The primary requirement for this mode conversion process to take place is that the O-mode cutoff be near, or coincident with, the left-hand cutoff of the slow X-mode. This requires that the O-mode be launched at an oblique angle to the total magnetic field.…”

Section: Mode Conversion Of the O-mode To The Ebwmentioning

confidence: 99%

“…3 Then the O-mode power is directly coupled to the slow X-mode, which in turn mode converts to EBWs at the upper hybrid resonance. This technique, referred to as the O-X-B mode conversion process, has been previously studied [3][4][5][6][7] and used successfully on Wendelstein 7-AS. 8 In the following we will show that effective O-X-B mode conversion requires conditions in addition to the coincidence of the O-mode and X-mode cutoffs.…”

Section: Introductionmentioning

confidence: 99%

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Excitation, propagation, and damping of electron Bernstein waves in tokamaks

Ram¹,

Schultz²

2000

Physics of Plasmas

144

186

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The conventional ordinary O-mode and the extraordinary X-mode in the electron cyclotron range of frequencies are not suitable for core heating in high-β spherical tokamak plasmas, like the National Spherical Torus Experiment [M. Ono, S. Kaye, M. Peng et al., in Proceedings of the 17th International Atomic Energy Agency Fusion Energy Conference, (International Atomic Energy Agency, Vienna, 1999), Vol. 3, p. 1135], as they are weakly damped at high harmonics of the electron cyclotron frequency. However, electron Bernstein waves (EBW) can be effective for heating and driving currents in spherical tokamak plasmas. Power can be coupled to EBWs via mode conversion of either the X-mode or the O-mode. The two mode conversions are optimized in different regions of the parameter space spanned by the parallel wavelength and wave frequency. The conditions for optimized mode conversion to EBWs are evaluated analytically and numerically using a cold plasma model and an approximate kinetic model. From geometric optics ray tracing it is found that the EBWs damp strongly near the Doppler-broadened resonance at harmonics of the electron cyclotron frequency.

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“…The conversion of O mode to the slow X mode has been extensively studied, theoretically, in the literature [12,15,16,17,18,19]. The coupling of O mode power to slow X mode occurs near a critical parallel wave number, given by Eq.…”

Section: Mode Conversion From An O Modementioning

confidence: 99%

Excitation and emission of electron cyclotron waves in spherical tori

Ram

Bers

2003

Nucl. Fusion

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Abstract. The conventional ordinary and extraordinary modes in the electron cyclotron range of frequencies are not suitable for heating of and/or driving currents in spherical tori (ST) plasmas. However, electron Bernstein waves offer an attractive possibility for heating and current drive in this range of frequencies. In this paper, we summarize our theoretical and numerical results which describe the excitation of electron Bernstein waves in ST plasmas when the extraordinary mode or the ordinary mode are coupled into the plasma from an external source. In our discussion on the conversion of the ordinary mode to electron Bernstein waves (via the slow extraordinary mode) we illustrate very important physics, relevant to this conversion process, that has been ignored in previous studies. The particular physics has to do with the conversion of the slow extraordinary mode to the fast extraordinary mode that can then propagate out of the plasma and thus reduce the mode conversion to electron Bernstein waves. This reduction in the mode conversion can occur even when the wave numbers are such that the ordinary mode cutoff and the slow extraordinary mode cutoff are coincident in space. Furthermore, we also consider the emission of electron Bernstein waves from a thermal plasma. This emission mode converts to extraordinary and ordinary modes in the vicinity of the upper hybrid resonance. We describe the general relationship between the conversion coefficients when exciting electron Bernstein waves using either the extraordinary mode or the ordinary mode, and the emission coefficients when thermally emitted electron Bernstein waves convert to the extraordinary and ordinary modes.

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Full-wave calculations of the O-X mode conversion process

Cited by 39 publications

References 17 publications

ECRH/EBWH system for NSTX-U

ECRH/EBWH system for NSTX-U

Excitation, propagation, and damping of electron Bernstein waves in tokamaks

Excitation and emission of electron cyclotron waves in spherical tori

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