Ray-tracing through EC resonance and the wave energy flux

Westerhof, E.; Tokman, M. D.; Gavrilova, M. A.

doi:10.1016/s0920-3796(00)00475-0

Cited by 8 publications

(5 citation statements)

References 8 publications

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“…The required injection angles for the quasi-optical case typically differ by about 1 • . This is caused by the use of the warm, weakly relativistic dispersion relation in the quasi-optical calculations, which leads to deviations from the cold plasma ray in the region of the ECR [23,24]. In all cases a significant broadening of the quasi-optical power deposition profile as compared with the TORBEAM calculations is seen.…”

Section: Mirror X(m) Y(m) Z(m)mentioning

confidence: 95%

“…For rays with large curvature or for large beam widths, such that ξ | | 1, this method becomes inapplicable, because the coordinate system becomes ambiguous (since h becomes negative). It has been found that the warm plasma geometrical optics ray and the trajectory of the beam centre of power flux can obtain a large curvature in the region of ECR [23,24], which makes them inapplicable as reference ray for the method of calculation proposed below. This problem is considered later in detail.…”

Section: Accompanying Coordinate Systemmentioning

confidence: 99%

“…Moreover, in a number of cases it becomes necessary to smooth the GO ray that is proposed as the initial guess for the reference ray. This is caused by the oscillations of the GO ray trajectory in the ECR region [23,24]. Again, the condition for the uniqueness of the curvilinear coordinate system can be broken.…”

Section: Examples Of Wave Beam Dynamics Obtained From the Quasi-optic...mentioning

confidence: 99%

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ECRH power deposition from a quasi-optical point of view

2008

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A quasi-optical description of the propagation and damping of the slowly varying wave amplitude across an arbitrary electron cyclotron wave beam is presented. This model goes well beyond those implemented in existing beam tracing codes, which typically require the spatial inhomogeneity across the wave beam to be small. The present model allows an accurate description of the wave beam evolution in the region of electron cyclotron power deposition, where the latter condition is quite generally broken. The additional physical effects from spatial inhomogeneity and dispersion included in the quasi-optical model are discussed in relation to their consequences for the power deposition profile. Quite generally, a broader power deposition profile is obtained in the quasi-optical calculations. The importance of these effects is analysed in a number of scans varying the injection geometry for typical conditions in both the ITER and the TEXTOR tokamak. Optimization of the power deposition profile towards a minimal width is found to require a focused wave beam with a waist of typically 2 cm width localized near the electron cyclotron resonance region. Calculations are also presented for beams injected from the ITER Upper Port electron cyclotron resonance heating (ECRH) launcher as it is currently being designed. These show that the additional power deposition profile broadening from quasi-optical effects may result in a drop in the predicted efficiency for neoclassical tearing mode or sawtooth control by up to a factor of 2.

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Section: Mirror X(m) Y(m) Z(m)mentioning

confidence: 95%

Section: Accompanying Coordinate Systemmentioning

confidence: 99%

Section: Examples Of Wave Beam Dynamics Obtained From the Quasi-optic...mentioning

confidence: 99%

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ECRH power deposition from a quasi-optical point of view

2008

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“…The ray-tracing uses a version of RELRAY [11] in which the refraction is essentially the cold plasma approximation modified to account for the relativistic shifts of the cutoffs [10] but ignoring the anomalous dispersion around cyclotron resonances, thereby avoiding the numerical complications associated with the anomalous dispersion [12] and connections to Bernstein branches [13].…”

Section: Appendixmentioning

confidence: 99%

Operations space diagram for ECRH and ECCD

Bindslev¹

2004

Nucl. Fusion

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A Clemmov–Mullaly–Allis (CMA) type diagram, the ECW–CMA diagram, for representing the operational possibilities of electron cyclotron heating and current drive (ECRH/ECCD) systems for fusion plasmas is presented. In this diagram, with normalized density and normalized magnetic field coordinates, the parameter range in which it is possible to achieve a given task (e.g. O-mode current drive for stabilizing a neoclassical tearing mode) appears as a region. With also the Greenwald density limit shown, this diagram condenses the information on operational possibilities, facilitating the overview required at the design phase. At the operations phase it may also prove useful in setting up experimental scenarios by showing operational possibilities, avoiding the need for survey type ray-tracing at the initial planning stages. The diagram may also serve the purpose of communicating operational possibilities to non-experts. JET and ITER like plasmas are used, but the method is generic.

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“…As the source, we use one of the two gyrotrons with powers/frequencies 300 kW/110 GHz and 800 kW/140 GHz. The existing input system [24] ensures efficient focusing of the radiation with a focal-spot area of about a few square centimeters, which corresponds to a drive-wave intensity of 100−300 kW/cm 2 . Figure 3 shows the behavior of the dispersion curves for the case of LF drive wave (i.e., for a dense plasma).…”

Section: Using the Parametrically Induced Transparency Effect In Toromentioning

confidence: 99%

A new approach for diagnostics of dense magnetoactive plasmas using the effect of parametrically induced transparency

Kryachko

Tokman

Westerhof

2007

Radiophys Quantum Electron

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UDC 533.9We study theoretically the effect of parametrically induced transparency. The main idea of this effect is transport of the upper-hybrid radiation of overdense toroidal plasmas in vacuum through the opaque region by parametric shift of the radiation frequency. We propose that the microwave radiation employed for electron-cyclotron heating at the second cyclotron harmonic in tokamaks is used as the drive wave. Calculations performed for the TEXTOR tokamak demonstrate that this effect is promising for diagnostics of dense plasmas in toroidal devices if a gyrotron with an ouput power of several hundred kilowatts is used.

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Ray-tracing through EC resonance and the wave energy flux

Cited by 8 publications

References 8 publications

ECRH power deposition from a quasi-optical point of view

ECRH power deposition from a quasi-optical point of view

Operations space diagram for ECRH and ECCD

A new approach for diagnostics of dense magnetoactive plasmas using the effect of parametrically induced transparency

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