Electron Bernstein Wave Heating Calculations for TJ-II Plasmas

Castejón, F.; Tereshchenko, M.; Sarksyan, K. A.; Fernández, Á.; Cappa, Á.; Batanov, G. M.; Sakharov, A.; Martı́n, Rosario

doi:10.13182/fst04-a571

Cited by 13 publications

(13 citation statements)

References 7 publications

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“…In these conditions, the O-X-B heating scheme will start being effective. The EBW ray-tracing does not start until the maximum density in the plasma reaches a threshold value 1.1 × 10 19 m −3 at which heating by the O-X-B process is not negligible, as was shown in [10]. Besides the increase in temperature (from approximately 200 to 400 eV after the ECRH cutoff), the addition of this heating power clearly helps in prolonging the discharge.…”

Section: Resultsmentioning

confidence: 82%

“…Preliminary studies based on the cold plasma dispersion relation showed that the O-X-B mode conversion [10] at first harmonic is the most suitable scheme for plasma heating by Electron Bernstein Waves in TJ-II. These former studies were later confirmed with TRUBA [6], a ray tracing code prepared for electromagnetic and electrostatic modes propagation studies which can deal automatically with the O-X-B conversion process of each single ray.…”

Section: Ray Tracing Calculations In Tj-iimentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 82%

Section: Ray Tracing Calculations In Tj-iimentioning

confidence: 99%

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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“…The code was used in its ray tracing modality since the beam tracing is not valid when the scale of the variations of plasma conditions along the propagation direction is similar to the scale of the variations over the wave front, which is the case close to the critical layers such as the O mode cutoff and the upper hybrid resonance in TJ-II. As shown in the next section, the O-X-B1 conversion is only efficient for central densities n e (0) > 1.2 × 10 19 m −3 [8]. Moreover, the absorption is enhanced for the higher densities that can be reached by means of gas puffing.…”

Section: Looking For the Optimum Injection Position And The Subsequen...mentioning

confidence: 78%

“…Previous works (see [7] and [8]) have concluded that the most suitable scheme for EBW heating in TJ-II is the O-X-B1 mode conversion, i.e. the O mode launched at first harmonic (f = 28 GHz) is converted into the X mode at the O mode cutoff layer.…”

Section: Introduction: the Ebw Heating Scheme In The Tj-ii Flexible H...mentioning

confidence: 99%

Computation of EBW heating in the TJ-II stellarator

Castejón¹,

Cappa²,

Tereshchenko

et al. 2008

Nucl. Fusion

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The theoretical properties of electron Bernstein wave (EBW) plasma heating in the TJ-II stellarator are presented in this work. Previous studies carried out in this device have demonstrated that the O–X–B mode conversion at the fundamental electron cyclotron harmonic is the best scenario for plasma heating. This scheme presents high absorbed power for central densities above 1.2 × 1019 m−3 and has no upper density limit. In this paper, the ray tracing code TRUBA has been used in its non-relativistic modality to optimize the power injection position and to design a launching system that provides the optimum theoretical results. The main characteristics of the system, whose final design is based on the former calculations, are described. To explore the importance of relativistic effects and to compare them with the non-relativistic calculations, the weakly relativistic dispersion relation, valid for and thus suitable for EBW at low cyclotron harmonics, has been obtained and included in TRUBA. Although they are of little importance for the optimization calculations, the relativistic effects are shown to be not negligible both in the ray trajectories and in the power absorption estimations for temperatures above 1 keV.

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“…Electron cyclotron resonance heating is not possible for dense regions more than n e ≈ 1.7 × 10 19 m −3 because the second harmonic is limited by the cut-off density for this frequency. On the other hand, by providing two 800 kW neutral beam injection systems, it is possible to heat plasma above this limit again with electron cyclotron resonance heating, but now via electron Bernstein waves 18 . The applied scenario here is via O-X-B double mode conversion.…”

Section: Details Of Modeling a Physical Systemmentioning

confidence: 99%

Kinetic simulation of the O-X conversion process in dense magnetized plasmas

et al. 2013

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The ordinary-extraordinary-Bernstein (O-X-B) double conversion is considered and the O-X conversion simulated with a kinetic particle model for parameters of the TJ-II stellarator. This simulation has been done with the particle-in-cell code, XOOPIC (X11-based object-oriented particle-in-cell). XOOPIC is able to model the non-monotonic density and magnetic profile of TJ-II. The first step of conversion, O-X conversion, is observed clearly. By applying some optimizations, such as increasing the grid resolution and number of computational particles in the region of the X-B conversion, the simulation of the second step is also possible. By considering the electric and magnetic components of launched and reflected waves, the O-mode wave and the X-mode wave can be easily detected. Via considering the power of the launched O-mode wave and the converted X-mode wave, the efficiency of O-X conversion for the best theoretical launch angle is obtained, which is in good agreement with previous computed efficiencies via full-wave simulations. For the optimum angle of 47 • between the wave-vector of the incident O-mode wave and the external magnetic field, the conversion efficiency is 66%.

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Electron Bernstein Wave Heating Calculations for TJ-II Plasmas

Cited by 13 publications

References 7 publications

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

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

Computation of EBW heating in the TJ-II stellarator

Kinetic simulation of the O-X conversion process in dense magnetized plasmas

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