Coupling characteristics of the ITER-relevant lower hybrid antenna in Tore Supra: experiments and modelling

Preynas, M.; Ekedahl, A.; Fedorczak, N.; Goniche, M.; Guilhem, D.; Gunn, J.; Hillairet, J.; Litaudon, X.; Achard, J.; Berger‐By, G.; Belo, J.; Corbel, E.; Delpech, L.; Ohsako, T.; Prou, M.

doi:10.1088/0029-5515/51/2/023001

Cited by 31 publications

(33 citation statements)

References 19 publications

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“…Coupling experiments at low power level (200 kW, i.e. power density ∼2 MW/m 2 ) yielded very good agreement with linear coupling simulations [39] performed with ALOHA taking into account the realistic 3D antenna geometry, for density at the antenna mouth ranging from 0.5 × 10 17 m −3 to 8 × 10 17 m −3 (cut-off density = 1.7 × 10 17 m −3 at the frequency 3.7 GHz). The power coupling capability of the PAM in conditions with strong edge perturbations and at large plasmaantenna distance was also demonstrated.…”

Section: Long Pulse Operation With the Iter-relevant Lhcd System In Tsupporting

confidence: 52%

Advances in Lower Hybrid Current Drive for Tokamak Long Pulse Operation: Technology and Physics

Hoang¹,

Delpech²,

Bae

et al. 2012

Plasma and Fusion Research

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The paper gives a picture of the present status and understanding of technology and physics of Lower Hybrid Current Drive for long pulse operation in tokamaks, including the development of continuous wave (CW) high power klystrons, and its evolutions towards ITER. 3.7 GH / 700 kW CW klystrons produced in series by Thales Electron Devices are now in operation on Tore Supra. First series of eight klystrons delivered more than 4 MW to sustain non-inductive plasmas during 50 s. Moreover, a prototype of 500 kW CW klystron operating at 5 GHz developed for KSTAR by Toshiba Electron Tubes and Devices, and foreseen for ITER, is able to produce RF output powers of 300 kW / 800 s and 450 kW / 20 s on matched load. The situation on wave coupling and antennas is reported, with the latest Tore Supra results of the new CW Passive-Active Multi-junction (PAM) launcher: the antenna concept foreseen for ITER. First experiments with the PAM antenna in Tore Supra have provided extremely encouraging results in terms of power handling and coupling. Relevant ITER power density of ∼25 MW/m 2 (2.7 MW of power injected into the plasma) has been maintained over ∼80 s. In addition, LH power of 2.7 MW has been coupled at a plasma-antenna distance of 10 cm.

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Section: Long Pulse Operation With the Iter-relevant Lhcd System In Tsupporting

confidence: 52%

Advances in Lower Hybrid Current Drive for Tokamak Long Pulse Operation: Technology and Physics

Hoang¹,

Delpech²,

Bae

et al. 2012

Plasma and Fusion Research

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“…Uniform variations of density in front of the antenna by any process (ponderomotive effects at high input power, gas feed,…) do not modify spectral lobe positions, but their relative heights, changing the overall directivity, i.e. the relative fraction of power that generates co-or counter-current in the plasma [13]. The determination of the directivity has a large impact in code predictions of the total LH current, especially for antennas who turns out to be very sensitive to edge density variations like at 2.45 GHz in EAST tokamak.…”

Section: Numerical Tools Used By Lh Current Drive First Principle Modmentioning

confidence: 99%

Current Challenges in the First Principle Quantitative Modelling of the Lower Hybrid Current Drive in Tokamaks

Peysson

Bonoli²,

Chen

et al. 2017

EPJ Web Conf.

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Abstract.The Lower Hybrid (LH) wave is widely used in existing tokamaks for tailoring current density profile or extending pulse duration to steady-state regimes. Its high efficiency makes it particularly attractive for a fusion reactor, leading to consider it for this purpose in ITER tokamak. Nevertheless, if basics of the LH wave in tokamak plasma are well known, quantitative modeling of experimental observations based on first principles remains a highly challenging exercise, despite considerable numerical efforts achieved so far. In this context, a rigorous methodology must be carried out in the simulations to identify the minimum number of physical mechanisms that must be considered to reproduce experimental shot to shot observations and also scalings (density, power spectrum). Based on recent simulations carried out for EAST, Alcator C-Mod and Tore Supra tokamaks, the state of the art in LH modeling is reviewed. The capability of fast electron bremsstrahlung, internal inductance l i and LH driven current at zero loop voltage to constrain all together LH simulations is discussed, as well as the needs of further improvements (diagnostics, codes, LH model), for robust interpretative and predictive simulations.

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“…The SOL radial width is 8 cm, which is representative to the Tore Supra tokamak. The background density is set to n e = 2.6×n c , where n c is the cut-off density at 2πω LH =3.7 GHz, to avoid reflections due to densities nearing cut-off in the presence of high fluctuation amplitudes up to 50% [8]. The fluctuations are represented by a thin perturbed layer varying along the axial direction assuming a monochromatic wave-like parallel dependence with a random phase.…”

Section: Full Wave Calculations and Density Fluctuationmentioning

confidence: 99%

Interaction between the lower hybrid wave and density fluctuations in the scrape-off layer

Peysson¹,

Madi²,

Decker

et al. 2015

AIP Conference Proceedings

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Abstract. In the present paper, the perturbation of the launched power spectrum of the Lower Hybrid wave at the separatrix by electron density fluctuations in the scrape-off layer is investigated. Considering a slab geometry with magnetic field lines parallel to the toroidal direction, the full wave equation is solved using Comsol Multiphysics® for a fully active multi-junction like LH antenna made of two modules. When electron density fluctuations are incorporated in the dielectric tensor over a thin perturbed layer in front of the grill, it is shown that the power spectrum may be strongly modified from the antenna mouth to the plasma separatrix as the wave propagates. The diffraction effect leads to the appearance of multiple satellite lobes with randomly varying positions, a feature consistent with the recently developed model that has been applied successfully to high density discharges on the Tokamak Tore Supra corresponding to the large spectral gap regime [Decker J. et al. Phys. Plasma 21 (2014) 092504]. The perturbation is found to be maximum for the Fourier components of the fluctuating spectrum in the vicinity of the launched LH wavelength.

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Coupling characteristics of the ITER-relevant lower hybrid antenna in Tore Supra: experiments and modelling

Cited by 31 publications

References 19 publications

Advances in Lower Hybrid Current Drive for Tokamak Long Pulse Operation: Technology and Physics

Advances in Lower Hybrid Current Drive for Tokamak Long Pulse Operation: Technology and Physics

Current Challenges in the First Principle Quantitative Modelling of the Lower Hybrid Current Drive in Tokamaks

Interaction between the lower hybrid wave and density fluctuations in the scrape-off layer

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