Optimization of a lower hybrid current drive launcher for ITER

Belo, J.; Goniche, M.; Hillairet, J.; Bizarro, João P. S.

doi:10.1016/j.fusengdes.2015.01.056

Cited by 7 publications

(4 citation statements)

References 15 publications

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“…Finally, a careful theoretical analysis of the LHCD spectral noise, which is the seed of the PI, possibly complemented by experimental measurements, should be performed. We plan to apply the present modeling with at least some of the above improvements to analyze experimental scenarios, for example those of [11], [59] and [97] as well as the LHCD scenarios envisaged for ITER [87] or other reactor relevant tokamaks.…”

Section: Discussionmentioning

confidence: 99%

“…As a result, the PI growth rates are typically of the order of a few times ω r . To give an idea of the values of p and q expected in LHCD scenarios, we consider first the LHCD experiment planned in ITER [87], operating at 5.0 GHz LH wave frequency and with ∼12 eV electron temperature envisaged in the SOL before the region of steep gradients near the separatrix. Assuming k z = 6 cm −1 , so that ω r ∼ = 1.4 10 7 rad s −1 for deuterium plasma, the above electric field reference unit has a value of E u ∼ = 0.41 stV cm −1 .…”

Section: Lh Waves In Homogeneous Collisional and Collisionless Plasmasmentioning

confidence: 99%

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Nonlinear lower hybrid wave equations in collisional tokamak plasmas

Castaldo,

Napoli

2024

Plasma Phys. Control. Fusion

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. A new set of coupled integro-differential nonlinear lower hybrid (LH) wave equations is derived in the framework of a kinetic theory coupled to the Maxwell equations to study the parametric instabilities (PI) produced by LH waves in collisional tokamak plasma. Previous models of nonlinear LH wave equations have been significantly improved. The wave equations derived overcome the limits and the incorrectness of the standard theory of the PI in inhomogeneous plasma. They allow treating the full spectrum in parallel and poloidal wavenumber of the coupled LH power wave, diffraction effects and possible cascade phenomena, which are elements of the nonlinear LH physics ignored in the standard PI theory. Numerical solutions of the new nonlinear LH wave equations are proposed. The relevant LH frequency spectra produced by PI are calculated, exhibiting characteristic features of PI observed in LH experiments. It is shown that the LH sideband amplification can be overestimated by orders of magnitude by the standard theory of PI. A benchmark of the new model is provided for spatially homogeneous plasmas. The role of the collisions for PI has been assessed. We demonstrate that previous analysis significantly overestimated their stabilization effect.

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Section: Discussionmentioning

confidence: 99%

Section: Lh Waves In Homogeneous Collisional and Collisionless Plasmasmentioning

confidence: 99%

Nonlinear lower hybrid wave equations in collisional tokamak plasmas

Castaldo,

Napoli

2024

Plasma Phys. Control. Fusion

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“…A detailed conceptual study of PAM launchers at 3.7 GHz and 5.0 GHz was carried out for JET [25] and ITER [26,27], although the LHCD system has been removed on both machines. The PAM characteristic of good coupling with the edge density very close or even lower than the cut-off value has been demonstrated on several devices, for instance, FTU with wave frequency at 8.0 GHz [28], Tore Supra [29] and HL-2 A [30] with 3.7 GHz, and EAST with 2.45 GHz [13].…”

Section: Introductionmentioning

confidence: 99%

Design and analysis of a PAM launcher at 4.6 GHz for a new LHCD system on EAST

Li,

Liu,

Yang

et al. 2024

Nucl. Fusion

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To improve the current drive (CD) capability in long-pulse (up to ~ 1000 s) H-mode operation, it has been decided to develop a new lower hybrid current drive (LHCD) system at 4.6 GHz with an active cooling passive active multijunction (PAM) launcher on EAST. In this paper, both the RF and the physical properties of this PAM are studied numerically. The same nominal parallel refractive index (N|| = k||c/ω, where k|| is the parallel wavenumber, c the velocity of light, and ω the wave frequency) of 2.04 as the existing 4.6 GHz full active multijunction (FAM) is chosen. Ray-tracing calculations indicate that good accessibility could be achieved when the LH waves radiate with this nominal N|| in typical long-pulse H-mode plasmas. The coupling performance in terms of power reflection coefficient (RC), power spectrum, maximum electric field, power directivity (DP) and global CD capability is evaluated with the ALOHA code based on the linear coupling theory. Good coupling performance with averaged RC ≦ 1% and DP ~ 70% could be expected with the density (ne) in front of the PAM close to the cut-off value (ne_co). The simulated RC remains below 6.5% over a wide density range 0.5 ≦ ne/ne_co ≦ 10, which is similar to the plasma edge conditions produced by edge localized mode (ELM) activity. A detailed comparison with the existing 4.6 GHz FAM launcher is also performed.

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“…A number of ITER microwave diagnostics will operate below this frequency, including plasma position reflectometers in the range 15-75GHz [1], density reflectometers operating down to similar frequencies [2], collective Thomson scattering (CTS) for fast-ion measurements at 55-65 GHz [3,4], and the electron cyclotron emission (ECE) diagnostic itself down to 70GHz [5]. In addition, 5GHz antennas have been considered for external lower hybrid current drive (LHCD) during long-pulse ITER operation [6,7].…”

Section: Introductionmentioning

confidence: 99%

Modeling the electron cyclotron emission below the fundamental resonance in ITER

Rasmussen

Stejner

Figini

et al. 2019

Plasma Phys. Control. Fusion

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The electron cyclotron emission (ECE) in fusion devices is nontrivial to model in detail at frequencies well below the fundamental resonance where the plasma is optically thin. However, doing so is important for evaluating the background for microwave diagnostics operating in this frequency range.Here we present a general framework for estimating the ECE levels of fusion plasmas at such frequencies using ensemble-averaging of rays traced through many randomized wall reflections. This enables us to account for the overall vacuum vessel geometry, self-consistently include cross-polarization, and quantify the statistical uncertainty on the resulting ECE spectra. Applying this to ITER conditions, we find simulated ECE levels that increase strongly with frequency and plasma temperature in the considered range of 55-75 GHz. At frequencies smaller than 70 GHz, we predict an X-mode ECE level below 100 eV in the ITER baseline plasma scenario, but with corresponding intensities reaching keV levels in the hotter hybrid plasma scenario. Benchmarking against the SPECE raytracing code reveals good agreement under relevant conditions, and the predicted strength of Xmode to O-mode conversion induced by wall reflections is consistent with estimates from existing fusion devices. We discuss possible implications of our findings for ITER microwave diagnostics such as ECE, reflectometry, and collective Thomson scattering.

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Optimization of a lower hybrid current drive launcher for ITER

Cited by 7 publications

References 15 publications

Nonlinear lower hybrid wave equations in collisional tokamak plasmas

Nonlinear lower hybrid wave equations in collisional tokamak plasmas

Design and analysis of a PAM launcher at 4.6 GHz for a new LHCD system on EAST

Modeling the electron cyclotron emission below the fundamental resonance in ITER

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