ECRH effect on the electric potential and turbulence in the TJ-II stellarator and T-10 tokamak plasmas

Melnikov, A. V.; Krupnik, L. I.; Ascasíbar, E.; Cappa, Á.; Chmyga, A. A.; Deshko, G. N.; Drabinskij, M.A.; Eliseev, L.G.; Hidalgo, C.; Khabanov, P.O.; Khrebtov, S. M.; Kharchev, Ν. K.; Komarov, A. D.; Kozachek, A.S.; Лысенко, С. Е.; Molinero, A.; Pablos, J.L. de; Ufimtsev, M. V.; Zenin, V.N.

doi:10.1088/1361-6587/aac97f

Cited by 27 publications

(13 citation statements)

References 95 publications

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“…It should be noted that in TEXTOR [14] both LFQC and HFQC maxima were observed together with SLF and BB fluctuations (figure 17 in [14]). LFQC fluctuations were observed in T-10 also with the single-channel HIBP diagnostic [9,23].…”

Section: Qc Fluctuationsmentioning

confidence: 81%

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3D structure of density fluctuations in the T-10 tokamak and new approach for current profile estimation

et al. 2019

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Previous investigations of small-scale density fluctuation by means of correlation reflectometry in T-10 tokamak revealed the existence of several density fluctuation types and strong radial and poloidal variation of their amplitudes and correlation properties. This paper is focused on the new measurements of the 3D spatial distributions of the amplitudes, the radial correlation lengths and the long range correlations along the field lines for the different turbulence types. The properties of the density fluctuations were systematically studied with the improved reflectometers, data analyzing and acquisition hardware. The density fluctuations were measured by heterodyne correlation reflectometry using ordinary mode. New T-10 antenna set have horn antennae arrays at four places distributed toroidally and poloidally over tokamak torus. The experiments confirmed previously found strong poloidal amplitude asymmetry of the broad band and the quasi-coherent oscillations and the uniform poloidal distribution of stochastic low frequency fluctuations. The presence of those turbulence types was also proved by the measurements of perturbation properties using heavy ion beam probe diagnostic. The radial correlation measurements were performed at four poloidal angles to understand the poloidal dependence of the radial correlation length for the different fluctuation types. The significant decrease of the radial correlation lengths towards the high magnetic field side was observed for quasi-coherent and stochastic low frequency turbulence types. The long range correlations along the field lines were measured by the reflectometers in two cross-section separated by 1/4 of the torus. The reflectometers have the same frequency thus provide reflection from the same magnetic surface. Reflection radii are chosen by the frequency variation of the launched wave from shot to shot in a series of reproducible discharges. The measurements were carried out at the low and the high magnetic field side with two currents and simultaneous reverse of the direction of the toroidal magnetic field and the plasma current. Resonance radii were also calculated using 3D tracing of the magnetic field line and demonstrate good agreement with experiments. These results allow to propose the new approach for the current profile measurements in tokamaks.

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Section: Qc Fluctuationsmentioning

confidence: 81%

“…Later these fluctuations were also observed at TEXTOR [10], FTU [11], Tore Supra [12], JET [13] and ASDEX-U [14]. LFQC were also observed in T-10 with the single-channel Heavy Ion Beam Probe (HIBP) diagnostic [15].…”

Section: Quasi-coherent Fluctuationsmentioning

confidence: 91%

3D structure of density fluctuations in the T-10 tokamak and new approach for current profile estimation

et al. 2019

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“…Studies have been made on the physical properties of specific modes, and several external actuators have been proposed and demonstrated in tokamaks and helical devices for controlling and/or stabilizing EP-driven modes [4]. Promising control techniques are based on (i) varying the energetic-ion sources to modify the gradients in the energetic ion-distribution [5][6][7][8][9][10], (ii) localized electron cyclotron heating (ECH) to modify the energetic-ion slowing-down distribution [11][12][13][14][15][16][17][18], (iii) a localized electron cyclotron current drive (ECCD) for modifying the equilibrium [19,20] and (iv) externally applied 3D perturbative magnetic fields for manipulating the energetic-ion distribution and thus the wave drive [21,22].…”

Section: Introductionmentioning

confidence: 99%

“…For instance, in the TJ-II helical device, the behavior of AEs was changed from a steady mode to a chirping mode when ECH power was applied to a neutral beam injection (NBI) plasma [16]. Further off-axis electron cyclotron resonance heating (ECRH) power resulted in a strong reduction of the chirping mode amplitude [17,18]. In the Heliotron J helical device, it was demonstrated that EPMs and global AEs (GAEs) were stabilized by both coand counter-ECCD [19,20].…”

Section: Introductionmentioning

confidence: 99%

Effect of ECH/ECCD on energetic-particle-driven MHD modes in helical plasmas

et al. 2020

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The effect of electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) on energetic-particle (EP)-driven magnetohydrodynamic (MHD) modes is studied in the helical devices LHD, TJ-II and Heliotron J. We demonstrate that EP-driven MHD modes, including Alfvén eigenmodes (AEs) and energetic particle modes (EPMs), can be controlled by ECH/ECCD. In the LHD device, which has a moderate rotational transform and a high magnetic shear, co-ECCD enhances toroidal AEs (TAEs) and global AEs (GAEs), while counter-ECCD stabilizes them, which improves the neutron rate compared with the co-ECCD case. Counter-ECCD decreases the core rotational transform and increases the magnetic shear, strengthening the continuum damping on the shear Alfvén continua (SAC). In the TJ-II device, which has a high rotational transform, moderate magnetic shear and low toroidal field period, helical AEs (HAEs) appear when the HAE frequency gap of the SAC is changed by counter-ECCD combined with a bootstrap current and neutral-beam-driven current. On the other hand, both co- and counter-ECCD are effective in stabilizing GAEs and EPMs in the Heliotron J device, which has a low rotational transform and low magnetic shear. The experimental results indicate that the magnetic shear has a stabilizing effect regardless of its sign. Modeling analysis using the FAR3d code shows that the growth rates are reduced by both co- and counter-ECCD in Heliotron J, reproducing the experimental results. ECH only affects EP-driven MHD modes, and the experimental results show that the effect depends on the magnetic configuration. In Heliotron J, some modes are stabilized with an increase in ECH power in the low-bumpiness magnetic configuration, while some modes are destabilized in the high- and medium-bumpiness magnetic configurations.

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“…Electron density n e and temperature T e radial profiles are measured using Thomson scattering (TS) once per discharge [20], time evolution of the central chord line-averaged density is measured by the microwave interferometer. TJ-II is equipped with the unique dual HIBP diagnostics [21,22], which is capable to measure local values of the plasma electrostatic potential ϕ and its fluctuations from the edge to the core of the plasma column [23]. The schematic of HIBP-II system is shown in figure 1.…”

Section: Experimental Set Upmentioning

confidence: 99%

Density profile reconstruction using HIBP in ECRH plasmas in the TJ-II stellarator

et al. 2019

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A: Heavy Ion Beam Probing (HIBP) is a unique tool for plasma potential measurements. In the TJ-II stellarator (CIEMAT, Madrid, Spain) HIBP is capable to move the sample volume (SV) from Low Field Side (LFS) of a plasma column through the plasma center to High Field Side (HFS), so the time evolution of plasma potential ϕ and secondary beam total current I tot radial profiles can be obtained during one shot. I tot is proportional to the plasma density n e at the SV, it is affected by attenuation factors along the beam trajectory. The work shows the method for the n e radial profile reconstruction from HIBP I tot signal. Using the method, for the first time n e radial profiles are reconstructed from HIBP I tot signal in TJ-II regimes with electron cyclotron resonance heating (ECRH) and the line-averaged electron density ne up to 0.8 • 10 19 m −3 . Reconstructed n e (ρ) profiles are consistent with Thomson scattering data.

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ECRH effect on the electric potential and turbulence in the TJ-II stellarator and T-10 tokamak plasmas

Cited by 27 publications

References 95 publications

3D structure of density fluctuations in the T-10 tokamak and new approach for current profile estimation

3D structure of density fluctuations in the T-10 tokamak and new approach for current profile estimation

Effect of ECH/ECCD on energetic-particle-driven MHD modes in helical plasmas

Density profile reconstruction using HIBP in ECRH plasmas in the TJ-II stellarator

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