Confinement studies in the TJ-II stellarator

Alejaldre, C.; Alonso, Javier; Almoguera, L.; Bär, E.; Baciero, A.; Balbín, Rosa; Blaumoser, M.; Botija, J.; Brañas, B.; Cal, E. de la; Cappa, Á.; Carrasco, R. C.; Castejón, F.; Cepero, J. R.; Crémy, C.; Delgado, J. M. P. Q.; Doncel, J.; Dulya, C.; Estrada, T.; Fernández, Á.; Fuentes, C.; Díaz, Antonio; a-Cortés, I Garcí; Guasp, J.; Herranz, J.; Hidalgo, C.; Jiménez, Javier; Kirpitchev, I.; Krivenski, V.; Labrador, I.; Lapayese, F.; Likin, K. M.; Linier, M; Löpez‐Fraguas, A.; López-Sánchez, Almudena; Luna, E. de la; Martı́n, Rosario; Martinez, A.; Martínez-Laso, L.; Medrano, M.; Méndez, P.; McCarthy, K. J.; Medina, F.; Ochando, M. A.; Pacios, Luis F.; Pastor, I.; Pedrosa, M. A.; Peña, A. de la; Portas, A.; Qin, Jie; Rodrı́guez-Rodrigo, L.; Salas, Alvaro H.; Sánchez, E.; Sánchez, J.; Tabarés, F.L.; Tafalla, D.; Tribaldos, V.; Vega, J.; Zurro, B.; Akulina, D. K.; Fedyanin, O.I.; Grebenshchikov, S. E.; Kharchev, N. K.; Meshcheryakov, A. I.; Sarksian, K. A.; Barth, R.; Dijk, G. van; Meiden, H. van der

doi:10.1088/0741-3335/41/12b/307

Cited by 17 publications

(7 citation statements)

References 3 publications

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“…No qualitative changes are expected in the neoclassical radial transport of these configurations since the main Fourier components of the magnetic field strength do not change too much [26,15]. Still, the flexibility of TJ-II allows for exploring a large set of configurations (on a shot-to-shot basis [27] or continuously [28]) and a general study of the variation of the transport coefficients and the neoclassical balance may be of interest. More precise calculations for selected discharges are underway.…”

Section: Introductionmentioning

confidence: 99%

Study of the neoclassical radial electric field of the TJ-II flexible heliac

Velasco¹,

Castejón²

2011

Plasma Phys. Control. Fusion

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Section: Introductionmentioning

confidence: 99%

Study of the neoclassical radial electric field of the TJ-II flexible heliac

Velasco¹,

Castejón²

2011

Plasma Phys. Control. Fusion

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“…Indeed, one of the main lines of research at the flexible heliac TJ-II is the relation between confinement and the magnetic configuration [5,6,7,8,9]. Ref.…”

Section: Introductionmentioning

confidence: 99%

“…This is especially important for shearless devices, such as W7-X [3] or TJ-II [4]. Indeed, one of the main lines of research at the flexible heliac TJ-II is the relation between confinement and the magnetic configuration [5][6][7][8][9]. Reference [10] offers a review of results at TJ-II and other stellarators.…”

Section: Introductionmentioning

confidence: 99%

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Calculation of the bootstrap current profile for the TJ-II stellarator

Velasco¹,

Allmaier

Löpez‐Fraguas³

et al. 2011

Plasma Phys. Control. Fusion

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Calculations of the bootstrap current for the TJ-II stellarator are presented. DKES and NEO-MC codes are employed; the latter has allowed, for the first time, the precise computation of the bootstrap transport coefficient in the long mean free path regime of this device. The low error bars allow a precise convolution of the monoenergetic coefficients, which is confirmed by error analysis. The radial profile of the bootstrap current is presented for the first time for the 100 44 64 configuration of TJ-II for three different collisionality regimes. The bootstrap coefficient is then compared to that of other configurations of TJ-II regularly operated. The results show qualitative agreement with toroidal current measurements; precise comparison with real discharges is ongoing.

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“…Many experiments carried out in the last decade have confirmed long-standing claims that plasma confinement in toroidal devices strongly depends on the electric and magnetic fields at the plasma edge [1][2][3][4][5]. The former fields are related to the observed anomalous particle transport at the plasma edge, which has been shown to be largely controlled by lowfrequency electrostatic drift waves [2].…”

Section: Introductionmentioning

confidence: 86%

Chaotic transport in reversed shear tokamaks

et al. 2008

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For tokamak models using simplified geometries and reversed shear plasma profiles, we have numerically investigated how the onset of Lagrangian chaos at the plasma edge may affect the plasma confinement in two distinct but closely related problems. Firstly, we have considered the motion of particles in drift waves in the presence of an equilibrium radial electric field with shear. We have shown that the radial particle transport caused by this motion is selective in phase space, being determined by the resonant drift waves and depending on the parameters of both the resonant waves and the electric field profile. Moreover, we have shown that an additional transport barrier may be created at the plasma edge by increasing the electric field. In the second place, we have studied escape patterns and magnetic footprints of chaotic magnetic field lines in the region near a tokamak wall, when there are resonant modes due to the action of an ergodic magnetic limiter. A non-monotonic safety factor profile has been used in the analysis of field line topology in a region of negative magnetic shear. We have observed that, if internal modes are perturbed, the distributions of field line connection lengths and magnetic footprints exhibit spatially localized escape channels. For typical physical parameters of a fusion plasma, the two Lagrangian chaotic processes considered in this work can be effective in usual conditions so as to influence plasma confinement. The reversed shear effects discussed in this work may also contribute to evaluate the transport barrier relevance in advanced confinement scenarios in future tokamak experiments.

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Confinement studies in the TJ-II stellarator

Cited by 17 publications

References 3 publications

Study of the neoclassical radial electric field of the TJ-II flexible heliac

Study of the neoclassical radial electric field of the TJ-II flexible heliac

Calculation of the bootstrap current profile for the TJ-II stellarator

Chaotic transport in reversed shear tokamaks

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