Ergodic divertor impact on Tore Supra plasma edge

Grosman, A.; Evans, T. E.; Ghendrih, Ph.; Agostini, Eric; Bruneau, J.; Michelis, C. De; Fall, T.; Gil, C.; Guilhem, D.; Hess, W.; Hutter, T.; Lassalle, J.; Martín, G.; Mattioli, M.; Millot, P.; Monier‐Garbet, P.; Mourgues, F.; Nguyen, Frédéric; Paume, M.; Samain, A.; Vallet, J.C.

doi:10.1016/0022-3115(90)90095-5

Cited by 17 publications

(10 citation statements)

References 4 publications

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“…Changes in the plasma shape and edge-localized mode activity were small after application of non-axisymmetric magnetic fields. Other previous experiments in DIII-D [8], TEXT [9] and Tore Supra [10] also showed a degradation in confinement and/or electron density reduction after application of non-axisymmetric magn etic fields. However, in discharges with higher plasma col lisionality and higher density in DIII-D, no reductions in the plasma-energy confinement time or pedestal electron density were found [8].…”

Section: Introductionsupporting

confidence: 52%

Robust nonlinear burn control in ITER to handle uncertainties in the fuel-line concentrations

Pajares

Schuster

2019

Nucl. Fusion

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Tight regulation of the burn condition in ITER has been proven possible in simulations by the use of robustification techniques even under emulated time-dependent variations in the fuel concentration. One of the most fundamental control problems arising in ITER and future burning-plasma tokamaks is the regulation of the plasma temperature and density to produce a determined amount of fusion power while avoiding possible thermal instabilities. Such problem, known as burn control, requires the development of controllers that integrate all the available actuators. Moreover, the complex burning-plasma dynamics and the uncertain nature of some of its components suggest that nonlinear, robust, burn controllers are necessary. For instance, the deuterium-tritium concentration in the fueling lines may vary over time and the estimation of such variation during operation may be difficult or not even possible. Available actuators for the regulation of the burn condition are auxiliary power modulation, fueling rate modulation, and impurity injection. Also, recent experiments in the DIII-D tokamak have shown that in-vessel coil-current modulation can be used for burn control purposes. The in-vessel coils generate non-axisymmetric magnetic fields that have the capability to decrease the plasma-energy confinement time, which allows for regulation of the plasma energy during positive energy perturbations. In this work, all these actuators are used to design a nonlinear burn controller which is robust to unknown variations in the deuterium-tritium concentration of the fueling lines. Furthermore, fueling rate modulation is not only used to control the plasma density, but also to control the plasma energy, if necessary, by means of isotopic fuel tailoring. The model-based nonlinear controller is synthesized from a zero-dimensional model of the burning-plasma dynamics. A nonlinear simulation study is carried out to illustrate the successful controller performance in ITER-like scenarios in which unknown variations of the deuterium-tritium concentration of the fueling lines are emulated.

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Section: Introductionsupporting

confidence: 52%

Robust nonlinear burn control in ITER to handle uncertainties in the fuel-line concentrations

Pajares

Schuster

2019

Nucl. Fusion

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“…(b) All experimental data from ergodic divertors [18][19][20][21][22][23][24] show rather flat density and temperature profiles in the ergodic zone.…”

Section: Modellingmentioning

confidence: 99%

First modelling of the TEXTOR DED near field divertor

1998

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As the first step in the modelling of the plasma-wall interaction of the proposed dynamic ergodic divertor (DED) of TEXTOR-94, the topology of the magnetic field lines of the divertor is analysed. Despite the strong ergodization, the magnetic field lines intersecting the wall in one poloidal turn form continuous sets. These sets are visualized by a two dimensional (2-D) imaging technique; the field lines are traced one poloidal turn clockwise and counter-clockwise from the outer midplane, marking those lines intersecting the wall. An overlay of the marked starting points defines areas with the properties of a scrape-off layer (SOL) and areas with field lines ending on one side in the ergodic layer and one side on the wall. The edge plasma can be described by a 2-D model; the model treats part of the plasma as that of a conventional SOL and another part as that with `half open' field lines connecting the divertor target plate with the ergodic layer. Calculations of the power flux distribution in the DED near field divertor are presented.

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“…Resonant magnetic field perturbations ͑RMPs͒ are known to significantly change the magnetic field topology and therefore the plasma dynamics in a tokamak device. [1][2][3][4][5][6][7] Such resonant perturbations are, in general, characterized by a magnetic field component perpendicular to the flux surfaces and a zero derivative along the unperturbed magnetic field lines at particular ͑resonant͒ flux surfaces. They can be caused by imperfections in the coil arrangements or by means of additional RMP coils to introduce deliberately large deviations from the usual axisymmetric tokamak confinement field.…”

Section: Introductionmentioning

confidence: 99%

Plasma currents induced by resonant magnetic field perturbations in tokamaks

Reiser

Chandra

2009

Physics of Plasmas

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The plasma response on externally applied resonant magnetic field perturbations is studied by means of numerical simulations. It is shown that dependent on collisionality and perturbation strength, plasma currents build up which can compensate the external field. These plasma currents are accompanied by out-of-phase currents and poloidal flows at the resonant surfaces. With an increasing perturbation field the screening of the externally applied field decreases and at a certain level, the vacuum field approximation holds for the total magnetic field.

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Ergodic divertor impact on Tore Supra plasma edge

Cited by 17 publications

References 4 publications

Robust nonlinear burn control in ITER to handle uncertainties in the fuel-line concentrations

Robust nonlinear burn control in ITER to handle uncertainties in the fuel-line concentrations

First modelling of the TEXTOR DED near field divertor

Plasma currents induced by resonant magnetic field perturbations in tokamaks

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