Regular patterns in the plasma edge with the ergodic divertor

Ghendrih, Ph.; Grosman, A.; Nguyen, Frédéric

doi:10.1016/0022-3115(94)00646-6

Cited by 14 publications

(9 citation statements)

References 4 publications

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“…The transport problem in the ergodic area (I) is treated in a simplified manner. The effect of ergodicity is taken into account by enhancing the transport coefficients as is discussed, for example, in Refs [11,2]. The distorted field lines are therefore not traced to calculate the parallel transport in the ergodic region as well.…”

Section: Calculational Domainmentioning

confidence: 99%

“…The scientific goal of the DED perturbation coil device in static and (quasi-static) low frequency operation is distribution of the heat fluxes from the core plasma to the wall elements over a large area, suppressing zones of high impact. Experimental results for the Tore Supra Ergodic Divertor (ED) [1][2][3] have shown that the local heat and particle fluxes are defined both by the near field of the coil device and by the ergodic layer. Recent numerical studies on the perturbation field generated by the DED coil device confirmed these results for TEXTOR-DED [4].…”

Section: Introductionmentioning

confidence: 99%

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Two dimensional modelling approach to transport properties of the TEXTOR-DED laminar zone

2000

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Abstract. An important operational range for TEXTOR-DED is the case of a high ergodization at the plasma edge. Under these conditions, the edge magnetic field forms a proper ergodic layer and a laminar zone. The laminar zone is established by magnetic field lines which intersect wall elements after only a few toroidal turns (open ergodic system). For this, both the heat and particle transport in the plasma edge are dominated by the laminar zone which shows a well defined structure compared with that of the ergodic layer. For the present analysis the regions containing field lines with connection lengths corresponding to one or to two poloidal turns are of particular interest; the radial width of these regions is of the same order as the width of the unperturbed SOL of a 'classical' limiter or divertor configuration. Field lines running poloidally twice around the torus introduce a particular new feature, they impose a connection between radially separated areas and thus enhance the radial temperature and particle transport. A new 2-D modelling approach code for the laminar zone of an ergodic divertor has been developed which is strongly oriented on the topology of the magnetic field lines in the plasma edge. A 2-D finite element method is used in order to model the perpendicular transport of particles and energy. For obtaining a solution of the parallel transport, an analytical model is discussed providing expressions for averaged particle and energy sources. By considering the topological properties of the magnetic field and corresponding assumptions in the code, the transport calculation in the perturbed plasma edge gives a first insight into the generic transport properties of the TEXTOR-DED laminar zone. As an important application for later experiments the power fluxes to the wall elements are estimated. They show a strong variation perpendicular to the perturbation coils and a medium variation over the helical divertor footprints.

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Section: Calculational Domainmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Two dimensional modelling approach to transport properties of the TEXTOR-DED laminar zone

2000

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“…It was found, however, that this picture is oversimplified. For the ergodic divertor of, for example, Tore Supra [5,6] or TEXTOR DED [7], three layers must be distinguished:…”

Section: Introductionmentioning

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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“…[10]). An example of the infrared image recorded by the calibrated camera operating in the full frame mode is shown in Fig.…”

Section: The Heat Flux Distribution Over the Divertor Target Platesmentioning

confidence: 99%

“…In contrast to the proper ergodic zone, the connection length of neighboring magnetic field lines have smooth and continuous properties, with some sharp boundaries. This region is called laminar zone [7] and it is restricted to a small radial extent near the ergodizing coils.…”

Section: Introductionmentioning

confidence: 99%