The effects of field reversal on the W7-AS island divertor at low densities

Feng, Y.; Herre, G.; Grigull, P.; Sardei, F.; Team, W As

doi:10.1088/0741-3335/40/3/003

Cited by 24 publications

(30 citation statements)

References 7 publications

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“…Although full 3D models of stellarator plasma edge transport are becoming available [48,211], they do not yet treat self-consistently the electric potential, or contain drifts and currents [212]. It is thus useful to obtain knowledge about the electric field structure of island divertors using the current 2D tokamak simulation tools.…”

Section: Topology Effects: Stellarator Island Divertormentioning

confidence: 99%

Plasma Edge Physics with B2‐Eirene

Schneider

Bonnin

Borraß

et al. 2006

Contrib. Plasma Phys.

484

426

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The B2‐Eirene code package was developed to give better insight into the physics in the scrape‐off layer (SOL), which is defined as the region of open field‐lines intersecting walls. The SOL is characterised by the competition of parallel and perpendicular transport defining by this a 2D system. The description of the plasma‐wall interaction due to the existence of walls and atomic processes are necessary ingredients for an understanding of the scrape‐off layer. This paper concentrates on understanding the basic physics by combining the results of the code with experiments and analytical models or estimates. This work will mainly focus on divertor tokamaks, but most of the arguments and principles can be easily adapted also to other concepts like island divertors in stellarators or limiter devices. The paper presents the basic equations for the plasma transport and the basic models for the neutral transport. This defines the basic ingredients for the SOLPS (Scrape‐Off Layer Plasma Simulator) code package. A first level of understanding is approached for pure hydrogenic plasmas based both on simple models and simulations with B2‐Eirene neglecting drifts and currents. The influence of neutral transport on the different operation regimes is here the main topic. This will finish with time‐dependent phenomena for the pure plasma, so‐called Edge Localised Modes (ELMs). Then, the influence of impurities on the SOL plasma is discussed. For the understanding of impurity physics in the SOL one needs a rather complex combination of different aspects. The impurity production process has to be understood, then the effects of impurities in terms of radiation losses have to be included and finally impurity transport is necessary. This will be introduced with rising complexity starting with simple estimates, analysing then the detailed parallel force balance and the flow pattern of impurities. Using this, impurity compression and radiation instabilities will be studied. This part ends, combining all the elements introduced before, with specific, detailed results from different machines. Then, the effect of drifts and currents is introduced and their consequences presented. Finally, some work on deriving scaling laws for the anomalous turbulent transport based on automatic edge transport code fitting procedures will be described. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Topology Effects: Stellarator Island Divertormentioning

confidence: 99%

Plasma Edge Physics with B2‐Eirene

Schneider

Bonnin

Borraß

et al. 2006

Contrib. Plasma Phys.

484

426

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“…B-field reversal experiments show a clear dependence of the particle deposition pattern on the B-field direction, indicating the drift effects. E × B drift effects have been modelled with the EMC3/EIRENE code using a simple model neglecting the potential variation on island surfaces to explain the measured poloidal density asymmetries in the islands [26]. The model has been improved by integrating the parallel momentum equation for electrons to determine the 3D potential distribution [27].…”

Section: Deposition Patternsmentioning

confidence: 99%

3D Edge Modeling and Island Divertor Physics

Feng

Sardei

Kißlinger

et al. 2004

Contrib. Plasma Phys.

214

224

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The paper presents an overview on the state of the art of 3D fluid transport modeling in the boundaries of 3D toroidal confinement devices and on applications to island divertor physics. Typically, such edge configurations are characterized by the coexistence of closed magnetic surfaces, islands and open stochastic regions, e.g. in helical devices like W7-AS, W7-X, LHD and in tokamaks like TEXTOR-DED. Two main approach branches falling within the current numeric catalogue of the 3D modeling are the finite volume and Monte Carlo methods. They differ essentially in the elementary treatment of the local transport. While in a finite volume method interpolation of the fluid fluxes through the interfaces by appropriate choice of a shape function is essential for the discretization process, the full fluid dynamics are, in a Monte Carlo approach, simulated by means of a local stochastic process, with the fluxes passing through cell boundary surfaces being a net result of the random process. In this paper, we present the numerics and strategies proposed in different models. Concerning the practical applications to a realistic 3D experiment, W7-AS provides not only a practical fully 3D island divertor configuration but also sufficient experimental data for code validation. We present the main simulation results from the 3D edge Monte Carlo code EMC3/EIRENE and discuss the island divertor physics with respect to tokamak divertors.

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“…In this paper, the 3D fluid code, EMC3 [9], based on a similar Monte Carlo solution procedure, is applied to the DED plasma edge configuration, again for a static operational scenario. EMC3 has initially been developed as a fully 3D edge transport code for the stellarators W7-AS and W7-X [10,11]. The code solves the plasma fluid equations of mass, momentum and electron and ion energy, coupled self-consistently, and in almost any arbitrary magnetic and wall surface geometry.…”

Section: Introductionmentioning

confidence: 99%

3D numerical transport study of the edge ergodized plasma in TEXTOR-DED

et al. 2004

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Transport properties of the edge ergodized plasma in TEXTOR-DED (Finken K H and Wolf G H 1997 Fusion Eng. Des. 37 337) are studied using the 3D plasma edge transport code package, EMC3-EIRENE, prior to the forthcoming experimental campaign. EMC3 solves the steady-state plasma fluid equations of mass, momentum and energy, in almost any arbitrary 3D magnetic and bounding surface configurations. It is iteratively coupled with EIRENE, a 3D kinetic neutral particle transport code. Two different levels of ergodization have been selected in order to assess the additional effects of ergodicity on edge plasma transport. The code predicts a significant change in the radial profile of electron temperature for the higher ergodization and a pronounced correlation between the plasma flow fields and the magnetic field structure. The role of the (outermost) 'laminar zone' on the energy deposition pattern onto the divertor is analysed. It is found that its influence depends sensitively on the degree of ergodization achieved.

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The effects of field reversal on the W7-AS island divertor at low densities

Cited by 24 publications

References 7 publications

Plasma Edge Physics with B2‐Eirene

Plasma Edge Physics with B2‐Eirene

3D Edge Modeling and Island Divertor Physics

3D numerical transport study of the edge ergodized plasma in TEXTOR-DED

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