Theory of the Ergodic Divertor

Samain, A.; Błeński, T.; Ghendrih, Ph.; Grosman, A.

doi:10.1002/ctpp.2150300126

Cited by 30 publications

(10 citation statements)

References 9 publications

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“…This chaotic behavior is a basic property of ergodic divertors. Here, namely, the stochastic behavior of field lines is identified with stochastic behavior of particles, and with their stochastic diffusion [4][5][6].…”

Section: B = V R X V0* -V F ( R X V R (2)mentioning

confidence: 99%

Full hamiltonian description of the interaction of particles with magnetic islands in Tokamak

Cahyna

Krlín

2006

Czech J Phys

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In this letter, the effect of full Hamiltonian approach to plasma particle dynamics, in the presence of magnetic islands in a tokamak, is discussed. Usually, for the estimation of the diffusion of particles, the stochasticity regime of magnetic field lines is considered as sufficient. We have found that for ions in Hamiltonian description, the diffusive character of their trajectories considerably differs from the diffusive character of magnetic field lines. This then could have, among others, an influence on the performance of the ergodic divertor.PACS: 52.65.Cc, 52.25.Gj I n t r o d u c t i o nIn the pioneering period of the study of Hamiltonian deterministic chaos, the possibility of generation of chaos of static magnetic field lines was found [1]. This appeared due to the formal identity of equations, describing the geometry of magnetic field lines with the canonical Hamiltonian equations. Such possibility follows from the two following equations:Here, ~b(x) is a function which is constant on the magnetic surfaces (specifically, the toroidal flux inside a surface) and the second equation in (1) expresses the tangency of B to the magnetic surface r = const. The equilibrium magnetic field, which satisfies the condition (1), may be represented by the Clebsch form [2, 3]Here, F ( r is the dimensionless poloidal flux and 0* is the intrinsic coordinate standing for the poloidal angle. (The definition of 0* will be precised later.) Using the toroidal angle ( as a running parameter [2,4], field lines can be represented by the following equations: d e OF dO* OF d~ --0 0 ' ' d~ -0---r

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Section: B = V R X V0* -V F ( R X V R (2)mentioning

confidence: 99%

Full hamiltonian description of the interaction of particles with magnetic islands in Tokamak

Cahyna

Krlín

2006

Czech J Phys

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“…Since the modules are inside the vacuum vessel, they can be used as magnetically assisted limiters and are consequently equipped with both cooling and neutralizer plates, with titanium pumping between each bar. Ergodicity of the magnetic field lines is created by a radial magnetic perturbation, 6B r , giving rise to magnetic island chains around the surface, q = l-#ml (where fand m are the poloidal and toroidal mode numbers, respectively) [13]. In TORE SUPRA, 2 = 18±3 and m = 6, i.e.…”

Section: Ergodic Divertor Operationmentioning

confidence: 99%

“…It is expected that in the ergodic layer the field lines diffuse radially, leading to increased particle and heat transport coefficients. The resulting effect should be the creation of a dense and cold edge region [13], leading to a lower sputtering rate (because of the decreased temperature), higher pumping efficiency and a strongly radiating layer, minimizing the heat deposition problem. Moreover, the large hydrogen outflux could also in principle lead to plasma decontamination because of the friction force dragging out the impurities [5].…”

Section: Ergodic Divertor Operationmentioning

confidence: 99%

Plasma decontamination during preliminary ergodic divertor experiments in TORE SUPRA

et al. 1991

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Preliminary experiments in the TORE SUPRA tokamak using the ergodic divertor configuration have shown a strong effect on plasma impurities. The result is a decontamination of the central plasma which is due to a decreased carbon content. This is the consequence of a screening effect of the peripheral ergodic layer which is due to an important increase of the recycling impurity flux, as well as of a modification of the impurity source terms.

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“…sputtering) can be reduced significantly. Thus the combined effects of the increased electron density and decreased electron temperature at the plasma boundary in conjunction with the enhanced radial transport are responsible for the beneficial effects observed on devices with ergodic divertors [19][20][21]; from those the expected improved radiation efficiency of the impurities and the better impurity screening is an issue for TEXTOR experiments. An overview over the edge structure of the DED plasma is shown in Fig.…”

Section: The Laminar Zonementioning

confidence: 99%

Overview of Experiments with the Dynamic Ergodic Divertor on TEXTOR

Finken

Abdullaev

Biel

et al. 2006

Contrib. Plasma Phys.

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The Dynamic Ergodic Divertor (DED) has recently been taken into operation on TEXTOR. The device is rather flexible and allows the investigation of very different questions. In the present context we concentrate on the divertor aspect and on results of the m/n=12/4 base mode. The DED-field generates the proper ergodic zone and an area of open magnetic field lines, the laminar zone and the tangle structure. The properties of the laminar zone resemble the divertor region of a poloidal divertor. However, the distribution of the density and temperature is highly 3D and strongly related to the structure of the laminar and ergodic zones. The structures of the heat and particle fluxes to the wall agree well with the predicted patterns. A prominent feature of the ergodization is the creation of an edge electric field which results in a rotation of the plasma.

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Theory of the Ergodic Divertor

Abstract: AbsaactWe consider the basic possibility offered by ergodic divertors. which is to establish a high density, low temperature plasma shell diffusely C O M~ tothe wall.

Cited by 30 publications

References 9 publications

Full hamiltonian description of the interaction of particles with magnetic islands in Tokamak

Full hamiltonian description of the interaction of particles with magnetic islands in Tokamak

Plasma decontamination during preliminary ergodic divertor experiments in TORE SUPRA

Overview of Experiments with the Dynamic Ergodic Divertor on TEXTOR

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