Influence of magnetic field configurations on divertor plasma parameters in the W7-AS stellarator

Grigull, P.; McCormick, K.; Feng, Y.; Werner, A.; Brakel, R.; Ehmler, H.; Gadelmeier, F.; Hartmann, D.; Hildebrandt, D.; Jaenicke, R.; Kißlinger, J.; Klinger, T.; König, R.; Naujoks, D.; Niedermeyer, H.; Ramasubramanian, N.; Sardei, F.; Wagner, F.; Wenzel, U.; Team, W As

doi:10.1016/s0022-3115(02)01499-x

Cited by 44 publications

(58 citation statements)

References 2 publications

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“…The maximum density in the strike lines was only 3.5 * 10 19 m −3 , as measured by the Langmuir probes [4], ie. a factor of 20 below that in the HDZ nearby.…”

Section: Introductionmentioning

confidence: 82%

A helical hydrogen-MARFE-like phenomenon in the divertor of the Wendelstein 7-AS stellarator

Wenzel¹,

Koenig

Pedersen

2014

Nucl. Fusion

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Abstract. In the island divertor of the W7-AS stellarator a high-density zone (HDZ) near the divertor plates was discovered some years ago [1] with electron densities up to 7 * 10 20 m −3 . We shed further light on this phenomenon by determining the poloidal and radial location of this zone and discussing potential implications of these findings. The high-density zone is in the vicinity of, but clearly separated from the nearest X-point line. The carbon emission is clearly spatially separated, residing near or at the x-point lines. The HDZ shows many similarities with the hydrogen or wall MARFE in Textor-94 [2]. The structure is associated with a strongly increased neutral pressure, thus enabling efficient pumping. This offers the possibility for a very efficient exhaust regime in a stellarator with island divertor such as W7-X, simultaneously with significantly reduced convective heat loads onto the divertor itself. The spatial separation of the HDZ and the carbon radiation region may imply that such a state can be reached even in a non-carbon machine, and might therefore be DEMO-relevant.

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“…The maximum density in the strike lines was only 3.5 * 10 19 m −3 , as measured by the Langmuir probes [4], ie. a factor of 20 below that in the HDZ nearby.…”

Section: Introductionmentioning

confidence: 82%

A helical hydrogen-MARFE-like phenomenon in the divertor of the Wendelstein 7-AS stellarator

Wenzel¹,

Koenig

Pedersen

2014

Nucl. Fusion

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“…Despite the temperature dependence of S/XB for the CII transition, the correspondence of both profiles is quite good. Two strike lines were labeled with B and D according to the designation of the island fans in [4]. From field line simulations it follows that for target tiles 1-11 the island fans B and D intersect the target plates as observed.…”

Section: Data Evaluationmentioning

confidence: 96%

“…3 shows the maximum H α intensity at the target plate as a function of the separatrix upstream density. Data is plotted for the standard discharge of W7-AS from two selected target tiles for which a comparison with the Langmuir probes is possible: the inner strike point at tile 13 (strike point A) and the outer strike point at tile 5 (strike point D, see [4] for details of the divertor geometry). For edge densities up to 6.2 * 10…”

Section: Data Evaluationmentioning

confidence: 99%

Carbon influx from the island divertor of the Wendelstein-7AS stellarator

Wenzel

Thomsen

Grigull

2007

Journal of Nuclear Materials

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Target plate fluxes (C,H) were measured in the island divertor experiment of W7-AS by CCD cameras equipped with interference filters. Strike point patterns depend strongly on the confinement regime. Carbon fluxes are given for attached divertor plasmas under HDH and normal confinement conditions. Our studies show that the basic picture of the radiation zones which has emerged from the investigation of tokamak divertors has to be completed for the island divertor by additional radiation zones in the X-point regions.

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“…The detachment becomes stable only if power transport and radiation are in balance at a position inside the island SOL. Both experiment and modeling have shown that this balance can only be established in a divertor geometry having large plasma-tocore distances and small connection lengths [22,23]. In these cases, the modeling predicts the formation, at detachment conditions, of a carbon radiation belt inside the islands at the HFS.…”

Section: W7-asmentioning

confidence: 98%

Non-axisymmetric SOL-transport study for tokamaks and stellarators

Sardei

Feng

Kißlinger

et al. 2007

Journal of Nuclear Materials

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The paper addresses basic features of non-axisymmetric edge transport induced in tokamaks by local limiters or external magnetic perturbations and in low-shear stellarators by the presence of edge magnetic islands. 3D simulations and, if available for comparison, experimental results are presented and discussed for three devices, ITER during start-up operation, TEXTOR-DED and W7-AS, having edge topologies totally different from each other. The modeling is performed with the EMC3/EIRENE code, which treats self-consistently plasma, neutral and impurity transport in a general 3D Scrape-Off Layer (SOL) with arbitrarily complex geometry of magnetic configuration and plasma-facing components. Shown are code predictions of the power load on the ITER start-up limiters as well as modeling results on the transport in the TEXTOR-DED stochastic edge and on the physics of stable detachment in W7-AS. Experimental observations confirming the code simulations are referenced for both TEXTOR-DED and W7-AS, a direct comparison between modeling and experimental results is shown for W7-AS.

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Influence of magnetic field configurations on divertor plasma parameters in the W7-AS stellarator

Cited by 44 publications

References 2 publications

A helical hydrogen-MARFE-like phenomenon in the divertor of the Wendelstein 7-AS stellarator

A helical hydrogen-MARFE-like phenomenon in the divertor of the Wendelstein 7-AS stellarator

Carbon influx from the island divertor of the Wendelstein-7AS stellarator

Non-axisymmetric SOL-transport study for tokamaks and stellarators

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