Local island divertor experiments on LHD

Komori, A.; Ohyabu, N.; Masuzaki, S.; Morisaki, T.; Suzuki, H.; Takahashi, C.; Sakakibara, S.; Watanabe, K. Y.; Minami, Takashi; Morita, S.; Tanaka, K.; Ohdachi, S.; Kubo, S.; Inoue, Noriyuki; Yamada, H.; Nishimura, K.; Okamura, S.; Matsuoka, K.; Motojima, O.; Fujiwara, Masami; Iiyoshi, A.; Lyon, J. F.; England, A.C.; Greenwood, Dazza; Lee, D.K.; Overbey, D.R.; Rome, J.A.; Schechter, D. E.; Wilson, C.T.

doi:10.1016/j.jnucmat.2004.10.165

Cited by 52 publications

(35 citation statements)

References 10 publications

(7 reference statements)

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“…Here, we choose the HD as an example for our comparative studies. Divertor transport studies and numerical and experimental results for the LID are refereed to in [16][17][18][19]. The rotational transform in the edge region of the HD configurations covers many resonances which overlap each other, forming a stochastic layer of ∼10 cm thickness.…”

Section: Divertor Concept and Geometrymentioning

confidence: 99%

Comparative divertor-transport study for helical devices

et al. 2009

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Abstract. Using the island divertors (IDs) of W7-AS and W7-X and the helical divertor (HD) of LHD as examples, the paper presents a comparative divertor transport study for three typical helical devices of different machine-size following two distinct divertor concepts, aiming at identifying common physics issues/effects for mutual validation and combined studies. Based on EMC3/EIRENE simulations supported by experimental results, the paper first reviews and compares the essential transport features of the W7-AS ID and the LHD HD in order to build a base and framework for a predictive study of W7-X. The fundamental role of low-order magnetic islands in both divertor concepts is emphasised. Preliminary EMC3/EIRENE simulation results for W7-X are presented and discussed with respect to W7-AS and LHD in order to show how the individual field and divertor topologies affect the divertor transport and performance. For instance, a high recycling regime, which is absent from W7-AS and LHD, is predicted to exist for W7-X. The paper focuses on identifying and understanding the role of divertors for high density plasma operations in helical devices. In this regard, special attention is paid to investigating the divertor function for controlling intrinsic impurities. Impurity transport behaviour and wall-sputtering processes of CX-neutrals are studied under different divertor plasma conditions. A divertor retention effect on intrinsic impurities at high SOL collisonalities is predicted for all the three devices. The required SOL plasma conditions and the underlying mechanisms are analysed in detail. Numerical results are discussed in conjunction with the experimental observations for high density divertor plasmas in W7-AS and LHD. Different SOL transport regimes are numerically identified for the standard divertor configuration of W7-X and the possible consequences on high density plasmas are assessed. All the EMC3-EIRENE simulations presented in this paper are based on vacuum fields and comparisons with local diagnostics are made for low-ß plasmas.

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Section: Divertor Concept and Geometrymentioning

confidence: 99%

Comparative divertor-transport study for helical devices

et al. 2009

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“…As a result, magnetic islands represent a loss of confinement volume [9][10][11][12][13]. In the edge of stellarators, however, they serve a useful function by diverting the field so as to separate the hot plasma in the confinement region from the material surfaces [14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Theory and observations of magnetic islands

2009

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Abstract. Islands are a ubiquitous feature of magnetically confined plasmas. They arise as the result of plasma instabilities as well as imperfections in the coils. Effective techniques have been developed for keeping their width small. Even thin islands, however, are observed to have nonlocal effects on the profiles of rotation and current. This has stimulated interest in using magnetic islands to control plasma transport. They are also of interest as a tool to improve our understanding of microscopic plasma dynamics.

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“…The plasma experiments have been conducted under two divertor configurations in LHD. One is the helical divertor (HD) [2][3][4][5][6][7][8][9][10] and the other is the local island divertor (LID) [11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%