Journal Article

PreJuSER-37979

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Operational limits under different wall conditions on TEXTOR-94

Rapp, J.FZJ* ; Biel, W.FZJ* ; Gerhauser, H.FZJ* ; Huber, A.FZJ* ; Koslowski, H. R.FZJ* ; Lehnen, M.FZJ* ; Philipps, V.FZJ* ; Pospieszczyk, A.FZJ* ; Reiser, D.FZJ* ; Samm, U.FZJ* ; Sergienko, G. ; Tokar, M. Z.FZJ* ; Zagorski, R.

2001
Elsevier Science Amsterdam [u.a.]

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Please use a persistent id in citations: doi:10.1016/S0022-3115(00)00553-5

Abstract: Generally the operational range of tokamaks is limited by the beta and the density limit. Experimentally it was found, that the appearance of MARFEs [B. Lipschultz, J. Nucl. Mater. 145-147 (1987) 15] inhibited an increase of the density significantly above the so-called Greenwald density (n(GW)) [M. Greenwald et al., Nucl. Fus. 28 (1988) 2199]. In TEXTOR-94 the onset of MARFEs has been investigated under different wall conditions. With fresh siliconization and fresh boronization the appearance of MARFEs can be postponed to higher densities (N-GW = (n) over bar (e/)n(GW) = 1.7). At those high densities (n) over bar (e) = 8 x 10(19) m(-3) the Z(eff) is reduced to 1.3. But as important as the reduction of the global impurity content is the suppressed carbon release on the high-field-side (HFS) just after wall conditioning, Modeling of the MARFE onset by the codes B2-Eirene and TECXY demonstrates that an instability on the HFS due to deuterium recycling and radiation only leads to the formation of MARFEs at higher line-averaged densities in comparison to calculations which include carbon impurities. Complete suppression of MARFEs has been achieved by controlled displacement of the plasma column to the low-field-side (LFS), which reduces the local recycling and impurity release at the inner bumper limiter. This resulted in the highest densities achieved at TEXTOR-94 of N-GW = 2.1 independent of wall conditions. In this case the maximum achievable density is limited by a radiative collapse. (C) 2001 Published by Elsevier Science B.V.

Keyword(s): J ; coating (auto) ; impurity (auto) ; plasma properties (auto)

Note: Record converted from VDB: 12.11.2012

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Contributing Institute(s):

1. Institutsbereich I (IPP-1)
2. Institutsbereich II (IPP-2)

Research Program(s):

1. Instabilitäten und transportvorgänge im Plasma (22.76.0)
2. Teilchen- und Energietransport in der Plasmarandschicht (22.88.5)
3. Apparative Methoden zum Teilchenkreislauf und zur Leistungsauskopplung (22.73.5)

Appears in the scientific report 2001

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