%0 Journal Article
%A Rapp, J.
%A Biel, W.
%A Gerhauser, H.
%A Huber, A.
%A Koslowski, H. R.
%A Lehnen, M.
%A Philipps, V.
%A Pospieszczyk, A.
%A Reiser, D.
%A Samm, U.
%A Sergienko, G.
%A Tokar, M. Z.
%A Zagorski, R.
%T Operational limits under different wall conditions on TEXTOR-94
%J Journal of nuclear materials
%V 290-293
%@ 0022-3115
%C Amsterdam [u.a.]
%I Elsevier Science
%M PreJuSER-37979
%P 1148 - 1154
%D 2001
%Z Record converted from VDB: 12.11.2012
%X 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.
%K J (WoSType)
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000167676700229
%R 10.1016/S0022-3115(00)00553-5
%U https://juser.fz-juelich.de/record/37979