TY  - JOUR
AU  - Rapp, J.
AU  - Biel, W.
AU  - Gerhauser, H.
AU  - Huber, A.
AU  - Koslowski, H. R.
AU  - Lehnen, M.
AU  - Philipps, V.
AU  - Pospieszczyk, A.
AU  - Reiser, D.
AU  - Samm, U.
AU  - Sergienko, G.
AU  - Tokar, M. Z.
AU  - Zagorski, R.
TI  - Operational limits under different wall conditions on TEXTOR-94
JO  - Journal of nuclear materials
VL  - 290-293
SN  - 0022-3115
CY  - Amsterdam [u.a.]
PB  - Elsevier Science
M1  - PreJuSER-37979
SP  - 1148 - 1154
PY  - 2001
N1  - Record converted from VDB: 12.11.2012
AB  - 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.
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000167676700229
DO  - DOI:10.1016/S0022-3115(00)00553-5
UR  - https://juser.fz-juelich.de/record/37979
ER  -