Multifaceted asymmetric radiation from the edge-like asymmetric radiative collapse of density limited plasmas in the Large Helical Device

Neutral beam injection heated discharges at the density limit in the Large Helical Device [O. Motojima, H. Yamada, A. Komori et al., Phys. Plasmas 6, 1843 (1999)] are terminated with asymmetric radiative collapse (ARC) exhibiting several properties in common with the MARFE (multifaceted asymmetric radiation from the edge) phenomenon: (1) A highly poloidally asymmetric radiation profile which is stronger on the inboard side. (2) This asymmetry is well correlated with the signal from the multichord interferometer. (3) Moreover, evidence from several diagnostics at different toroidal locations supports the possibility that ARC may be toroidally symmetric. However in contrast to MARFE, ARC is only observed in the period just prior to the quench of the plasma.

[1]  Bruce Lipschultz,et al.  Review of MARFE phenomena in tokamaks , 1987 .

[2]  T. Petrie,et al.  The role of thermal instabilities in limiting the density in DIII-D , 2000 .

[3]  S. Wolfe,et al.  Marfe: an edge plasma phenomenon , 1984 .

[4]  L. Giannone,et al.  Physics of the density limit in the W7-AS stellarator , 2000 .

[5]  K. Kawahata,et al.  Plasma characteristics of long-pulse discharges heated by neutral beam injection in the Large Helical Device , 2000 .

[6]  V. Erckmann,et al.  H-mode of W7-AS stellarator , 1994 .

[7]  N. Ohyabu.  Density limit in tokamaks , 1979 .

[8]  H. Takeuchi,et al.  MARFE phenomena on neutral beam heated JT-60 plasmas , 1990 .

[9]  W. Stacey.  Thermal stability of the tokamak plasma edge , 1997 .

[10]  Y. Takeiri,et al.  Scalings of energy confinement and density limit in stellarator/heliotron devices , 1990 .

[11]  W. Stacey.  Density limits in tokamaks , 1997 .

[12]  K. F. Mast,et al.  Disruptions in JET , 1989 .

[13]  Georg Kühner,et al.  Radiation measurements and modeling of the density limit on the W7-AS stellarator , 1999 .

[14]  F. C. Schüller,et al.  Density limits in TEXTOR-94 auxiliary heated discharges , 1999 .

[15]  M. Hughes,et al.  A study of the effect of impurity radiation from the peripheral plasma of a tokamak reactor , 1981 .

[16]  Kozo Yamazaki,et al.  Initial physics achievements of large helical device experiments , 1999 .

[17]  H. Wobig,et al.  On Radiative Density Limits and Anomalous Transport in Stellarators , 2000 .

[18]  K. Itoh,et al.  Detached and attached plasma in stellarators , 1988 .

[19]  K. Kawahata,et al.  Far infrared laser interferometer system on the Large Helical Device , 1999 .

[20]  W. Schneider,et al.  Thermal instabilities and poloidal asymmetries in the tokamak edge plasma , 1986 .