Poloidally asymmetric plasma response with ECH deposition near q=1 in TCV

A small component of ECCD exists when heating off-axis with no toroidal injection due to the field helicity. The sign of the ECCD will change depending on the absorption location in a poloidal plane, the beam injection relative to delB(vac), and the direction of the toroidal magnetic field. The importance of the ECCD component can be confirmed by the behavior of the sawteeth when the ECH deposition crosses the q=1 surface. The sawtooth period is very sensitive to the local shear at q=1 and it is shown that difference in sawtooth period when heating above and below the midplane are consistent with the presence of a small ECCD component. Experiments have also shown that the sawtooth period is strongly determined by the absorbed ECH power near the q=1 surface. In particular significant changes in the sawtooth period are observed as the absorption location is varied on a scale smaller than the beam spot size. A narrow region of rapidly changing confinement is shown to exist near the q=1 surface to be located outside the q=1 surface by a factor of 1.3 in radii. The region can be used as a method for measuring the beam deposition width in the plasma. (C) 2001 Elsevier Science B.V. All rights reserved.


Published in:
Fusion Engineering and Design, 53, 241-248
Year:
2001
ISSN:
0920-3796
ISBN:
0920-3796
Laboratories:
SPC
CRPP




 Record created 2008-04-16, last modified 2018-09-13


Rate this document:

Rate this document:
1
2
3
 
(Not yet reviewed)