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, and the direction of the toroidally magnetic field. The importance of the ECCD component can be confirmed by the behaviour of the sawteeth when the ECH deposition crosses the q=1 surface. 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 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 density near the q=1 surface. In particular significant changes in the sawtooth period are observed as the absorption location is varied on a smaller scale than the beam spot size. An energy barrier associated with q=1 surface is shown to be located outside the q=1 surface by a factor of 1.3 in radii. The barrier can be used as a method for measuring the beam deposition width in the plasma.
Bibliographic Reference: Paper presented: IAEA Technical Committee meeting on ECRH Physics and Technology for Fusion devices and EC-11, Oh-ari (JP), 4-8th October (1999)
Availability: Available from Librarian, Centre de Recherches en Physique des Plasmas, EPF, Lausanne (CH)
ISBN: ISSN 0458-5895
Record Number: 199911519 / Last updated on: 1999-10-29
Original language: en
Available languages: en