Observation and interpretation of profile consistency features in the TCV tokomaks
A large variety of plasma conditions has been created in Tokamak à Configuration Variable (TCV). Over the entire range of sawtoothing stationary Ohmic conditions investigated, a remarkable correlation between electron pressure profiles and conductivity profiles was observed. The broadness of the pressure profile is also seen to be strongly correlated with the location of the sawtooth inversion radius. The profiles become broader and the sawtooth inversion radius increases as the average current density is increased. These �profile consistency� features are in apparent agreement with theoretical considerations based on minimum energy states of the plasma or on stationary entropy. Further analysis however shows that the observations can be accounted for by sawtooth activity. Sawtoothing causes a flattening of all profiles inside the sawtooth inversion radius located near the outermost q=1 surface. This core flattening leads to a strong correlation of profile broadness factors which is rather insensitive to the profile shapes in the confinement zone. The location of the outermost q=1 surface given by the model current profile is in excellent agreement with the sawtooth inversion radius from x-ray tomography. We conclude that the observed features cannot be considered as supportive of theories of plasma profile relaxation to states of minimum energy or stationary entropy, but are the consequence of marginal stability to the internal kink mode in the plasma core and neoclassical conductivity in the confinement zone.
Bibliographic Reference: Article: 1998 International Congress on Plasma Physics, 25th EPS Conference on Controlled Fusion and Plasma Physics, Prague (CZ), June 29 � July 3, 1998
Record Number: 199811278 / Last updated on: 1998-10-27
Original language: en
Available languages: en