Effect of localised electron cyclotron heating on energy confinement and MHD in TCV
Electron cyclotron (EC) heating experiments were started on low elongation plasmas, to study EC dominated confinement properties. For these studies, the EC power was an order of magnitude larger than the Ohmic power during electron cyclotron resonance heating (ECRH). The power degradation exponent is generally as observed: alpha(p) approximately equals. However, there are indications that the power degradation may also depend on the safety factor q(a) and plasma triangularity delta(a). The coupled power deduced from diamagnetic coil measurements is compared to the absorbed power deduced from ray tracing and transport calculations. Both generally indicate a fraction of missing power. There is little dependence of tau(Ee) on the heating location provided that it is inside the q=1 surface. For heating on q=1, the sawteeth period is maximised, leading to the highest obtainable central temperatures. As the heating location is moved further outside the q=1 surface, tau(Ee) decreases. These observations stress the role of the q=1 surface in confinement. Different relaxations and magnetohydrodynamic (MHD) activities are triggered when scanning or sweeping the location of power deposition. The link between the measured confinement times and the sawtooth relaxation resulting from different deposition locations will be emphasized.
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: 199811265 / Last updated on: 1998-10-27
Original language: en
Available languages: en