Characterization of the angular momentum transport in ASDEX

Abstract

Angular momentum transport studies were conducted for nearly stationary situations of about 50 neutral-beam-heated ASDEX discharges under a variety of experimental conditions. Comparison of the confinement times of angular momentum and energy reveals close similarities between thermal and perpendicular momentum transport. Scaling laws are derived for the dependence of the central rotation speed, the momentum confinement time and the radially-averaged momentum diffusivity from the main experimental parameters of L-mode discharges. A well-developed isotope effect, significant power degradation and a favourable current scaling are found to be characteristic features of momentum confinement. The L-mode results are compared with the momentum transport behaviour during the improved confinement phase of H-mode, pellet-fuelled and counter-NI discharges. For the H-mode, the confinement improvement is comparable for momentum and energy. The peaked density profile scenarios exhibit a considerably more pronounced increase in momentum confinement than in energy confinement.