DENSITY BUILD-UP IN JET
Density buildup in JET is analyzed. Penetration of the discharge by cold neutrals making multiple charge-exchange reactions is not sufficient to give the observed fuelling rate. Analysis of density sawtooth behavior shows that the neoclassical pinch suffices to refuel the core of the discharge between sawtooth disruptions. Hollow profiles (dn/dr>o) are seldom observed, even during rapid increases in edge sources, suggesting that a pinch mechanism extends well beyond the core region. Diffusion is the dominant process in the edge plasma, as evidenced by large recycling in this region. It is thus necessary to postulate an edge neutral source consisting of cold and hot components. The cold population is heated while recycling. The hot neutrals (20 eV) are then able to penetrate to a radius where a pinch is operative. The role of neoclassical pinch in sustaining the whole density profile has been assessed, and comparisons with empirical models made. The role of impurities is also investigated.
Bibliographic Reference: 27TH ANNUAL MEETING OF THE DIVISION OF PLASMA PHYSICS, SAN DIEGO (USA) NOV. 4-8, 1985 PAPER 6P52, P.1525
Record Number: 1989124103900 / Last updated on: 1987-01-01
Available languages: en