Localized turbulence suppression and increased flow shear near the q=2 surface during internal-transport-barrier formation.
Broadband turbulent fluctuations in the plasma density are transiently suppressed when low-order rational q surfaces first appear in negative central magnetic shear plasmas on the DIII-D tokamak, which can lead to the formation of internal transport barriers. Increased localized flow shear is simultaneously observed. It transiently exceeds the measured turbulence decorrelation rate, providing a mechanism to trigger the formation of the transport barrier. This increased flow shear and turbulence suppression propagates radially outward, following the q=2 surface.
University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin, 53706, USA.
M W
MW
Shafer
G R
GR
McKee
M E
ME
Austin
K H
KH
Burrell
R J
RJ
Fonck
D J
DJ
Schlossberg