Measurement of Turbulence Decorrelation during Transport Barrier Evolution in a High Temperature Fusion Plasma
Authors: R. Nazikian, K. Shinohara, G.J. Kramer, E. Valeo, K. Hill, T.S. Hahm, G. Rewoldt, S. Ide, Y. Koide, Y. Oyama, H. Shirai, and W. Tang
Date of PPPL Report: May 2005
Published in: Physical Review Letters 94:13 (8 April 2005) Article No. 135002/1-4.
A low power polychromatic beam of microwaves is used to diagnose the behavior of turbulent fluctuations in the core of the JT-60U tokamak during the evolution of the internal transport barrier. A continuous reduction in the size of turbulent structures is observed concomitant with the reduction of the density scale length during the evolution of the internal transport barrier. The density correlation length decreases to the order of the ion gyroradius, in contrast to the much longer scale lengths observed earlier in the discharge, while the density fluctuation level remain similar to the level before transport barrier formation.