2D turbulence imaging in DIII-D via beam emission spectroscopy

Abstract

Two-dimensional measurements of density fluctuations have been performed in DIII-D using the beam emission spectroscopy diagnostic. The 32 spatial channels are arranged to image a 5 × 6 cm2 (radial×poloidal) region in the plasma cross section, at a nominal 1 cm spatial resolution and separation. The typical decorrelation time, poloidal and radial correlation lengths, as well as a time-averaged flow field plot are obtained from spatial and temporal correlation analyses. A biorthogonal decomposition algorithm is applied to expand the data set into a set of modes that are orthogonal in time and in space, thus providing a simultaneous analysis of the space and time dependencies of fluctuation data. © 2001 American Institute of Physics.