NSTX transport study via density fluctuation measurement of FIReTIP system*

The density fluctuation level measured by the Far Infra Red Tangential Interferometry/Polarimetry (FIReTIP) system on National Spherical Torus Experiment (NSTX) is compared with the energy confinement for the study of turbulence transport. In the 2008 campaign, FIReTIP system was operational with 6 channels including a new channel (CH5) at the tangency radius of 132 cm. Since CH5 measures line integrated density over the turbulence dominated region from the pedestal to Scrape-Off-Layer, the density fluctuation level measured by CH5 provides correlated information with the turbulence induced transport of NSTX boundary. The density fluctuation levels are compared with the stored energy from EFIT equilibria for L-mode and H-mode cases. The possible relation to the turbulent diffusion based on the gyrocenter shift will be discussed.