NSTX H-mode measurement in conjunction with gyrocenter shift via FIReTIP system

The Far Infrared Tangential Interferometer/Polarimeter (FIReTIP) which spans the entire plasma is used to measure electron density fluctuations during the low confinement mode (L-mode) to high confinement mode (H-mode) transition on the National Spherical Tokamak Experiment (NSTX). The measured neutral density distribution and the radial electric field evolution are compared to the calculations based on the gyrocenter shift [K. C. Lee, \textit{Phys. Plasmas}\textbf{13}, 062505 (2006)].The statistical analysis of electron density fluctuations measured by the FIReTIP system including data from a newly installed additional channel will be reported. Also, the role of the neutral density gradient on the L to H transition associated with the radial electric field formation and turbulence suppression will be discussed.