Investigation of core electron gyroscale fluctuations in reverse shear and monotonic-q discharges on NSTX*

Electron thermal transport is the dominant loss mechanism across NSTX profiles and within tokamak internal transport barriers. Reverse shear discharges can exhibit improved electron thermal confinement compared to similar monotonic-q discharges. The improved electron confinement may be associated with reduced electron gyroscale fluctuations. With this motivation, a five-channel scattering system is employed to study core electron gyroscale fluctuations in reverse shear and monotonic-q discharges on NSTX. \ Scattering measurements and the subsequent density fluctuation spectra are localized in both real space and $k$-space. The NSTX scattering system can measure fluctuations with $k_\perp\leq20\mbox{ cm}^{-1}$ and $k_\perp\rho_e\leq0.7$ at five discrete wavenumbers. The $k$- space resolution is $\Delta k_\perp\approx0.7\mbox{ cm}^{-1}$. Steerable optics can position the scattering volume at any location throughout the plasma minor radius. In addition to fluctuation spectra, MSE q-profiles, \texttt{TRANSP} transport calculations and gyrokinetic simulations are also presented.