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.