Microwave scattering system design for ρ _e scale turbulence measurements on NSTX

Despite suppression of ρ _i scale turbulent fluctuations, electron thermal transport remains anomalous in NSTX. For this reason, a microwave scattering system will be deployed to directly observe the ω and k spectra of ρ _e scale turbulent fluctuations and characterize the effect on electron thermal transport. The scattering system will employ a Gaussian probe beam produced by a high power 280 GHz microwave source. A five-channel heterodyne detection system will measure radial turbulent spectra in the range k _r|=Q-20 cm ^-1. Inboard and outboard launch configurations cover most of the normalized minor radius. Improved spatial localization of measurements is achieved with low aspect ratio and high magnetic shear configurations. This article will address the global design of the scattering system, such as choice of frequency, size, launching system, and detection system.