Simultaneous High-k Scattering and Microwave Imaging Reflectometry on NSTX-U*

An 8-channel 693 GHz poloidal high-k scattering system is under development, replacing a 5-channel 280 GHz toroidal scattering system, to study high-k density fluctuations on NSTX-U. The far-infrared probe beam is launched from Bay G towards Bay L, where large aperture optics collect radiation at 8 simultaneous scattering angles ranging from 2 to 15°. This yields measurement of poloidal wavenumbers from 7 cm^-1 to >40 cm^-1, while translatable optics allow placement of the scattering volume from r/a = 0.1 out to the pedestal region (r/a ~ 0.99). A microwave imaging reflectometry (MIR) system will co-exist with the High-k Scattering system on Bay L, with MIR optics positioned above that of the scattering system, to monitor low-k_θ (< 3 cm^-1) density fluctuations. Details of the 5×4 channel (5 poloidal, 4 radial) MIR system, spanning frequencies of 51 to 75 GHz, will be presented together with that of the High-k Scattering system.