NSTX-U High-k Scattering and FIReTIP Diagnostic System Status

A 693 GHz poloidal high-k scattering system will replace a previous 280 GHz tangential scattering system to study high-k electron density fluctuations on NSTX-U. The probe beam launched from Bay G is aimed toward Bay L, where receiver optics image the scattered waves onto an 8-channel receiver. The reduced wavelength and new poloidal scattering geometry extend poloidal wavenumber measurement from the previous limit of 7 cm^-1 up to >30 cm^-1. Steerable launch optics coupled with receiver optics mounted on a 4-axis receiver carriage allow the scattering volume to be placed from r⁄a=0.3 out to the pedestal region. The Far Infrared Tangential Interferometer/Polarimeter (FIReTIP) will provide time-resolved, chord-integrated electron density and tangential B-field data on NSTX-U. The FIReTIP beam will enter on Bay G, reflect from a Bay B internal retroreflector, and exit back through Bay G. A HeNe interferometer will correct the FIReTIP data for mechanical motions along the shared chord and provide density feedback control signals to the NSTX-U Real-time Control and Protection system. Details of both diagnostic systems, including installation and commissioning schedules, will be presented.