Measurement of low and intermediate-k internal density and magnetic field turbulence and turbulence flow velocity to understand confinement in NSTX-U plasmas*

In order to better understand the density and magnetic turbulence, turbulence flow, and related transport, three mm-wave diagnostics are lab tested and are being installed in NSTX-U. The first one is a fluctuation reflectometer (FR) system with 8 channels each in Q-band and V-band to investigate the fast ion modes. Both of these FR systems have pair of in-vessel antennas; in each band one of the antennas launches the mm-wave and the other one collects the low-k reflectometer signal. The other two 4-channel E-band systems at a different diagnostics port which share the same quasioptics and electronics are (i) Doppler Backscattering (DBS) system to measure internal low to intermediate-k density fluctuations and their flow velocity and (ii) Cross Polarization Scattering (CPS) system to measure internal and local magnetic field fluctuations. The measured multi-field turbulence is important to understand the confinement properties of NSTX-U plasmas. Raytracing calculations will be shown to understand the fluctuation collection region as well as their wavenumbers. Lab tests of beam profiles as well as the poloidal/toroidal steering capabilities using a piezo-motor driven lens will be presented. The electronics behind the mm wave signal generation as well as detection and further acquisition will also be presented. Different actuators to control polarizer, beam steering and polarization selection will be controlled remotely.