Helicon generated plasma fluctuations and low-frequency turbulence and flows in the DIII-D tokamak

Localized internal DIII-D plasma measurements are presented from broadband plasma fluctuations around 476 MHz (driven by an external helicon wave antenna), turbulence, Alfvén eigenmodes (AE’s) and low harmonic ion cyclotron emission (ICE; f ~ 2f_ci, 3f_ci) from a unique E-band DBS system. The observation of broadband fluctuations around 476 MHz is conjectured to be due to interaction of the injected helicon with local plasma turbulence. These observations demonstrate the capabilities of a new system which extends application of DBS to a high-frequency spectral domain (using adjustable frequency down conversion of a selectable frequency range <~1GHz) while allowing simultaneous measurement of turbulence (f < 10 MHz) and poloidal turbulence flow velocity. The new system has good temporal resolution (sub-millisecond) and excellent wavenumber coverage (k_θ ~ 1-20 cm^-1 and k_r ~ 20-30 cm^-1) along with selectable O- or X-mode polarization launch. The DBS helicon measurements will be used to validate modeling tools (e.g., GENRAY and AORSA) that predict helicon wave propagation, absorption and current drive location for the newly installed helicon current drive system on DIII-D.