title: Simultaneous measurement of magnetic and density fluctuations via cross-polarization scattering and Doppler backscattering on the DIII-D tokamak.
abstract: An upgraded cross-polarization scattering (CPS) system for the simultaneous measurement of internal magnetic fluctuations B̃ and density fluctuations ñ is presented. The system has eight radial quadrature channels acquired simultaneously with an eight-channel Doppler backscattering system (measures density fluctuations ñ and flows). 3-D ray tracing calculations based on the GENRAY ray tracing code are used to illustrate the scattering and geometric considerations involved in the CPS implementation on DIII-D. A unique quasi-optical design and IF electronics system allow direct comparison of B̃ and ñ during dynamic or transient plasma events (e.g., Edge Localized Modes or ELMs, L to H-mode transitions, etc.). The system design allows the interesting possibility of both magnetic-density (B̃-ñ) fluctuation and magnetic-temperature (B̃-T̃) fluctuation cross-phase measurements suitable for detailed tests of turbulence simulations.
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90098, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Rhodes
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90098, USA.
authors.forename: K
authors.initials: K
authors.lastname: Barada
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90098, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Peebles
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90098, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Crocker