title: Faraday-effect polarimeter diagnostic for internal magnetic field fluctuation measurements in DIII-D.
abstract: Motivated by the need to measure fast equilibrium temporal dynamics, non-axisymmetric structures, and core magnetic fluctuations (coherent and broadband), a three-chord Faraday-effect polarimeter-interferometer system with fast time response and high phase resolution has recently been installed on the DIII-D tokamak. A novel detection scheme utilizing two probe beams and two detectors for each chord results in reduced phase noise and increased time response [δb ∼ 1G with up to 3 MHz bandwidth]. First measurement results were obtained during the recent DIII-D experimental campaign. Simultaneous Faraday and density measurements have been successfully demonstrated and high-frequency, up to 100 kHz, Faraday-effect perturbations have been observed. Preliminary comparisons with EFIT are used to validate diagnostic performance. Principle of the diagnostic and first experimental results is presented.
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: W X
authors.initials: WX
authors.lastname: Ding
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Brower
authors.affiliation: Palomar Scientific Instruments, San Marcos, California 92069, USA.
authors.forename: D
authors.initials: D
authors.lastname: Finkenthal
authors.affiliation: General Atomics, San Diego, California 92186, USA.
authors.forename: C
authors.initials: C
authors.lastname: Muscatello
authors.affiliation: General Atomics, San Diego, California 92186, USA.
authors.forename: D
authors.initials: D
authors.lastname: Taussig
authors.affiliation: General Atomics, San Diego, California 92186, USA.
authors.forename: R
authors.initials: R
authors.lastname: Boivin