title: Far-infrared polarimetry diagnostic for measurement of internal magnetic field dynamics and fluctuations in the C-MOD Tokamak (invited).
abstract: A laser-based (2.55 THz) mulitchord polarimeter is now operational on Alcator C-Mod and is used to make measurements of the internal magnetic field structure as well as plasma fluctuations. The polarimeter is designed to measure the Faraday effect for high-field (up to 8.3 T) and high-density (up to 5 × 10(20) m(-3)) ITER relevant plasma conditions. Initial 3 chord tests are consistent with magnetic equilibrium reconstructions and indicate no measurable contamination from the toroidal magnetic field due to the Cotton-Mouton effect or misalignment. Time response of <1 μs enables the measurement of fast equilibrium temporal dynamics as well as high-frequency fluctuations.
authors.affiliation: University of California-Los Angeles, Los Angeles, California 90095, USA. wfbergerson@ucla.edu
authors.forename: W F
authors.initials: WF
authors.lastname: Bergerson
authors.forename: P
authors.initials: P
authors.lastname: Xu
authors.forename: J H
authors.initials: JH
authors.lastname: Irby
authors.forename: D L
authors.initials: DL
authors.lastname: Brower
authors.forename: W X
authors.initials: WX
authors.lastname: Ding
authors.forename: E S
authors.initials: ES
authors.lastname: Marmar