A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D

Chen, J.; Ding, W. X.; Brower, D. L.; Finkenthal, D.; Boivin, R.

doi:10.1063/1.5035276

Title: A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D

Journal Article · Fri Jul 06 00:00:00 EDT 2018 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.5035276· OSTI ID:1609205

^[1]; Ding, W. X. ^[1]; Brower, D. L. ^[1]; Finkenthal, D. ^[2]; Boivin, R. ^[3]

Univ. of California, Los Angeles, CA (United States)
Palomar Scientific Instruments, San Marcos, CA (United States)
General Atomics, San Diego, CA (United States)

A Faraday-effect-based radial-interferometer-polarimeter diagnostic has been developed to explore fast magnetic dynamics in high-performance DIII-D plasmas. The instrument measures radial magnetic field perturbations using three chords positioned near the magnetic axis. Newly developed solid-state sources operating at 650 GHz provide phase noise down to 0.01°/$$\sqrt{kHz}$$ and tunable bandwidth up to 10 MHz. Various systematic errors which can contaminate the polarimetric measurement have been investigated in detail. Distortion of circular polarization due to non-ideal optical components is calibrated using a rotating quarter wave plate technique. The impact of perpendicular magnetic field, i.e., the Cotton-Mouton effect, is evaluated. The error due to non-collinearity of probe beams is minimized to less than 0.5° for electron density up to 7 × 10¹⁹ m^-3 by alignment optimization. Optical feedback, due to multiple reflections induced by the double-pass configuration, is identified and reduced. Lastly, coherent and broadband high-frequency magnetic fluctuations for DIII-D H-mode plasmas are observed.

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Research Organization:: General Atomics, San Diego, CA (United States); Univ. of California, San Diego, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Grant/Contract Number:: FC02-04ER54698; FG03-01ER54615; FG03-01ER546151

OSTI ID:: 1609205

Alternate ID(s):: OSTI ID: 1459237

Journal Information:: Review of Scientific Instruments, Vol. 89, Issue 10; ISSN 0034-6748

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 7 works

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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
instruments & instrumentation
physics
birefringence
polarimeters
Faraday effect
lasers
electron density
optical polarimetry
interferometry

Title: A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D

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