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

Abstract

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 × 10 19 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.

Authors:
ORCiD logo [1];  [1];  [1];  [2];  [3]
  1. Univ. of California, Los Angeles, CA (United States)
  2. Palomar Scientific Instruments, San Marcos, CA (United States)
  3. General Atomics, San Diego, CA (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States); Univ. of California, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1609205
Alternate Identifier(s):
OSTI ID: 1459237
Grant/Contract Number:  
FC02-04ER54698; FG03-01ER54615; FG03-01ER546151
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 89; Journal Issue: 10; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; instruments & instrumentation; physics; birefringence; polarimeters; Faraday effect; lasers; electron density; optical polarimetry; interferometry

Citation Formats

Chen, J., Ding, W. X., Brower, D. L., Finkenthal, D., and Boivin, R. A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D. United States: N. p., 2018. Web. doi:10.1063/1.5035276.
Chen, J., Ding, W. X., Brower, D. L., Finkenthal, D., & Boivin, R. A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D. United States. https://doi.org/10.1063/1.5035276
Chen, J., Ding, W. X., Brower, D. L., Finkenthal, D., and Boivin, R. Fri . "A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D". United States. https://doi.org/10.1063/1.5035276. https://www.osti.gov/servlets/purl/1609205.
@article{osti_1609205,
title = {A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D},
author = {Chen, J. and Ding, W. X. and Brower, D. L. and Finkenthal, D. and Boivin, R.},
abstractNote = {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.},
doi = {10.1063/1.5035276},
url = {https://www.osti.gov/biblio/1609205}, journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 10,
volume = 89,
place = {United States},
year = {2018},
month = {7}
}

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Far-infrared polarimetry diagnostic for measurement of internal magnetic field dynamics and fluctuations in the C-MOD Tokamak (invited)
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Method for correction of measured polarization angles from motional Stark effect spectroscopy for the effects of electric fields
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High spatial resolution interferometry and polarimetry in hot plasmas
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Effects of stray lights on Faraday rotation measurement for polarimeter-interferometer system on EAST
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journal, August 2016


Faraday-effect polarimeter diagnostic for internal magnetic field fluctuation measurements in DIII-D
journal, August 2016


Impact of the Cotton–Mouton effect on Faraday polarimetry measurements using circular polarization
journal, June 2018