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

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 × 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.

Authors:

^[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)

Publication Date:: Fri Jul 06 00:00:00 EDT 2018

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:: 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.

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                    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

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                    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.

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@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},

  journal      = {Review of Scientific Instruments},

  number       = 10,

  volume       = 89,

  place        = {United States},

  year         = {Fri Jul 06 00:00:00 EDT 2018},

  month        = {Fri Jul 06 00:00:00 EDT 2018}

}

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

Abstract

Citation Formats

High resolution polarimeter-interferometer system for fast equilibrium dynamics and MHD instability studies on Joint-TEXT tokamak (invited) journal, November 2014

Collinearity alignment of probe beams in a laser-based Faraday effect diagnostic journal, October 2012

Overview of gyrokinetic studies of finite- β microturbulence journal, June 2015

Theoretical and numerical evaluation of polarimeter using counter-circularly-polarized-probing-laser under the coupling between Faraday and Cotton-Mouton effect journal, April 2016

Bifurcation of quiescent H-mode to a wide pedestal regime in DIII-D and advances in the understanding of edge harmonic oscillations journal, June 2017

Experimental validation of Mueller-Stokes theory and investigation of the influence of the Cotton-Mouton effect on polarimetry in a magnetized fusion plasma journal, October 2013

Measurement of Internal Magnetic Field Fluctuations in a Reversed-Field Pinch by Faraday Rotation journal, January 2003

Far-infrared polarimetry diagnostic for measurement of internal magnetic field dynamics and fluctuations in the C-MOD Tokamak (invited) journal, October 2012

Approximate method to extract the pure Faraday and Cotton–Mouton effects from polarimetry measurements in a tokamak journal, July 2004

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Method for correction of measured polarization angles from motional Stark effect spectroscopy for the effects of electric fields journal, November 2016

High spatial resolution interferometry and polarimetry in hot plasmas journal, June 1995

Effects of stray lights on Faraday rotation measurement for polarimeter-interferometer system on EAST journal, January 2018

Spurious oscillations affecting FIR polarimetry measurements journal, October 2004

Laser polarimetric measurement of equilibrium and fluctuating magnetic fields in a reversed field pinch (invited) journal, March 2003

Progress of the in-building J-TEXT FIR three-wave polarimeter journal, January 2012

Demonstration of two-laser P olarimeter- I nterferomet er ( PIer ) scheme for simultaneous measurements of Faraday rotation angle and electron density on HL-2A journal, November 2017

Multichannel far-infrared polarimeter-interferometer system on the MST reversed field pinch journal, January 2001

Tests of a two-color interferometer and polarimeter for ITER density measurements journal, October 2017

A real-time laser feedback control method for the three-wave laser source used in the polarimeter-interferometer diagnostic on Joint-TEXT tokamak journal, December 2014

Measurement of local, internal magnetic fluctuations via cross-polarization scattering in the DIII-D tokamak (invited) journal, August 2016

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

Initial measurements of plasma current and electron density profiles using a polarimeter/interferometer (POINT) for long pulse operation in EAST (invited) journal, October 2016

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

High resolution polarimeter-interferometer system for fast equilibrium dynamics and MHD instability studies on Joint-TEXT tokamak (invited)
journal, November 2014

Collinearity alignment of probe beams in a laser-based Faraday effect diagnostic
journal, October 2012

Overview of gyrokinetic studies of finite- β microturbulence
journal, June 2015

Theoretical and numerical evaluation of polarimeter using counter-circularly-polarized-probing-laser under the coupling between Faraday and Cotton-Mouton effect
journal, April 2016

Bifurcation of quiescent H-mode to a wide pedestal regime in DIII-D and advances in the understanding of edge harmonic oscillations
journal, June 2017

Experimental validation of Mueller-Stokes theory and investigation of the influence of the Cotton-Mouton effect on polarimetry in a magnetized fusion plasma
journal, October 2013

Measurement of Internal Magnetic Field Fluctuations in a Reversed-Field Pinch by Faraday Rotation
journal, January 2003

Far-infrared polarimetry diagnostic for measurement of internal magnetic field dynamics and fluctuations in the C-MOD Tokamak (invited)
journal, October 2012

Approximate method to extract the pure Faraday and Cotton–Mouton effects from polarimetry measurements in a tokamak
journal, July 2004

A far-infrared ‘polari-interferometer’ for simultaneous electron density and magnetic field measurements in plasmas
journal, December 1978

Method for correction of measured polarization angles from motional Stark effect spectroscopy for the effects of electric fields
journal, November 2016

High spatial resolution interferometry and polarimetry in hot plasmas
journal, June 1995

Effects of stray lights on Faraday rotation measurement for polarimeter-interferometer system on EAST
journal, January 2018

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journal, October 2004

Laser polarimetric measurement of equilibrium and fluctuating magnetic fields in a reversed field pinch (invited)
journal, March 2003

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journal, November 2017

Multichannel far-infrared polarimeter-interferometer system on the MST reversed field pinch
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