Internal Alfvén eigenmode observations on DIII-D

M. A. Van Zeeland; M. E. Austin; T. N. Carlstrom; T. Deterly; D. K. Finkenthal; C. T. Holcomb; R. J. Jayakumar; G. J. Kramer; M. A. Makowski; G. R. McKee; R. Nazikian; W. A. Peebles; T. L. Rhodes; W. M. Solomon; E. J. Strait

doi:10.1088/0029-5515/46/10/S03

Internal Alfvén eigenmode observations on DIII-D

M. A. Van Zeeland, M. E. Austin, T. N. Carlstrom, T. Deterly, D. K. Finkenthal, C. T. Holcomb, R. J. Jayakumar, G. J. Kramer, M. A. Makowski, G. R. McKee, R. Nazikian, W. A. Peebles, T. L. Rhodes, W. M. Solomon, E. J. Strait

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Abstract

Recent upgrades to many of the diagnostic systems on DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 614) such as the CO₂ interferometer, far-infrared scattering, beam-emission spectroscopy (BES), and quadrature reflectometer have significantly extended their capabilities and made possible the experimental study of Alfvén eigenmodes (AEs) through observation of the AE induced density perturbation. Measurements have revealed the presence of several different classes of AEs in DIII-D discharges including the toroidal Alfvén eigenmode (TAE), reverse shear AE (RSAE or Alfvén cascade) and ellipticity induced Alfvén eigenmode. Based on a simple model for the RSAE frequency, a sensitive diagnostic for the evolution of the minimum magnetic safety factor (q_min) is presented and results are compared with motional Stark effect (MSE) measurements. Strong localization of high toroidal mode number RSAEs to regions near the minimum of the magnetic safety factor is exhibited on the CO₂ interferometer and BES measurements. Based on this observation, a method for providing constraints on the radial location of q_min is demonstrated and a favourable comparison to MSE measurements is made. Detailed measurements of TAEs using a new all-digital large bandwidth two-colour CO₂ interferometer system show a strong asymmetry between vertical and radial viewing interferometer chords confirming previously reported results. Additionally, effects related to line-integrated observations are clearly illustrated by comparison to local BES measurements and potential issues related to this are discussed.

Original language	English (US)
Article number	S03
Pages (from-to)	S880-S887
Journal	Nuclear Fusion
Volume	46
Issue number	10
DOIs	https://doi.org/10.1088/0029-5515/46/10/S03
State	Published - Oct 1 2006

All Science Journal Classification (ASJC) codes

Nuclear and High Energy Physics
Condensed Matter Physics

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10.1088/0029-5515/46/10/S03

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Van Zeeland, M. A., Austin, M. E., Carlstrom, T. N., Deterly, T., Finkenthal, D. K., Holcomb, C. T., Jayakumar, R. J., Kramer, G. J., Makowski, M. A., McKee, G. R., Nazikian, R., Peebles, W. A., Rhodes, T. L., Solomon, W. M., & Strait, E. J. (2006). Internal Alfvén eigenmode observations on DIII-D. Nuclear Fusion, 46(10), S880-S887. Article S03. https://doi.org/10.1088/0029-5515/46/10/S03

@article{3d656119e17d460c90afa1c3b460a32f,

title = "Internal Alfv{\'e}n eigenmode observations on DIII-D",

abstract = "Recent upgrades to many of the diagnostic systems on DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 614) such as the CO2 interferometer, far-infrared scattering, beam-emission spectroscopy (BES), and quadrature reflectometer have significantly extended their capabilities and made possible the experimental study of Alfv{\'e}n eigenmodes (AEs) through observation of the AE induced density perturbation. Measurements have revealed the presence of several different classes of AEs in DIII-D discharges including the toroidal Alfv{\'e}n eigenmode (TAE), reverse shear AE (RSAE or Alfv{\'e}n cascade) and ellipticity induced Alfv{\'e}n eigenmode. Based on a simple model for the RSAE frequency, a sensitive diagnostic for the evolution of the minimum magnetic safety factor (qmin) is presented and results are compared with motional Stark effect (MSE) measurements. Strong localization of high toroidal mode number RSAEs to regions near the minimum of the magnetic safety factor is exhibited on the CO2 interferometer and BES measurements. Based on this observation, a method for providing constraints on the radial location of qmin is demonstrated and a favourable comparison to MSE measurements is made. Detailed measurements of TAEs using a new all-digital large bandwidth two-colour CO2 interferometer system show a strong asymmetry between vertical and radial viewing interferometer chords confirming previously reported results. Additionally, effects related to line-integrated observations are clearly illustrated by comparison to local BES measurements and potential issues related to this are discussed.",

author = "\{Van Zeeland\}, \{M. A.\} and Austin, \{M. E.\} and Carlstrom, \{T. N.\} and T. Deterly and Finkenthal, \{D. K.\} and Holcomb, \{C. T.\} and Jayakumar, \{R. J.\} and Kramer, \{G. J.\} and Makowski, \{M. A.\} and McKee, \{G. R.\} and R. Nazikian and Peebles, \{W. A.\} and Rhodes, \{T. L.\} and Solomon, \{W. M.\} and Strait, \{E. J.\}",

year = "2006",

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doi = "10.1088/0029-5515/46/10/S03",

language = "English (US)",

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pages = "S880--S887",

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T1 - Internal Alfvén eigenmode observations on DIII-D

AU - Van Zeeland, M. A.

AU - Austin, M. E.

AU - Carlstrom, T. N.

AU - Deterly, T.

AU - Finkenthal, D. K.

AU - Holcomb, C. T.

AU - Jayakumar, R. J.

AU - Kramer, G. J.

AU - Makowski, M. A.

AU - McKee, G. R.

AU - Nazikian, R.

AU - Peebles, W. A.

AU - Rhodes, T. L.

AU - Solomon, W. M.

AU - Strait, E. J.

PY - 2006/10/1

Y1 - 2006/10/1

N2 - Recent upgrades to many of the diagnostic systems on DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 614) such as the CO2 interferometer, far-infrared scattering, beam-emission spectroscopy (BES), and quadrature reflectometer have significantly extended their capabilities and made possible the experimental study of Alfvén eigenmodes (AEs) through observation of the AE induced density perturbation. Measurements have revealed the presence of several different classes of AEs in DIII-D discharges including the toroidal Alfvén eigenmode (TAE), reverse shear AE (RSAE or Alfvén cascade) and ellipticity induced Alfvén eigenmode. Based on a simple model for the RSAE frequency, a sensitive diagnostic for the evolution of the minimum magnetic safety factor (qmin) is presented and results are compared with motional Stark effect (MSE) measurements. Strong localization of high toroidal mode number RSAEs to regions near the minimum of the magnetic safety factor is exhibited on the CO2 interferometer and BES measurements. Based on this observation, a method for providing constraints on the radial location of qmin is demonstrated and a favourable comparison to MSE measurements is made. Detailed measurements of TAEs using a new all-digital large bandwidth two-colour CO2 interferometer system show a strong asymmetry between vertical and radial viewing interferometer chords confirming previously reported results. Additionally, effects related to line-integrated observations are clearly illustrated by comparison to local BES measurements and potential issues related to this are discussed.

AB - Recent upgrades to many of the diagnostic systems on DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 614) such as the CO2 interferometer, far-infrared scattering, beam-emission spectroscopy (BES), and quadrature reflectometer have significantly extended their capabilities and made possible the experimental study of Alfvén eigenmodes (AEs) through observation of the AE induced density perturbation. Measurements have revealed the presence of several different classes of AEs in DIII-D discharges including the toroidal Alfvén eigenmode (TAE), reverse shear AE (RSAE or Alfvén cascade) and ellipticity induced Alfvén eigenmode. Based on a simple model for the RSAE frequency, a sensitive diagnostic for the evolution of the minimum magnetic safety factor (qmin) is presented and results are compared with motional Stark effect (MSE) measurements. Strong localization of high toroidal mode number RSAEs to regions near the minimum of the magnetic safety factor is exhibited on the CO2 interferometer and BES measurements. Based on this observation, a method for providing constraints on the radial location of qmin is demonstrated and a favourable comparison to MSE measurements is made. Detailed measurements of TAEs using a new all-digital large bandwidth two-colour CO2 interferometer system show a strong asymmetry between vertical and radial viewing interferometer chords confirming previously reported results. Additionally, effects related to line-integrated observations are clearly illustrated by comparison to local BES measurements and potential issues related to this are discussed.

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VL - 46

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JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 10

M1 - S03

ER -

Internal Alfvén eigenmode observations on DIII-D

Abstract

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