β-Suppression of Alfvén Cascade Modes in the National Spherical Torus Experiment

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The coupling of Alfvén Cascade (AC) modes or reversed-shear Alfvén eigenmodes (rsAE) to Geodesic Acoustic Modes (GAM) implies that the range of the AC frequency sweep is reduced as the electron β is increased. This model provides an explanation for the otherwise surprising absence of AC modes in reverse shear NSTX plasmas, given the rich spectrum of beam-driven instabilities typically seen in NSTX. In experiments done at very low β to investigate this prediction, AC modes were seen, and as the βe was increased from shot to shot, the range of the AC frequency sweep was reduced, in agreement with ... continued below

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Fredrickson, E D; Gorelenkov, N N; Heidbrink, W W; Kubota, S; Levinton, F M; Yuh, H et al. June 29, 2007.

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Description

The coupling of Alfvén Cascade (AC) modes or reversed-shear Alfvén eigenmodes (rsAE) to Geodesic Acoustic Modes (GAM) implies that the range of the AC frequency sweep is reduced as the electron β is increased. This model provides an explanation for the otherwise surprising absence of AC modes in reverse shear NSTX plasmas, given the rich spectrum of beam-driven instabilities typically seen in NSTX. In experiments done at very low β to investigate this prediction, AC modes were seen, and as the βe was increased from shot to shot, the range of the AC frequency sweep was reduced, in agreement with this theoretical prediction.

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660Kb

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  • Report No.: PPPL-4253
  • Grant Number: DE-ACO2-76CHO3073
  • Office of Scientific & Technical Information Report Number: 962716
  • Archival Resource Key: ark:/67531/metadc925984

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  • June 29, 2007

Added to The UNT Digital Library

  • Nov. 13, 2016, 7:26 p.m.

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  • Dec. 13, 2016, 12:17 p.m.

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Fredrickson, E D; Gorelenkov, N N; Heidbrink, W W; Kubota, S; Levinton, F M; Yuh, H et al. β-Suppression of Alfvén Cascade Modes in the National Spherical Torus Experiment, report, June 29, 2007; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc925984/: accessed September 22, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.