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Title: Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma

Abstract

A shear Alfvén wave at slightly below the ion-cyclotron frequency overcomes the ion-cyclotron damping and grows because of the strong anisotropy of the ion temperature in the magnetic mirror configuration, and is called the Alfvén ion-cyclotron (AIC) wave. Density fluctuations caused by the AIC waves and the ion-cyclotron range of frequencies (ICRF) waves used for ion heating have been detected using a reflectometer in a wide radial region of the GAMMA 10 tandem mirror plasma. Various wave-wave couplings are clearly observed in the density fluctuations in the interior of the plasma, but these couplings are not so clear in the magnetic fluctuations at the plasma edge when measured using a pick-up coil. A radial dependence of the nonlinearity is found, particularly in waves with the difference frequencies of the AIC waves; bispectral analysis shows that such wave-wave coupling is significant near the core, but is not so evident at the periphery. In contrast, nonlinear coupling with the low-frequency background turbulence is quite distinct at the periphery. Nonlinear coupling associated with the AIC waves may play a significant role in the beta- and anisotropy-limits of a mirror-confined plasma through decay of the ICRF heating power and degradation of the plasma confinementmore » by nonlinearly generated waves.« less

Authors:
; ; ; ; ; ; ; ; ; ; ;  [1]
  1. Plasma Research Center, University of Tsukuba, Tsukuba 305-8577 (Japan)
Publication Date:
OSTI Identifier:
22490114
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal Issue: 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALFVEN WAVES; ANISOTROPY; COUPLINGS; CYCLOTRON FREQUENCY; DAMPING; DENSITY; EXCITATION; FLUCTUATIONS; GAMMA 10 DEVICES; ICR HEATING; ION CYCLOTRON-RESONANCE; ION TEMPERATURE; MAGNETIC MIRROR CONFIGURATIONS; NONLINEAR PROBLEMS; PLASMA; PLASMA CONFINEMENT; TURBULENCE

Citation Formats

Ikezoe, R., E-mail: ikezoe@prc.tsukuba.ac.jp, Ichimura, M., Okada, T., Hirata, M., Yokoyama, T., Iwamoto, Y., Sumida, S., Jang, S., Takeyama, K., Yoshikawa, M., Kohagura, J., Shima, Y., and Wang, X. Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma. United States: N. p., 2015. Web. doi:10.1063/1.4930216.
Ikezoe, R., E-mail: ikezoe@prc.tsukuba.ac.jp, Ichimura, M., Okada, T., Hirata, M., Yokoyama, T., Iwamoto, Y., Sumida, S., Jang, S., Takeyama, K., Yoshikawa, M., Kohagura, J., Shima, Y., & Wang, X. Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma. United States. https://doi.org/10.1063/1.4930216
Ikezoe, R., E-mail: ikezoe@prc.tsukuba.ac.jp, Ichimura, M., Okada, T., Hirata, M., Yokoyama, T., Iwamoto, Y., Sumida, S., Jang, S., Takeyama, K., Yoshikawa, M., Kohagura, J., Shima, Y., and Wang, X. 2015. "Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma". United States. https://doi.org/10.1063/1.4930216.
@article{osti_22490114,
title = {Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma},
author = {Ikezoe, R., E-mail: ikezoe@prc.tsukuba.ac.jp and Ichimura, M. and Okada, T. and Hirata, M. and Yokoyama, T. and Iwamoto, Y. and Sumida, S. and Jang, S. and Takeyama, K. and Yoshikawa, M. and Kohagura, J. and Shima, Y. and Wang, X.},
abstractNote = {A shear Alfvén wave at slightly below the ion-cyclotron frequency overcomes the ion-cyclotron damping and grows because of the strong anisotropy of the ion temperature in the magnetic mirror configuration, and is called the Alfvén ion-cyclotron (AIC) wave. Density fluctuations caused by the AIC waves and the ion-cyclotron range of frequencies (ICRF) waves used for ion heating have been detected using a reflectometer in a wide radial region of the GAMMA 10 tandem mirror plasma. Various wave-wave couplings are clearly observed in the density fluctuations in the interior of the plasma, but these couplings are not so clear in the magnetic fluctuations at the plasma edge when measured using a pick-up coil. A radial dependence of the nonlinearity is found, particularly in waves with the difference frequencies of the AIC waves; bispectral analysis shows that such wave-wave coupling is significant near the core, but is not so evident at the periphery. In contrast, nonlinear coupling with the low-frequency background turbulence is quite distinct at the periphery. Nonlinear coupling associated with the AIC waves may play a significant role in the beta- and anisotropy-limits of a mirror-confined plasma through decay of the ICRF heating power and degradation of the plasma confinement by nonlinearly generated waves.},
doi = {10.1063/1.4930216},
url = {https://www.osti.gov/biblio/22490114}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 9,
volume = 22,
place = {United States},
year = {Tue Sep 15 00:00:00 EDT 2015},
month = {Tue Sep 15 00:00:00 EDT 2015}
}