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Title: Multitude of Core-Localized Shear Alfvén Waves in a High-Temperature Fusion Plasma

Abstract

Evidence is provided for a multitude of discrete frequency Alfvén waves in the core of magnetically confined high-temperature fusion plasmas. Multiple diagnostic instruments verify wave excitation over a wide spatial range from the device size at the longest wavelengths down to the thermal ion Larmor radius. At the shortest scales, the poloidal wavelengths are like the scale length of electrostatic drift wave turbulence. Theoretical analysis verifies a dominant interaction of the modes with particles in the thermal ion distribution traveling well below the Alfvén velocity.

Authors:
 [1];  [2];  [1];  [3];  [4];  [5];  [1];  [6];  [1];  [6];  [3];  [5];  [6];  [4];  [4];  [1];  [3];  [7];  [4]
  1. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
  2. Univ. of Texas, Austin, TX (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Univ. of California, Los Angeles, CA (United States)
  5. Univ. of Wisconsin, Madison, WI (United States)
  6. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  7. Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States); Univ. of Texas, Austin, TX (United States); Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1171037
DOE Contract Number:
DE-AC02-76CH03073; DE-FG03- 97ER54415; DE-FC02-04ER54698; DE-FG03- 01ER5461; DE-FG03-96ER54373; W-7405-ENG-48; DE-AC05-76OR00033
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 96; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Nazikian, R., Berk, H. L., Budny, R. V., Burrell, K. H., Doyle, E. J., Fonck, R. J., Gorelenkov, N. N., Holcomb, C., Kramer, G. J., Jayakumar, R. J., La Haye, R. J., McKee, G. R., Makowski, M. A., Peebles, W. A., Rhodes, T. L., Solomon, W. M., Strait, E. J., VanZeeland, M. A., and Zeng, L.. Multitude of Core-Localized Shear Alfvén Waves in a High-Temperature Fusion Plasma. United States: N. p., 2006. Web. doi:10.1103/PhysRevLett.96.105006.
Nazikian, R., Berk, H. L., Budny, R. V., Burrell, K. H., Doyle, E. J., Fonck, R. J., Gorelenkov, N. N., Holcomb, C., Kramer, G. J., Jayakumar, R. J., La Haye, R. J., McKee, G. R., Makowski, M. A., Peebles, W. A., Rhodes, T. L., Solomon, W. M., Strait, E. J., VanZeeland, M. A., & Zeng, L.. Multitude of Core-Localized Shear Alfvén Waves in a High-Temperature Fusion Plasma. United States. doi:10.1103/PhysRevLett.96.105006.
Nazikian, R., Berk, H. L., Budny, R. V., Burrell, K. H., Doyle, E. J., Fonck, R. J., Gorelenkov, N. N., Holcomb, C., Kramer, G. J., Jayakumar, R. J., La Haye, R. J., McKee, G. R., Makowski, M. A., Peebles, W. A., Rhodes, T. L., Solomon, W. M., Strait, E. J., VanZeeland, M. A., and Zeng, L.. Wed . "Multitude of Core-Localized Shear Alfvén Waves in a High-Temperature Fusion Plasma". United States. doi:10.1103/PhysRevLett.96.105006.
@article{osti_1171037,
title = {Multitude of Core-Localized Shear Alfvén Waves in a High-Temperature Fusion Plasma},
author = {Nazikian, R. and Berk, H. L. and Budny, R. V. and Burrell, K. H. and Doyle, E. J. and Fonck, R. J. and Gorelenkov, N. N. and Holcomb, C. and Kramer, G. J. and Jayakumar, R. J. and La Haye, R. J. and McKee, G. R. and Makowski, M. A. and Peebles, W. A. and Rhodes, T. L. and Solomon, W. M. and Strait, E. J. and VanZeeland, M. A. and Zeng, L.},
abstractNote = {Evidence is provided for a multitude of discrete frequency Alfvén waves in the core of magnetically confined high-temperature fusion plasmas. Multiple diagnostic instruments verify wave excitation over a wide spatial range from the device size at the longest wavelengths down to the thermal ion Larmor radius. At the shortest scales, the poloidal wavelengths are like the scale length of electrostatic drift wave turbulence. Theoretical analysis verifies a dominant interaction of the modes with particles in the thermal ion distribution traveling well below the Alfvén velocity.},
doi = {10.1103/PhysRevLett.96.105006},
journal = {Physical Review Letters},
number = 10,
volume = 96,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2006},
month = {Wed Mar 01 00:00:00 EST 2006}
}
  • Evidence is presented for a multitude of discrete frequency Alfven waves in the core of magnetically confined high-temperature fusion plasmas. Multiple diagnostic instruments confirm wave excitation over a wide spatial range from the device size at the longest wavelengths down to the thermal ion Larmor radius. At the shortest scales, the poloidal wavelengths are comparable to the scale length of electrostatic drift wave turbulence. Theoretical analysis confirms a dominant interaction of the modes with particles in the thermal ion distribution traveling well below the Alfven velocity.
  • Using two-dimensional hybrid-kinetic simulations, we explore the nonlinear “interruption” of standing and traveling shear-Alfvén waves in collisionless plasmas. Interruption involves a self-generated pressure anisotropy removing the restoring force of a linearly polarized Alfvénic perturbation, and occurs for wave amplitudes δB /B 0≳β –1/2 (where β is the ratio of thermal to magnetic pressure). We use highly elongated domains to obtain maximal scale separation between the wave and the ion gyroscale. For standing waves above the amplitude limit, we find that the large-scale magnetic field of the wave decays rapidly. The dynamics are strongly affected by the excitation of oblique firehosemore » modes, which transition into long-lived parallel fluctuations at the ion gyroscale and cause significant particle scattering. Traveling waves are damped more slowly, but are also influenced by small-scale parallel fluctuations created by the decay of firehose modes. Our results demonstrate that collisionless plasmas cannot support linearly polarized Alfvén waves above δB /B 0–1/2. Here, they also provide a vivid illustration of two key aspects of low-collisionality plasma dynamics: (i) the importance of velocity-space instabilities in regulating plasma dynamics at high β, and (ii) how nonlinear collisionless processes can transfer mechanical energy directly from the largest scales into thermal energy and microscale fluctuations, without the need for a scale-by-scale turbulent cascade.« less
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  • 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 themore » 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.« less