Beam Distribution Modification By Alfven Modes

doi:10.2172/971204

Title: Beam Distribution Modification By Alfven Modes

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Abstract

Modification of a deuterium beam distribution in the presence of low amplitude Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes in a toroidal magnetic confinement device is examined. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam transport, and that the experimental amplitudes are only slightly above this threshold. The modes produce a substantial central flattening of the beam distribution.

Authors:: White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.

Publication Date:: Mon Jan 25 00:00:00 EST 2010

Research Org.:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Org.:: USDOE Office of Science (SC)

OSTI Identifier:: 971204

Report Number(s):: PPPL-4483
TRN: US1001706

DOE Contract Number:: DE-ACO2-09CH11466

Resource Type:: Technical Report

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLITUDES; BEAM TRANSPORT; DEUTERIUM; DISTRIBUTION; MAGNETIC CONFINEMENT; MODIFICATIONS; REVERSED SHEAR; Alfven Waves, Beam Plasma Interactions, Wave Interaction Particles

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                    White, R. B., Gorelenkov, N., Heidbrink, W. W., and Van Zeeland, M. A. Beam Distribution Modification By Alfven Modes.  United States: N. p., 2010. 
        Web.  doi:10.2172/971204.

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                    White, R. B., Gorelenkov, N., Heidbrink, W. W., & Van Zeeland, M. A. Beam Distribution Modification By Alfven Modes.  United States.  doi:10.2172/971204.

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                    White, R. B., Gorelenkov, N., Heidbrink, W. W., and Van Zeeland, M. A. Mon .  
        "Beam Distribution Modification By Alfven Modes".  United States.  
        doi:10.2172/971204.  https://www.osti.gov/servlets/purl/971204.

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@article{osti_971204,

  title        = {Beam Distribution Modification By Alfven Modes},

  author       = {White, R. B. and Gorelenkov, N. and Heidbrink, W. W. and Van Zeeland, M. A.},

  abstractNote = {Modification of a deuterium beam distribution in the presence of low amplitude Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes in a toroidal magnetic confinement device is examined. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam transport, and that the experimental amplitudes are only slightly above this threshold. The modes produce a substantial central flattening of the beam distribution.},

  doi          = {10.2172/971204},

  journal      = {},

  number       = ,

  volume       = ,

  place        = {United States},

  year         = {Mon Jan 25 00:00:00 EST 2010},

  month        = {Mon Jan 25 00:00:00 EST 2010}

}

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DOI: 10.2172/971204

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Beam Distribution Modification by Alfven Modes

White, R. B. ; Gorelenkov, N. ; Heidbrink, W. W. ; ...

Modification of a deuterium beam distribution in the presence of low amplitude Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes in a toroidal magnetic confinement device is examined. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam transport, and that the experimental amplitudes are only slightly above this threshold. The modes produce a substantial central flattening of the beam distribution.
DOI: 10.2172/973208

Full Text Available
Beam distribution modification by Alfven modes

White, R. B. ; Gorelenkov, N. ; Heidbrink, W. W. ; ... - Physics of Plasmas

Modification of a deuterium beam distribution in the presence of low amplitude toroidal Alfven eigenmodes and reversed shear Alfven eigenmodes in a toroidal magnetic confinement device is examined. Comparison to experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam transport, and that the experimental amplitudes are only slightly above this threshold. The modes produce a substantial central flattening of the beam distribution.
DOI: 10.1063/1.3327208
Observations of neutral beam and ICRF tail ion losses due to Alfven modes in TFTR

Darrow, D.S. ; Zweben, S.J. ; Chang, Z.

Fast ion losses resulting from MHD modes at the Alfven frequency, such as the TAE, have been observed in TFTR. The modes have been driven both by neutral beam ions, at low B{sub T}, and by H-minority ICRF tail ions at higher B{sub T}. The measurements indicate that the loss rate varies linearly with the mode amplitude, and that the fast ion losses during the mode activity can be significant, e.g. up to 10% of the input power is lost in the worst case.
DOI: 10.2172/231967

Full Text Available
Observation of Compressional Alfven Modes during Neutral Beam Heating on the National Spherical Torus Experiment

E.D. Fredrickson ; N. Gorelenkov ; C.Z. Cheng ; ...

Neutral-beam-driven compressional Alfven eigenmodes (CAE) at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment (NSTX). The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from approximately 0.2 to approximately 1.2 omega(subscript ''ci''). The frequency has a scaling with toroidal field and plasma density consistent with Alfven waves. The modes have been observed with high bandwidth magnetic pick-up coils and with a reflectometer.
DOI: 10.2172/788445

Full Text Available
Particle Distribution Modification by Low Amplitude Modes

White, R. B. ; Gorelenkov, N. ; Heidbrink, W. W. ; ...

Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distributionmore »« less
DOI: 10.2172/963535

Full Text Available