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Title: Theory and observation of the onset of nonlinear structures due to eigenmode destabilization by fast ions in tokamaks

Alfvén waves can induce the ejection of fast ions in different forms in tokamaks. In order to develop predictive capabilities to anticipate the nature of fast ion transport, a methodology is proposed to differentiate the likelihood of energetic-particle-driven instabilities to produce frequency chirping or fixed-frequency oscillations. Furthermore, the proposed method employs numerically calculated eigenstructures and multiple resonance surfaces of a given mode in the presence of energetic ion drag and stochasticity (due to collisions and micro-turbulence). Toroidicity-induced, reversed-shear and beta-induced Alfvén-acoustic eigenmodes are used as examples. Waves measured in experiments are characterized, and compatibility is found between the proposed criterion predictions and the experimental observation or lack of observation of chirping behavior of Alfvénic modes in different tokamaks. It is found that the stochastic diffusion due to micro-turbulence can be the dominant energetic particle detuning mechanism near the resonances in many plasma experiments, and its strength is the key as to whether chirping solutions are likely to arise. We proposed a criterion that constitutes a useful predictive tool in assessing whether the nature of the transport for fast ion losses in fusion devices will be dominated by convective or diffusive processes.
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  1. Univ. of Sao Paulo (Brazil). Inst. of Physics; Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies
  3. Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  4. Univ. of California, Irvine, CA (United States)
  5. General Atomics, San Diego, CA (United States)
Publication Date:
Grant/Contract Number:
2012/22830-2; 2014/03289-4; AC02-09CH11466; FC02-04ER54698
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 12; Journal ID: ISSN 1070-664X
American Institute of Physics (AIP)
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1413027